Detonation nanodiamonds (DNDs) were functionalized by ruthenium porphyrins and used as catalysts ... more Detonation nanodiamonds (DNDs) were functionalized by ruthenium porphyrins and used as catalysts in the cyclopropanation reaction of olefins. The heterogeneous catalyst was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and XPS (X-ray photoelectron spectroscopy). The XPS was used to control the binding of the ruthenium porphyrin to the DNDs’ surface. This catalyst was used in the cyclopropanation reactions of simple olefins and was reused with no loss of activity in four consecutive cycles, after recovering each time by simple centrifugation.
The paper reports on the feasibility of obtaining graphene nanomaterials with remarkable structur... more The paper reports on the feasibility of obtaining graphene nanomaterials with remarkable structural and chemical features from shungite rocks. The investigation of the composition and structural modifications induced in the pristine, natural C-containing mineraloid by a specifically designed physicochemical purification treatment is performed by a combined use of several techniques (scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman and X-ray photoelectron spectroscopies). The adopted material processing enables efficient extraction of the C phase in the form of thin polycrystalline platelets of a few hundred nanometers sizes, and formed by 6-10 graphene sheets. About 80% of such nanostructures are characterized by a regular sp C honeycomb lattice and an ordered stacking of graphene layers with a d-spacing of ∼0.34 nm. The low oxygen content (∼5%), mainly found in the form of hydroxyl functional groups, provides the graphene plat...
Characterization of Semiconductor Heterostructures and Nanostructures, 2008
Abstract The aim of this chapter is to show mainly the potentiality of the cathodoluminescence (C... more Abstract The aim of this chapter is to show mainly the potentiality of the cathodoluminescence (CL) technique and to what extent it can be applied in the study of III–nitrides heterostructures. A quite recent and unusual application of the CL technique, namely power-dependent CL, will be presented, exploiting and discussing the influence of different injection power conditions, from low to high injection regimes (the latter occurring for n ≫ n0 free carrier concentration, with typical values ranging from about 1016−1020 injected e–h pairs cm−3). It has therefore been decided to abbreviate the basics of the technique, which can be easily found in dedicated textbooks, in favor of a deeper discussion of the experimental examples and of some peculiarities of the technique.
Materials Science in Semiconductor Processing, 2016
Abstract 1D semiconductor nanostructures, owing to their low dimensionality, exhibit novel proper... more Abstract 1D semiconductor nanostructures, owing to their low dimensionality, exhibit novel properties that find application in many device fields. In addition, they can present crystal structures different from their common ones, due to the size effect or to their growth mechanism. Ge-Sb-Te compounds are the most widely employed materials for phase-change memory devices that must be downscaled to nanosize to reduce the power consumption. This imposes a better understanding of the phase transition mechanism, as well as a deeper knowledge of the structure of the phases involved in the transition. In this work, we present how the TEM techniques, in particular high resolution STEM-HAADF combined with proper simulations, allow identifying and assessing the crystal structure of uncommon/unforeseen polymorphs in phase-change Ge-Sb-Te nanowires.
Multi-quantum well photovoltaic cells offer a number of advantages over conventional ``single-gap... more Multi-quantum well photovoltaic cells offer a number of advantages over conventional ``single-gap''cells for thermophotovoltaic applications, first of all because they can reach a higher open circuit voltage under the same radiation source and with the same absorption edge. Material quality issues and the constraints imposed by the commercial available substrates indicate that InxGa1-xAs/InyGa1-yAs/InP strain-balanced heterostructures are suitable to obtain good
High sensitivity zinc oxide (ZnO) tetrapods (TPs) have been functionalized by nucleating cadmium ... more High sensitivity zinc oxide (ZnO) tetrapods (TPs) have been functionalized by nucleating cadmium sulphide (CdS) nanoparticles (NPs) directly on their surface with a spotted coverage thanks to an optimized synthesis in dimethylformamide (DMF). The obtained hybrid coupled material has been used to realize a gas sensing device with a highly porous nanostructured network, in which the proper alternation of ZnO-TPs and CdS-NPs gives rise to unconventional chemoresistive behaviours. Among the different tested gases and vapours, the sensor showed a unique fingerprint response-inversion between 300 °C and 400 °C only for nitrogen dioxide (NO2) and acetic acid (CH3COOH).
One of the main limitations to the application of gold nanorods (Au NRs) as surface-enhanced Rama... more One of the main limitations to the application of gold nanorods (Au NRs) as surface-enhanced Raman scattering (SERS) probes for in situ monitoring of chemical processes is their instability in oxidative environments. Oxidation induces progressive anisotropic shortening of the NRs, which are eventually dissolved once this process has been completed. This paper compares two types of Au NRs, obtained through different routes and characterized by similar aspect ratios but different sizes. The key factors influencing the resistance of Au NRs to oxidation were systematically investigated, showing that the reduction of free bromide species and the increase of the particle size allowed the NRs to maintain their stability under harsh environments for several weeks. The most stable Au NRs were also demonstrated to be highly efficient SERS substrates in a series of Raman experiments involving molecular probes, treated under either oxidizing or nonoxidizing conditions, which simulate the oxidation of organic pollutants in water. These hallmarks make these "stainless" Au NRs attractive tools for ultrasensitive diagnostic under real working conditions.
Detonation nanodiamonds (DNDs) were functionalized by ruthenium porphyrins and used as catalysts ... more Detonation nanodiamonds (DNDs) were functionalized by ruthenium porphyrins and used as catalysts in the cyclopropanation reaction of olefins. The heterogeneous catalyst was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and XPS (X-ray photoelectron spectroscopy). The XPS was used to control the binding of the ruthenium porphyrin to the DNDs’ surface. This catalyst was used in the cyclopropanation reactions of simple olefins and was reused with no loss of activity in four consecutive cycles, after recovering each time by simple centrifugation.
The paper reports on the feasibility of obtaining graphene nanomaterials with remarkable structur... more The paper reports on the feasibility of obtaining graphene nanomaterials with remarkable structural and chemical features from shungite rocks. The investigation of the composition and structural modifications induced in the pristine, natural C-containing mineraloid by a specifically designed physicochemical purification treatment is performed by a combined use of several techniques (scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, Raman and X-ray photoelectron spectroscopies). The adopted material processing enables efficient extraction of the C phase in the form of thin polycrystalline platelets of a few hundred nanometers sizes, and formed by 6-10 graphene sheets. About 80% of such nanostructures are characterized by a regular sp C honeycomb lattice and an ordered stacking of graphene layers with a d-spacing of ∼0.34 nm. The low oxygen content (∼5%), mainly found in the form of hydroxyl functional groups, provides the graphene plat...
Characterization of Semiconductor Heterostructures and Nanostructures, 2008
Abstract The aim of this chapter is to show mainly the potentiality of the cathodoluminescence (C... more Abstract The aim of this chapter is to show mainly the potentiality of the cathodoluminescence (CL) technique and to what extent it can be applied in the study of III–nitrides heterostructures. A quite recent and unusual application of the CL technique, namely power-dependent CL, will be presented, exploiting and discussing the influence of different injection power conditions, from low to high injection regimes (the latter occurring for n ≫ n0 free carrier concentration, with typical values ranging from about 1016−1020 injected e–h pairs cm−3). It has therefore been decided to abbreviate the basics of the technique, which can be easily found in dedicated textbooks, in favor of a deeper discussion of the experimental examples and of some peculiarities of the technique.
Materials Science in Semiconductor Processing, 2016
Abstract 1D semiconductor nanostructures, owing to their low dimensionality, exhibit novel proper... more Abstract 1D semiconductor nanostructures, owing to their low dimensionality, exhibit novel properties that find application in many device fields. In addition, they can present crystal structures different from their common ones, due to the size effect or to their growth mechanism. Ge-Sb-Te compounds are the most widely employed materials for phase-change memory devices that must be downscaled to nanosize to reduce the power consumption. This imposes a better understanding of the phase transition mechanism, as well as a deeper knowledge of the structure of the phases involved in the transition. In this work, we present how the TEM techniques, in particular high resolution STEM-HAADF combined with proper simulations, allow identifying and assessing the crystal structure of uncommon/unforeseen polymorphs in phase-change Ge-Sb-Te nanowires.
Multi-quantum well photovoltaic cells offer a number of advantages over conventional ``single-gap... more Multi-quantum well photovoltaic cells offer a number of advantages over conventional ``single-gap''cells for thermophotovoltaic applications, first of all because they can reach a higher open circuit voltage under the same radiation source and with the same absorption edge. Material quality issues and the constraints imposed by the commercial available substrates indicate that InxGa1-xAs/InyGa1-yAs/InP strain-balanced heterostructures are suitable to obtain good
High sensitivity zinc oxide (ZnO) tetrapods (TPs) have been functionalized by nucleating cadmium ... more High sensitivity zinc oxide (ZnO) tetrapods (TPs) have been functionalized by nucleating cadmium sulphide (CdS) nanoparticles (NPs) directly on their surface with a spotted coverage thanks to an optimized synthesis in dimethylformamide (DMF). The obtained hybrid coupled material has been used to realize a gas sensing device with a highly porous nanostructured network, in which the proper alternation of ZnO-TPs and CdS-NPs gives rise to unconventional chemoresistive behaviours. Among the different tested gases and vapours, the sensor showed a unique fingerprint response-inversion between 300 °C and 400 °C only for nitrogen dioxide (NO2) and acetic acid (CH3COOH).
One of the main limitations to the application of gold nanorods (Au NRs) as surface-enhanced Rama... more One of the main limitations to the application of gold nanorods (Au NRs) as surface-enhanced Raman scattering (SERS) probes for in situ monitoring of chemical processes is their instability in oxidative environments. Oxidation induces progressive anisotropic shortening of the NRs, which are eventually dissolved once this process has been completed. This paper compares two types of Au NRs, obtained through different routes and characterized by similar aspect ratios but different sizes. The key factors influencing the resistance of Au NRs to oxidation were systematically investigated, showing that the reduction of free bromide species and the increase of the particle size allowed the NRs to maintain their stability under harsh environments for several weeks. The most stable Au NRs were also demonstrated to be highly efficient SERS substrates in a series of Raman experiments involving molecular probes, treated under either oxidizing or nonoxidizing conditions, which simulate the oxidation of organic pollutants in water. These hallmarks make these "stainless" Au NRs attractive tools for ultrasensitive diagnostic under real working conditions.
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Papers by Laura Lazzarini