Amine Functionalized Silicate Sol Gel Matrix Research Articles

M13 virus-templated open mouth-like platinum nanostructures prepared by electrodeposition: Influence of M13-virus on structure and electrocatalytic activity

Biomaterials have a great potential to become templates for nanomaterials due to their unique dimensions and surface functionalities. Herein, we report engineered M13-virus entrapped open mouth-like Pt nanostructures by electrodeposition and explored its electrocatalytic properties for oxygen reduction reaction in an alkaline medium. Engineered M13-viruses was used as an additive to obtain biotemplated Pt nanostructures. The amine-functionalized silicate sol-gel matrix modified ITO electrode, pre-concentrated the M13-viruses from electrolyte through hydrogen bonding interaction. In solution-phase synthesis, agglomeration between the bio-mineralized M13-viruses is a serious issue for colloidal stability, the present electrodeposition approach providing solution for such issue. The present structure is having high porosity and exhibits increased electrochemically active surface area with notable structure-dependent electrocatalytic activity. • Open mouth-like biotemplated Pt nanostructures. • Encapsulation of M13-virus by Pt NSs via electrodeposition. • Increased electrochemically active surface area. • Enhanced Pt activity for ORR in alkaline medium.

Hematite/M (M = Au, Pd) Catalysts Derived from a Double-Hollow Prussian Blue Microstructure: Simultaneous Catalytic Reduction of o- and p-Nitrophenols.

Present study deals with hematite/M (M = Au, Pd) catalysts converted from a double-hollow Prussian blue microstructure (DHPM). The unique Prussian blue (PB) microstructure (MS) is prepared by a template-free solvothermal synthetic route in a single-step reaction. An amine-functionalized silicate sol-gel matrix (SSG) has served as the structure-directing agent cum stabilizer for making DHPM. Synthesized DHPM is having a unique structure: a hollow core and an in situ etched porous surface. Growth mechanism is explored and revealed by analyzing several experimental parameters such as HCl concentration, Fe source, effect of the added EtOH, silane concentration, and role of silanes' amine groups. It is identified that the superstructure consisted of well-aligned PB cubes growing radially from the core of the superstructure. Metal (Au and Pd) nanoparticles (NPs) are deposited on both interior and exterior of the PB MS through galvanic displacement reaction, and thus metal NP-loaded hematite phase iron oxide (α-Fe2O3) nanomaterials were derived by annealing them in air. Catalytic activities of the hematite/M(M = Au, Pd) MS are investigated toward simultaneous catalytic reduction of o-nitrophenol and p-nitrophenol. The resultant hematite/Pd MS showed high structural stability and catalytic active sites than the hematite/Au MS, which enhances the catalytic properties for the simultaneous catalytic reduction of both nitrophenols.

Electrochemical detection of hydrogen peroxide based on silver nanoparticles via amplified electron transfer process

A simple electrochemical sensor platform for hydrogen peroxide (H2O2) using silver nanoparticles (Ag NPs) entrenched in silicate matrix (APS(SG)) is reported. The redox molecules such as potassium ferricyanide ([Fe(CN)6]3−), methyl viologen (MV2+) and ruthenium hexamine ([Ru(NH3)6]3+) were utilized to investigate the electron transfer behavior of the APS(SG)–Ag NPs. The glassy carbon (GC) electrode modified with amine-functionalized silicate sol–gel matrix (GC/APS(SG)) exhibited a complete suppression of the electrochemical response toward MV2+ and [Ru(NH3)6]3+. However, GC/APS(SG) electrode displayed a twofold increase in the peak currents and fast electron transfer kinetics toward [Fe(CN)6]3− in comparison with GC electrode, suggesting that GC/APS(SG) electrode demonstrated an excellent anion exchange property. The GC electrode modified with APS(SG)–Ag NPs (GC/APS(SG)–Ag NPs) showed an improved electron transfer kinetics when neither positive nor negative charge of the electroactive species in the electrolyte. The GC/APS(SG)–Ag NP electrode was effectively further applied for the electrocatalytic and sensor applications toward H2O2. The present sensor exhibited the reduction of H2O2 at less negative potential and showed the experimental low detection limit of 25.0 µM with the sensitivity of 0.042 µA/µM. In addition, the developed APS(SG)–Ag NP-based amperometric sensor presented fast response, good stability and reproducibility.

Platinum Electrodeposition on in-Situ Grown Prussian Blue Nanostructures and Reduced Graphene Oxide Composite for Synergistic Methanol Oxidation

We report a synthesis for in-situ growth of Prussian blue nanostructures (PB NSs) at the amine functionalized silicate sol–gel matrix (TPDT)–RGO composite via the electrostatic interaction. Pt nanostructures are electrodeposited onto the preformed ITO/TPDT–RGO–PB electrode to prepare the RGO/PB/Pt catalyst. The significance of the present method is that the PB NSs are in-situ grown by inter-connecting the RGO layers, led to 3D porous nanostructure. The modified electrodes are characterized by FESEM, EDAX, XRD, XPS and electrochemical techniques. The RGO/PB/Pt catalyst exhibits synergistic electrocatalytic activity and high stability towards methanol oxidation. The porous nature of the TPDT and PB, and unique electron transfer mediating behavior of PB integrated with RGO in the presence of Pt nanostructures, facilitated synergistic electrocatalytic activity for methanol oxidation.

Prussian Blue Nanocubes on Reduced Graphene Oxide As a Modified Platinum Electrode for Synergistic Methanol Oxidation

We report a facile synthetic strategy for the in-situ growth of high-quality Prussian blue nanocubes (PBNCs) at the amine functionalized silicate sol–gel matrix (TPDT)–RGO composite via the electrostatic interaction. Subsequently, Pt nanostructures are electrodeposited onto the preformed ITO/TPDT–RGO–PB electrode to prepare the RGO/PB/Pt catalyst. The significance of the present method is that the PBNCs could be in-situ grown by inter-connecting the RGO layers, led to 3D cage-like porous nanostructure. The modified electrodes are characterized by FESEM, EDAX, XRD, XPS and electrochemical techniques. The RGO/PB/Pt catalyst exhibits the synergistic electrocatalytic activity and high stability towards the methanol oxidation. The porous nature of the TPDT and PB, and unique electron transfer mediating behavior of PB integrated with RGO in the presence of Pt nanostructures facilitated synergistic electrocatalytic activity for methanol oxidation.

In Situ Growth of Prussian Blue Nanostructures at Reduced Graphene Oxide as a Modified Platinum Electrode for Synergistic Methanol Oxidation.

Herein, we report a facile synthetic strategy for the in situ growth of Prussian blue nanostructures (PB NSs) at the amine-functionalized silicate sol-gel matrix (TPDT)-RGO composite via the electrostatic interaction. Subsequently, Pt nanostructures are electrodeposited onto the preformed ITO/TPDT-RGO-PB electrode to prepare the RGO/PB/Pt catalyst. The significance of the present method is that the PB NSs are in situ grown by interconnecting the RGO layers, leading to 3D cage-like porous nanostructure. The modified electrodes are characterized by FESEM, EDAX, XRD, XPS, and electrochemical techniques. The RGO/PB/Pt catalyst exhibits synergistic electrocatalytic activity and high stability toward methanol oxidation. The porous nature of the TPDT and PB and unique electron-transfer mediating behavior of PB integrated with RGO in the presence of Pt nanostructures facilitated synergistic electrocatalytic activity for methanol oxidation.

Amperometric sensing of NADH at gold nanorods stabilized in amine-functionalized silicate sol–gel matrix modified electrode

The gold nanorods stabilized in amine-functionalized silicate sol–gel matrix (Au–TPDT NRs) in aqueous medium are prepared and their application toward the electrochemical sensing of reduced β-nicotinamide adenine dinucleotide (NADH) is demonstrated. The prepared Au–TPDT NRs is characterized by using absorption spectroscopy and transmission electron microscopy. The electrochemical characteristics of the Au–TPDT NRs modified electrode are studied by using cyclic voltammetry. The electrocatalysis and electrochemical sensing of NADH at physiological pH using the Au–TPDT NRs modified electrode are investigated. The amperometric sensing of NADH shows enhanced electrocatalytic activity for the Au–TPDT NRs modified electrode without incorporating any mediator due to the synergetic catalytic effect of Au NRs and TPDT silicate sol–gel matrix. The amperometric current increased linearly with increasing the NADH concentration in the range from 1 to 13 µM and the lowest detection limit is estimated as 0.38 µM. The present work demonstrates that the GC/Au–TPDT NRs modified electrode is simple to prepare and shows good response for the electrochemical detection of NADH.

Reduced graphene oxide–gold nanorod composite material stabilized in silicate sol–gel matrix for nitric oxide sensor

A facile synthetic method for the preparation of reduced graphene oxide–gold nanorods embedded in an amine functionalized silicate sol–gel matrix (RGO–Au–TPDT NRs) composite in an aqueous medium and its applications towards the electrochemical sensing of nitric oxide (NO) are reported. The electrochemical characteristics of the RGO–Au–TPDT NRs modified electrode are studied by using cyclic voltammetry. The electrocatalysis and amperometric sensing of NO are studied at physiological pH by using the RGO–Au–TPDT NRs modified electrode. The RGO–Au–TPDT NRs modified electrode shows excellent electrocatalytic activity towards the oxidation of NO due to the synergistic catalytic effect of the RGO–Au–TPDT NRs composite material. The amperometric current is increased linearly while increasing the NO concentration in the range between 10 and 140 nM and the lowest detection limit is estimated as 6.5 nM. The GC–RGO–Au–TPDT NRs modified electrode is simple to prepare and shows fast amperometric response towards NO detection.

Selective sensing of Hg2+ ions by optical and colorimetric methods using gold nanorods embedded in a functionalized silicate sol–gel matrix

A simple method was developed for the preparation of gold nanorods embedded in an amine functionalized silicate sol–gel matrix (Au–TPDT NRs) in an aqueous medium and its application towards optical sensing of mercuric (Hg2+) ions was demonstrated. A colorimetric sensor was developed for Hg2+ ions using the Au NRs embedded in an amine functionalized silicate sol–gel matrix. The optical and colorimetric detection of Hg2+ ions was carried out using the Au NRs embedded in a functionalized silicate sol–gel matrix based on the localized surface plasmon resonance (LSPR) of the Au NRs and the absorption spectra showed a significant blue shift in the LSPR band upon addition of Hg2+ ions. It was observed that the addition of optimum concentration of Hg2+ ions into the Au–TPDT NR solution led to a decrease in the intensity of the LSPR band and the color changed due to change in the morphology of Au NRs through formation of an AuHg amalgam. The selective detection of Hg2+ ions using the Au–TPDT NRs in the presence of other environmentally relevant metal ions was reported by optical and colorimetric methods. This method was successfully applied for the determination of Hg2+ ions in real water samples.

Bimetallic Au/Ag nanorods embedded in functionalized silicate sol–gel matrix as an efficient catalyst for nitrobenzene reduction

A simple method for the preparation of bimetallic gold/silver nanorods embedded in amine functionalized silicate sol–gel matrix (Au/Ag–TPDT NRs) in aqueous medium and their application towards the catalytic reduction of nitrobenzene is reported. The Au/Ag–TPDT NRs are prepared by using N1-[3-trimethoxysilyl)propyl]diethylene triamine (TPDT) as a reducing as well as stabilizing agent. The catalytic activity of the Au/Ag–TPDT NRs is evaluated by studying the catalytic reduction of nitrobenzene to aniline upon the addition of NaBH4 in an aqueous solution. The Au/Ag–TPDT NRs was found to be a good catalyst when compared to the Au–TPDT NRs and Au NRs for the reduction of nitrobenzene to aniline at room temperature. The enhanced catalytic activity of Au/Ag–TPDT NRs is due to the synergistic effect of Au and Ag present in the bimetallic Au/Ag–TPDT NRs. The reaction rate constants (k) are estimated to be 0.4050, 0.2515 and 0.1235min−1 for Au/Ag–TPDT NRs, Au–TPDT NRs and Au NRs, respectively. The electrocatalytic reduction of nitrobenzene at pH 7 using the Au/Ag–TPDT NRs modified electrode is also investigated and compared with the Au–TPDT NRs. The higher electrocatalytic activity of Au/Ag–TPDT NRs is due to the synergistic effect of Au and Ag present in the bimetallic Au/Ag–TPDT NRs. The results of the study demonstrate that the Au/Ag–TPDT NRs are efficient catalyst for the catalytic reduction of nitrobenzene.

Functionalized Silicate Supported TiO<sub>2</sub>-ZnO Nanocomposite Film and its Application in Simultaneous Photocatalytic Degradation of Toxic Molecules

The TiO2-ZnO nanocomposite materials ((TiO2-ZnO)NCM) with different molar ratios (Ti:Zn) was synthesized by chemical route and dispersed in functionalized silicate sol-gel matrix (Silicate/(TiO2-ZnO)NCM)). The as prepared Silicate/(TiO2-ZnO)NCM were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The dispersion of the small amount of (TiO2-ZnO)NCM in silicate sol-gel matrix paves the way for the preparation of solid-state thin film photocatalyst which is advantageous for the separation of the catalyst from solution, the substrates and the reaction products. The simultaneous photoinduced oxidation of methylene blue (MB) dye and reduction of Cr (VI) to Cr (III) was examined at different amine functionalized silicate sol-gel embedded (TiO2-ZnO)NCM films. The (TiO2-ZnO)NCM dispersed into the amine functionalized silicate sol-gel matrix (TPDT) exhibited enhanced photocatalytic activity when compared to the (TiO2-ZnO)NCM without the silicate sol-gel. The functionalized silicate sol-gel supported (TiO2-ZnO)NCM is a potential candidate for energy conversion and environment remediation and cleaning applications.

Silver nanoparticles embedded in cyclodextrin–silicate composite and their applications in Hg(ii) ion and nitrobenzene sensing

Different synthetic routes were described to prepare silver (Ag) nanoparticles (NPs) embedded in an amine functionalized silicate sol-gel matrix (TPDT) by employing different combination of reagents such as silicate sol-gel (TPDT), β-cyclodextrin (CD)-TPDT, TPDT-surfactant (BDAC), CD-TPDT-BDAC and CD-TPDT-BDAC/ascorbic acid (AA). The spectral and colorimetric detection of Hg(II) ions were carried out using the Ag NPs which showed a significant blue shift in the surface plasmon resonance (SPR) band upon the addition of Hg(II) ions. It was found that the addition of optimum level of Hg(II) ions into the Ag NPs completely quenched the SPR band and deformed the shape of the Ag NPs due to the formation of anisotropic Ag amalgam crystals (AgHg). The selective detection of Hg(II) ions using the Ag NPs in the presence of other environmentally relevant metal ions by spectral and colorimetric methods was also reported. Furthermore, the prepared Ag nanostructure modified electrodes were employed for the electrocatalytic reduction and sensing of nitrobenzene.

Synthesis of core/shell Au/Ag nanorods embedded in functionalized silicate sol–gel matrix and their applications in electrochemical sensors

A facile synthetic method was developed for the preparation of bimetal core/shell Au/Ag nanorods embedded in amine functionalized silicate sol–gel matrix (Aucore/Agshell–TPDT NRs) in aqueous medium and its application toward the electrochemical detection of hydrogen peroxide (H2O2) and nitrite ions was demonstrated. The electrochemical characteristics of the Aucore/Agshell–TPDT NRs modified electrode were studied by cyclic voltammetry. The electrocatalysis and amperometric sensing of hydrogen peroxide and nitrite ions at physiological pH using the Aucore/Agshell–TPDT NRs modified electrode were investigated. The amperometric sensor showed enhanced electrocatalytic activity toward the detection of H2O2 and nitrite ions without the support of any mediator due to the synergetic catalytic effect of Au core and Ag shell. The amperometric current increased linearly with increasing the H2O2 concentration in the range from 100nM to 1.2μM and the lowest detection limit was estimated using the standard procedure as 40nM. The amperometric current increased linearly with increasing the nitrite ions concentration in the range from 100nM to 1μM and the lowest detection limit was estimated using the standard procedure as 60nM. The results of the study demonstrated that the GC/Aucore/Agshell–TPDT NRs modified electrode is simple to prepare that shows fast response, good stability and reproducible results and hence it is a promising material for the preparation of modified electrodes and electrochemical sensors.

Synthesis of silicate sol–gel matrix embedded silver nanostructures: Efficient nanocatalyst for the reduction of 4-nitrophenol

Amine functionalized silicate sol–gel matrix embedded silver nanoparticles (Ag NPs) were prepared in the presence of β-cyclodextrin (β-CD–Ag–TPDT NPs) by a single-step process. The formation of sub-10nm tetra twinned Ag nanostructures was confirmed by high resolution transmission electron microscopy studies. The reduction of 4-nitrophenol by NaBH4 was used as a model to study the catalytic efficiency of the as prepared Ag nanostructures. The 4-nitrophenol forms an inclusion complex with the hydrophobic β-CD cavity because of the strong affinity of β-CD to the phenyl ring moieties. The catalytic reduction of 4-nitrophenol included in the β-CD cavity by NaBH4 was monitored in the presence of the Ag NPs using the absorption spectrophotometer by the kinetic mode analysis. The catalytic performance of the β-CD–Ag–TPDT NPs was greatly enhanced towards the 4-nitrophenol reduction reaction. The tetra twinned shaped β-CD–Ag–TPDT NPs with the size of sub-10nm showed higher catalytic activity than the β-CD–Ag NPs and Ag–TPDT NPs.

Polymer-embedded gold and gold/silver nanoparticle-modified electrodes and their applications in catalysis and sensors

Metal nanoparticles encapsulated by silicate sol-gel matrix find numerous applications particularly in electrocatalysis and sensors. In our previous reports, we have reported the mono- and bi-metal gold, silver, and core/shell gold/silver nanoparticles embedded in functionalized silicate sol-gel matrices. Modified electrodes were fabricated using mono- and bi-metallic gold, silver, and core/shell gold/silver nanoparticles embedded in silicate sol-gel, and they were used for the electrocatalysis and sensing of H2O2 and simultaneous detection of hydrazine, sulfite, and nitrite. We have prepared the gold nanoparticles encapsulated by amine-functionalized silicate sol-gel matrix in a single step without using any external reducing agents. The gold nanoparticles were also synthesized by using amine-functionalized silane monomer in the presence of β-cyclodextrin (β-CD), resulting in metal/polymer core/shell nanostructures. This nanocomposite material showed a synergistic stabilizing effect when compared to either silicate sol-gel matrix or β-CD alone as stabilizer. The synthesized gold nanoparticles were characterized using UV–vis spectroscopy and high-resolution transmission electron microscopy. Modified electrodes were prepared by using the gold nanoparticles embedded in silicate sol-gel matrix, and their electrochemical characteristics were studied.