a Nanoscopy, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy b Nano Carbon Ma... more a Nanoscopy, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy b Nano Carbon Materials, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy c Dibris, University of Genoa, Via All'Opera Pia 13, 16145 Genoa, Italy d Nikon Center, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy *Current affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University, 37232 Nashville Tennessee, USA. E-mail: marta.damora@iit.it
Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therape... more Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therapeutic agents, such as drug molecules or large biomolecules, proteins (e.g. DNA or RNA) into their targets. In particular, gold nanoparticles (Au NPs) with their low inherent toxicity, tunable stability and high surface area provide unique attributes facilitating new delivery strategies. A biodegradable, photocurable polymer resin, polypropylene fumarate (PPF) along with Au NPs were utilized to synthesize a hybrid nanocomposite resin, directly exploitable in stereolithography (SL) processes. To increase the particles' colloidal stability, the Au NP nanofillers were coated with polyvinyl pyrrolidone (PVP). The resulting resin was used to fabricate a new type of composite scaffold via mask projection excimer laser stereolithography. The thermal properties of the nanocomposite scaffolds were found to be sensitive to the concentration of NPs. The mechanical properties were augmented by the NPs up to 0.16μM, though further increase in the concentration led to a gradual decrease. Au NP incorporation rendered the biopolymer scaffolds photosensitive, i.e. the presence of Au NPs enhanced the optical absorption of the scaffolds as well, leading to possible localized temperature rise when irradiated with 532nm laser, known as the photothermal effect.
The localization of light known as Anderson localization is a common phenomenon characterizing ag... more The localization of light known as Anderson localization is a common phenomenon characterizing aggregates of metallic nanostructures. The electromagnetic energy of visible light can be localized inside nanostructures below the diffraction limit by converting the optical modes into nonradiative surface plasmon resonances. The energy of the confined photons is correlated to the size and shape of the nanostructured system. In this work, we studied the photoluminescence dependence of aggregates of 14 nm diameter gold nanoparticles (AuNPs) synthesized by drop-casting a liquid suspension on two different substrates of glass and quartz. The AuNP aggregates were characterized by electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The dielectric constant of the surrounding medium plays a crucial role in determining the aggregate geometry, which affects the Anderson localization of light in the aggregates and hence causes a red-shift in the plasmonic resonance and in ...
Journal of Photochemistry and Photobiology A: Chemistry, 2014
ABSTRACT Gold nanorods (AuNRs) were synthesized by photochemical method, through irradiation of a... more ABSTRACT Gold nanorods (AuNRs) were synthesized by photochemical method, through irradiation of a reaction solution, containing gold precursor, surfactant and a mild reducing agent to speed up the process. The effects of the irradiation parameters on the morphology of the formed AuNRs were investigated by UV–Vis absorption spectra and transmission electron microscopy. Specifically, the control of the UV irradiance (irradiation power per unit area) and irradiation time allowed the preparation of AuNRs with a wide range of sizes. Increase of the irradiation power leads to the formation of smaller AuNRs, with concomitant decrease of length and diameter. Since both axes show a simultaneous size decrease, the produced AuNRs have increased aspect ratio. Overall we show that application of high UV irradiance for short times favors the synthesis of small AuNRs with increased anisotropy. We propose that the rise of the irradiation power primarily accelerates the reduction of the gold precursor, promoting in such way the formation of smaller seeds. Short irradiation times guard against dissolution effects on the formed nanorods.
The localization of light known as Anderson localization is a common phenomenon characterizing ag... more The localization of light known as Anderson localization is a common phenomenon characterizing aggregates of metallic nano-structures. The electromagnetic energy of visible light can be localized inside nanostructures below the diffraction limit by converting the optical modes into nonradiative surface plasmon resonances. The energy of the confined photons is correlated to the size and shape of the nanostructured system. In this work, we studied the photoluminescence dependence of aggregates of 14 nm diameter gold nanoparticles (AuNPs) synthesized by drop-casting a liquid suspension on two different substrates of glass and quartz. The AuNP aggregates were characterized by electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The dielectric constant of the surrounding medium plays a crucial role in determining the aggregate geometry, which affects the Anderson localization of light in the aggregates and hence causes a red-shift in the plasmonic resonance and in the photolumines-cence emission. The geometry of the gold nanoparticle aggregates determine the strength of the Anderson localization, and hence, the light emission from the aggregates. The photoluminescence lifetime was found to be dependent on the AuNP aggregate geometry and the dielectric constant of the medium.
Therapeutic stem cell transplantation bears the promise of new directions in organ and tissue rep... more Therapeutic stem cell transplantation bears the promise of new directions in organ and tissue replacement, but a number of its difficulties and perils are also well known. Our goal was to develop a method of transplantation by which the transplanted cells remain confined to the transplantation site and induce favorable processes. With the help of mask-projection excimer laser stereolithography, 3D hybrid nanoscaffolds were fabricated from biodegradable , photocurable PPF:DEF resin with incorporated gold nanoparticles (Au NPs). The scaffolds were tested in vitro and in vivo in order to find out about their biocompatibility and fitness for our purposes. In vitro, macrophages and mouse autologous adipose stem cells (ASCs) were seeded over the hybrid scaffolds and non-hybrid (with Au NPs) scaffolds for 4 days. The hybrid nanocomposite greater stem cell dispension and stem cell adhesion than PPF scaffolds without Au NPs, but such a difference was not seen in the case of macrophages. In vivo, stem cells, scaffoldings and scaffoldings covered in stem cells were transplanted under the back skin of mice. After 14 days, blood samples were taken and the affected skin area was excised. Cytokine and chemokine profiling did not indicate elevated immunomediators in the sera of experimental animals. Interestingly, the au-tologous-stem-cell-seeded hybrid nanocomposite scaffold induced muscle tissue regeneration after experimental wound generation in vivo. We could not observe such stem cell-induced tissue regeneration when no scaffolding was used. We conclude that PPF:DEF resin nanoscaffolds with incorporated gold nanoparticles offer a safe and efficient alternative for the enhancement of local tissue remodeling. The results also support the idea that adipose derived stem cells are an optimal cell type for the purposes of regenerative musculoskeletal tissue engineering.
A B S T R A C T Synthesis of gold nanorods by photochemical reduction of gold precursor in cation... more A B S T R A C T Synthesis of gold nanorods by photochemical reduction of gold precursor in cationic surfactant aqueous solution is studied in detail. The effect of concentration of cationic surfactant, Hexadecyltrimethy-lammonium Bromide, in the nanorods growth solution is examined and the optimum concentration for the synthesis estimated. Increase of the surfactant concentration, from the widely used 80 mM up to 160 mM, leads to considerable enhancement of the gold nanorods aspect ratio. The experimental results couple the improvements on the synthesis achieved increasing the surfactant concentration with the maximization of gold bromide complexes in the precursor solution. On the one hand dissociated bromide ions exchange with chloride stabilizes the gold against disproponation. So obtained strong gold bromide complexes play the role of gold precursor available for the photochemical process. On the other hand dissociated surfactant cations support the anisotropy of the growth through selective Hexadecyl-trimethylammonium bilayer formation on AuNRs surfaces where bromide ions are preferentially adsorbed.
KEY WORDS: Carbon nano-onions, silver nanoparticles, Zebrafish embryos, light sheet fluorescence ... more KEY WORDS: Carbon nano-onions, silver nanoparticles, Zebrafish embryos, light sheet fluorescence microscopy Nanomaterials are currently used in the daily life in different fields such as cosmetics and food industry, tissue engineering, drug delivery and biomedical imaging. The increased human and environmental exposures to nanomaterials give rise to an urgent need for a complete study of their possible toxic effects. In this study, we focus our attention on the biological effects induced by two different classes of nanomaterials on zebrafish during development: carbon nano-onions (CNOs) and silver nanoparticles (Ag NPs). CNOs are a class of carbon nanomaterials which presents high cellular uptake and low citotoxicity [1]. In particular, BODIPY functionalized CNOs are suitable for high resolution imaging [2]. In this study, we focus our attention on the biocompatibility of BODIPY CNOs in zebrafish during the development and we characterize all the macroscopic effects by assessing different end-points and exposure periods. Furthermore, we use 3D fluorescence imaging techniques, such as selective plane illumination microscopy (SPIM) to perform a bio-distribution study of CNOs in zebrafish embryos and larvae. On the other hand, previous studies on Ag NPs have already investigates the toxicity induced by these nanoparticles on zebrafish during development analyzing different macroscopic effects [3]. However, little is known about the possible interaction of Ag NPs with sub cellular structures. Here we study the biological effects of small-sized Ag NPs through a multi-level investigation on zebrafish larvae, with particular attention at the microscopic level. In particular, the use of advanced microscopy techniques (such as confocal microscopy, and light sheet fluorescence microscopy) [4, 5] allows for 3D high resolution imaging of Ag NPs effects on the cytoskeletal architecture.
Gold nanorods (AuNRs) are eligible for a variety of biological applications including cell imagin... more Gold nanorods (AuNRs) are eligible for a variety of biological applications including cell imaging, sensing, and photothermal therapy thanks to their optical properties. The aim of this work is to show how AuNRs could be employed as non-photobleachable optical contrast agents for biomedical applications. In order to demonstrate the feasibility of their use as optical trackers, we employed two-photon emission confocal microscopy on cells incubated with PEGylated AuNRs. Remarkably, AuNRs were localized mostly in the perinuclear zone and microscopy characterization showed the presence of a considerable number of rods inside cell nuclei. Furthermore, we estimated the toxicity and the efficiency of cellular uptake of the PEGylated AuNRs as a function of administered dose on HeLa/3T3 cell lines and on zebrafish during development, employed as an in vivo model. Eventually, we observed good agreement between in vivo and in vitro experiments. The employed AuNRs were prepared through a photochemical protocol here improved by tuning the amount of the cationic surfactant cetyltrimethylammonium bromide for the achievement of AuNRs at two different aspect ratios. Furthermore we also investigated if the AuNR aspect ratio influenced the toxicity and the efficiency of cellular uptake of the PEGylated AuNRs in HeLa/3T3 cell lines and in zebrafish embryos. S Online supplementary data available from stacks.iop.org/NANO/27/255101/mmedia
Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therape... more Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therapeutic agents, such as drug molecules or large biomolecules, proteins (e.g. DNA or RNA) into their targets. In particular, gold nanoparticles (Au NPs) with their low inherent toxicity, tunable stability and high surface area provide unique attributes facilitating new delivery strategies. A biodegradable, photocurable polymer resin, polypropylene fumarate (PPF) along with Au NPs were utilized to synthesize a hybrid nanocomposite resin, directly exploitable in stereolithography (SL) processes. To increase the particles' colloidal stability, the Au NP nanofillers were coated with polyvinyl pyrrolidone (PVP). The resulting resin was used to fabricate a new type of composite scaffold via mask projection excimer laser stereolithography. The thermal properties of the nanocomposite scaffolds were found to be sensitive to the concentration of NPs. The mechanical properties were augmented by the NPs up to 0.16 μM, though further increase in the concentration led to a gradual decrease. Au NP incorporation rendered the biopolymer scaffolds photosensitive, i.e. the presence of Au NPs enhanced the optical absorption of the scaffolds as well, leading to possible localized temperature rise when irradiated with 532 nm laser, known as the photothermal effect.
Gold nanorods (AuNRs) were synthesized by photochemical method, through irradiation of a reaction... more Gold nanorods (AuNRs) were synthesized by photochemical method, through irradiation of a reactionsolution, containing gold precursor, surfactant and a mild reducing agent to speed up the process. Theeffects of the irradiation parameters on the morphology of the formed AuNRs were investigated by UV–Visabsorption spectra and transmission electron microscopy. Specifically, the control of the UV irradiance(irradiation power per unit area) and irradiation time allowed the preparation of AuNRs with a widerange of sizes. Increase of the irradiation power leads to the formation of smaller AuNRs, with concomitantdecrease of length and diameter. Since both axes show a simultaneous size decrease, the produced AuNRshave increased aspect ratio. Overall we show that application of high UV irradiance for short times favorsthe synthesis of small AuNRs with increased anisotropy. We propose that the rise of the irradiation powerprimarily accelerates the reduction of the gold precursor, promoting in such way the formation of smallerseeds. Short irradiation times guard against dissolution effects on the formed nanorods.
a combinationofchemicalreductionandUVphotoirradiation.Goldligandcomplexes,presentinthe
stock solu... more a combinationofchemicalreductionandUVphotoirradiation.Goldligandcomplexes,presentinthe stock solution,areinitiallyreduced,byascorbicacidasmildreducingagent.Thegoldionsnucleation and colloidgrowthproceedsthenbysubsequentUVirradiationoftheso-obtainedprecursorsolution. We presentasystematicstudyoftheeffectofincubationoftheprecursorsolutiononthedispersion state andaspectratiooftheproducednanorods.Incubationoftheprecursorsolutionallowsthe synthesisofhigheraspectrationanorodswithnarrowersizedistributioncomparedtothoseobtained withoutincubation.Weproposeamechanismforthegoldnanorodsformationincludingtwostages,a nucleationandadiffusivegrowth.Thisallowsustoexplainthesynthesisimprovementasaconsequence of theincreaseinthesizeofthegoldligandcomplexesaggregates,leadingtoadecreaseofthenanorods growthrate.
Polymer nanocomposites attracted an increasing attention in the last two decades on account of th... more Polymer nanocomposites attracted an increasing attention in the last two decades on account of their capability for tailoring the chemical-physical characteristics of any polymer by properly choosing and tuning the properties and quantity of the nanofillers. Diverse synthetic strategies can be followed for fabricating polymer nanocomposites including physical mixing, chemical grafting, in-situ synthesis of one component in the presence of the others, and finally layer-by-layer deposition. The dispersed nanostructures, incorporated with the polymer in nanocomposite materials, can be chosen into a wide spectrum of naturally existing and artificially synthesized nanomaterials, encompassing layered silicate clay, carbon fibers, carbon nanotubes, and inorganic nanoparticles of different origins, shapes, sizes, and surface affinities. The properties of polymer nanocomposites depend on the properties of their components including polymers and the dispersed nanostructures. By selectively choosing of the polymer and the dispersed nanostructures counterpart, the properties of the resulted nanocomposites can be tuned covering a wide range of multidisciplinary applications. This includes electronics, optoelectronics, engineering high performance hybrid, anti-corrosion, and smart coating materials, drug delivery and sensors. The Sensors applications for Polymer/Nanoparticles nanocomposite materials were highly expanded during last decade covering a wide range of daily life demands counting industrial, environmental, militarily and medical. Polymer/nanoparticles nanocomposites endow the scientists the ability to enhance sensor performance by developing nanocomposites as transducer materials. The development of new techniques for anchoring new receptors to the nanocomposite transducer materials spreads the use of sensors to new applications. The use of polymer/nanoparticles nanocomposites as transducer materials demands the precise control of the size and shape of the embedded nanoparticles, of the dispersion of the nanoparticles in the matrix and of the mechanism of the interaction of nanoparticles with the host materials. Selectively choosing the nanoparticles and the polymeric matrix in some cases it is possible to avoid the use of receptors, exploiting the sensitivities of the physical and chemical properties of both of nanoparticles and polymers towards external stimuli. At the same time, the nanocomposite has to operate as transducer to transfer the response to the detector. Due to them unique properties, including surface plasmonic resonance and chemical affinity, metallic nanoparticles are extensively used in sensors fabrication especially in biological field (biosensors). The properties of metallic nanoparticles change to a large extent with their size and shape, which gives them a high flexibility, profited in different applications. The attractive properties of gold nanorods drove researchers to develop different synthetic methodologies to control their dimensions and dispersion state. In this study, I am going to investigate the synthesis of gold nanorods (AuNRs) by photochemical synthesis trying to explore the factors controlling the growth of AuNRs. Photochemical method is one of the synthetic strategies used for AuNRs preparation and is considered a promising evolution of the more popular seed-mediated method, since it is less time consuming and avoids the use of seeds that can give rise to structure complications.. The absence of any separation between nucleation and growth steps is the main disadvantage of photochemical method. The incubation of gold nanorods precursor solution in dark before irradiation and the irradiance and time of irradiation will be investigated in detail. The effect of precursor solution dark incubation, prior UV irradiation, is proposed for enhancing the dispersion of the produced gold nanorods. AuNRs are synthesized in an aqueous solution of hexadecyltrimethylammonium bromide (CTAB) via combination of chemical reduction and UV photoirradiation. The gold ligand complexes (Au(III)-CTAB), present in the stock solution, are initially reduced (to Au(I)-CTAB), by ascorbic acid as mild reducing agent. The gold ions nucleation and colloids growth proceeds then by subsequent UV irradiation at wavelength 254 nm of the precursor solution. We present a systematic study of the effect of incubation of the precursor solution in dark on the dispersion state and morphology of the produced nanorods. Incubation of the precursor solution allows the synthesis of higher aspect ratio nanorods with narrower size distribution compared to those obtained without incubation. We propose a mechanism for the gold nanorods formation including two stages, a nucleation and a diffusive growth. This allows us to explain the synthesis improvement as a consequence of the increase in the size of CTAB and Au(I)- CTAB complexes aggregates, leading to a decrease of the nanorods growth rate. Another factor affecting the morphology and the dispersion state of AuNRs produced by photochemical synthesis is the fluence of UV light, used to irradiate the precursor solution. The light intensity and the irradiation time have been studied in order to further clarify the mechanism of nucleation and growth of AuNRs. The light parameters were also optimized for better dispersion and aspect ratio of the produced nanorods. AuNRs were synthesized, by irradiation of the precursor solution with different fluences, obtained tuning one after the other the time of irradiation and the irradiance, keeping steady the other variable. The effect of the time of irradiation and of the irradiance on the morphology of the formed AuNRs was investigated by UV-Vis absorption spectra and transmission electron microscopy. Tuning the fluence we were able to control the AuNRs morphology and therefore its aspect ratio. Suitable tweaking of the fluence allowed us to synthesize superfine AuNRs with small sizes (down to about 7 nm for average diameter and 30 nm for average length) and average aspect ratio about 5. The experimental results point out two possible regimes throughout the synthesis, whether the fluence is exceeding or not a threshold fluence. Lengthening of the irradiation time leads first to nucleation and growth of a larger number of AuNRs. Through the synthesis progress, as threshold fluence is overcome, AuNRs dissolution in favor of the more stable bigger spherical nanoparticles starts. We impute the threshold fluence to the reduction and exhaustion of the gold precursor in the reaction solution. The experimental results show that the time of irradiation allows mainly the control of the yield of the synthesis. Further prolongation of the irradiation time after the maximization of the synthesis yield leads to AuNRs deterioration. The main effect of UV irradiance is the focusing of the AuNRs growth, irradiance rise promoting smaller seeds growth. To fully profit the focusing obtained by irradiance rise, the time of irradiation has to be reduced in order not to exceed the fluence threshold.
a Nanoscopy, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy b Nano Carbon Ma... more a Nanoscopy, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy b Nano Carbon Materials, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy c Dibris, University of Genoa, Via All'Opera Pia 13, 16145 Genoa, Italy d Nikon Center, Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genoa, Italy *Current affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University, 37232 Nashville Tennessee, USA. E-mail: marta.damora@iit.it
Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therape... more Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therapeutic agents, such as drug molecules or large biomolecules, proteins (e.g. DNA or RNA) into their targets. In particular, gold nanoparticles (Au NPs) with their low inherent toxicity, tunable stability and high surface area provide unique attributes facilitating new delivery strategies. A biodegradable, photocurable polymer resin, polypropylene fumarate (PPF) along with Au NPs were utilized to synthesize a hybrid nanocomposite resin, directly exploitable in stereolithography (SL) processes. To increase the particles' colloidal stability, the Au NP nanofillers were coated with polyvinyl pyrrolidone (PVP). The resulting resin was used to fabricate a new type of composite scaffold via mask projection excimer laser stereolithography. The thermal properties of the nanocomposite scaffolds were found to be sensitive to the concentration of NPs. The mechanical properties were augmented by the NPs up to 0.16μM, though further increase in the concentration led to a gradual decrease. Au NP incorporation rendered the biopolymer scaffolds photosensitive, i.e. the presence of Au NPs enhanced the optical absorption of the scaffolds as well, leading to possible localized temperature rise when irradiated with 532nm laser, known as the photothermal effect.
The localization of light known as Anderson localization is a common phenomenon characterizing ag... more The localization of light known as Anderson localization is a common phenomenon characterizing aggregates of metallic nanostructures. The electromagnetic energy of visible light can be localized inside nanostructures below the diffraction limit by converting the optical modes into nonradiative surface plasmon resonances. The energy of the confined photons is correlated to the size and shape of the nanostructured system. In this work, we studied the photoluminescence dependence of aggregates of 14 nm diameter gold nanoparticles (AuNPs) synthesized by drop-casting a liquid suspension on two different substrates of glass and quartz. The AuNP aggregates were characterized by electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The dielectric constant of the surrounding medium plays a crucial role in determining the aggregate geometry, which affects the Anderson localization of light in the aggregates and hence causes a red-shift in the plasmonic resonance and in ...
Journal of Photochemistry and Photobiology A: Chemistry, 2014
ABSTRACT Gold nanorods (AuNRs) were synthesized by photochemical method, through irradiation of a... more ABSTRACT Gold nanorods (AuNRs) were synthesized by photochemical method, through irradiation of a reaction solution, containing gold precursor, surfactant and a mild reducing agent to speed up the process. The effects of the irradiation parameters on the morphology of the formed AuNRs were investigated by UV–Vis absorption spectra and transmission electron microscopy. Specifically, the control of the UV irradiance (irradiation power per unit area) and irradiation time allowed the preparation of AuNRs with a wide range of sizes. Increase of the irradiation power leads to the formation of smaller AuNRs, with concomitant decrease of length and diameter. Since both axes show a simultaneous size decrease, the produced AuNRs have increased aspect ratio. Overall we show that application of high UV irradiance for short times favors the synthesis of small AuNRs with increased anisotropy. We propose that the rise of the irradiation power primarily accelerates the reduction of the gold precursor, promoting in such way the formation of smaller seeds. Short irradiation times guard against dissolution effects on the formed nanorods.
The localization of light known as Anderson localization is a common phenomenon characterizing ag... more The localization of light known as Anderson localization is a common phenomenon characterizing aggregates of metallic nano-structures. The electromagnetic energy of visible light can be localized inside nanostructures below the diffraction limit by converting the optical modes into nonradiative surface plasmon resonances. The energy of the confined photons is correlated to the size and shape of the nanostructured system. In this work, we studied the photoluminescence dependence of aggregates of 14 nm diameter gold nanoparticles (AuNPs) synthesized by drop-casting a liquid suspension on two different substrates of glass and quartz. The AuNP aggregates were characterized by electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The dielectric constant of the surrounding medium plays a crucial role in determining the aggregate geometry, which affects the Anderson localization of light in the aggregates and hence causes a red-shift in the plasmonic resonance and in the photolumines-cence emission. The geometry of the gold nanoparticle aggregates determine the strength of the Anderson localization, and hence, the light emission from the aggregates. The photoluminescence lifetime was found to be dependent on the AuNP aggregate geometry and the dielectric constant of the medium.
Therapeutic stem cell transplantation bears the promise of new directions in organ and tissue rep... more Therapeutic stem cell transplantation bears the promise of new directions in organ and tissue replacement, but a number of its difficulties and perils are also well known. Our goal was to develop a method of transplantation by which the transplanted cells remain confined to the transplantation site and induce favorable processes. With the help of mask-projection excimer laser stereolithography, 3D hybrid nanoscaffolds were fabricated from biodegradable , photocurable PPF:DEF resin with incorporated gold nanoparticles (Au NPs). The scaffolds were tested in vitro and in vivo in order to find out about their biocompatibility and fitness for our purposes. In vitro, macrophages and mouse autologous adipose stem cells (ASCs) were seeded over the hybrid scaffolds and non-hybrid (with Au NPs) scaffolds for 4 days. The hybrid nanocomposite greater stem cell dispension and stem cell adhesion than PPF scaffolds without Au NPs, but such a difference was not seen in the case of macrophages. In vivo, stem cells, scaffoldings and scaffoldings covered in stem cells were transplanted under the back skin of mice. After 14 days, blood samples were taken and the affected skin area was excised. Cytokine and chemokine profiling did not indicate elevated immunomediators in the sera of experimental animals. Interestingly, the au-tologous-stem-cell-seeded hybrid nanocomposite scaffold induced muscle tissue regeneration after experimental wound generation in vivo. We could not observe such stem cell-induced tissue regeneration when no scaffolding was used. We conclude that PPF:DEF resin nanoscaffolds with incorporated gold nanoparticles offer a safe and efficient alternative for the enhancement of local tissue remodeling. The results also support the idea that adipose derived stem cells are an optimal cell type for the purposes of regenerative musculoskeletal tissue engineering.
A B S T R A C T Synthesis of gold nanorods by photochemical reduction of gold precursor in cation... more A B S T R A C T Synthesis of gold nanorods by photochemical reduction of gold precursor in cationic surfactant aqueous solution is studied in detail. The effect of concentration of cationic surfactant, Hexadecyltrimethy-lammonium Bromide, in the nanorods growth solution is examined and the optimum concentration for the synthesis estimated. Increase of the surfactant concentration, from the widely used 80 mM up to 160 mM, leads to considerable enhancement of the gold nanorods aspect ratio. The experimental results couple the improvements on the synthesis achieved increasing the surfactant concentration with the maximization of gold bromide complexes in the precursor solution. On the one hand dissociated bromide ions exchange with chloride stabilizes the gold against disproponation. So obtained strong gold bromide complexes play the role of gold precursor available for the photochemical process. On the other hand dissociated surfactant cations support the anisotropy of the growth through selective Hexadecyl-trimethylammonium bilayer formation on AuNRs surfaces where bromide ions are preferentially adsorbed.
KEY WORDS: Carbon nano-onions, silver nanoparticles, Zebrafish embryos, light sheet fluorescence ... more KEY WORDS: Carbon nano-onions, silver nanoparticles, Zebrafish embryos, light sheet fluorescence microscopy Nanomaterials are currently used in the daily life in different fields such as cosmetics and food industry, tissue engineering, drug delivery and biomedical imaging. The increased human and environmental exposures to nanomaterials give rise to an urgent need for a complete study of their possible toxic effects. In this study, we focus our attention on the biological effects induced by two different classes of nanomaterials on zebrafish during development: carbon nano-onions (CNOs) and silver nanoparticles (Ag NPs). CNOs are a class of carbon nanomaterials which presents high cellular uptake and low citotoxicity [1]. In particular, BODIPY functionalized CNOs are suitable for high resolution imaging [2]. In this study, we focus our attention on the biocompatibility of BODIPY CNOs in zebrafish during the development and we characterize all the macroscopic effects by assessing different end-points and exposure periods. Furthermore, we use 3D fluorescence imaging techniques, such as selective plane illumination microscopy (SPIM) to perform a bio-distribution study of CNOs in zebrafish embryos and larvae. On the other hand, previous studies on Ag NPs have already investigates the toxicity induced by these nanoparticles on zebrafish during development analyzing different macroscopic effects [3]. However, little is known about the possible interaction of Ag NPs with sub cellular structures. Here we study the biological effects of small-sized Ag NPs through a multi-level investigation on zebrafish larvae, with particular attention at the microscopic level. In particular, the use of advanced microscopy techniques (such as confocal microscopy, and light sheet fluorescence microscopy) [4, 5] allows for 3D high resolution imaging of Ag NPs effects on the cytoskeletal architecture.
Gold nanorods (AuNRs) are eligible for a variety of biological applications including cell imagin... more Gold nanorods (AuNRs) are eligible for a variety of biological applications including cell imaging, sensing, and photothermal therapy thanks to their optical properties. The aim of this work is to show how AuNRs could be employed as non-photobleachable optical contrast agents for biomedical applications. In order to demonstrate the feasibility of their use as optical trackers, we employed two-photon emission confocal microscopy on cells incubated with PEGylated AuNRs. Remarkably, AuNRs were localized mostly in the perinuclear zone and microscopy characterization showed the presence of a considerable number of rods inside cell nuclei. Furthermore, we estimated the toxicity and the efficiency of cellular uptake of the PEGylated AuNRs as a function of administered dose on HeLa/3T3 cell lines and on zebrafish during development, employed as an in vivo model. Eventually, we observed good agreement between in vivo and in vitro experiments. The employed AuNRs were prepared through a photochemical protocol here improved by tuning the amount of the cationic surfactant cetyltrimethylammonium bromide for the achievement of AuNRs at two different aspect ratios. Furthermore we also investigated if the AuNR aspect ratio influenced the toxicity and the efficiency of cellular uptake of the PEGylated AuNRs in HeLa/3T3 cell lines and in zebrafish embryos. S Online supplementary data available from stacks.iop.org/NANO/27/255101/mmedia
Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therape... more Nanoparticle incorporation into scaffold materials is a valuable route to deliver various therapeutic agents, such as drug molecules or large biomolecules, proteins (e.g. DNA or RNA) into their targets. In particular, gold nanoparticles (Au NPs) with their low inherent toxicity, tunable stability and high surface area provide unique attributes facilitating new delivery strategies. A biodegradable, photocurable polymer resin, polypropylene fumarate (PPF) along with Au NPs were utilized to synthesize a hybrid nanocomposite resin, directly exploitable in stereolithography (SL) processes. To increase the particles' colloidal stability, the Au NP nanofillers were coated with polyvinyl pyrrolidone (PVP). The resulting resin was used to fabricate a new type of composite scaffold via mask projection excimer laser stereolithography. The thermal properties of the nanocomposite scaffolds were found to be sensitive to the concentration of NPs. The mechanical properties were augmented by the NPs up to 0.16 μM, though further increase in the concentration led to a gradual decrease. Au NP incorporation rendered the biopolymer scaffolds photosensitive, i.e. the presence of Au NPs enhanced the optical absorption of the scaffolds as well, leading to possible localized temperature rise when irradiated with 532 nm laser, known as the photothermal effect.
Gold nanorods (AuNRs) were synthesized by photochemical method, through irradiation of a reaction... more Gold nanorods (AuNRs) were synthesized by photochemical method, through irradiation of a reactionsolution, containing gold precursor, surfactant and a mild reducing agent to speed up the process. Theeffects of the irradiation parameters on the morphology of the formed AuNRs were investigated by UV–Visabsorption spectra and transmission electron microscopy. Specifically, the control of the UV irradiance(irradiation power per unit area) and irradiation time allowed the preparation of AuNRs with a widerange of sizes. Increase of the irradiation power leads to the formation of smaller AuNRs, with concomitantdecrease of length and diameter. Since both axes show a simultaneous size decrease, the produced AuNRshave increased aspect ratio. Overall we show that application of high UV irradiance for short times favorsthe synthesis of small AuNRs with increased anisotropy. We propose that the rise of the irradiation powerprimarily accelerates the reduction of the gold precursor, promoting in such way the formation of smallerseeds. Short irradiation times guard against dissolution effects on the formed nanorods.
a combinationofchemicalreductionandUVphotoirradiation.Goldligandcomplexes,presentinthe
stock solu... more a combinationofchemicalreductionandUVphotoirradiation.Goldligandcomplexes,presentinthe stock solution,areinitiallyreduced,byascorbicacidasmildreducingagent.Thegoldionsnucleation and colloidgrowthproceedsthenbysubsequentUVirradiationoftheso-obtainedprecursorsolution. We presentasystematicstudyoftheeffectofincubationoftheprecursorsolutiononthedispersion state andaspectratiooftheproducednanorods.Incubationoftheprecursorsolutionallowsthe synthesisofhigheraspectrationanorodswithnarrowersizedistributioncomparedtothoseobtained withoutincubation.Weproposeamechanismforthegoldnanorodsformationincludingtwostages,a nucleationandadiffusivegrowth.Thisallowsustoexplainthesynthesisimprovementasaconsequence of theincreaseinthesizeofthegoldligandcomplexesaggregates,leadingtoadecreaseofthenanorods growthrate.
Polymer nanocomposites attracted an increasing attention in the last two decades on account of th... more Polymer nanocomposites attracted an increasing attention in the last two decades on account of their capability for tailoring the chemical-physical characteristics of any polymer by properly choosing and tuning the properties and quantity of the nanofillers. Diverse synthetic strategies can be followed for fabricating polymer nanocomposites including physical mixing, chemical grafting, in-situ synthesis of one component in the presence of the others, and finally layer-by-layer deposition. The dispersed nanostructures, incorporated with the polymer in nanocomposite materials, can be chosen into a wide spectrum of naturally existing and artificially synthesized nanomaterials, encompassing layered silicate clay, carbon fibers, carbon nanotubes, and inorganic nanoparticles of different origins, shapes, sizes, and surface affinities. The properties of polymer nanocomposites depend on the properties of their components including polymers and the dispersed nanostructures. By selectively choosing of the polymer and the dispersed nanostructures counterpart, the properties of the resulted nanocomposites can be tuned covering a wide range of multidisciplinary applications. This includes electronics, optoelectronics, engineering high performance hybrid, anti-corrosion, and smart coating materials, drug delivery and sensors. The Sensors applications for Polymer/Nanoparticles nanocomposite materials were highly expanded during last decade covering a wide range of daily life demands counting industrial, environmental, militarily and medical. Polymer/nanoparticles nanocomposites endow the scientists the ability to enhance sensor performance by developing nanocomposites as transducer materials. The development of new techniques for anchoring new receptors to the nanocomposite transducer materials spreads the use of sensors to new applications. The use of polymer/nanoparticles nanocomposites as transducer materials demands the precise control of the size and shape of the embedded nanoparticles, of the dispersion of the nanoparticles in the matrix and of the mechanism of the interaction of nanoparticles with the host materials. Selectively choosing the nanoparticles and the polymeric matrix in some cases it is possible to avoid the use of receptors, exploiting the sensitivities of the physical and chemical properties of both of nanoparticles and polymers towards external stimuli. At the same time, the nanocomposite has to operate as transducer to transfer the response to the detector. Due to them unique properties, including surface plasmonic resonance and chemical affinity, metallic nanoparticles are extensively used in sensors fabrication especially in biological field (biosensors). The properties of metallic nanoparticles change to a large extent with their size and shape, which gives them a high flexibility, profited in different applications. The attractive properties of gold nanorods drove researchers to develop different synthetic methodologies to control their dimensions and dispersion state. In this study, I am going to investigate the synthesis of gold nanorods (AuNRs) by photochemical synthesis trying to explore the factors controlling the growth of AuNRs. Photochemical method is one of the synthetic strategies used for AuNRs preparation and is considered a promising evolution of the more popular seed-mediated method, since it is less time consuming and avoids the use of seeds that can give rise to structure complications.. The absence of any separation between nucleation and growth steps is the main disadvantage of photochemical method. The incubation of gold nanorods precursor solution in dark before irradiation and the irradiance and time of irradiation will be investigated in detail. The effect of precursor solution dark incubation, prior UV irradiation, is proposed for enhancing the dispersion of the produced gold nanorods. AuNRs are synthesized in an aqueous solution of hexadecyltrimethylammonium bromide (CTAB) via combination of chemical reduction and UV photoirradiation. The gold ligand complexes (Au(III)-CTAB), present in the stock solution, are initially reduced (to Au(I)-CTAB), by ascorbic acid as mild reducing agent. The gold ions nucleation and colloids growth proceeds then by subsequent UV irradiation at wavelength 254 nm of the precursor solution. We present a systematic study of the effect of incubation of the precursor solution in dark on the dispersion state and morphology of the produced nanorods. Incubation of the precursor solution allows the synthesis of higher aspect ratio nanorods with narrower size distribution compared to those obtained without incubation. We propose a mechanism for the gold nanorods formation including two stages, a nucleation and a diffusive growth. This allows us to explain the synthesis improvement as a consequence of the increase in the size of CTAB and Au(I)- CTAB complexes aggregates, leading to a decrease of the nanorods growth rate. Another factor affecting the morphology and the dispersion state of AuNRs produced by photochemical synthesis is the fluence of UV light, used to irradiate the precursor solution. The light intensity and the irradiation time have been studied in order to further clarify the mechanism of nucleation and growth of AuNRs. The light parameters were also optimized for better dispersion and aspect ratio of the produced nanorods. AuNRs were synthesized, by irradiation of the precursor solution with different fluences, obtained tuning one after the other the time of irradiation and the irradiance, keeping steady the other variable. The effect of the time of irradiation and of the irradiance on the morphology of the formed AuNRs was investigated by UV-Vis absorption spectra and transmission electron microscopy. Tuning the fluence we were able to control the AuNRs morphology and therefore its aspect ratio. Suitable tweaking of the fluence allowed us to synthesize superfine AuNRs with small sizes (down to about 7 nm for average diameter and 30 nm for average length) and average aspect ratio about 5. The experimental results point out two possible regimes throughout the synthesis, whether the fluence is exceeding or not a threshold fluence. Lengthening of the irradiation time leads first to nucleation and growth of a larger number of AuNRs. Through the synthesis progress, as threshold fluence is overcome, AuNRs dissolution in favor of the more stable bigger spherical nanoparticles starts. We impute the threshold fluence to the reduction and exhaustion of the gold precursor in the reaction solution. The experimental results show that the time of irradiation allows mainly the control of the yield of the synthesis. Further prolongation of the irradiation time after the maximization of the synthesis yield leads to AuNRs deterioration. The main effect of UV irradiance is the focusing of the AuNRs growth, irradiance rise promoting smaller seeds growth. To fully profit the focusing obtained by irradiance rise, the time of irradiation has to be reduced in order not to exceed the fluence threshold.
Uploads
Papers by Gasser Nagah
as drug molecules or large biomolecules, proteins (e.g. DNA or RNA) into their targets. In particular, gold nanoparticles
(Au NPs) with their low inherent toxicity, tunable stability and high surface area provide unique attributes
facilitating new delivery strategies. A biodegradable, photocurable polymer resin, polypropylene fumarate
(PPF) along with Au NPs were utilized to synthesize a hybrid nanocomposite resin, directly exploitable in
stereolithography (SL) processes. To increase the particles' colloidal stability, the Au NP nanofillers were coated
with polyvinyl pyrrolidone (PVP). The resulting resin was used to fabricate a new type of composite scaffold via
mask projection excimer laser stereolithography. The thermal properties of the nanocomposite scaffolds were
found to be sensitive to the concentration of NPs. The mechanical properties were augmented by the NPs up to
0.16 μM, though further increase in the concentration led to a gradual decrease. Au NP incorporation rendered
the biopolymer scaffolds photosensitive, i.e. the presence of Au NPs enhanced the optical absorption of the
scaffolds as well, leading to possible localized temperature rise when irradiated with 532 nm laser, known as
the photothermal effect.
stock solution,areinitiallyreduced,byascorbicacidasmildreducingagent.Thegoldionsnucleation
and colloidgrowthproceedsthenbysubsequentUVirradiationoftheso-obtainedprecursorsolution.
We presentasystematicstudyoftheeffectofincubationoftheprecursorsolutiononthedispersion
state andaspectratiooftheproducednanorods.Incubationoftheprecursorsolutionallowsthe
synthesisofhigheraspectrationanorodswithnarrowersizedistributioncomparedtothoseobtained
withoutincubation.Weproposeamechanismforthegoldnanorodsformationincludingtwostages,a
nucleationandadiffusivegrowth.Thisallowsustoexplainthesynthesisimprovementasaconsequence
of theincreaseinthesizeofthegoldligandcomplexesaggregates,leadingtoadecreaseofthenanorods
growthrate.
capability for tailoring the chemical-physical characteristics of any polymer by properly choosing and tuning the
properties and quantity of the nanofillers. Diverse synthetic strategies can be followed for fabricating polymer
nanocomposites including physical mixing, chemical grafting, in-situ synthesis of one component in the
presence of the others, and finally layer-by-layer deposition. The dispersed nanostructures, incorporated with
the polymer in nanocomposite materials, can be chosen into a wide spectrum of naturally existing and
artificially synthesized nanomaterials, encompassing layered silicate clay, carbon fibers, carbon nanotubes, and
inorganic nanoparticles of different origins, shapes, sizes, and surface affinities. The properties of polymer
nanocomposites depend on the properties of their components including polymers and the dispersed
nanostructures. By selectively choosing of the polymer and the dispersed nanostructures counterpart, the
properties of the resulted nanocomposites can be tuned covering a wide range of multidisciplinary applications.
This includes electronics, optoelectronics, engineering high performance hybrid, anti-corrosion, and smart
coating materials, drug delivery and sensors. The Sensors applications for Polymer/Nanoparticles
nanocomposite materials were highly expanded during last decade covering a wide range of daily life demands
counting industrial, environmental, militarily and medical. Polymer/nanoparticles nanocomposites endow the
scientists the ability to enhance sensor performance by developing nanocomposites as transducer materials. The
development of new techniques for anchoring new receptors to the nanocomposite transducer materials spreads
the use of sensors to new applications. The use of polymer/nanoparticles nanocomposites as transducer materials
demands the precise control of the size and shape of the embedded nanoparticles, of the dispersion of the
nanoparticles in the matrix and of the mechanism of the interaction of nanoparticles with the host materials.
Selectively choosing the nanoparticles and the polymeric matrix in some cases it is possible to avoid the use of
receptors, exploiting the sensitivities of the physical and chemical properties of both of nanoparticles and
polymers towards external stimuli. At the same time, the nanocomposite has to operate as transducer to transfer
the response to the detector. Due to them unique properties, including surface plasmonic resonance and
chemical affinity, metallic nanoparticles are extensively used in sensors fabrication especially in biological field
(biosensors). The properties of metallic nanoparticles change to a large extent with their size and shape, which
gives them a high flexibility, profited in different applications. The attractive properties of gold nanorods drove
researchers to develop different synthetic methodologies to control their dimensions and dispersion state.
In this study, I am going to investigate the synthesis of gold nanorods (AuNRs) by photochemical
synthesis trying to explore the factors controlling the growth of AuNRs. Photochemical method is one of the
synthetic strategies used for AuNRs preparation and is considered a promising evolution of the more popular
seed-mediated method, since it is less time consuming and avoids the use of seeds that can give rise to structure
complications.. The absence of any separation between nucleation and growth steps is the main disadvantage of photochemical method. The incubation of gold nanorods precursor solution in dark before irradiation and the
irradiance and time of irradiation will be investigated in detail.
The effect of precursor solution dark incubation, prior UV irradiation, is proposed for enhancing the
dispersion of the produced gold nanorods. AuNRs are synthesized in an aqueous solution of
hexadecyltrimethylammonium bromide (CTAB) via combination of chemical reduction and UV
photoirradiation. The gold ligand complexes (Au(III)-CTAB), present in the stock solution, are initially reduced
(to Au(I)-CTAB), by ascorbic acid as mild reducing agent. The gold ions nucleation and colloids growth
proceeds then by subsequent UV irradiation at wavelength 254 nm of the precursor solution. We present a
systematic study of the effect of incubation of the precursor solution in dark on the dispersion state and
morphology of the produced nanorods. Incubation of the precursor solution allows the synthesis of higher aspect
ratio nanorods with narrower size distribution compared to those obtained without incubation. We propose a
mechanism for the gold nanorods formation including two stages, a nucleation and a diffusive growth. This
allows us to explain the synthesis improvement as a consequence of the increase in the size of CTAB and Au(I)-
CTAB complexes aggregates, leading to a decrease of the nanorods growth rate.
Another factor affecting the morphology and the dispersion state of AuNRs produced by
photochemical synthesis is the fluence of UV light, used to irradiate the precursor solution. The light intensity
and the irradiation time have been studied in order to further clarify the mechanism of nucleation and growth of
AuNRs. The light parameters were also optimized for better dispersion and aspect ratio of the produced
nanorods. AuNRs were synthesized, by irradiation of the precursor solution with different fluences, obtained
tuning one after the other the time of irradiation and the irradiance, keeping steady the other variable. The effect
of the time of irradiation and of the irradiance on the morphology of the formed AuNRs was investigated by
UV-Vis absorption spectra and transmission electron microscopy. Tuning the fluence we were able to control
the AuNRs morphology and therefore its aspect ratio. Suitable tweaking of the fluence allowed us to synthesize
superfine AuNRs with small sizes (down to about 7 nm for average diameter and 30 nm for average length) and
average aspect ratio about 5. The experimental results point out two possible regimes throughout the synthesis,
whether the fluence is exceeding or not a threshold fluence. Lengthening of the irradiation time leads first to
nucleation and growth of a larger number of AuNRs. Through the synthesis progress, as threshold fluence is
overcome, AuNRs dissolution in favor of the more stable bigger spherical nanoparticles starts. We impute the
threshold fluence to the reduction and exhaustion of the gold precursor in the reaction solution. The
experimental results show that the time of irradiation allows mainly the control of the yield of the synthesis.
Further prolongation of the irradiation time after the maximization of the synthesis yield leads to AuNRs
deterioration. The main effect of UV irradiance is the focusing of the AuNRs growth, irradiance rise promoting
smaller seeds growth. To fully profit the focusing obtained by irradiance rise, the time of irradiation has to be
reduced in order not to exceed the fluence threshold.
as drug molecules or large biomolecules, proteins (e.g. DNA or RNA) into their targets. In particular, gold nanoparticles
(Au NPs) with their low inherent toxicity, tunable stability and high surface area provide unique attributes
facilitating new delivery strategies. A biodegradable, photocurable polymer resin, polypropylene fumarate
(PPF) along with Au NPs were utilized to synthesize a hybrid nanocomposite resin, directly exploitable in
stereolithography (SL) processes. To increase the particles' colloidal stability, the Au NP nanofillers were coated
with polyvinyl pyrrolidone (PVP). The resulting resin was used to fabricate a new type of composite scaffold via
mask projection excimer laser stereolithography. The thermal properties of the nanocomposite scaffolds were
found to be sensitive to the concentration of NPs. The mechanical properties were augmented by the NPs up to
0.16 μM, though further increase in the concentration led to a gradual decrease. Au NP incorporation rendered
the biopolymer scaffolds photosensitive, i.e. the presence of Au NPs enhanced the optical absorption of the
scaffolds as well, leading to possible localized temperature rise when irradiated with 532 nm laser, known as
the photothermal effect.
stock solution,areinitiallyreduced,byascorbicacidasmildreducingagent.Thegoldionsnucleation
and colloidgrowthproceedsthenbysubsequentUVirradiationoftheso-obtainedprecursorsolution.
We presentasystematicstudyoftheeffectofincubationoftheprecursorsolutiononthedispersion
state andaspectratiooftheproducednanorods.Incubationoftheprecursorsolutionallowsthe
synthesisofhigheraspectrationanorodswithnarrowersizedistributioncomparedtothoseobtained
withoutincubation.Weproposeamechanismforthegoldnanorodsformationincludingtwostages,a
nucleationandadiffusivegrowth.Thisallowsustoexplainthesynthesisimprovementasaconsequence
of theincreaseinthesizeofthegoldligandcomplexesaggregates,leadingtoadecreaseofthenanorods
growthrate.
capability for tailoring the chemical-physical characteristics of any polymer by properly choosing and tuning the
properties and quantity of the nanofillers. Diverse synthetic strategies can be followed for fabricating polymer
nanocomposites including physical mixing, chemical grafting, in-situ synthesis of one component in the
presence of the others, and finally layer-by-layer deposition. The dispersed nanostructures, incorporated with
the polymer in nanocomposite materials, can be chosen into a wide spectrum of naturally existing and
artificially synthesized nanomaterials, encompassing layered silicate clay, carbon fibers, carbon nanotubes, and
inorganic nanoparticles of different origins, shapes, sizes, and surface affinities. The properties of polymer
nanocomposites depend on the properties of their components including polymers and the dispersed
nanostructures. By selectively choosing of the polymer and the dispersed nanostructures counterpart, the
properties of the resulted nanocomposites can be tuned covering a wide range of multidisciplinary applications.
This includes electronics, optoelectronics, engineering high performance hybrid, anti-corrosion, and smart
coating materials, drug delivery and sensors. The Sensors applications for Polymer/Nanoparticles
nanocomposite materials were highly expanded during last decade covering a wide range of daily life demands
counting industrial, environmental, militarily and medical. Polymer/nanoparticles nanocomposites endow the
scientists the ability to enhance sensor performance by developing nanocomposites as transducer materials. The
development of new techniques for anchoring new receptors to the nanocomposite transducer materials spreads
the use of sensors to new applications. The use of polymer/nanoparticles nanocomposites as transducer materials
demands the precise control of the size and shape of the embedded nanoparticles, of the dispersion of the
nanoparticles in the matrix and of the mechanism of the interaction of nanoparticles with the host materials.
Selectively choosing the nanoparticles and the polymeric matrix in some cases it is possible to avoid the use of
receptors, exploiting the sensitivities of the physical and chemical properties of both of nanoparticles and
polymers towards external stimuli. At the same time, the nanocomposite has to operate as transducer to transfer
the response to the detector. Due to them unique properties, including surface plasmonic resonance and
chemical affinity, metallic nanoparticles are extensively used in sensors fabrication especially in biological field
(biosensors). The properties of metallic nanoparticles change to a large extent with their size and shape, which
gives them a high flexibility, profited in different applications. The attractive properties of gold nanorods drove
researchers to develop different synthetic methodologies to control their dimensions and dispersion state.
In this study, I am going to investigate the synthesis of gold nanorods (AuNRs) by photochemical
synthesis trying to explore the factors controlling the growth of AuNRs. Photochemical method is one of the
synthetic strategies used for AuNRs preparation and is considered a promising evolution of the more popular
seed-mediated method, since it is less time consuming and avoids the use of seeds that can give rise to structure
complications.. The absence of any separation between nucleation and growth steps is the main disadvantage of photochemical method. The incubation of gold nanorods precursor solution in dark before irradiation and the
irradiance and time of irradiation will be investigated in detail.
The effect of precursor solution dark incubation, prior UV irradiation, is proposed for enhancing the
dispersion of the produced gold nanorods. AuNRs are synthesized in an aqueous solution of
hexadecyltrimethylammonium bromide (CTAB) via combination of chemical reduction and UV
photoirradiation. The gold ligand complexes (Au(III)-CTAB), present in the stock solution, are initially reduced
(to Au(I)-CTAB), by ascorbic acid as mild reducing agent. The gold ions nucleation and colloids growth
proceeds then by subsequent UV irradiation at wavelength 254 nm of the precursor solution. We present a
systematic study of the effect of incubation of the precursor solution in dark on the dispersion state and
morphology of the produced nanorods. Incubation of the precursor solution allows the synthesis of higher aspect
ratio nanorods with narrower size distribution compared to those obtained without incubation. We propose a
mechanism for the gold nanorods formation including two stages, a nucleation and a diffusive growth. This
allows us to explain the synthesis improvement as a consequence of the increase in the size of CTAB and Au(I)-
CTAB complexes aggregates, leading to a decrease of the nanorods growth rate.
Another factor affecting the morphology and the dispersion state of AuNRs produced by
photochemical synthesis is the fluence of UV light, used to irradiate the precursor solution. The light intensity
and the irradiation time have been studied in order to further clarify the mechanism of nucleation and growth of
AuNRs. The light parameters were also optimized for better dispersion and aspect ratio of the produced
nanorods. AuNRs were synthesized, by irradiation of the precursor solution with different fluences, obtained
tuning one after the other the time of irradiation and the irradiance, keeping steady the other variable. The effect
of the time of irradiation and of the irradiance on the morphology of the formed AuNRs was investigated by
UV-Vis absorption spectra and transmission electron microscopy. Tuning the fluence we were able to control
the AuNRs morphology and therefore its aspect ratio. Suitable tweaking of the fluence allowed us to synthesize
superfine AuNRs with small sizes (down to about 7 nm for average diameter and 30 nm for average length) and
average aspect ratio about 5. The experimental results point out two possible regimes throughout the synthesis,
whether the fluence is exceeding or not a threshold fluence. Lengthening of the irradiation time leads first to
nucleation and growth of a larger number of AuNRs. Through the synthesis progress, as threshold fluence is
overcome, AuNRs dissolution in favor of the more stable bigger spherical nanoparticles starts. We impute the
threshold fluence to the reduction and exhaustion of the gold precursor in the reaction solution. The
experimental results show that the time of irradiation allows mainly the control of the yield of the synthesis.
Further prolongation of the irradiation time after the maximization of the synthesis yield leads to AuNRs
deterioration. The main effect of UV irradiance is the focusing of the AuNRs growth, irradiance rise promoting
smaller seeds growth. To fully profit the focusing obtained by irradiance rise, the time of irradiation has to be
reduced in order not to exceed the fluence threshold.