H-Glass Supported Hybrid Gold Nano-Islands for Visible-Light-Driven Hydrogen Evolution.

Flat panel reactors, coated with photocatalytic materials, offer a sustainable approach for the commercial production of hydrogen (H2) with zero carbon footprint. Despite this, achieving high solar-to-hydrogen (STH) conversion efficiency with these reactors is still a significant challenge due to the low utilization efficiency of solar light and rapid charge recombination. Herein, hybrid gold nano-islands (HGNIs) are developed on transparent glass support to improve the STH efficiency. Plasmonic HGNIs are grown on an in-house developed active glass sheet composed of sodium aluminum phosphosilicate oxide glass (H-glass) using the thermal dewetting method at 550 °C under an ambient atmosphere. HGNIs with various oxidation states (Au0, Au+, and Au-) and multiple interfaces are obtained due to the diffusion of the elements from the glass structure, which also facilitates the lifetime of the hot electron to be ≈2.94 ps. H-glass-supported HGNIs demonstrate significant STH conversion efficiency of 0.6%, without any sacrificial agents, via water dissociation. This study unveils the specific role of H-glass-supported HGNIs in facilitating light-driven chemical conversions, offering new avenues for the development of high-performance photocatalysts in various chemical conversion reactions for large-scale commercial applications.

Development of nano-porous hydroxyapatite coated e-glass for potential bone-tissue engineering application: An in vitro approach.

To reconstruct the defects caused by craniectomies autologous, bone grafting was usually used, but they failed most commonly due to bone resorption, infections and donor-site morbidity. In the present investigation, an effort has been made for the first time to check the feasibility and advantage of using hydroxyapatite (HAp) coated e-glass as component of bone implants. Sol-gel synthesized coatings were found to be purely hydroxyapatite from XRD with graded and interconnected pores all over the surface observable in TEM. The interconnected porous nature of ceramics are found to increase bioactivity by acting to up-regulate the process of osseointegration through enhanced nutrient transfer and induction of angiogenesis. From TEM studies and nano indentation studies, we have shown that pores were considered to be appropriate for nutrient supply without compromising the strength of sample while in contact with physiological fluid. After SBF immersion test, porous surface was found to be useful for nucleation of apatite crystals, hence increasing the feasibility and bioactivity of sample. However, our quasi-dynamic study showed less crystallization but had significant formation of apatite layer. Overall, the in vitro analyses show that HAp coated e-glass leads to significant improvement of implant properties in terms of biocompatibility, cell viability and proliferation, osteoinductivity and osteoconductivity. HAp coating of e-glass can potentially be utilized in fabricating durable and strong bioactive non-metallic implants and tissue engineering scaffolds.

In Situ Synthesis of Mesoporous TiO2 Nanofibers Surface-Decorated with AuAg Alloy Nanoparticles Anchored by Heterojunction Exhibiting Enhanced Solar Active Photocatalysis.

We designed an electrospinning synthesis protocol to obtain in situ, the mesoporous TiO2 nanofibers, which are surface-decorated with plasmonic AuAg nanoparticles (AuAg-mTNF-H). Such alloy nanoparticles are found to be partially exposed on the surface of the nanofibers. Characterization by HRTEM and EDS confirmed the formation of 1:1 AuAg alloy nanoparticles on the surface of TiO2 nanofibers with heterojunction at the interfaces. On the basis of electron microscopic characterization, we proposed that, during the formation of the nanofibers, the incorporated metal ions with surface capping of negative charges migrated toward the outer surface of the nascent fibers under the influence of high positive voltage required for electrospinning. As a result, after the subsequent thermal treatment, the crystallization of TiO2 nanofibers and the formation of alloy nanoparticles took place, leading to the formation of a deep heterojunction through partial embedment of the nanoparticles. The formation of AuAg alloy also restricted the oxidation of Ag, thus making the nanoparticles highly stable in ambient condition. Accordingly, such unique AuAg-mTNF-H photocatalyst shows strong light absorption property covering the entire range of visible wavelengths with stability. The solar light harvesting property of AuAg-mTNF-H was verified by monitoring solar light induced H2 evolution via water splitting and photodecomposition of MB. In both the cases AuAg-mTNF-H showed excellent H2 evolution and photodecomposition of dye.

Bimetallic Pd96Fe4 nanodendrites embedded in graphitic carbon nanosheets as highly efficient anode electrocatalysts.

A facile route to anchor a nanoalloy catalyst on graphitic carbon nanosheets (GCNs) has been developed for preparing high-performance electrode materials for application in direct alcohol fuel cells (DAFCs). Uniformly dispersed bimetallic Pd-Fe nanoparticles (NPs) with tunable composition have been immobilized on GCNs derived from mesocarbon microbeads (MCMBs) by a one-pot radiolytic reduction method. The Pd-Fe/GCN hybrid shows promising electrocatalytic activity for the methanol, ethanol, ethylene glycol, tri-ethylene glycol and glycerol oxidation reactions in alkaline medium. The as-prepared flower-shape Pd96Fe4/GCN nanohybrids have high mass activity for the ethanol oxidation reaction (EOR), which is ∼36 times (11 A per mg Pd) higher than that of their monometallic counterparts. Moreover, the onset oxidation potential for the EOR on the Pd96Fe4/GCN nanohybrids negatively shifts ca. 780 mV compared to that on commercial Pd/C electrocatalysts, suggesting fast kinetics and superior electrocatalytic activity. Additionally, chronoamperometry measurements display good long-term cycling stability of the Pd96Fe4/GCN nanohybrids for the EOR and also demonstrate only ∼7% loss in forward current density after 1000 cycles. The superior catalytic activity and stability may have originated from the modified electronic structure of the Pd-Fe nanoalloys and excellent physicochemical properties of the graphitic nanosheets. The present synthetic route using GCNs as the supporting material will contribute to further design of multimetallic nanoarchitectures with controlled composition and desired functions for fuel cell applications.

Electrospun ZrO2 nanofibers: precursor controlled mesopore ordering and evolution of garland-like nanocrystal arrays.

We observed that the hydrolysis-condensation reaction of precursors makes a significant difference in constructing ordered mesopores in electrospun ZrO2 nanofibers. Transmission-SAXS studies confirm the generation of uniform clusters of size ∼1.44 nm in the ZrOCl2·8H2O (inorganic salt) derived sol due to its relatively slow hydrolysis-condensation process. These initial -Zr-O-Zr- clusters acted as building blocks to form uniform 3D ordered cubic (Pm3[combining macron]m) mesopores in the presence of Pluronic F127 surfactant. In contrast, the commonly used Zr-alkoxide (zirconium n-propoxide) precursor, which is highly hydrolysable even after the use of a controlling agent, generates larger clusters with broad size distributions due to the uncontrolled hydrolysis-condensation of alkoxy groups. Accordingly, in the presence of F127, the alkoxide derived sol yielded disordered mesopores in the resultant fibers. XRD under dynamic heating conditions (up to 900 °C) and the corresponding TEM studies of the ZrOCl2·8H2O derived nanofibers confirmed the retention of mesopores even in the extremely thin nanofibers (diameter ∼15-25 nm) after the amorphous to crystal phase transformation (cubic/tetragonal). An interesting morphological transformation has been observed in the nanofibers at 900 °C where the fibers have been uniformly segmented by distinct single nanocrystals (width ∼15-65 nm) with mesopores. Further heat-treatment at 1100 °C made these segmented nanofibers nonporous, and a garland-like appearance with monoclinic nanocrystal arrays was formed.

Nano- and micro-tribological behaviours of plasma nitrided Ti6Al4V alloys.

Plasma nitriding of the Ti-6Al-4V alloy (TA) sample was carried out in a plasma reactor with a hot wall vacuum chamber. For ease of comparison these plasma nitrided samples were termed as TAPN. The TA and TAPN samples were characterized by XRD, Optical microscopy, FESEM, TEM, EDX, AFM, nanoindentation, micro scratch, nanotribology, sliding wear resistance evaluation and in vitro cytotoxicity evaluation techniques. The experimental results confirmed that the nanohardness, Young's modulus, micro scratch wear resistance, nanowear resistance, sliding wear resistance of the TAPN samples were much better than those of the TA samples. Further, when the data are normalized with respect to those of the TA alloy, the TAPN sample showed cell viability about 11% higher than that of the TA alloy used in the present work. This happened due to the formation of a surface hardened embedded nitrided metallic alloy layer zone (ENMALZ) having a finer microstructure characterized by presence of hard ceramic Ti2N, TiN etc. phases in the TAPN samples, which could find enhanced application as a bioimplant material.

Highly Active Multimetallic Palladium Nanoalloys Embedded in Conducting Polymer as Anode Catalyst for Electrooxidation of Ethanol.

Fabrication of multimetallic nanocatalysts with controllable composition remains a challenge for the development of low-cost electrocatalysts, and incorporating metal-based catalysts into active carbon nanoarchitectures represents an emerging strategy to improve the catalytic performance of electrocatalysts. Herein, a facile method developed for Pd nanoparticle (NP)-based multimetallic alloys incorporated on polypyrrole (Ppy) nanofibers by in situ nucleation and growth of NPs using colloidal radiolytic technique is described. Electrochemical measurement suggests that the as-prepared catalysts demonstrate dramatically enhanced electrocatalytic activity for ethanol oxidation in alkaline medium. The ultrasmall Pd30Pt29Au41/Ppy nanohybrids (∼8 nm) exhibit excellent electrocatalytic activity, which is ∼5.5 times higher than that of its monometallic counterparts (12 A/mg Pd, 5 times higher activity compared to that of Pd/C catalyst). Most importantly, the ternary nanocatalyst shows no obvious change in chemical structure and long-term stability, reflected in the 2% loss in forward current density during 1000 cycles. The superior catalytic activity and durability of the nanohybrids have been achieved due to the formation of Pt-Pd-Au heterojunctions with cooperative action of the three metals in the alloy composition, and the strong interactions between the Ppy nanofiber support with the metal NPs. The facile synthetic approach provides a new generation of polymer-supported metal alloy hybrid nanostructures as potential electrocatalysts with superior catalytic activity for fuel cell applications.

Nanotribological response of a plasma nitrided bio-steel.

AISI 316L is a well known biocompatible, austenitic stainless steel (SS). It is thus a bio-steel. Considering its importance as a bio-prosthesis material here we report the plasma nitriding of AISI 316L (SS) followed by its microstructural and nanotribological characterization. Plasma nitriding of the SS samples was carried out in a plasma reactor with a hot wall vacuum chamber. For ease of comparison these plasma nitrided samples were termed as SSPN. The experimental results confirmed the formations of an embedded nitrided metal layer zone (ENMLZ) and an interface zone (IZ) between the ENMLZ and the unnitrided bulk metallic layer zone (BMLZ) in the SSPN sample. These ENMLZ and IZ in the SSPN sample were richer in iron nitride (FeN) chromium nitride (CrN) along with the austenite phase. The results from nanoindentation, microscratch, nanoscratch and sliding wear studies confirmed that the static contact deformation resistance, the microwear, nanowear and sliding wear resistance of the SSPN samples were much better than those of the SS samples. These results were explained in terms of structure-property correlations.

Cu-Au-Ag alloy nanoparticles incorporated silica films using a new three-layer deposition technique.

Formation of Au-Ag-Cu ternary alloy nanoparticles (NPs) is difficult mainly because the system Cu/Ag is immiscible. We present a new synthetic technique to generate such ternary alloy NPs in silica film matrix employing a three-layer (3L) coating design. In this methodology three successive coating layers were deposited on silica glass substrates from separately prepared Cu-, Au- and Ag-ion incorporated inorganic-organic hybrid silica sols by dipping method. The Au layer is kept in the middle because it is miscible with both the Ag and Cu. The 3L film assembly was subjected to UV- and heat-treatment at 450-750 degrees C in H2-N2 atmosphere. UV-treatment generates small Au and Ag NPs in the respective layers and Cu remains as Cu2+; subsequent heat-treatment in H2-N2 induces the formation of ternary alloy NPs by the interlayer diffusion of nanometals. The final heat-treated film (750 degrees C/H2-N2) shows single and sharp plasmon band centered at 480 nm in the UV-visible spectrum indicating the formation of alloy (solid solution) NPs. GIXRD study shows one set of diffraction peaks which are shifted towards higher angle with respect to the Au or Ag diffraction peaks. FESEM, GIXRD, HRTEM, and SAED analyses reveal that the alloy has a composition close to (Au + Ag)0.88Cu0.12. The EDS analyses using the nano probe attached with TEM confirm the presence of Au, Ag and Cu in all the alloy NPs.