Dr. Nallal Muthuchamy is a Post Doc researcher at Pusan NU, S.Korea. He received his P.hD in Chemistry Education from KNU, S. Korea Address: Korea, Republic of
In this study, we utilized functionalized metal organic frameworks (MOFs) as a host matrix to emb... more In this study, we utilized functionalized metal organic frameworks (MOFs) as a host matrix to embed silver and palladium (AgPd) bimetallic nanoparticles. The physicochemical properties of the as-synthesized materials were characterized Via UV, FT-IR, XRD, SEM, TEM, XPS, BET and TGA analysis. The as-synthesized materials presented excellent activities toward the electrochemical detection of 4-nitrophenol and its reduction by NaBH 4 under ambient conditions. The constructed sensor displayed selective and sensitive determination of 4-NP in the linear concentration range 100-370 μM with a limit of detection of Σ32 nM. Moreover, because of its high specific surface area, high conductivity, and fast charge transfer ability, the sensor displayed good electro-catalytic activity. Moreover, it exhibited excellent selectivity toward 4-NP in the presence of common interfering species. The synthesized catalyst exhibited good catalytic activity for the reduction of 4-NP. It was reusable for five consecutive cycles without a significant loss in its catalytic activity. The applicability of the constructed sensor was explored via the detection of 4-NP in tap water samples at a recovery of ∼100.97%.
Development of a novel approach for synthesizing nanostructured catalysts and achieving further i... more Development of a novel approach for synthesizing nanostructured catalysts and achieving further improvements in catalytic activity, effectiveness, and efficiency remains a major challenge. In this report, we describe the preparation of a nanostructured PdO/ZnO@mSiO 2 hybrid nanocatalyst featuring well-dispersed PdO nanoparticles within hollow ZnO@mSiO 2. The as-prepared PdO/ZnO@mSiO 2 hybrid nanocatalyst exhibited good morphological features, derived from the controlled stepwise synthesis from Pd/PS@ZIF-8@mSiO 2 (PS = polystyrene). The morphology, size, oxidation state, crystallinity, and thermal stability of the prepared PdO/ZnO@mSiO 2 hybrid nanocatalyst were confirmed by a series of physicochemical techniques. The PdO/ZnO@mSiO 2 hybrid nanocatalyst showed very high catalytic efficiency in the reduction of 4-nitrophenol and various nitroarenes under eco-friendly conditions. Therefore, the PdO/ZnO@mSiO 2 hybrid nanocatalyst is a promising alternative catalyst for applications in environmental remediation.
A new, highly selective, sensitive and stable enzymatic glucose sensor was fabricated on glassy c... more A new, highly selective, sensitive and stable enzymatic glucose sensor was fabricated on glassy carbon electrode (GCE) using zinc oxide (ZnO) nanoparticles embedded nitrogen-doped carbon sheets (ZnO@NDCS), glucose oxidase (GOx) (assigned as GCE/ZnO@NDCS/GOx). First, ZnO@NDCS were synthesized by a simple hydro-thermal method. Zn powder, aqueous ammonia, and peach extract were served as the precursor for ZnO NPs, nitrogen and carbon, respectively. The fabricated GCE/ZnO@NDCS/GOx biosensor exhibited a high and reproducible sensitivity of 231.7 μA mM −1 cm −2. Also, showed a wide linear range from 0.2 to 12 mM with a correlation coefficient R 2 = 0.998 and lowest detection limit (based on S/N ratio = 3) of 6.3 μM. The GCE/ ZnO@NDCS/GOx biosensor is acceptably stable, selective, and it was successfully applied to the quantitative monitoring of glucose in human blood serum. The synthesized ZnO@NDCS nanocomposite may be found useful in other applications in the fields of solar cells and optoelectronic devices. These encouraging results suggest a simple and effective method obtain electrode material for the enzymatic glucose sensor.
Research on the synthesis of nanomaterials using metal-organic frameworks (MOFs), which are chara... more Research on the synthesis of nanomaterials using metal-organic frameworks (MOFs), which are characterized by multi-functionality and porosity, as precursors have been accomplished through various synthetic approaches. In this study, copper and copper oxide nanoparticles were fabricated within 30 min by a simple and rapid method involving the reduction of a copper(II)-containing MOF with sodium borohydride solution at room temperature. The obtained nanoparticles consist of a copper core and a copper oxide shell exhibited catalytic activity in the oxygen reduction reaction. The as-synthesized Cu@Cu 2 O core-shell nanocatalyst exhibited an enhanced limit current density as well as onset potential in the electrocatalytic oxygen reduction reaction (ORR). Moreover, the nanoparticles exhibited good catalytic activity in the Huisgen cycloaddition of various substituted azides and alkynes under mild reaction conditions.
A novel three component (titanium dioxide nanowire (TiO 2 NW), poly(3-aminophenyl boronic acid) (... more A novel three component (titanium dioxide nanowire (TiO 2 NW), poly(3-aminophenyl boronic acid) (PAPBA) and gold nanoparticles (Au NPs)) based ternary nanocomposite (TNC) (designated as TiO 2 NW/PAPBA-Au TNC) was prepared by a simple two-stage synthetic approach and utilized for the fabrication of a non-enzymatic (enzyme-free) glucose (NEG) sensor. In stage 2, the PAPBA-Au NC was formed by oxidative polymerization of 3-APBA using HAuCl 4 as oxidant on the surface of pre-synthesized TiO 2 NW via electrospinning (stage 1). The formation of PAPBA-Au NC as the shell on the surface of the TiO 2 NW (core) was confirmed by field emission scanning electron microscopy (FE-SEM). Notably, we obtained a good peak to peak separation, and a high peak current for the redox Fe(CN) 6 3À/4À process indicating excellent electron transfer capability at the glassy carbon electrode (GCE)/TiO 2 NW/PAPBA-Au TNC interface. Also, the fabricated TiO 2 NW/PAPBA-Au TNC provides excellent electrocatalytic activity towards glucose detection in neutral (pH ¼ 7.0) phosphate buffer solution. The detection of glucose was monitored using differential pulse voltammetry. The obtained sensitivity and detection limits are superior to many of the TiO 2 based enzymatic and non-enzymatic glucose sensors reported in the literature. Furthermore, the TiO 2 NW/PAPBA-Au TNC sensor is preferred because of its high selectivity to glucose in the presence of co-existing interfering substances and practical application for monitoring glucose in human blood serum samples.
In this work, an ultra-sensing photoelectrochemical (PEC) glucose biosensor has been constructed ... more In this work, an ultra-sensing photoelectrochemical (PEC) glucose biosensor has been constructed from the bio-derived nitrogen-doped carbon sheets (NDC) wrapped titanium dioxide nanoparticles (NDC-TiO 2 NPs) followed by the covalent immobilization of glucose oxidase (GODx) on them (designated as a GODx/NDC-TiO 2 NPs/ITO biosensor). Initially, the TiO 2 NPs was synthesized by sol-gel method and then NDC-TiO 2 NPs was synthesized utilizing a green source of Prunus persica (peach fruit) through a simple hydrothermal process. The synthesized NDC-TiO 2 NPs composite was characterized by FESEM, HRTEM, Raman spectroscopy, XRD, ATR-FTIR spec-troscopy and XPS to determine composition and phase purity. These fabricated GODx/NDC-TiO 2 NPs/ITO bio-sensor exhibited a good charge separation, highly enhanced and stable photocurrent responses with switching PEC behavior under the light (λ > 400 nm). As a result, GODx/NDC-TiO 2 NPs/ITO PEC glucose sensor exhibits a good photocurrent response to detection of glucose concentrations (0.05-10 μM) with an ultra-low detection limit of 13 nM under optimized PEC experimental conditions. Also, the PEC glucose sensor revealed a high selectivity, good stability, long time durability, and capability to analyze the glucose levels in real human serum. Also, the further development of this work may provide new insights into preparing other bio-derived carbon nanostructure-based photocatalysts for PEC applications.
Hydrogels find applications in various fields, and the ever-growing spectrum of available monomer... more Hydrogels find applications in various fields, and the ever-growing spectrum of available monomers, crosslinking, and nanotechnologies widen the application of polymer hydrogels. Herein, we describe the preparation of a new graphene (G)-and polyaniline (PANI)-containing functional polymer gel (G/PANI/FG) through a facile crosslinking copolymerization approach. Several characterization techniques such as field-emission scanning electron microscopy, Fourier-transform infrared, and X-ray photoelectron spectroscopy were employed to understand the physicochemical characteristics of the G/PANI/FG. The new G/PANI/FG was used as an adsorbent for chromium (VI) and exhibited the highest Cr (VI) removal efficiency (~97%). The inclusion of G and PANI in the gel results in high surface area, 3D porous structure, and Cr (VI)-chelating amine sites, which enhanced the Cr (VI) removal efficiency and thermal stability of the gel adsorbent. The results of our study revealed that G/PANI/FG is suited for the removal of Cr (VI) from aqueous solution.
In this work, an efficient photoelectrochemical (PEC) biosensing platform has been designed and d... more In this work, an efficient photoelectrochemical (PEC) biosensing platform has been designed and developed based on graphene (G) through modifying it into an electroconductive polymer nanosponge (EPNS) and with the incorporation of titanium dioxide nanowires (TiO2 NW) (designated as TiO2 (G) NW@EPNS). Functioning as an efficient immobilization matrix for immobilization of the enzyme Cytochrome C (Cyt C), TiO2 (G) NW@EPNS delivers features for an efficient PEC biosensor, such as fast kinetics of direct electron transfer (DET) to the electrode and effective separation of photogenerated holes and electrons. TiO 2 (G) NW@EPNS exhibited DET to the electrode with a highly heterogeneous electron transfer rate constant of 6.29 70.002 s À 1. The existence of TiO 2 , G and EPNS in conjunction facilitates DET between the electrode surface and the protein. The fabricated PEC nitrite ion (− NO 2) biosensor showed superior analytical performances such as wide linear range (0.5–9000 mM), lowest detection limit (0.225 mM) and excellent specificity for − NO 2 in the presence other interferences at a very low bias potential (À 0.11 V). This study opens up the feasibility of fabricating a PEC biosensor for any analyte using a matrix comprising of G and a photoactive material and EPNS, because these components synergistically contribute to effective immobilization of on enzyme, DET to the electrode and simple read-out under the light.
A novel non-enzymatic photoelectrochemical (PEC) glucose sensor was first constructed based on th... more A novel non-enzymatic photoelectrochemical (PEC) glucose sensor was first constructed based on the unique two-dimensional (2D) bismuth oxychloride-graphene nanohybrid sheets (BiOCl-G NHS). We have utilized a facile hydrothermal approach for the preparation of BiOCl-G NHS. Results from cyclic vol-tammetric and differential pulse voltammetric measurements revealed that the BiOCl-G NHS electrode is capable of generating photocurrent for glucose when its surface is irradiated with a light source (wavelength¼ 365 nm). The photocurrents produced for the presence of glucose at the bias potential of þ0.50 V showed a linear dependence on glucose concentration in the range between 0.5 and 10 mM and had a detection limit of 0.22 mM. The PEC detection of glucose at BiOCl-G NHS was not influenced by the presence of other common interfering species. The glucose levels, as determined by the BiOCl-G NHS sensor, agreed well with those obtained by the commercial glucometers. This novel non-enzymatic PEC glucose sensor exhibited good performances, such as a wider concentration range (500 mM-10 mM), high sensitivity (1.878 mM mM À 1 cm À 2 (500 mM–2 mM) and 127.2 mM mM À 1 cm À 2 (2 mM–10 mM)), good selectivity, reproducibility (RSD ¼2.4%) and applicability to real sample (human serum).
Herein, we fabricated a novel electrochemical–photoelectrochemical (PEC) dual-mode cholesterol bi... more Herein, we fabricated a novel electrochemical–photoelectrochemical (PEC) dual-mode cholesterol bio-sensor based on graphene (G) sheets interconnected-graphene embedded titanium nanowires (TiO 2 ChOx bioelectrode were characterized by cyclic voltammetry and UV–vis diffuse reflection spectroscopy. The cyclic voltammetry of immobilized ChOx showed a pair of well-defined redox peaks indicating direct electron transfer (DET) of ChOx. The amperometric reduction peak current (at À 0.05 V) linearly increased with increase in cholesterol concentration. The G/Ti(G) 3DNS/CS/ChOx bioelectrode was selective to cholesterol with a remarkable sensitivity (3.82 μA/cm 2 mM) and a lower detection limit (6 μM). Also, G/Ti(G) 3DNS/CS/ChOx functioned as photoelectrode and exhibited selective detection of cholesterol under a low bias voltage and light irradiation. Kinetic parameters, reproducibility, repeatability, storage stability and effect of temperature and pH were evaluated. We envisage that G/Ti(G) 3DNS with its prospective characteristics, would be a promising material for wide range of biosensing applications.
The fabrication of a highly sensitive electrochemical non-enzymatic glucose sensor based on coppe... more The fabrication of a highly sensitive electrochemical non-enzymatic glucose sensor based on copper nanoparticles (Cu NPs) dispersed in a graphene (G)-ferrocene (Fc) redox polymer multicomponent na-nobead (MCNB) is reported. The preparation of MCNB involves three major steps, namely: i) the preparation of a poly(aniline-co-anthranilic acid)-grafted graphene (G-PANI(COOH), ii) the covalent linking of ferrocene to G-PANI(COOH) via a polyethylene imine (PEI), and iii) the electrodeposition of Cu NPs. The prepared MCNB (designated as G-PANI(COOH)-PEI-Fc/Cu-MCNB), contains a conductive G-PANI(COOH), electron mediating Fc, and electrocatalytic Cu NPs that make it suitable for ultrasensitive non-enzymatic electrochemical sensing. The morphology, structure, and electro activities of MCNB were characterized. Electrochemical measurements showed that the G-PANI(COOH)-PEI-Fc/Cu-MCNB/GCE modified electrode exhibited good electrocatalytic behavior towards the detection of glucose in a wide linear range (0.50 to 15 mM), with a low detection limit (0.16 mM) and high sensitivity (14.3 mA mM À 1 cm À 2). Besides , the G-PANI(COOH)-PEI-Fc/Cu-MCNB/GCE sensor electrode did not respond to the presence of electroactive interferrants (such as uric acid, ascorbic acid, and dopamine) and saccharides or carbohydrates (fructose, lactose, D-isoascorbic acid, and dextrin), demonstrating its selectivity towards glucose. The fabricated NEG sensor exhibited high precision for measuring glucose in serum samples, with an average RSD of 4.3% and results comparable to those of commercial glucose test strips. This reliability and stability of glucose sensing indicates that G-PANI(COOH)-PEI-Fc/Cu-MCNB/GCE would be a promising material for the non-enzymatic detection of glucose in physiological fluids.
A new " seed mediated " strategy was designed and demonstrated for the higher loading of silver n... more A new " seed mediated " strategy was designed and demonstrated for the higher loading of silver nanoparticles (Ag NPs) onto silica (SiO 2) to obtain a Ag NPs enriched SiO 2 (designated as Ag(E)–SiO 2) catalyst. Simplified two steps were utilized for the preparation of Ag(E)–SiO 2. In the first step, SiO 2 was functionalized with a negatively charged p-toluene sulfonic acid ion and embedded with a few Ag NPs(seed) and obtained as Ag(seed)–SiO 2 (p-TSA À). In the subsequent step, excessive Ag + ions were pre-concentrated onto the SiO 2 surface using the negative charges on the SiO 2 surface and reduced to Ag NPs. The pre-existing Ag NPs(seed) and pre-concentrated Ag + ions enabled the growth of a further layer of Ag NPs to obtain Ag(E)–SiO 2. Results from FTIR spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements clearly supported our strategy of simultaneous functionalization of SiO 2 and Ag(seed) formation through the first step. Detailed FESEM, TEM and XPS analysis revealed higher loading ($80 weight% (wt%)) of Ag NPs in Ag(E)–SiO 2 with a metallic valence state. The catalysts, Ag(seed)–SiO 2 (p-TSA À) and Ag(E)–SiO 2 , containing low Ag ($10 wt%) and higher Ag loading ($80 wt%) of Ag NPs, respectively, were tested for the reduction of toxic organic compounds such as 4-nitrophenol (4-NP) and methylene blue (MB). The Ag(E)–SiO 2 catalyst exhibited superior catalytic performance for 4-NP/MB reduction as compared to Ag(seed)–SiO 2 (p-TSA À) (conventional) as well as over several other Ag NPs supported catalysts reported in the literature. The enhanced catalytic performance of Ag(E)–SiO 2 for 4-NP and MB reduction suggests that our new strategy is promising for the preparation of efficient supported catalysts for water purification and related applications.
In this study, we utilized functionalized metal organic frameworks (MOFs) as a host matrix to emb... more In this study, we utilized functionalized metal organic frameworks (MOFs) as a host matrix to embed silver and palladium (AgPd) bimetallic nanoparticles. The physicochemical properties of the as-synthesized materials were characterized Via UV, FT-IR, XRD, SEM, TEM, XPS, BET and TGA analysis. The as-synthesized materials presented excellent activities toward the electrochemical detection of 4-nitrophenol and its reduction by NaBH 4 under ambient conditions. The constructed sensor displayed selective and sensitive determination of 4-NP in the linear concentration range 100-370 μM with a limit of detection of Σ32 nM. Moreover, because of its high specific surface area, high conductivity, and fast charge transfer ability, the sensor displayed good electro-catalytic activity. Moreover, it exhibited excellent selectivity toward 4-NP in the presence of common interfering species. The synthesized catalyst exhibited good catalytic activity for the reduction of 4-NP. It was reusable for five consecutive cycles without a significant loss in its catalytic activity. The applicability of the constructed sensor was explored via the detection of 4-NP in tap water samples at a recovery of ∼100.97%.
Development of a novel approach for synthesizing nanostructured catalysts and achieving further i... more Development of a novel approach for synthesizing nanostructured catalysts and achieving further improvements in catalytic activity, effectiveness, and efficiency remains a major challenge. In this report, we describe the preparation of a nanostructured PdO/ZnO@mSiO 2 hybrid nanocatalyst featuring well-dispersed PdO nanoparticles within hollow ZnO@mSiO 2. The as-prepared PdO/ZnO@mSiO 2 hybrid nanocatalyst exhibited good morphological features, derived from the controlled stepwise synthesis from Pd/PS@ZIF-8@mSiO 2 (PS = polystyrene). The morphology, size, oxidation state, crystallinity, and thermal stability of the prepared PdO/ZnO@mSiO 2 hybrid nanocatalyst were confirmed by a series of physicochemical techniques. The PdO/ZnO@mSiO 2 hybrid nanocatalyst showed very high catalytic efficiency in the reduction of 4-nitrophenol and various nitroarenes under eco-friendly conditions. Therefore, the PdO/ZnO@mSiO 2 hybrid nanocatalyst is a promising alternative catalyst for applications in environmental remediation.
A new, highly selective, sensitive and stable enzymatic glucose sensor was fabricated on glassy c... more A new, highly selective, sensitive and stable enzymatic glucose sensor was fabricated on glassy carbon electrode (GCE) using zinc oxide (ZnO) nanoparticles embedded nitrogen-doped carbon sheets (ZnO@NDCS), glucose oxidase (GOx) (assigned as GCE/ZnO@NDCS/GOx). First, ZnO@NDCS were synthesized by a simple hydro-thermal method. Zn powder, aqueous ammonia, and peach extract were served as the precursor for ZnO NPs, nitrogen and carbon, respectively. The fabricated GCE/ZnO@NDCS/GOx biosensor exhibited a high and reproducible sensitivity of 231.7 μA mM −1 cm −2. Also, showed a wide linear range from 0.2 to 12 mM with a correlation coefficient R 2 = 0.998 and lowest detection limit (based on S/N ratio = 3) of 6.3 μM. The GCE/ ZnO@NDCS/GOx biosensor is acceptably stable, selective, and it was successfully applied to the quantitative monitoring of glucose in human blood serum. The synthesized ZnO@NDCS nanocomposite may be found useful in other applications in the fields of solar cells and optoelectronic devices. These encouraging results suggest a simple and effective method obtain electrode material for the enzymatic glucose sensor.
Research on the synthesis of nanomaterials using metal-organic frameworks (MOFs), which are chara... more Research on the synthesis of nanomaterials using metal-organic frameworks (MOFs), which are characterized by multi-functionality and porosity, as precursors have been accomplished through various synthetic approaches. In this study, copper and copper oxide nanoparticles were fabricated within 30 min by a simple and rapid method involving the reduction of a copper(II)-containing MOF with sodium borohydride solution at room temperature. The obtained nanoparticles consist of a copper core and a copper oxide shell exhibited catalytic activity in the oxygen reduction reaction. The as-synthesized Cu@Cu 2 O core-shell nanocatalyst exhibited an enhanced limit current density as well as onset potential in the electrocatalytic oxygen reduction reaction (ORR). Moreover, the nanoparticles exhibited good catalytic activity in the Huisgen cycloaddition of various substituted azides and alkynes under mild reaction conditions.
A novel three component (titanium dioxide nanowire (TiO 2 NW), poly(3-aminophenyl boronic acid) (... more A novel three component (titanium dioxide nanowire (TiO 2 NW), poly(3-aminophenyl boronic acid) (PAPBA) and gold nanoparticles (Au NPs)) based ternary nanocomposite (TNC) (designated as TiO 2 NW/PAPBA-Au TNC) was prepared by a simple two-stage synthetic approach and utilized for the fabrication of a non-enzymatic (enzyme-free) glucose (NEG) sensor. In stage 2, the PAPBA-Au NC was formed by oxidative polymerization of 3-APBA using HAuCl 4 as oxidant on the surface of pre-synthesized TiO 2 NW via electrospinning (stage 1). The formation of PAPBA-Au NC as the shell on the surface of the TiO 2 NW (core) was confirmed by field emission scanning electron microscopy (FE-SEM). Notably, we obtained a good peak to peak separation, and a high peak current for the redox Fe(CN) 6 3À/4À process indicating excellent electron transfer capability at the glassy carbon electrode (GCE)/TiO 2 NW/PAPBA-Au TNC interface. Also, the fabricated TiO 2 NW/PAPBA-Au TNC provides excellent electrocatalytic activity towards glucose detection in neutral (pH ¼ 7.0) phosphate buffer solution. The detection of glucose was monitored using differential pulse voltammetry. The obtained sensitivity and detection limits are superior to many of the TiO 2 based enzymatic and non-enzymatic glucose sensors reported in the literature. Furthermore, the TiO 2 NW/PAPBA-Au TNC sensor is preferred because of its high selectivity to glucose in the presence of co-existing interfering substances and practical application for monitoring glucose in human blood serum samples.
In this work, an ultra-sensing photoelectrochemical (PEC) glucose biosensor has been constructed ... more In this work, an ultra-sensing photoelectrochemical (PEC) glucose biosensor has been constructed from the bio-derived nitrogen-doped carbon sheets (NDC) wrapped titanium dioxide nanoparticles (NDC-TiO 2 NPs) followed by the covalent immobilization of glucose oxidase (GODx) on them (designated as a GODx/NDC-TiO 2 NPs/ITO biosensor). Initially, the TiO 2 NPs was synthesized by sol-gel method and then NDC-TiO 2 NPs was synthesized utilizing a green source of Prunus persica (peach fruit) through a simple hydrothermal process. The synthesized NDC-TiO 2 NPs composite was characterized by FESEM, HRTEM, Raman spectroscopy, XRD, ATR-FTIR spec-troscopy and XPS to determine composition and phase purity. These fabricated GODx/NDC-TiO 2 NPs/ITO bio-sensor exhibited a good charge separation, highly enhanced and stable photocurrent responses with switching PEC behavior under the light (λ > 400 nm). As a result, GODx/NDC-TiO 2 NPs/ITO PEC glucose sensor exhibits a good photocurrent response to detection of glucose concentrations (0.05-10 μM) with an ultra-low detection limit of 13 nM under optimized PEC experimental conditions. Also, the PEC glucose sensor revealed a high selectivity, good stability, long time durability, and capability to analyze the glucose levels in real human serum. Also, the further development of this work may provide new insights into preparing other bio-derived carbon nanostructure-based photocatalysts for PEC applications.
Hydrogels find applications in various fields, and the ever-growing spectrum of available monomer... more Hydrogels find applications in various fields, and the ever-growing spectrum of available monomers, crosslinking, and nanotechnologies widen the application of polymer hydrogels. Herein, we describe the preparation of a new graphene (G)-and polyaniline (PANI)-containing functional polymer gel (G/PANI/FG) through a facile crosslinking copolymerization approach. Several characterization techniques such as field-emission scanning electron microscopy, Fourier-transform infrared, and X-ray photoelectron spectroscopy were employed to understand the physicochemical characteristics of the G/PANI/FG. The new G/PANI/FG was used as an adsorbent for chromium (VI) and exhibited the highest Cr (VI) removal efficiency (~97%). The inclusion of G and PANI in the gel results in high surface area, 3D porous structure, and Cr (VI)-chelating amine sites, which enhanced the Cr (VI) removal efficiency and thermal stability of the gel adsorbent. The results of our study revealed that G/PANI/FG is suited for the removal of Cr (VI) from aqueous solution.
In this work, an efficient photoelectrochemical (PEC) biosensing platform has been designed and d... more In this work, an efficient photoelectrochemical (PEC) biosensing platform has been designed and developed based on graphene (G) through modifying it into an electroconductive polymer nanosponge (EPNS) and with the incorporation of titanium dioxide nanowires (TiO2 NW) (designated as TiO2 (G) NW@EPNS). Functioning as an efficient immobilization matrix for immobilization of the enzyme Cytochrome C (Cyt C), TiO2 (G) NW@EPNS delivers features for an efficient PEC biosensor, such as fast kinetics of direct electron transfer (DET) to the electrode and effective separation of photogenerated holes and electrons. TiO 2 (G) NW@EPNS exhibited DET to the electrode with a highly heterogeneous electron transfer rate constant of 6.29 70.002 s À 1. The existence of TiO 2 , G and EPNS in conjunction facilitates DET between the electrode surface and the protein. The fabricated PEC nitrite ion (− NO 2) biosensor showed superior analytical performances such as wide linear range (0.5–9000 mM), lowest detection limit (0.225 mM) and excellent specificity for − NO 2 in the presence other interferences at a very low bias potential (À 0.11 V). This study opens up the feasibility of fabricating a PEC biosensor for any analyte using a matrix comprising of G and a photoactive material and EPNS, because these components synergistically contribute to effective immobilization of on enzyme, DET to the electrode and simple read-out under the light.
A novel non-enzymatic photoelectrochemical (PEC) glucose sensor was first constructed based on th... more A novel non-enzymatic photoelectrochemical (PEC) glucose sensor was first constructed based on the unique two-dimensional (2D) bismuth oxychloride-graphene nanohybrid sheets (BiOCl-G NHS). We have utilized a facile hydrothermal approach for the preparation of BiOCl-G NHS. Results from cyclic vol-tammetric and differential pulse voltammetric measurements revealed that the BiOCl-G NHS electrode is capable of generating photocurrent for glucose when its surface is irradiated with a light source (wavelength¼ 365 nm). The photocurrents produced for the presence of glucose at the bias potential of þ0.50 V showed a linear dependence on glucose concentration in the range between 0.5 and 10 mM and had a detection limit of 0.22 mM. The PEC detection of glucose at BiOCl-G NHS was not influenced by the presence of other common interfering species. The glucose levels, as determined by the BiOCl-G NHS sensor, agreed well with those obtained by the commercial glucometers. This novel non-enzymatic PEC glucose sensor exhibited good performances, such as a wider concentration range (500 mM-10 mM), high sensitivity (1.878 mM mM À 1 cm À 2 (500 mM–2 mM) and 127.2 mM mM À 1 cm À 2 (2 mM–10 mM)), good selectivity, reproducibility (RSD ¼2.4%) and applicability to real sample (human serum).
Herein, we fabricated a novel electrochemical–photoelectrochemical (PEC) dual-mode cholesterol bi... more Herein, we fabricated a novel electrochemical–photoelectrochemical (PEC) dual-mode cholesterol bio-sensor based on graphene (G) sheets interconnected-graphene embedded titanium nanowires (TiO 2 ChOx bioelectrode were characterized by cyclic voltammetry and UV–vis diffuse reflection spectroscopy. The cyclic voltammetry of immobilized ChOx showed a pair of well-defined redox peaks indicating direct electron transfer (DET) of ChOx. The amperometric reduction peak current (at À 0.05 V) linearly increased with increase in cholesterol concentration. The G/Ti(G) 3DNS/CS/ChOx bioelectrode was selective to cholesterol with a remarkable sensitivity (3.82 μA/cm 2 mM) and a lower detection limit (6 μM). Also, G/Ti(G) 3DNS/CS/ChOx functioned as photoelectrode and exhibited selective detection of cholesterol under a low bias voltage and light irradiation. Kinetic parameters, reproducibility, repeatability, storage stability and effect of temperature and pH were evaluated. We envisage that G/Ti(G) 3DNS with its prospective characteristics, would be a promising material for wide range of biosensing applications.
The fabrication of a highly sensitive electrochemical non-enzymatic glucose sensor based on coppe... more The fabrication of a highly sensitive electrochemical non-enzymatic glucose sensor based on copper nanoparticles (Cu NPs) dispersed in a graphene (G)-ferrocene (Fc) redox polymer multicomponent na-nobead (MCNB) is reported. The preparation of MCNB involves three major steps, namely: i) the preparation of a poly(aniline-co-anthranilic acid)-grafted graphene (G-PANI(COOH), ii) the covalent linking of ferrocene to G-PANI(COOH) via a polyethylene imine (PEI), and iii) the electrodeposition of Cu NPs. The prepared MCNB (designated as G-PANI(COOH)-PEI-Fc/Cu-MCNB), contains a conductive G-PANI(COOH), electron mediating Fc, and electrocatalytic Cu NPs that make it suitable for ultrasensitive non-enzymatic electrochemical sensing. The morphology, structure, and electro activities of MCNB were characterized. Electrochemical measurements showed that the G-PANI(COOH)-PEI-Fc/Cu-MCNB/GCE modified electrode exhibited good electrocatalytic behavior towards the detection of glucose in a wide linear range (0.50 to 15 mM), with a low detection limit (0.16 mM) and high sensitivity (14.3 mA mM À 1 cm À 2). Besides , the G-PANI(COOH)-PEI-Fc/Cu-MCNB/GCE sensor electrode did not respond to the presence of electroactive interferrants (such as uric acid, ascorbic acid, and dopamine) and saccharides or carbohydrates (fructose, lactose, D-isoascorbic acid, and dextrin), demonstrating its selectivity towards glucose. The fabricated NEG sensor exhibited high precision for measuring glucose in serum samples, with an average RSD of 4.3% and results comparable to those of commercial glucose test strips. This reliability and stability of glucose sensing indicates that G-PANI(COOH)-PEI-Fc/Cu-MCNB/GCE would be a promising material for the non-enzymatic detection of glucose in physiological fluids.
A new " seed mediated " strategy was designed and demonstrated for the higher loading of silver n... more A new " seed mediated " strategy was designed and demonstrated for the higher loading of silver nanoparticles (Ag NPs) onto silica (SiO 2) to obtain a Ag NPs enriched SiO 2 (designated as Ag(E)–SiO 2) catalyst. Simplified two steps were utilized for the preparation of Ag(E)–SiO 2. In the first step, SiO 2 was functionalized with a negatively charged p-toluene sulfonic acid ion and embedded with a few Ag NPs(seed) and obtained as Ag(seed)–SiO 2 (p-TSA À). In the subsequent step, excessive Ag + ions were pre-concentrated onto the SiO 2 surface using the negative charges on the SiO 2 surface and reduced to Ag NPs. The pre-existing Ag NPs(seed) and pre-concentrated Ag + ions enabled the growth of a further layer of Ag NPs to obtain Ag(E)–SiO 2. Results from FTIR spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements clearly supported our strategy of simultaneous functionalization of SiO 2 and Ag(seed) formation through the first step. Detailed FESEM, TEM and XPS analysis revealed higher loading ($80 weight% (wt%)) of Ag NPs in Ag(E)–SiO 2 with a metallic valence state. The catalysts, Ag(seed)–SiO 2 (p-TSA À) and Ag(E)–SiO 2 , containing low Ag ($10 wt%) and higher Ag loading ($80 wt%) of Ag NPs, respectively, were tested for the reduction of toxic organic compounds such as 4-nitrophenol (4-NP) and methylene blue (MB). The Ag(E)–SiO 2 catalyst exhibited superior catalytic performance for 4-NP/MB reduction as compared to Ag(seed)–SiO 2 (p-TSA À) (conventional) as well as over several other Ag NPs supported catalysts reported in the literature. The enhanced catalytic performance of Ag(E)–SiO 2 for 4-NP and MB reduction suggests that our new strategy is promising for the preparation of efficient supported catalysts for water purification and related applications.
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