Anitha Devadoss

A mechanically bendable superhydrophobic steel surface with self-cleaning and corrosion-resistant properties

We present an effective way to develop superhydrophobic steel surface which shows stable superhydrophobicity under harsh mechanical bending. The roughness on the steel surface was created by etching in acid solution and its surface energy was lowered by subsequent hydrophobic silane treatment. The steel etching time in sulfuric acid solution was optimized to 8 h which provides high surface roughness required for superhydrophobicity. A water contact angle of 164 ± 3° and a sliding angle of 9 ± 2° were obtained for the steel surface after surface chemical modification by methyltrichlorosilane. We bent this superhydrophobic steel to 90° and 180° and studied the wetting properties on the bent area, which showed absolutely no change in superhydrophobicity. This superhydrophobic steel surface showed excellent self-cleaning behaviour as well as maintained its superhydrophobic wetting properties under a stream of water jet. Further, the stability of the wetting state was evaluated using a sandpaper abrasion test, adhesive tape peeling test, and under prolonged UV irradiation. Energy-dispersive X-ray spectroscopy was used to confirm the surface chemical composition of the superhydrophobic steel surface. This approach can be applied to steel surfaces of any size and shape to advance their industrial applications.

Synergistic metal-metal oxide nanoparticles supported electrocatalytic graphene for improved photoelectrochemical glucose oxidation.

We report the fabrication of graphene-WO3-Au hybrid membranes and evaluate their photocatalytic activity towards glucose oxidase mediated enzymatic glucose oxidation. The dual-functionality of gold nanoparticles in the reinforcement of visible light activity of graphene-WO3 membranes and improving the catalytic activity of immobilized enzymes for unique photoelectrochemical sensing application is demonstrated. This work provides new insights into the fabrication of light-sensitive hybrid materials and facilitates their application in future.

Self-cleaning and superhydrophobic CuO coating by jet-nebulizer spray pyrolysis technique

We demonstrate for the first time the fabrication of a superhydrophobic CuO coating with excellent self-cleaning ability by a custom-made jet nebulizer spray pyrolysis technique. A stable Cassie–Baxter superhydrophobic wetting state (water contact angle, ~154°) was maintained even after high speed water jet impact on a monoclinic CuO crystallite coating, which realizes the robust feature of coating. The mist-type aerosol distribution from the nebulizer controls the resultant morphology of the CuO film, thereby tuning the superhydrophobic properties. The low-cost (~

The Application of Graphene and Its Derivatives to Energy Conversion, Storage, and Environmental and Biosensing Devices

1) portable pocket-sized nebulizer affords reliable CuO superhydrophobic coatings on a wide range of desired host surfaces.

Modulating the interaction between gold and TiO2 nanowires for enhanced solar driven photoelectrocatalytic hydrogen generation.

Graphene (GR) and its derivatives are promising materials on the horizon of nanotechnology and material science and have attracted a tremendous amount of research interest in recent years. The unique atom-thick 2D structure with sp(2) hybridization and large specific surface area, high thermal conductivity, superior electron mobility, and chemical stability have made GR and its derivatives extremely attractive components for composite materials for solar energy conversion, energy storage, environmental purification, and biosensor applications. This review gives a brief introduction of GRs unique structure, band structure engineering, physical and chemical properties, and recent energy-related progress of GR-based materials in the fields of energy conversion (e.g., photocatalysis, photoelectrochemical water splitting, CO2 reduction, dye-sensitized and organic solar cells, and photosensitizers in photovoltaic devices) and energy storage (batteries, fuel cells, and supercapacitors). The vast coverage of advancements in environmental applications of GR-based materials for photocatalytic degradation of organic pollutants, gas sensing, and removal of heavy-metal ions is presented. Additionally, the use of graphene composites in the biosensing field is discussed. We conclude the review with remarks on the challenges, prospects, and further development of GR-based materials in the exciting fields of energy, environment, and bioscience.

Graphene Field Effect Transistors for Biomedical Applications: Current Status and Future Prospects

The interaction strength of Au nanoparticles with pristine and nitrogen doped TiO2 nanowire surfaces was analysed using density functional theory and their significance in enhancing the solar driven photoelectrocatalytic properties was elucidated. In this article, we prepared 4-dimethylaminopyridine capped Au nanoparticle decorated TiO2 nanowire systems. The density functional theory calculations show {101} facets of TiO2 as the preferred phase for dimethylaminopyridine-Au nanoparticles anchoring with a binding energy of -8.282 kcal mol(-1). Besides, the interaction strength of Au nanoparticles was enhanced nearly four-fold (-35.559 kcal mol(-1)) at {101} facets via nitrogen doping, which indeed amplified the Au nanoparticle density on nitrided TiO2. The Au coated nitrogen doped TiO2 (N-TiO2-Au) hybrid electrodes show higher absorbance owing to the light scattering effect of Au nanoparticles. In addition, N-TiO2-Au hybrid electrodes block the charge leakage from the electrode to the electrolyte and thus reduce the charge recombination at the electrode/electrolyte interface. Despite the beneficial band narrowing effect of nitrogen in TiO2 on the electrochemical and visible light activity in N-TiO2-Au hybrid electrodes, it results in low photocurrent generation at higher Au NP loading (3.4 × 10(-7) M) due to light blocking the N-TiO2 surface. Strikingly, even with a ten-fold lower Au NP loading (0.34 × 10(-7) M), the synergistic effects of nitrogen doping and Au NPs on the N-TiO2-Au hybrid system yield high photocurrent compared to TiO2 and TiO2-Au electrodes. As a result, the N-TiO2-Au electrode produces nearly 270 μmol h(-1) cm(-2) hydrogen, which is nearly two-fold higher than the pristine TiO2 counterpart. The implications of these findings for the design of efficient hybrid photoelectrocatalytic electrodes are discussed.

Hydrogen and CO2 Reduction Reactions: Mechanisms and Catalysts

Since the discovery of the two-dimensional (2D) carbon material, graphene, just over a decade ago, the development of graphene-based field effect transistors (G-FETs) has become a widely researched area, particularly for use in point-of-care biomedical applications. G-FETs are particularly attractive as next generation bioelectronics due to their mass-scalability and low cost of the technology’s manufacture. Furthermore, G-FETs offer the potential to complete label-free, rapid, and highly sensitive analysis coupled with a high sample throughput. These properties, coupled with the potential for integration into portable instrumentation, contribute to G-FETs’ suitability for point-of-care diagnostics. This review focuses on elucidating the recent developments in the field of G-FET sensors that act on a bioaffinity basis, whereby a binding event between a bioreceptor and the target analyte is transduced into an electrical signal at the G-FET surface. Recognizing and quantifying these target analytes accurately and reliably is essential in diagnosing many diseases, therefore it is vital to design the G-FET with care. Taking into account some limitations of the sensor platform, such as Debye–Hükel screening and device surface area, is fundamental in developing improved bioelectronics for applications in the clinical setting. This review highlights some efforts undertaken in facing these limitations in order to bring G-FET development for biomedical applications forward.

Single-step electrospun TiO2–Au hybrid electrodes for high selectivity photoelectrocatalytic glutathione bioanalysis

The electrocatalytic reduction of water to useful fuel via the hydrogen evolution reaction or CO2 reduction may afford a sustainable energy supply for the future. In this chapter, we discuss the recent developments on electrocatalytic materials for hydrogen (H2) evolution reaction and carbon dioxide (CO2) reduction which have been implemented in photocatalysis or photoelectrochemical reactions. The emerging strategies for replacing expensive platinum catalyst with earth abundant semiconductor materials in view of managing cost and material availability has been exclusively outlined here. Also, this chapter showcases novel materials, coatings and their recent strides to achieve high efficiency solar to fuel conversion from water and other pollutants. In summary, this chapter provides a holistic framework on a wide spectrum of materials, with consistent and meaningful comparisons between catalysts (hydrogen evolution electrocatalyst and photocatalyst) and etching insight into fundamentals and origin of catalysis.

Detecting Disease Biomarkers Using Nanocavities and Nanoparticle Composites

Understanding the fundamentals of photoelectrocatalytic (PEC) biomolecular oxidation benefits the development of next-generation PEC biosensors. In this work, single-step electrospun titanium-di-oxide-gold (TiO2-Au) hybrid nanofibers (HNF) are reported as being a potential candidate for PEC glutathione (GSH) bioanalysis. The chemical environment of TiO2 and TiO2-Au HNFs were studied with X-ray photoelectron spectroscopy and found to have a strong electronic interaction between TiO2 and the Au nanoparticles (NPs). The PEC measurements revealed that the intramolecular backbone hydrogen bonding of GSH molecules predominantly contributes highly active Au-GSH bio-nano interfaces, which facilitate the PEC oxidation rate of GSH and thus enhance the photocurrent. Furthermore, the Au NPs present act as auxiliary electron transport channels resulting in enhanced charge collection at the external circuit. As a result, the TiO2-Au electrode generated a two-fold higher photocurrent density of ∼84.4 μA cm-2 in the presence of 0.5 mM GSH, where the pristine TiO2 NFs displayed only a negligible influence. Likewise, the TiO2-Au HNF electrode showed a higher sensitivity of 0.002 mM and a wide linear detection range between 0.022 mM and 0.7 mM, with a superior selectivity towards GSH bioanalysis over ascorbic acid and glucose at -0.33 V (versus silver/silver chloride) than that obtained with pristine TiO2. The implications of these findings towards the development of a next-generation PEC biosensor are discussed.

Dominant Factors Governing the Rate Capability of a TiO2 Nanotube Anode for High Power Lithium Ion Batteries

The convergence of electrochemistry, materials, photonics and biomedical science at the nanoscale opens up significant opportunities for developing advanced sensors. In this contribution, we present examples of our use of nanometer dimensioned electrodes, nanocavities and nanoparticle-metallopolymer composites to create high sensitivity detection platforms and materials for detecting proteins and nucleic acids. The application of these approaches in the diagnosis and prognosis of cancers such as neuroblastoma, as well as point-of-care detection of infectious disease, will be discussed.