Electrocatalytic Glycerol Conversion: A Low-Voltage Pathway to Efficient Carbon-Negative Green Hydrogen and Value-Added Chemical Production.

Electrochemical glycerol oxidation reaction (GLYOR) could be a promising way to use the abundantly available glycerol for production of value-added chemicals and fuels. Completely avoiding the oxygen evolution reaction (OER) with GLYOR is an evolving strategy to reduce the overall cell potential and generate value-added chemicals and fuels on both the anode and cathode. We demonstrate the morphology-controlled palladium nanocrystals, afforded by colloidal chemistry, and their established morphology-dependent GLYOR performance. Although it is known that controlling the morphology of an electrocatalyst can modulate the activity and selectivity of the products, still it is a relatively underexplored area for many reactions, including GLYOR. Among nanocube (Pd-NC), truncated octahedron (Pd-TO), spherical and polycrystalline (Pd-PC) morphologies, the Pd-NC electrocatalyst deposited on a Ni foam exhibits the highest glycerol conversion (85%) along with 42% glyceric acid selectivity at a low applied potential of 0.6 V (vs reversible hydrogen electrode (RHE)) in 0.1 M glycerol and 1 M KOH at ambient temperature. Owing to the much favorable thermodynamics of GLYOR on the Pd-NC surface, the assembled electrolyzer requires an electricity input of only ∼3.7 kWh/m3 of H2 at a current density of 100 mA/cm2, in contrast to the requirement of ≥5 kWh/m3 of H2 with an alkaline/PEM electrolyzer. Sustainability has been successfully demonstrated at 10 and 50 mA/cm2 and up to 120 h with GLYOR in water and simulated seawater.

Possible handle for broadening the catalysis regime towards low temperatures: proof of concept and mechanistic studies with CO oxidation on surface modified Pd-TiO2.

The present work demonstrates the effect of temperature-dependent surface modification (SM) treatment and its influence in broadening the catalysis regime with Pd-TiO2 catalysts prepared by various methods. Due to SM induced changes, a shift in the onset of CO oxidation activity as well as broadening of the oxidation catalysis regime by 30 to 65 K to lower temperatures is observed compared to the temperature required for virgin counterparts. SM carried out at 523 K for PdPhoto-TiO2 exhibits the lowest onset (10% CO2 production - T10) and T100 for CO oxidation at 360 and 392 K, respectively, while its virgin counterpart shows T10 and T100 at 393 and 433 K, respectively. The SMd Pd-TiO2 catalysts were investigated using X-ray photoelectron spectroscopy (XPS), ultra-violet photoelectron spectroscopy (UPS) and atomic force microscopy (AFM). It is observed that diffusion of atomic oxygen into Pd-subsurfaces leads to SM and changes the nature of the surface significantly. These changes are demonstrated by work function (ϕ), surface potential, catalytic activity, and correlation among them. UPS results demonstrate the maximum increase in ϕ by 0.5 eV for PdPhoto-TiO2 after SM, compared to all other catalysts. XPS study shows a moderate to severe change in the oxidation states of Pd due to atomic oxygen diffusion into the subsurface layers of Pd. Kelvin probe force microscopy (KPFM) study also reveals corroborating evidence that the surface potential increases linearly with increasing temperature deployed for SM up to 523 K, followed by a marginal decrease at 573 K. The ϕ measured by KPFM and UPS shows a similar trend and correlates well with the changes in catalysis observed. Our results indicate that there is a strong correlation between surface physical and chemical properties, and ϕ changes could be considered as a global marker for chemical reactivity.

Detection of trace volatile organic compounds in spiked breath samples: a leap towards breathomics.

Breathomics is the future of non-invasive point-of-care devices. The field of breathomics can be split into the isolation of disease-specific volatile organic compounds (VOCs) and their detection. In the present work, an array of five quartz tuning fork (QTF)-based sensors modified by polymer with nanomaterial additive has been utilized. The array has been used to detect samples of human breath spiked with ∼0.5 ppm of known VOCs namely, acetone, acetaldehyde, octane, decane, ethanol, methanol, styrene, propylbenzene, cyclohexanone, butanediol, and isopropyl alcohol which are bio-markers for certain diseases. Polystyrene was used as the base polymer and it was functionalized with 4 different fillers namely, silver nanoparticles-reduced graphene oxide composite, titanium dioxide nanoparticles, zinc ferrite nanoparticles-reduced graphene oxide composite, and cellulose acetate. Each of these fillers enhanced the selectivity of a particular sensor towards a certain VOC compared to the pristine polystyrene-modified sensor. Their interaction with the VOCs in changing the mechanical properties of polymer giving rise to change in the resonant frequency of QTF is used as sensor response for detection. The interaction of functionalized polymers with VOCs was analyzed by FTIR and UV-vis spectroscopy. The collective sensor response of five sensors is used to identify VOCs using an ensemble classifier with 92.8% accuracy of prediction. The accuracy of prediction improved to 96% when isopropyl alcohol, ethanol, and methanol were considered as one class.

Co/Co3O4 Based Nanoparticles and Their Polymer Composites for Tuned Electromagnetic Interference Shielding Application.

The magnetic properties of the metal nanoparticles (NPs) can play remarkable role in electromagnetic interference shielding (EMI Shielding) of many defence and commercial electronic devices. In the present work, coconut oil and PVA capped magnetic cobalt/cobalt oxide nanoparticles (Co/Co3O4 NPs) were synthesized by chemical reduction method and impregnated in polymer matrix to verify their EMI shielding behaviour. The coconut oil capped Co/Co3O4 NPs with presence of hcp and fcc phases were prepared in the size domain of 7-10 nm and the effect of surfactant (the oil) on size and oxidation state was studied by varying the ratios. The shielding efficiencies of Co/Co3O4 NPs PVA nanocomposites were analysed by using vector network analyser (VNA) in X- and Ku-band ranging from 8 GHz-18 GHz. The VNA results showed increased shielding efficiency with increasing concentration of NPs.

Hydroxyapatite nanorods loaded with parathyroid hormone (PTH) synergistically enhance the net formative effect of PTH anabolic therapy.

Parathyroid hormone (PTH) has been a major contributor to the anabolic therapy for osteoporosis, but its delivery to bone without losing activity and avoiding adverse local effects remain a challenge. Being the natural component of bone, use of hydroxyapatite for this purpose brings a major breakthrough in synergistic anabolism. This study focuses on synthesis, characterization and evaluation of in vitro and in vivo efficacy of PTH (1-34) adsorbed hydroxyapatite nanocarrier for synergistic enhancement in the anabolic activity of PTH for bone regeneration. The negative zeta potential of this nanocarrier facilitated its affinity to the Ca2+ rich bone tissue and solubilization at low pH enhanced specific delivery of PTH to the resorption pits in osteoporotic bone. In this process, PTH retained its anabolic effect and at the same time an increase in bone mineral content indicated enhancement of the net formative effect of the PTH anabolic therapy.

Correlation between the magnetic-microstructure and microwave mitigation ability of MxCo(1-x)Fe2O4 based ferrite-carbon black/PVA composites.

A study of controlling the microwave mitigation properties of ferrite-carbon black/PVA composites by tuning the magnetic microstructure and spin arrangement of the ferrite particles is presented. MxCo(1-x)Fe2O4 (M: Ni2+, Mn2+ & Zn2+) nano-ferrites (NFs) were synthesized by a solvothermal method and these NFs were used to fabricate NF-CB hybrids and flexible NF-CB/PVA composite films. The magnetic force microscopy studies of the NFs reveal a unique single axis oriented domain structure for Zn-NFs and multi-domain magnetic microstructures for Mn-NFs and Ni-NFs. Mössbauer analysis of the NFs reveals highly distorted co-ordination of Fe3+ cations in Zn-NFs, whereas sub-lattice spins are canted in Mn-NFs and Ni-NFs. Despite the distorted magnetic lattice and broken coordination, the largest microwave shielding effectiveness (SE) of 32 dB is observed, over a bandwidth of 8 to 18 GHz, for Zn-NF-CB/PVA with a major contribution from absorption (SEA∼ 25 dB). The dielectric properties and Cole-Cole plots indicate enhanced interfacial polarization in Zn-NF-CB/PVA, which is attributed to the motion of polarons across multiple heterogeneous interfaces. These polarons are thought to be generated by distorted co-ordination of Fe3+, and d-d electron transition between Co2+⇋ Fe3+ cations at the B-site of Zn-NF. Distorted co-ordination of Fe3+ in Zn-NF along with unique single axis oriented magnetic domains play a crucial role in magnetic losses, as µ'' is almost double in Zn-NF based composites as compared to other composites. Due to their excellent and tunable microwave absorption properties, NF-CB/PVA composites could be employed for next generation stealth applications.

Investigation of Disorder in Mixed Phase, sp²-sp³ Bonded Graphene-Like Nanocarbon.

Disorder in a mixed phase, sp2-sp3 bonded graphene-like nanocarbon (GNC) lattice has been extensively studied for its electronic and field emission properties. Morphological investigations are performed using scanning electron microscopy (SEM) which depicts microstructures comprising of atomically flat terraces (c-planes) with an abundance of edges (ab planes which are orthogonal to c-planes). Scanning tunneling microscopy (STM) is used to observe the atomic structure of basal planes whereas field emission microscopy (FEM) is found to be suitable for resolving nanotopography of edges. STM images revealed the hexagonal and non-hexagonal atomic arrangements in addition to a variety of defect structures. Scanning tunneling spectroscopy is carried out to study the effect of this short-range disorder on the local density of states. Current versus voltage (I-V) characteristics have been recorded at different defect sites and are compared with respect to the extent of the defect. As sharp edges of GNC are expected to be excellent field emitters, because of low work function and high electric field, enhancement in current is observed particularly when applied electric field is along basal planes. Therefore, it is worthwhile to investigate field emission from these samples. The FEM images show a cluster of bright spots at low voltages which later transformed into an array resembling ledges of ab-planes with increasing voltage. Reproducible I-V curves yield linear Fowler-Nordheim plots supporting field emission as the dominant mechanism of electron emission. Turn on field for 10 µA current is estimated to be ~3 V/µm.

Temperature Dependent Electron Transport Properties of Gold Nanoparticles and Composites: Scanning Tunneling Spectroscopy Investigations.

Scanning tunneling spectroscopy (STS) is used for investigating variations in electronic properties of gold nanoparticles (AuNPs) and its composite with urethane-methacrylate comb polymer (UMCP) as function of temperature. Films are prepared by drop casting AuNPs and UMCP in desired manner on silicon substrates. Samples are further analyzed for morphology under scanning electron microscopy (SEM) and atomic force microscopy (AFM). STS measurements performed in temperature range of 33 °C to 142 °C show systematic variation in current versus voltage (I-V) curves, exhibiting semiconducting to metallic transition/Schottky behavior for different samples, depending upon preparation method and as function of temperature. During current versus time (I-t) measurement for AuNPs, random telegraphic noise is observed at room temperature. Random switching of tunneling current between two discrete levels is observed for this sample. Power spectra derived from I-t show 1/f2 dependence. Statistical analysis of fluctuations shows exponential behavior with time width τ ≈ 7 ms. Local density of states (LDOS) plots derived from I-V curves of each sample show systematic shift in valance/conduction band edge towards/away from Fermi level, with respect to increase in temperature. Schottky emission is best fitted electron emission mechanism for all samples over certain range of bias voltage. Schottky plots are used to calculate barrier heights and temperature dependent measurements helped in measuring activation energies for electron transport in all samples.

Microwave absorption properties of reduced graphene oxide strontium hexaferrite/poly(methyl methacrylate) composites.

The key factors to consider when designing microwave absorber materials for eradication of electromagnetic (EM) pollution are absorption of incident EM waves and good impedance matching. By keeping these things in mind, flexible microwave absorber composite films can be fabricated by simple gel casting techniques using reduced graphene oxide (RGO) and strontium ferrite (SF) in a poly(methyl methacrylate) (PMMA) matrix. SF nanoparticles are synthesized by the well known sol-gel method. Subsequently, reduced graphene oxide (RGO) and SF nanocomposite (RGOSF) are prepared through a chemical reduction method using hydrazine. The structure, morphology, chemical composition, thermal stability and magnetic properties of the nanocomposite are characterized in detail by various techniques. The SF particles are found to be nearly 500 nm and decorated on RGO sheets as revealed by field emission scanning electron microscopy and transmission electron microscopy analysis. Fourier transform infrared and and Raman spectroscopy clearly show the presence of SF in the graphene sheet by the lower peak positions. Finally, ternary polymer composites of RGO/SF/PMMA are prepared by an in situ polymerization method. Magnetic and dielectric studies of the composite reveal that the presence of RGO/SF/PMMA lead to polarization effects contributing to dielectric loss. Also, RGO surrounding SF provides a conductive network in the polymer matrix which is in turn responsible for the magnetic loss in the composite. Thus, the permittivity as well as the permeability of the composite can be controlled by an appropriate combination of RGO and SF in PMMA. More than 99% absorption efficiency is achieved by a suitable combination of magneto-dielectric coupling in the X-band frequency range by incorporating 9 wt% of RGO and 1 wt% of SF in the polymer matrix.

An attempt to correlate surface physics with chemical properties: molecular beam and Kelvin probe investigations of Ce1-xZrxO2 thin films.

What is the correlation between physical properties of the surfaces (such as surface potential, electronic nature of the surface), and chemical and catalysis properties (such as chemisorption, sticking probability of surface)? An attempt has been made to explore any correlation that might exist between the physical and chemical properties of thin film surfaces. Kelvin probe microscopy (KPM) and the molecular beam (MB) methods were employed to carry out the surface potential, and oxygen adsorption and oxygen storage capacity (OSC) measurements on Ce1-xZrxO2 thin films. A sol-gel synthesis procedure and spin-coating deposition method have been applied to make continuous nanocrystalline Ce1-xZrxO2 (x = 0-1) (CZ) thin films with uniform thickness (35-50 nm); however, surface roughness and porosity inherently changes with CZ composition. MB studies of O2 adsorption on CZ reveal high OSC for Ce0.9Zr0.1O2, which also exhibits highly porous and significantly rough surface characteristics. The surface potential observed from KPM studies varied between 30 and 80 mV, with Ce-rich compositions exhibiting the highest surface potential. Surface potential shows large changes after reduction or oxidation of the CZ film demonstrating the influence of Ce3+/Ce4+ on surface potential, which is also a key to catalytic activity for ceria-based catalysts. The surface potential measured from KPM and the OSC measured from MB vary linearly and they depend on the Ce3+/Ce4+ ratio. More and detailed studies are suggested to arrive at a correlation between the physical and chemical properties of the surfaces.

Curcumin-Loaded, Self-Assembled Aloevera Template for Superior Antioxidant Activity and Trans-Membrane Drug Release.

Fine combination of natural botanical extracts to evaluate and maximize their medicinal efficacy has been studied for long. However, their limited shelf-life, complicated extraction protocols, and difficult compositional analysis have always been a problem. It is due to this that such materials take time to convert them into a proper pharmaceutical technology or product. In this context, we report on synthesis of self-assembled template of one of the most popular natural product, aloevera. This forms a fine porous membrane like structure, in which a natural drug, curcumin has been immobilized/trapped. The so-made curcumin-loaded-aloevera (CLA) structures have been carefully evaluated using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), atomic force microscopy (AFM), UV-vis spectroscopy and fluorescence microscopy. While FTIR shows that there is no chemical interaction between aloevera and curcumin, the pores are finely occupied by curcumin molecules. Fine microscopy structures reveal their distribution and fluorescence microscopy confirm the presence of curcumin within the pores. TGA shows 15% loading of the curcumin in the template and UV-visible spectroscopy data shows independent peaks of both, aloevera (196 nm and 256 nm) and curcumin (423 nm), respectively. When subjected to antioxidant studies, using DPPH assays, CLAs show a synergistically superior DPPH radical scavenging activity as compared to only curcumin and only aloevera extract. Same is true for hydroxyl and NO2 radicals. Trans-membrane release study reveals that there is no significant difference in the amount of curcumin release from CLAs till initial 30 min, however, it increases steadily thereafter. CLA is found to facilitate efficient release of curcumin in 5 h, which is higher as compared to the curcumin alone.

Electromagnetic interference shielding in 1-18 GHz frequency and electrical property correlations in poly(vinylidene fluoride)-multi-walled carbon nanotube composites.

Electromagnetic interference (EMI) shielding properties in the 1-18 GHz frequency range for multi-walled carbon nanotube (MWNT)-poly(vinylidene fluoride) (PVDF) composites are reported. A simple and gentle acid-treatment of MWNT showed a percolation threshold (PT) of 0.15 wt% in the PVDF matrix as against 0.35 wt% for unfunctionalized MWNT. Acid-treatment of MWNT significantly improves dispersion, interfacial adhesion with the matrix and the EMI shielding properties of PVDF composites. Further, the EMI shielding properties are correlated with the electrical properties. Using composite films of 0.3 mm thickness, the maximum shielding effectiveness (SET) values for 4 wt% unfunctionalized MWNT composites are found to be about 110, 45, 30, 26, and 58 dB for L (1-2 GHz), S (2-4 GHz), C (4-5.8 GHz), J (5.8-8 GHz), and X (8-12 GHz) bands, while the corresponding values for only 0.5 wt% acid functionalized MWNT composites are about 98, 45, 26, 19, and 47 dB, respectively. The electrical conductivity for both the cases is ∼10(-3) S cm(-1) and the weight contents of CNTs are higher than the PT for the respective composites. The comparable EMI SE and electrical conductivity values for both the composites at different weight fractions of CNTs suggest that there is a critical electrical conductivity above which the composites attain improved EMI shielding properties. Further, the shielding mechanism was found to be dominated by absorption loss. Therefore, the composites may also serve as a radar absorbing material.

Hysteretic DC electrowetting by field-induced nano-structurations on polystyrene films.

Electrowetting (EW) offers executive wetting control of conductive liquids on several polymer surfaces. We report a peculiar electrowetting response for aqueous drops on a polystyrene (PS) dielectric surface in the presence of silicone oil. After the first direct current (DC) voltage cycle, the droplet failed to regain Young's angle, yielding contact angle hysteresis, which is close to a value found in ambient air. We conjecture that the hysteretic EW response appears from in situ surface modification using electric field induced water-ion contact with PS surface inducing nano-structuration by electro-hydrodynamic (EHD) instability. Atomic force microscopy confirms the formation of nano-structuration on the electrowetted surface. The effects of molecular weight, applied electric field, water conductivity and pH on nano-structuration are studied. Finally, the EW based nano-structuration on PS surface is used for the enhanced loading of aqueous dyes on hydrophobic surfaces.

Graphene nanoribbon-PVA composite as EMI shielding material in the X band.

A very thin graphene nanoribbon/polyvinyl alcohol (GNR/PVA) composite film has been developed which is light weight and requires a very low concentration of filler to achieve electromagnetic interference (EMI) shielding as high as 60 dB in the X band. Atomic force microscope studies show very well conjugated filler concentration in the PVA matrix for varying concentrations of GNR supported by Raman spectroscopy data. The films show 14 orders of increase in conductivity with a GNR concentration of 0.75% [corrected] in PVA. This is possible because of the interconnected GNR network providing a very low percolation threshold as observed from the electrical measurements. Local density of states study of GNR using scanning tunnelling spectroscopy shows the presence of localized states near the Fermi energy. There are multiple advantages of GNR as an EMI shielding material in a polymer matrix. It has good dispersion in water, the conductive network in the composite shows very high electrical conductivity for a very low concentration of GNR and the presence of localized density of states near Fermi energy provides the spin states required for the absorbance of radiation energy in the X band.

Curcumin conjugated silica nanoparticles for improving bioavailability and its anticancer applications.

Curcumin, a yellow bioactive component of Indian spice turmeric, is known to have a wide spectrum of biological applications. In spite of various astounding therapeutic properties, it lacks in bioavailability mainly due to its poor solubility in water. In this work, we have conjugated curcumin with silica nanoparticles to improve its aqueous solubility and hence to make it more bioavailable. Conjugation and loading of curcumin with silica nanoparticles was further examined with transmission electron microscope (TEM) and thermogravimetric analyzer. Cytotoxicity analysis of synthesized silica:curcumin conjugate was studied against HeLa cell lines as well as normal fibroblast cell lines. This study shows that silica:curcumin conjugate has great potential for anticancer application.

Charge storage and electron transport properties of gold nanoparticles decorating a urethane-methacrylate comb polymer network.

We propose enhanced charge storage capacity of nanoparticles based polymer films. A flat band voltage window varying from 5-7 V is obtained leading to a trapped charge density of the order of 10(13) cm(-2). These results vary for two distinct morphologies obtained due to decoration of a urethane-methacrylate comb polymer (UMCP) network by gold nanoparticles (AuNPs). Films have been further investigated for morphology, optical, charge storage, and electron transport properties using techniques like scanning electron microscopy (SEM), atomic force microscopy (AFM), absorption spectroscopy (UV-Vis), scanning tunneling microscopy/spectroscopy (STM/STS) and capacitance versus voltage (C-V) measurements. SEM and AFM confirm either the deposition of AuNPs inside the UMCP network or the formation of ring like structures depending on the deposition sequence. STS measurements performed on both films are compared with bare UMCP and AuNPs films. Current versus voltage (I-V) characteristics so obtained are discussed in the light of electron transport mechanisms in such materials.