In Situ Growth of Interfacially Nanoengineered 2D-2D WS2/Ti3C2Tx MXene for the Enhanced Performance of Hydrogen Evolution Reactions.

In line with current research goals involving water splitting for hydrogen production, this work aims to develop a noble-metal-free electrocatalyst for a superior hydrogen evolution reaction (HER). A single-step interfacial activation of Ti3C2Tx MXene layers was employed by uniformly growing embedded WS2 two-dimensional (2D) nanopetal-like sheets through a facile solvothermal method. We exploited the interactions between WS2 nanopetals and Ti3C2Tx nanolayers to enhance HER performance. A much safer method was adopted to synthesize the base material, Ti3C2Tx MXene, by etching its MAX phase through mild in situ HF formation. Consequently, WS2 nanopetals were grown between the MXene layers and on edges in a one-step solvothermal method, resulting in a 2D-2D nanocomposite with enhanced interactions between WS2 and Ti3C2Tx MXene. The resulting 2D-2D nanocomposite was thoroughly characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses before being utilized as working electrodes for HER application. Among various loadings of WS2 into MXene, the 5% WS2-Ti3C2Tx MXene sample exhibited the best activity toward HER, with a low overpotential value of 66.0 mV at a current density of -10 mA cm-2 in a 1 M KOH electrolyte and a remarkable Tafel slope of 46.7 mV·dec-1. The intercalation of 2D WS2 nanopetals enhances active sites for hydrogen adsorption, promotes charge transfer, and helps attain an electrochemical stability of 50 h, boosting HER reduction potential. Furthermore, theoretical calculations confirmed that 2D-2D interactions between 1T/2H-WS2 and Ti3C2Tx MXene realign the active centers for HER, thereby reducing the overpotential barrier.

Electric Field-Driven Self-Assembly of Gold Nanoparticle Monolayers on Silicon Substrates.

Nanoparticles (NPs) bridge the gap between bulk materials and their equivalent molecular/atomic counterparts. The physical, optical, and electronic properties of individual NPs alter with the changes in their surrounding environment at the nanoscale. Similarly, the characteristics of thin films of NPs depend on their lateral and volumetric densities. Thus, attaining single monolayers of these NPs would play a vital role in the improved characteristics of semiconductor devices such as nanosensors, field effect transistors, and energy harvesting devices. Developing nanosensors, for instance, requires precise methods to fabricate a monolayer of NPs on selected substrates for sensing and other applications. Herein, we developed a physical fabrication method to form a monolayer of NPs on a planar silicon surface by creating an electric field of intensity 5.71 × 104 V/m between parallel plates of a capacitor, by applying a DC voltage. The physics of monolayer formation caused by an externally applied electric field on the gold NPs (Au-NPs) of size 20 nm in diameter and possesses a zeta potential of -250 to -290 mV, is further analyzed with the help of the finite element simulation. The enhanced electric field, in the order of 108 V/m, around the Au-NPs indicates a high surface charge density on the NPs, which results in a high electric force per unit area that guides them to settle uniformly on the surface of the silicon substrate.

Review on 2D Molybdenum Diselenide (MoSe2) and Its Hybrids for Green Hydrogen (H2) Generation Applications.

Hydrogen (H2) is a green and economical substitute to traditional fossil fuels due to zero carbon emissions. Water splitting technology is developing at a rapid speed to sustainably generate H2 through electro- and photolysis of water without the harmful emissions associated with steam methane reforming. Development of efficient catalysts for the hydrogen evolution reaction (HER) is pertinent for economical green H2 generation. In this regard, 2D transition metal dichalcogenides (TMDCs) are considered to be excellent alternatives to noble metal catalysts. Among other TMDCs, 2D MoSe2 is preferred due to the low Gibbs free energy for hydrogen adsorption, good electrical conductivity, and more metallic nature. Moreover, the physicochemical and electronic properties of MoSe2 can be easily tailored to suit HER application by simple synthetic strategies. Herein, we comprehensively review the application of 2D MoSe2 in the electrocatalytic HER, focusing on recent advancements in the modulation of the MoSe2 properties through nanostructure design, phase transformation, defect engineering, doping, and formation of heterostructures. We also discuss the role of 2D MoSe2 as a cocatalyst in the photocatalytic HER. The article concludes with a synopsis of current progress and prospective future trends.

Applications of nanotechnology in smart textile industry: A critical review.

Background: In recent years, nanotechnology has been playing an important role in designing smart fabrics. Nanomaterials have been employed to introduce in a sustainable manner, antimicrobial, ultraviolet resistant, electrically conductive, optical, hydrophobic and flame-retardant properties into textiles and garments. Nanomaterial based smart devices are now also being integrated with the textiles so as to perform various functions such as energy harvesting and storage, sensing, drug release and optics. These advancements have found wide applications in the fashion industry and are being developed for wider use in defence, healthcare and on-body energy harnessing applications. Aim of review: The objective of this work is to provide an insight into the current trends of using nanotechnology in the modern textile industries and to inspire and anticipate further research in this field. This review provides an overview of the most current advances concerning on-body electronics research and the wonders which could be realized by nanomaterials in modern textiles in terms of total energy reliance on our clothes. Key scientific concepts of review: The work underlines the various methods and techniques for the functionalization of nanomaterials and their integration into textiles with an emphasis on cost-effectiveness, comfort, wearability, energy conversion efficiency and eco-sustainability. The most recent trends of developing various nanogenerators, supercapacitors and photoelectronic devices on the fabric are highlighted, with special emphasis on the efficiency and wearability of the textile. The potential nanotoxicity associated with the processed textiles due to the tendency of these nanomaterials to leach into the environment along with possible remediation measures are also discussed. Finally, the future outlook regarding progress in the integration of smart nano-devices on textile fabrics is provided.

Reticular-Chemistry-Inspired Supramolecule Design as a Tool to Achieve Efficient Photocatalysts for CO2 Reduction.

Photocatalytic CO2 reduction into C1 products is one of the most trending research subjects of current times as sustainable energy generation is the utmost need of the hour. In this review, we have tried to comprehensively summarize the potential of supramolecule-based photocatalysts for CO2 reduction into C1 compounds. At the outset, we have thrown light on the inert nature of gaseous CO2 and the various challenges researchers are facing in its reduction. The evolution of photocatalysts used for CO2 reduction, from heterogeneous catalysis to supramolecule-based molecular catalysis, and subsequent semiconductor-supramolecule hybrid catalysis has been thoroughly discussed. Since CO2 is thermodynamically a very stable molecule, a huge reduction potential is required to undergo its one- or multielectron reduction. For this reason, various supramolecule photocatalysts were designed involving a photosensitizer unit and a catalyst unit connected by a linker. Later on, solid semiconductor support was also introduced in this supramolecule system to achieve enhanced durability, structural compactness, enhanced charge mobility, and extra overpotential for CO2 reduction. Reticular chemistry is seen to play a pivotal role as it allows bringing all of the positive features together from various components of this hybrid semiconductor-supramolecule photocatalyst system. Thus, here in this review, we have discussed the selection and role of various components, viz. the photosensitizer component, the catalyst component, the linker, the semiconductor support, the anchoring ligands, and the peripheral ligands for the design of highly performing CO2 reduction photocatalysts. The selection and role of various sacrificial electron donors have also been highlighted. This review is aimed to help researchers reach an understanding that may translate into the development of excellent CO2 reduction photocatalysts that are operational under visible light and possess superior activity, efficiency, and selectivity.

Recent Advances in Non-Enzymatic Glucose Sensors Based on Metal and Metal Oxide Nanostructures for Diabetes Management- A Review.

There is an undeniable growing number of diabetes cases worldwide that have received widespread global attention by many pharmaceutical and clinical industries to develop better functioning glucose sensing devices. This has called for an unprecedented demand to develop highly efficient, stable, selective, and sensitive non-enzymatic glucose sensors (NEGS). Interestingly, many novel materials have shown the promising potential of directly detecting glucose in the blood and fluids. This review exclusively encompasses the electrochemical detection of glucose and its mechanism based on various metal-based materials such as cobalt (Co), nickel (Ni), zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), titanium (Ti), iridium (Ir), and rhodium (Rh). Multiple aspects of these metals and their oxides were explored vis-à-vis their performance in glucose detection. The direct glucose oxidation via metallic redox centres is explained by the chemisorption model and the incipient hydrous oxide/adatom mediator (IHOAM) model. The glucose electrooxidation reactions on the electrode surface were elucidated by equations. Furthermore, it was explored that an effective detection of glucose depends on the aspect ratio, surface morphology, active sites, structures, and catalytic activity of nanomaterials, which plays an indispensable role in designing efficient NEGS. The challenges and possible solutions for advancing NEGS have been summarized.

An Overview of Copper Nanoparticles: Synthesis, Characterisation and Anticancer Activity.

In this review, we summarised the different methods for copper nanoparticle synthesis, including green methods. We highlighted that the synthesis of the copper nanoparticles from green sources is preferable as they serve as stable and reducing entities. Furthermore, we critically reviewed the effectiveness of copper- based nanoparticles in oncogenic treatments emphasizing breast, lung, colorectal, and skin cancers. Finally, we have summarised the recent progress made in copper-based nanoparticles and their applications to amplify and rectify present cancer treatment options. The synthesis, characterization, stabilization, and functionalization techniques of various copper-based nanoparticles have also been highlighted in each section. In conclusion, the review provides the outlook of copper nanoparticles in cancer diagnostics and therapeutics.

Molybdenum impregnated g-C3N4 nanotubes as potentially active photocatalyst for renewable energy applications.

Molybdenum (Mo) impregnated g-C3N4 (Mo-CN) nanotubes are fabricated via a thermal/hydrothermal process to augment photoelectrochemical properties during solar-driven water-splitting (SDWS) reactions. Graphitic-C3N4 is an attractive material for photocatalysis because of its suitable band energy, high thermal and chemical stability. The FE-SEM and HR-TEM comprehend the nanotube-like morphology of Mo-CN. The spectroscopic characterization revealed bandgap energy of 2.63 eV with high visible-light activity. The x-ray diffraction of pristine g-C3N4 and Mo-CN nanotubes discloses the formation of triazine-based nanocrystalline g-C3N4, which remains stable during hydrothermal impregnation of Mo. Furthermore, Mo-CN nanotubes possess high sp2-hybridized nitrogen content, and metallic/oxidized Mo nanoparticles (in a ratio of 1:2) are impregnated into g-C3N4. The XPS analysis confirms C, N, and Mo for known atomic and oxidation states in Mo-CN. Furthermore, high photocurrent efficiency (~ 5.5 mA/cm2) is observed from 5%-Mo-CN nanotubes. That displays efficient SDWS by 5%-Mo-CN nanotubes than other counterparts. Impedance spectroscopy illustrated the lowest charge transfer resistance (Rct) of 5%-Mo-CN nanotubes, which further confirms the fast electron transfer kinetics and efficient charge separation resulting in high photocurrent generation. Hence, 5%Mo-CN composite nanotubes can serve as a potential photocatalytic material for viable solar-driven water splitting.

High-speed solid state fluorination of Nb2O5 yields NbO2F and Nb3O7F with photocatalytic activity for oxygen evolution from water.

Solid state reactions are slow because the diffusion of atoms or ions through the reactant, intermediate and crystalline product phases is the rate-limiting step. This requires days or even weeks of high temperature treatment, and consumption of large amounts of energy. We employed spark-plasma sintering, an engineering technique that is used for high-speed consolidation of powders with a pulsed electric current passing through the sample to carry out the fluorination of niobium oxide in minute intervals. The approach saves time and large amounts of waste energy. Moreover, it allows the preparation of fluorinated niobium oxides on a gram scale using poly(tetrafluoroethylene) (®Teflon) scrap and without toxic chemicals. The synthesis can be upscaled easily to the kg range with appropriate sintering equipment. Finally, NbO2F and Nb3O7F prepared by spark plasma sintering show significant photoelectrocatalytic (PEC) oxygen evolution from water in terms of photocurrent density and incident photon-to-current efficiency (% IPCE), whereas NbO2F and Nb3O7F prepared by conventional high temperature chemistry show little to no PEC response. Our study is a proof of concept for the quick, clean and energy saving production of valuable photocatalysts from plastic waste.

A Generalized Method for High-Speed Fluorination of Metal Oxides by Spark Plasma Sintering Yields Ta3 O7 F and TaO2 F with High Photocatalytic Activity for Oxygen Evolution from Water.

A general method to carry out the fluorination of metal oxides with poly(tetrafluoroethylene) (PTFE, Teflon) waste by spark plasma sintering (SPS) on a minute scale with Teflon is reported. The potential of this new approach is highlighted by the following results. i) The tantalum oxyfluorides Ta3 O7 F and TaO2 F are obtained from plastic scrap without using toxic or caustic chemicals for fluorination. ii) Short reaction times (minutes rather than days) reduce the process time the energy costs by almost three orders of magnitude. iii) The oxyfluorides Ta3 O7 F and TaO2 F are produced in gram amounts of nanoparticles. Their synthesis can be upscaled to the kg range with industrial sintering equipment. iv) SPS processing changes the catalytic properties: while conventionally prepared Ta3 O7 F and TaO2 F show little catalytic activity, SPS-prepared Ta3 O7 F and TaO2 F exhibit high activity for photocatalytic oxygen evolution, reaching photoconversion efficiencies up to 24.7% and applied bias to photoconversion values of 0.86%. This study shows that the materials properties are dictated by the processing which poses new challenges to understand and predict the underlying factors.

Green emitting rare earth Gd2O3:Tb3+ nanoparticles for rapid imaging of latent fingerprint.

A series of green emitting Gd2O3:Tb3+ (Tb: 0%-10% mol) nanoparticles (NP) were synthesized using the hydrothermal method, then characterized and evaluated for latent fingerprint visualization. X-ray diffraction study (XRD) revealed a cubic structure of the nanoparticles and the total incorporation of the terbium in the Gd2O3 matrix. Field Emission-Scanning Electron Microscopy (FESEM), Energy Dispersive x-ray Spectrometry (EDX) and Transmission Electron Microscopy (TEM) were used to study the morphology and the elementary composition of the NP. Photoluminescence (PL) studies showed strong green emission around 540 nm due to the transition 5D4 â†’ 7F5. The luminescence color of the synthesized NP was characterized by the CIE 1931 chromaticity diagram. The potential use of the NP powders for the visualization of latent fingerprint under UV irradiation was assessed on various substrates. The latent fingerprint images revealed by the Gd2O3:Tb3+ NP powders are clear enough to extract and analyze reliable fingerprint features. The fingerprint quality was evaluated using three fingerprint quality assessment metrics and by extracting and measuring the visibility of the minutiae. The experimental results show very good quality images of the latent fingerprint acquired using the Gd2O3:Tb3+ NP and yield good minutiae extraction.

Nanomaterials-Based Sensors for Respiratory Viral Detection: A Review.

Contagious diseases are the principal cause of mortality, particularly respiratory viruses, a real menace for public health and economic development worldwide. Therefore, timely diagnosis and treatments are the only life-saving strategy to overcome any epidemic and particularly the ongoing prevailing pandemic COVID-19 caused by SARS-CoV-2. A rapid identification, point of care, portable, highly sensitive, stable, and inexpensive device is needed which is exceptionally satisfied by sensor technology. Consequently, the researchers have directed their attention to employing sensors targeting multiple analyses of pathogenic detections across the world. Nanostructured materials (nanoparticles, nanowires, nanobundles, etc.), owing to their unique characteristics such as large surface-to-volume ratio and nanoscale interactions, are widely employed to fabricate facile sensors to meet all the immediate emerging challenges and threats. This review is anticipated to foster researchers in developing advanced nanomaterials-based sensors for the increasing number of COVID-19 cases across the globe. The mechanism of respiratory viral detection by nanomaterials-based sensors has been reported. Moreover, the advantages, disadvantages, and their comparison with conventional sensors are summarized. Furthermore, we have highlighted the challenges and future potential of these sensors for achieving efficient and rapid detection.

Frontiers and Challenges in Electrochemical Corrosion Monitoring; Surface and Downhole Applications.

Corrosion sensing is essential to monitor and safeguard the materials' health and control the maintenance cost of corrosion-prone materials used in various industries. The petroleum industry is a major sufferer of corrosion costs among various industries due to pipelines and downhole applications. This review article encompasses an overview of various technologies used in early detection stages for more reliable corrosion sensing and warnings. This review provides a summary of corrosion types, corrosion causing chemical species, different destructive and non-destructive technologies used in monitoring corrosion and a comprehensive overview of the state-of-the-art of various electrochemical techniques used for surface and downhole corrosion monitoring. Finally, the existing challenges for corrosion monitoring in surface and downhole conditions and prospects are discussed.

Controlled Assembly of Cu/Co-Oxide Beaded Nanoclusters on Thiolated Graphene Oxide Nanosheets for High-Performance Oxygen Evolution Catalysts.

The use of water splitting modules is highly desired for the sustainable production of H2 as a future energy carrier. However, the sluggish kinetics and demand of high anodic potential are the bottlenecks for half-the cell oxygen evolution reaction (OER), which severely hamper the overall conversion efficiency. Although transition metal oxides based electrocatalysts have been envisioned as cost-effective and potential contenders for this quest, nevertheless, their low conductivity, instability, and limited number of active sites are among the common impediments that need to be addressed to eventually enhance their inherent catalytic potential for enhanced OER activity. Herein, the controlled assembly of transition metal oxides, that is, Cu@CuOx nanoclusters (NCs, ≈2 nm) and Co@CoOx beaded nanoclusters (BNCs, ≈2 nm), on thiol-functionalized graphene oxide (G-SH) nanosheets is reported to form novel and highly efficient electrocatalysts for OER. The thiol (-SH) functionality was incorporated by selective epoxidation on the surface of graphene oxide (GO) to achieve chemically exfoliated nanosheets to enhance its conductivity and trapping ability for metal oxides in nanoscale dimensions (≈2 nm). During the electrocatalytic reaction, overpotentials of 290 mV and 310 mV are required to achieve a current density of 10 mA cm-2 for BNCs and NCs, respectively, and the catalysts exhibit tremendous long-term stability (≈50 h) in purified alkaline medium (1 m KOH) with no dissolution in the electrolyte. Moreover, the smaller Tafel slopes (54 mV/dec for BNCs and 66 mV/dec for NCs), and a Faradic efficiency of approximately 96 % indicate not only the selectivity but also the tailored heterogeneous electrons transfer (HET) rate, which is required for fast electrode kinetics. It is anticipated that such ultrasmall metal oxide nanoclusters and their controlled assembly on a conducting surface (G-SH) may offer high electrochemical accessibility and a plethora of active sites owing to the drastic decrease in dimensions and thus can synergistically ameliorate the challenging OER process.

Interfacial Photoelectrochemical Catalysis: Solar-Induced Green Synthesis of Organic Molecules.

Many oxidation and reduction reactions in conventional organic synthesis rely on harsh conditions, toxic or corrosive substances, and environmentally damaging chemicals. In addition, competing reactions may take place, some of which produce hazardous waste products and, therefore, reaction selectivity suffers. To overcome such synthetic drawbacks, an enormous effort is being devoted to find alternative processes that operate much more efficiently, requiring milder conditions to contribute to a greener economy and provide urgently needed new pathways with enhanced selectivity. Fortunately, there is a strategy that has attracted global interest from multiple disciplines that involves the use of sunlight to perform artificial photosynthesis, in which a photoelectrochemical cell splits water into hydrogen fuel, reduces CO2 into "solar" fuels, and more recently, convert organic chemicals into higher value products. Recently, photoanode and photocathode materials have emerged as useful tools to perform organic oxidations and reductions for the synthesis of important molecules, other than just hydrogen or oxygen. Whereas many studies have focused on the degradation of unwanted and dangerous chemicals, solar-induced organic transformations have attracted much less attention. This Minireview summarizes some of latest research efforts in using photoelectrochemical cells to facilitate organic oxidation and reduction reactions to avoid valuable substances while avoiding toxic reagents and expensive precious metal catalysts. Future developments that will enable such technologies to broaden their scope are also considered.

Anticandidal and In vitro Anti-Proliferative Activity of Sonochemically synthesized Indium Tin Oxide Nanoparticles.

The present work demonstrates the synthesis, characterization and biological activities of different concentrations of tin doped indium oxide nanoparticles (Sn doped In2O3 NPs), i.e., (Sn/In = 5%, 10% and 15%). We have synthesized different size (38.11 nm, 18.46 nm and 10.21 nm) of Sn doped In2O3 NPs. by using an ultra-sonication process. The Sn doped In2O3 NPs were characterized by by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) which confirmed the successful doping of tin (Sn) with Indium oxide (In2O3). Anticandidal activity was performed by standard agar dilution method using Candida albicans for the study. The minimum inhibitory/fungicidal concentration (MIC/MFC) values recorded were, 8 & >8 mg/ml for pure In2O3 NPs, 4 & 8 mg/ml for 5%, 2 & 8 mg/ml for 10%, whereas 1 & >4 mg/ml for 15% Sn doped In2O3 NPs, respectively. The topographical alteration caused by Sn doped In2O3 NPs on Candida cells, was clearly observed by SEM examination. A significant enhancement in anticandidal activity was seen, when Candida cells were exposed to (Sn/In = 5%, 10% and 15%). Moreover, we have also evaluated the impact of Sn-In2O3 NPs on human colorectal carcinoma cells (HCT-116). The results demonstrated that Sn-In2O3 NPs (Sn/In = 5%, 10% and 15%), caused dose dependent decrease in the cancer cell viability as the low dosage (2.0 mg/mL) showed 62.11% cell viability, while 4.0, 8.0, 16.0, 32.0 mg/mL dosages showed 20.45%, 18.25%, 16.58%, and 15.58% cell viability. In addition, the treatment of Sn-In2O3 NPs also showed significant cellular and anatomical changes in cancer cells as examined by microscopes. We have also examined the impact of Sn-In2O3 NPs (5%, 10%, 15%) on normal cells (HEK-293) and the results demonstrate that Sn-In2O3 NPs did not reduce the cell viability of normal cells.

Ultrasmall Co@Co(OH)2 Nanoclusters Embedded in N-Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation.

Metal nanoclusters (NCs, size ≤2 nm) are emerging materials in catalysis owing to their unique catalytic and electronic properties such as high surface/volume ratio, high redox potential, plethora of surface active sites, and dynamic behavior on a suitable support during catalysis. Herein, in situ growth of ultrasmall and robust Co@ß-Co(OH)2 NCs (≈2 nm) hosted in a honeycomb-like 3D N-enriched carbon network was developed for water-oxidation catalysis with extremely small onset potential (1.44 V). Overpotentials of 220 and 270 mV were required to achieve a current density of 10 mA cm-2 and 100 mA cm-2 , respectively, in alkaline medium (1 m KOH). More promisingly, at η10 =240 mV, the prolonged oxygen evolution process (>130 h) with faradaic efficiency >95 % at a reaction rate of 22 s-1 at 1.46 V further substantiated the key role of the ultrasmall supported NCs, which outperformed the benchmark electrocatalysts (RuO2 /IrO2 ) and NCs reported so far. It is anticipated that the high redox potential of NCs with regeneratable active sites and their concerted synergistic effects with the N-enriched porous/flexible carbon network are inherently worth considering to enhance the mass/charge transport owing to the nanoscale interfacial collaboration across the electrode/electrolyte boundary, thereby efficiently energizing the sluggish/challenging oxygen evolution process.

Dye sensitized photoelectrolysis cells.

To advance the progress of photoelectrolysis, various promising devices integrated with p- and n-type photocatalysts and dye sensitized photoelectrodes have been systematically studied. This review discusses, from theory to practice, an integration strategy for state-of-the-art dye sensitized solar cells (DSSCs) with potential p- and n-type photo-electrocatalysts or directly with dye sensitized photoanodes and cathodes for hydrogen and oxygen production through water splitting. Thorough insight into the theoretical approach which systematically drives the photoelectrolysis reaction directly or in a coupled mode, with diverse configurations of DSSCs and other photovoltaic (PV) cells, is crucial to understand the underlying fundamental concepts and elucidate trends in such reactions, and will serve as a guide to design new electrocatalysts and their integration with new PV devices, while simultaneously underlining major gaps that are required to address the challenges. Likewise, challenges, opportunities and frontiers in tandem and hybrid perovskite electrolysis processes are also discoursed in the present tutorial review. We illustrate our analysis by encompassing these integrated systems to photo-electrolysis, artificial photosynthesis such as CO2 conversion into value-added chemical reduction-products, where advancements in new catalysts and solution-processed inexpensive PV devices can certainly enrich the overall performance of the renewable production of solar fuels, including solar driven carbonaceous fuels.

Site-directed chemically-modified magnetic enzymes: fabrication, improvements, biotechnological applications and future prospects.

Numerous enzymes of biotechnological importance have been immobilized on magnetic nanoparticles (MNP) via random multipoint attachment, resulting in a heterogeneous protein population with potential reduction in activity due to restriction of substrate access to the active site. Several chemistries are now available, where the modifier can be linked to a single specific amino acid in a protein molecule away from the active-site, thus enabling free access of the substrate. However, rarely these site-selective approaches have been applied to immobilize enzymes on nanoparticles. In this review, for the first time, we illustrate how to adapt site-directed chemical modification (SDCM) methods for immobilizing enzymes on iron-based MNP. These strategies are mainly chemical but may additionally require genetic and enzymatic methods. We critically examine each method and evaluate their scope for simple, quick, efficient, mild and economical immobilization of enzymes on MNP. The improvements in the catalytic properties of few available examples of immobilized enzymes are also discussed. We conclude the review with the applications and future prospects of site-selectively modified magnetic enzymes and potential benefits of this technology in improving enzymes, including cold-adapted homologues, modular enzymes, and CO2-sequestering, as well as non-iron based nanomaterials.

Metal Nanoclusters: New Paradigm in Catalysis for Water Splitting, Solar and Chemical Energy Conversion.

A sustainable future demands innovative breakthroughs in science and technology today, especially in the energy sector. Earth-abundant resources can be explored and used to develop renewable and sustainable resources of energy to meet the ever-increasing global energy demand. Efficient solar-powered conversion systems exploiting inexpensive and robust catalytic materials for the photo- and photo-electro-catalytic water splitting, photovoltaic cells, fuel cells, and usage of waste products (such as CO2 ) as chemical fuels are appealing solutions. Many electrocatalysts and nanomaterials have been extensively studied in this regard. Low overpotentials, catalytic stability, and accessibility remain major challenges. Metal nanoclusters (NCs, ≤3 nm) with dimensions between molecule and nanoparticles (NPs) are innovative materials in catalysis. They behave like a "superatom" with exciting size- and facet-dependent properties and dynamic intrinsic characteristics. Being an emerging field in recent scientific endeavors, metal NCs are believed to replace the natural photosystem II for the generation of green electrons in a viable way to facilitate the challenging catalytic processes in energy-conversion schemes. This Review aims to discuss metal NCs in terms of their unique physicochemical properties, possible synthetic approaches by wet chemistry, and various applications (mostly recent advances in the electrochemical and photo-electrochemical water splitting cycle and the oxygen reduction reaction in fuel cells). Moreover, the significant role that MNCs play in dye-sensitized solar cells and nanoarrays as a light-harvesting antenna, the electrochemical reduction of CO2 into fuels, and concluding remarks about the present and future perspectives of MNCs in the frontiers of surface science are also critically reviewed.