Ionic Liquid-Responsive Phase Transfer of Gold Nanoparticles: Anionic Metathesis.

In this work, a fresh approach has been proposed for the efficient transfer of gold nanoparticles (AuNPs) from an aqueous to organic phase by the metathesis reaction or anion exchange reaction. Here, we synthesized ionic liquid 1-butyl 3-hexadecyl imidazolium bromide [C4C16Im]Br-stabilized AuNPs which exhibit excellent stability in solution. Transfer of Au@[C4C16Im]Br from an aqueous to organic phase was investigated by the metathesis reaction with different hydrophobic ionic liquid-forming salts such as LiNTf2, LiClO4, and KPF6. The anionic exchange process in ionic liquids at the AuNP surface to make hydrophilic to hydrophobic AuNPs is demonstrated. It was found that hydrophobic ionic liquids provide the most effective transfer of AuNPs from the aqueous to organic phase. Interestingly, we have noticed no change in color, size, and shape of AuNPs for more than a month, indicating more efficient transfer of AuNPs in organic solvents, which remained stable for over a month. The ionic liquids with anions NTf2-, ClO4-, and PF6- make the AuNP surface hydrophobic, indicating their good dispersibility in nonpolar solvents. Finally, these AuNPs exhibit excellent sensitivity toward the refractive index of organic solvents, which is correlated with the surface plasmon resonance (SPR) λSPR bands.

Bioinspired Carbon Quantum Dots: An Antibiofilm Agents.

Carbon dots, very tiny carbon material with various surface passivations, have emerged as a new class of nanomaterials for various applications. Herein, we describe a simple, economical, and green approach for the synthesis of colloidal luminescent carbon dots (C-dots) by solvothermal method from fruit juice of Citrus limetta, an abundantly available plant in Asian countries. The existence of C-dots was confirmed by X-ray Diffraction and High Resolution Transmission Electron Microscopy studies. The C-dots size was observed to be 2-4 nm. We further evaluated the efficacy of C-dots to inhibit the attachment of Candida albicans MTCC 227, and biofilm formation on the polystyrene surfaces. The C-dots have effectively inhibited the attachment and formation of biofilm in Candida albicans at very low concentrations, which is hitherto unattempted. The ability of C-dots to inhibit biofilm formation may contribute to diverse applications of C-dots in biomedical field.

Porous Mn-doped cobalt oxide@C nanocomposite: a stable anode material for Li-ion rechargeable batteries.

Cobalt oxide is a transition metal oxide, well studied as an electrode material for energy storage applications, especially in supercapacitors and rechargeable batteries, due to its high charge storage ability. However, it suffers from low conductivity, which effectively hampers its long-term stability. In the present work, a simple strategy to enhance the conductivity of cobalt oxide is adopted to achieve stable electrochemical performance by means of carbon coating and Mn doping, via a simple and controlled, urea-assisted glycine-nitrate combustion process. Structural analysis of carbon coated Mn-doped Co3O4 (Mn-Co3O4@C) confirms the formation of nanoparticles (∼50 nm) with connected morphology, exhibiting spinel structure. The Mn-Co3O4@C electrode displays superior electrochemical performance as a Li-ion battery anode, delivering a specific capacity of 1250 mAh g-1. Mn-Co3O4@C demonstrates excellent performance in terms of long-term stability, keeping charge storage ability intact even at high current rates due to the synergistic effects of fast kinetics-provided by enriched electronic conductivity, which allows ions to move freely to active sites and electrons from reaction sites to substrate during redox reactions-and high surface area combined with mesoporous architecture. The fully assembled battery device using Mn-Co3O4@C and standard LiCoO2 electrode shows 90% capacity retention over 100 cycles.

Growth study of hierarchical Ag3PO4/LaCO3OH heterostructures and their efficient photocatalytic activity for RhB degradation.

We have demonstrated the synthesis of Ag3PO4/LaCO3OH (APO/LCO) heterostructured photocatalysts by an in situ wet chemical method. From pre-screening evaluations of photocatalysts with APO/(x wt% LCO) composites with mass ratios of x = 5, 10, 15, 20, 25 and 30 wt%, we found that the APO/LCO (20 wt%) exhibited a superior photocatalytic activity for organic pollutant remediation. Therefore, an optimised photocatalyst APO/LCO (20 wt%) is selected for the present study and we investigate the effect of a mixed solvent system (H2O:THF) on the morphology, which has a direct effect on the photocatalytic performance. Interestingly, a profound effect on the morphological features of APO/LCO20 heterostructures was observed with variation in the ratio of the solvent system. From the FESEM study it is observed that the LCO spherical nanoparticles are transformed into nanorods with the variation of THF into the solvent system. Moreover, these LCO nanorods make intimate contact with the APO microstructures which is helpful for the improvement of the photocatalytic activity. The photocatalytic activities of the APO/LCO composites with different solvent ratios were evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. Excellent photocatalytic activity was observed for the APO/LCO-2 (H2O : THF = 60 : 40) sample. This might be due to uniform covering of the APO microstructures by fine LCO rod-like structures offering intimate contact between the APO and LCO and providing proper channels for the degradation reactions. Furthermore, with an increasing THF volume ratio in the reaction system there was an increase of the dimensions of the LCO rod-like structures and also a loose compactness of their uniform intimate contact between the APO/LCO heterostructures. All in all, the enhanced photocatalytic activity of the APO/LCO heterostructures is attributed to the collective co-catalytic effect of LCO, by providing accelerated charge separation through the heterojunction interface, and THF, by helping to tune the unique morphological features which eventually facilitate the photocatalysis process.

Template Free Architecture of Hierarchical Nanostructured ZnIn2S4 Rose-Like Flowers for Solar Hydrogen Production.

We have demonstrated the controlled synthesis of hierarchical nanostructured ZnIn2S4 using a facile template free hydrothermal/solvothermal method. The effect of solvents on the morphology and microstructure of ZnIn2S4 has been studied by using water, methanol and ethylene glycol as a solvents. The hierarchical nanostructure, i.e., rose-like morphology composed of very thin (5­6 nm) nanoplates of length ˜1 µm which was obtained in aqueous mediated ZnIn2S4. The porous structure (distorted flowers) and agglomerated nanoparticles were obtained using methanol-and ethylene glycol-mediated ZnIn2S4. Considering the band gap in the visible region, ZnIn2S4 is used as a solar light driven photocatalyst. An ecofriendly photocatalytic process for the conversion of poisonous H2S into H2 which is a green unconventional energy source has been demonstrated. The nanostructured ZnIn2S4 is employed as a photocatalyst for hydrogen production from H2S via a solar light-driven eco-friendly approach. The stable photocatalytic activity of hydrogen evolution, i.e., 3964 µmol ⁻¹ was obtained using 0.5 gm of such hierarchical nanostructured ZnIn2S4 under visible light irradiation. The unique hierarchical nanostructured ZnIn2S4 ternary semiconductor having hexagonal layer is expected to have potential applications in solar cells, LEDs, charge storage, electrochemical recording, thermoelectricity, other prospective electronic and optical devices.

Hierarchical 3D ZnIn2S4/graphene nano-heterostructures: their in situ fabrication with dual functionality in solar hydrogen production and as anodes for lithium ion batteries.

Hierarchical 3D ZnIn2S4/graphene (ZnIn2S4/Gr) nano-heterostructures were successfully synthesized using an in-situ hydrothermal method. The dual functionality of these nano-heterostructures i.e. for solar hydrogen production and lithium ion batteries has been demonstrated for the first time. The ZnIn2S4/Gr nano-heterostructures were optimized by varying the concentrations of graphene for utmost hydrogen production. An inspection of the structure shows the existence of layered hexagonal ZnIn2S4 wrapped in graphene. The reduction of graphene oxide (GO) to graphene was confirmed by Raman and XPS analyses. The morphological analysis demonstrated that ultrathin ZnIn2S4 nanopetals are dispersed on graphene sheets. The optical study reveals the extended absorption edge to the visible region due to the presence of graphene and hence is used as a photocatalyst to transform H2S into eco-friendly hydrogen using solar light. The ZnIn2S4/Gr nano-heterostructure that is comprised of graphene and ZnIn2S4 in a weight ratio of 1 : 99 exhibits enhanced photocatalytically stable hydrogen production i.e. ∼6365 µmole h(-1) under visible light irradiation using just 0.2 g of nano-heterostructure, which is much higher as compared to bare hierarchical 3D ZnIn2S4. The heightened photocatalytic activity is attributed to the enhanced charge carrier separation due to graphene which acts as an excellent electron collector and transporter. Furthermore, the usage of nano-heterostructures and pristine ZnIn2S4 as anodes in lithium ion batteries confers the charge capacities of 590 and 320 mA h g(-1) after 220 cycles as compared to their initial reversible capacities of 645 and 523 mA h g(-1), respectively. These nano-heterostructures show high reversible capacity, excellent cycling stability, and high-rate capability indicating their potential as promising anode materials for LIBs. The excellent performance is due to the nanostructuring of ZnIn2S4 and the presence of a graphene layer, which works as a channel for the supply of electrons during the charge-discharge process. More significantly, their dual functionality in energy generation and storage is quite unique and commendable.

Novel functionality of organic 6,13-Pentacenequinone as a photocatalyst for hydrogen production under solar light.

6,13-Pentacenequinone (PQ), an intermediate for an organic semiconductor pentacene, was synthesized by single step solvent free solid state reaction at room temperature under ambient conditions which is hitherto unattempted. The phase purity has been confirmed by XRD and NMR. Optical study showed the absorption at 390 and 412 nm attributed to the π-π* and n-π* transitions, respectively. Cyclic voltammetry indicates the semiconducting nature of PQ having a band gap of 3 eV. The photoluminescence study revealed emissions at 408 and 432 nm. Considering the good thermal stability and absorption well within visible region, wisely, PQ has been used as a photocatalyst for the hydrogen production under solar light. Surprisingly we observed the utmost hydrogen evolution i.e. 4848 µmol/h/0.1 g (quantum efficiency 6.8%). The repeatability and reusability study confirmed the stability of the photocatalyst. The confirmation of the photocatalytic effect was also confirmed using methylene blue (MB) dye degradation under natural sunlight. The observed rate constant (Kapp) for photocatalytic MB degradation was 1.60 × 10(-2) min(-1). The use of an organic photocatalyst for hydrogen production has been demonstrated for the first time. This novel organic photocatalyst can also be explored for water splitting.

Solid state engineering of Bi2S3/rGO nanostrips: an excellent electrode material for energy storage applications.

The study presents a novel, one-pot, and scalable solid-state reaction scheme to prepare bismuth sulphide (Bi2S3)-reduced graphene oxide (rGO) nanocomposites using bismuth oxide (Bi2O3), thiourea (TU), and graphene oxide (GO) as starting materials for energy storage applications. The impact of GO loading concentration on the electrochemical performance of the nanocomposites was investigated. The reaction follows a diffusion substitution pathway, gradually transforming Bi2O3 powder into Bi2S3 nanostrips, concurrently converting GO into rGO. Enhanced specific capacitances were observed across all nanocomposite samples, with the Bi2S3@0.2rGO exhibiting the highest specific capacitance of 705 F g-1 at a current density of 1 A g-1 and maintaining a capacitance retention of 82% after 1000 cycles. The superior specific capacitance is attributed to the excellent homogeneity and synergistic relation between rGO and Bi2S3 nanostrips. This methodology holds promise for extending the synthesis of other chalcogenides-rGO nanocomposites.

Template-free synthesis of nanostructured Cd(x)Zn(1-x)S with tunable band structure for H2 production and organic dye degradation using solar light.

We have demonstrated a template-free large-scale synthesis of nanostructured Cd(x)Zn(1-x)S by a simple and a low-temperature solid-state method. Cadmium oxide, zinc oxide, and thiourea in various concentration ratios are homogenized at moderate temperature to obtain nanostructured Cd(x)Zn(1-x)S. We have also demonstrated that phase purity of the sample can be controlled with a simple adjustment of the amount of Zn content and nanocrystalline Cd(x)Zn(1-x)S(x = 0.5 and 0.9) of the hexagonal phase with 6-8 nm sized and 4-5 nm sized Cd(0.1)Zn(0.9)S of cubic phase can be easily obtained using this simple approach. UV-vis and PL spectrum indicate that the optical properties of as synthesized nanostructures can also be modulated by tuning their compositions. Considering the band gap of the nanostructured Cd(x)Zn(1-x)S well within the visible region, the photocatalytic activity for H2 generation using H2S and methylene blue dye degradation is performed under visible-light irradiation. The maximum H2 evolution of 8320 µmol h(-1)g(-1) is obtained using nanostructured Cd(0.1)Zn(0.9)S, which is four times higher than that of bulk CdS (2020 µmol h(-1) g(-1)) and the reported nanostructured CdS (5890 µmol h(-1)g(-1)). As synthesized Cd(0.9)Zn(0.1)S shows 2-fold enhancement in degradation of methylene blue as compared to the bulk CdS. It is noteworthy that the synthesis method adapted provides an easy, inexpensive, and pollution-free way to synthesize very tiny nanoparticles of Cd(x)Zn(1-x)S with a tunnable band structure on a large scale, which is quite difficult to obtain by other methods. More significantly, environmental benign enhanced H2 production from hazardous H2S using Cd(x)Zn(1-x)S is demonstrated for the first time.

Evaluation of anti-quorum sensing activity of silver nanowires.

A menace of antimicrobial resistance with growing difficulties in eradicating clinical pathogens owing to the biofilm has prompted us to take up a facile aqueous-phase approach for the synthesis of silver nanowires (SNWs) by using ethylene glycol as a reducing agent and polyvinylpyrrolidone (PVP) as a capping agent. This synthesis is a reflux reaction seedless process. The obtained SNWs were about 200-250 nm in diameter and up to 3-4 µm in length. The SNWs were characterized by field emission scanning electron microscopy, transmission electron microscopy, UV-Vis spectroscopy, and X-Ray powder diffraction, and the chemical composition of the sample was examined by energy dispersive X-ray spectrum. The SNWs did not show an antibacterial activity against test organisms, Bacillus subtilis NCIM 2063 and Escherichia coli NCIM 2931; however, it showed a promising property of a quorum sensing-mediated inhibition of biofilm in Pseudomonas aeruginosa NCIM 2948 and violacein synthesis in Chromobacterium violaceum ATCC 12472, which is hitherto unattempted, by polyol approach.

Silver-decorated orthorhombic nanotubes of lithium vanadium oxide: an impeder of bacterial growth and biofilm.

Reoccurrence of infectious diseases and ability of pathogens to resist antibacterial action has raised enormous challenges which may possibly be confronted by nanotechnology routes. In the present study, uniformly embedded silver nanoparticles in orthorhombic nanotubes of lithium vanadium oxide (LiV2O5/Ag) were explored as an impeder of bacterial growth and biofilm. The LiV2O5/Ag nanocomposites have impeded growth of Gram-positive Bacillus subtilis NCIM 2063 and Gram-negative Escherichia coli NCIM 2931 at 60 to 120 µg/mL. It also impeded the biofilm in Pseudomonas aeruginosa NCIM 2948 at 12.5 to 25 µg/mL. Impedance in the growth and biofilm occurs primarily by direct action of the nanocomposites on the cell surfaces of test organisms as revealed by surface perturbation in scanning electron microscopy. As the metabolic growth and biofilm formation phenomena of pathogens play a central role in progression of pathogenesis, LiV2O5/Ag nanocomposite-based approach is likely to curb the menace of reoccurrence of infectious diseases. Thus, LiV2O5/Ag nanocomposites can be viewed as a promising candidate in biofabrication of biomedical materials.

The synthesis and super capacitive characterization of microwave-assisted highly crystalline α-Fe2O3/Fe3O4 nanoheterostructures.

A facile microwave-assisted solvothermal process for the synthesis of narrow-size distributed α-Fe2O3, α-Fe2O3/Fe3O4, and Fe3O4 nanostructures was demonstrated using PVP as a surfactant. During the reaction, the influence of the reaction media, such as the mixture of ethylene glycol and water on the formation of α-Fe2O3, α-Fe2O3/Fe3O4, and Fe3O4 was systematically studied. Interestingly, pure aqueous medicated solvothermal reaction conferred phase pure rhombohedral Fe2O3 (hematite) and linearly upsurging the formation of cubic Fe3O4 (magnetite) with the increasing concentration of EG and further, in pure EG, it deliberated cubic Fe3O4. FESEM and FETEM images of α-Fe2O3/Fe3O4 nano heterostructure clearly showed the nanosized Fe3O4 particles of 4-6 nm decorated onto Fe2O3 nanoparticles. Further, the electrochemical properties of α-Fe2O3, α-Fe2O3/Fe3O4, and Fe3O4 nanoparticles were investigated with galvanostatic charge-discharge and cyclic voltammetry measurements using a 3-electrode system. The findings show that their specific capacitances are linked to the type of iron oxide. More significantly, the α-Fe2O3/Fe3O4 nanoheterostructure exhibited the utmost capacitance of 165 F g-1, which is greater than that of pristine α-Fe2O3 and Fe3O4. Enhancement in the electrochemical performance was found due to the improved charge transfer that occurred at the interface of the nanoheterostructure. The nanoparticles of Fe3O4 deposited on the Fe2O3 increased the active sites, which accelerated the process of adsorption and desorption of ions, thereby enhancing the interface-assisted charge transfer and reducing the internal resistance, which is ultimately responsible for enhanced capacitance. Such heterostructures of nano iron oxide may fulfill the requirements of electrodes in supercapacitors.

Ni loaded SnS2 hexagonal nanosheets for photocatalytic hydrogen generation via water splitting.

Herein we have prepared the Ni-decorated SnS2 nanosheets with varying concentrations of Ni from 1 to 10 mol% (1, 2.5, 5, and 10 mol%) and studied their various physicochemical and photocatalytic properties. The chemical reduction technique was utilized to load the Ni nanoparticles on SnS2 nanosheets. The synthesized Ni decorated SnS2 (denoted as Ni-SnS2) was characterized using different spectroscopic techniques such as X-ray diffraction, diffuse reflectance UV-vis and photoluminescence spectroscopy, field emission scanning electron microscopy (FESEM), and field emission transmission electron microscopy (FETEM). XRD revealed the formation of the highly crystalline hexagonal phase of SnS2 but for nickel loading there is no additional peak observed. Further, the as-prepared Ni-SnS2 nano-photocatalyst shows absorption behaviour in the visible region, and photoluminescence spectra of the Ni-SnS2 nanostructures show band edge emission centred at 524 nm, and the peak intensity decreases with Ni loading. The FE-SEM and FE-TEM confirm the formation of hexagonal sheets having evenly distributed Ni nanoparticles of size ∼5-10 nm. BET surface area analysis was observed to be enhanced with Ni loading. The photocatalytic performance of the prepared Ni-SnS2 nanosheets was evaluated for hydrogen generation via water splitting under a 400 W mercury vapour lamp. Among the prepared Ni-SnS2 nanostructures, the Ni loaded with 2.5 mol% provided the highest hydrogen production i.e., 1429.2 µmol 0.1 g-1 (% AQE 2.32) in four hours, almost 1.6 times that of pristine SnS2 i.e., 846 µmol 0.1 g-1. Furthermore, the photocatalytic performance of the catalyst is also correlated with the photoconductivity by measuring the photocurrent. The photoconductivity of the samples is revealed to be stable and the conductivity of 2.5 mol% Ni-SnS2 is higher i.e. 20 times that of other Ni-SnS2 and pristine SnS2 catalysts.

Highly Stable MWCNT@NVP Composite as a Cathode Material for Na-Ion Batteries.

A 3D framework with Nasicon structured polyanionic Na3V2(PO4)3 (NVP) has been emphasized as a leading cathode material for sodium-ion batteries (SIBs) due to its high working voltage plateau, structural stability, and good rate performance. Herein, pristine NVP and MWCNT@NVP composite synthesized via a facile solid-state method are examined and compared as cathode materials for Na-ion batteries. The morphological study confirms the uniform distribution of MWCNTs in the pristine NVP structure. Impedance spectroscopy clearly confirms more diffusion of Na ions for the MWCNT@NVP composite as compared to pristine NVP, considering its diffusion coefficient which directly implies on an increase in specific capacity. MWCNT@NVP (FNV-2) showed specific discharge capacity 110 mAhg-1 at 0.1C current rate which is almost stable at higher current rates with marginal fading. However, the pristine NVP shows capacity loss at a higher current rate. It is noteworthy that the MWCNT@NVP composite shows stable performance with marginal specific capacity fading (1%) compared to pristine (15%). This is because of the mechanical integrity and stability afforded to the composite by the intertwined MWCNT framework in the MWCNT@NVP composite matrix against electrode degradation during the electrochemical reaction. More significantly, even at a higher current rate, that is, at 10 C, the composite recorded a very stable and excellent Columbic efficiency of 97% with a reversible specific capacity of 94 mAhg-1 after 2000 cycles. An enhanced electrochemical performance, that is, rate capability and cycling stability, demonstrates the high potential of the MWCNT@NVP composite for Na-ion storage. Moreover, a sodium-ion full cell with hard carbon demonstrated a reversible capacity of 103 mAhg-1 at C/20 current rate, which clearly demonstrates that MWCNT@NVP is a promising cathode material for sodium-ion batteries.

Electroless Ni plated nanostructured TiO2 as a photocatalyst for solar hydrogen production.

Herein, we have demonstrated a facile electroless Ni coated nanostructured TiO2 photocatalyst for the first time. More significantly the photocatalytic water splitting shows excellent performance for hydrogen production which is hitherto unattempted. The structural study exhibits majorly the anatase phase along with the minor rutile phase of TiO2. Interestingly, electroless nickel deposited on the TiO2 nanoparticles of size 20 nm shows a cubic structure with nanometer scale Ni coating (1-2 nm). XPS supports the existence of Ni without any oxygen impurity. The FTIR and Raman studies support the formation of TiO2 phases without any other impurities. The optical study shows a red shift in the band gap due to optimum nickel loading. The emission spectra show variation in the intensity of the peaks with Ni concentration. The vacancy defects are pronounced in lower concentrations of Ni loading which shows the formation of a huge number of charge carriers. The electroless Ni loaded TiO2 has been used as a photocatalyst for water splitting under solar light. The primary results manifest that the hydrogen evolution of electroless Ni plated TiO2 is 3.5 times higher (1600 µmol g-1 h-1) than pristine TiO2 (470 µmol g-1 h-1). As shown in the TEM images, nickel is completely electroless plated on the TiO2 surface, which accelerates the fast transport of electrons to the surface. It suppresses the electron-hole recombination drastically which is responsible for higher hydrogen evolution using electroless Ni plated TiO2. The recycling study exhibits a similar amount of hydrogen evolution at similar conditions which shows the stability of the Ni loaded sample. Interestingly, Ni powder loaded TiO2 did not show any hydrogen evolution. Hence, the approach of electroless plating of nickel over the semiconductor surface will have potential as a good photocatalyst for hydrogen evolution.

Engineering of Solar Energy Harvesting Tb3+-Ion-Doped CdS Quantum Dot Glasses for Photodissociation of Hydrogen Sulfide.

The photocatalytic properties of CdS quantum dots (Q-dots) and Tb3+-doped CdS Q-dots dispersed in a borosilicate glass matrix were investigated for the photodissociation of hydrogen sulfide (H2S) into hydrogen (H2) gas and elemental sulfur (S). The Q-dot-containing glass samples were fabricated using the conventional melt-quench method and isothermal annealing between 550 and 600 °C for 6 h for controlling the growth of CdS and Tb3+-ion-doped CdS Q-dots. The structure, electronic band gap, and spectroscopic properties of the Q-dots formed in the glass matrix after annealing were analyzed using Raman and UV-visible spectroscopies, X-ray powder diffraction, and transmission electron microscopy. With increasing annealing temperature, the average size range of the Q-dots increased, corresponding to the decrease of electronic band gap from 3.32 to 2.24 eV. For developing the model for photocatalytic energy exchange, the excited state lifetime and photoluminescence emission were investigated by exciting the CdS and Tb3+-doped CdS quantum states with a 450 nm source. The results from the photoluminescence and lifetime demonstrated that the Tb3+-CdS photodissociation energy exchange is more efficient from the excited Q-dot states compared to the CdS Q-dot glasses. Under natural sunlight, the hydrogen production experiment was conducted, and an increase of 26.2% in hydrogen evolution rate was observed from 0.02 wt % Tb3+-doped CdS (3867 µmol/h/0.5 g) heat-treated at 550 °C when compared to CdS Q-dot glass with a similar heat treatment temperature (3064 µmol/h/0.5 g). Furthermore, the photodegradation stability of 0.02 wt % Tb3+-CdS was analyzed by reusing the catalyst glass powders four times with little evidence of degradation.

In situ synthesis of g-C3N4/Ti3C2Tx nano-heterostructures for enhanced photocatalytic H2 generation via water splitting.

Herein, we demonstrated the in situ synthesis of g-C3N4/Ti3C2Tx nano-heterostructures for hydrogen generation under UV visible light irradiation. The formation of the g-C3N4/Ti3C2Tx nano-heterostructures was confirmed via powder X-ray diffraction and supported by XPS. The FE-SEM images indicated the formation of layered structures of MXene and g-C3N4. HR-TEM images and SAED patterns confirmed the presence of g-C3N4 together with Ti3C2Tx nanosheets, i.e., the formation of nano-heterostructures of g-C3N4/Ti3C2Tx. The absorption spectra clearly showed the distinct band gaps of g-C3N4 and Ti3C2Tx in the nano-heterostructure. The increase in PL intensity and broadening of the peak with an increase in g-C3N4 indicated the suppression of electron-hole recombination. Furthermore, the nano-heterostructure was used as a photocatalyst for H2 generation from water and methylene blue dye degradation. The highest H2 evolution (1912.25 µmol/0.1 g) with good apparent quantum yield (3.1%) and an efficient degradation of MB were obtained for gCT-0.75, which was much higher compared to that of the pristine materials. The gCT-0.75 nano-heterostructure possessed a high surface area and abundant vacancy defects, facilitating the separation of charge carriers, which was ultimately responsible for this high photocatalytic activity. Additionally, TRPL clearly showed a higher decay time, which supports the enhancement in the photocatalytic activity of the gCT-0.75 nano-heterostructure. The nano-heterostructure with the optimum concentration of g-C3N4 formed a hetero-junction with the linked catalytic system, which facilitated efficient charge carrier separation also responsible for the enhanced photocatalytic activity.

Growth of Bi2Te3 quantum dots/rods in glass: a unique highly stable nanosystem with novel functionality for high performance magneto optical devices.

Magneto optical materials are currently of great interest, primarily for modern applications in optical isolation, modulation and switching in telecommunication. However, single crystals are the benchmark materials still used in these devices which are rather expensive and very difficult to fabricate. In this context, we are reporting herewith a stable and novel Bi(2)Te(3) quantum dot-glass nanosystem obtained using a controlled thermo-chemical method. The Q-dots of hexagonal Bi(2)Te(3) of size 4 to 14 nm were grown along the <1 1 3> direction. Surprisingly, we obtained quantum rods of Bi(2)Te(3) of size 6 × 10 nm for the first time. The strong quantum confinement in the nanosystem is clearly shown by the optical study. The band gap of the host glass was drastically reduced (from 4.00 to 1.88 eV) due to the growth of Bi(2)Te(3) quantum dots whereas photoluminescence showed a Stokes shift ~175 meV. Faraday Rotation (FR) investigations of the Bi(2)Te(3) quantum dot-glass nanosystem show a nonlinear response in Verdet constant with a decrease in the Bi(2)Te(3) dot sizes. The Bi(2)Te(3) Q-dot-glass nanosystem with ~4 nm dots shows significant enhancement (70 times) in Verdet constant compared to the host glass and more radically better than conventional single crystal (TGG). This is the first time that such a type of unique nanosystem has been architectured and has given extremely good magneto-optical performance. We strongly feel that this novel nanosystem has tremendous applications in magneto-optical devices. It is noteworthy that expensive single crystals can be replaced with this cost effective novel glass nanosystem. Interestingly, the present quantum dot-glass nanosystem can be transformed into optical fibers very easily, which will have an exceptionally high impact on the fabrication of high performance magneto optical devices.

Biofilm inhibition in Candida albicans with biogenic hierarchical zinc-oxide nanoparticles.

The present study demonstrates lignin (L), fragments of lignin (FL), and oxidized fragmented lignin (OFL) as templates for the synthesis of zinc oxide nanoparticles (ZnO NPs) viz., lignin-ZnO (L-ZnO), hierarchical FL-ZnO, and OFL-ZnO NPs. The X-ray diffraction patterns confirmed the formation of phase pure ZnO NPs with a hexagonal wurtzite structure. Electron microscopy confirmed the hierarchical structures with one-dimensional arrays of ZnO NPs with an average particle diameter of 40 nm. The as-synthesized L-ZnO, FL-ZnO, and OFL-ZnO NPs were tested in-vitro for growth and virulence inhibition (morphogenesis and biofilm) in Candida albicans. L-ZnO, FL-ZnO, and OFL-ZnO NPs all inhibited growth and virulence. Growth and virulence inhibitions were highest (more than 90%, respectively at 125, 31.2, and 62.5 µg/mL) in presence of FL-ZnO NPs, indicating that the hierarchical FL-ZnO NPs were potent growth and virulence inhibiting agent than non-hierarchical ZnO NPs. Furthermore, the real-time polymerase chain (RT-PCR) was used to study the virulence inhibition molecular mechanisms of L-ZnO, FL-ZnO, and OFL-ZnO NPs. RT-PCR results showed that the downregulation of phr1, phr2, efg1, hwp1, ras1, als3 and als4, and the upregulation of bcy1, nrg1, and tup1 genes inhibited the virulence in C. albicans. Lastly, we also performed in-vitro test cell cytotoxicity on the cell line, mouse embryo 3T3L1, and in-vivo toxicity on Rats, which showed that FL-ZnO NPs were biocompatible and nontoxic.

Polyaniline-wrapped MnMoO4 as an active catalyst for hydrogen production by electrochemical water splitting.

Developing efficient, low-cost, and environment-friendly electrocatalysts for hydrogen generation is critical for lowering energy usage in electrochemical water splitting. Moreover, for commercialization, fabricating cost-efficient, earth-abundant electrocatalysts with superior characteristics is of urgent need. Towards this endeavor, we report the synthesis of PANI-MnMoO4 nanocomposites using a hydrothermal approach and an in situ polymerization method with various concentrations of MnMoO4. The fabricated nanocomposite electrocatalyst exhibits bifunctional electrocatalytic activity towards the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) at a lower overpotential of 410 mV at 30 mA cm-2 and 155 mV at 10 mA cm-2, respectively in an alkaline electrolyte. Furthermore, while showing overall water splitting (OWS) performance, the optimized PM-10 (PANI-MnMoO4) electrode reveals the most outstanding OWS performance with a lower cell voltage of 1.65 V (vs. RHE) at a current density of 50 mA cm-2 with an excellent long-term cell resilience of 24 h.