Sadaf Bashir Khan

Mechanically robust antireflective coatings

Mechanical strength is an essential parameter that influences and limits the lifetime performance of antireflective (AR) coatings in optical devices. Specifically, amphiphobic AR coatings with reduced reflectance are of great significance as they considerably enlarge the range of fundamental applications. Herein, we describe the design and fabrication of amphiphobic AR coatings with reduced reflectance and enhanced mechanical resilience. Introducing a thin polytetrafluoroethylene (PTFE) layer on top of the bilayer SiO2 coating via vapor deposition method makes it highly liquid repellent. We achieved reduced reflectance (< 1%) over the entire visible wavelength range, as well as tunability according to the desired wavelength region. The fabricated film showed better thermal stability (up to 300 °C) with stable AR efficiency, when an ultrathin dense coat of Al2O3 was deposited via atomic layer deposition (ALD) on the polymer-based bilayer SiO2 antireflective coating (P-BSAR). The experimental results prove that the omnidirectional AR coating in this study exhibits multifunctional properties and should be suitable for the production of protective optical equipment and biocompatible polymer films for the displays of portable electronic devices.

Synthesis of Zn3(VO4)2/BiVO4 heterojunction composite for the photocatalytic degradation of methylene blue organic dye and electrochemical detection of H2O2

In this study, a Zn3(VO4)2/BiVO4 heterojunction nanocomposite photocatalyst was prepared using a hydrothermal route with different molar concentration ratios. The as-synthesized nanophotocatalyst was characterized using XRD, SEM, EDS, XPS, FT-IR, Raman, BET, UV-vis DRS, EPR and PL. The effect of molar ratio on composition and morphology was studied. The as-prepared nanocomposite exhibited excellent photocatalytic response by completely degrading the model pollutant methylene blue (MB) dye in 60 min at molar concentration ratio of 2 : 1. In basic medium at pH 12, the Zn3(VO4)2/BiVO4 nanocomposite degrades MB completely within 45 min. The nanocomposite was also successfully used for the electrochemical detection of an important analyte hydrogen peroxide (H2O2). This study opens up a new horizon for the potential applications of Zn3(VO4)2/BiVO4 nanocomposite in environmental wastewater remediation as well as biosensing sciences.

Visible light assisted photocatalytic degradation of crystal violet dye and electrochemical detection of ascorbic acid using a BiVO4/FeVO4 heterojunction composite

A BiVO4/FeVO4 nanocomposite photocatalyst was successfully synthesized via a hydrothermal method. The prepared heterojunction photocatalyst was characterized physically and chemically using XRD, SEM, EDX, XPS, BET, FT-IR, Raman, UV-vis DRS, EPR and photoluminescence techniques. BiVO4/FeVO4 was explored for its photocatalytic activity by the decomposition of crystal violet (CV) organic dye under visible radiation. This experiment showed that BiVO4/FeVO4 at a ratio of 2 : 1 completely degrades CV within 60 min. In addition, BiVO4/FeVO4 was investigated for the electrochemical detection of the useful analyte ascorbic acid using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry techniques. This work reveals the potential of the BiVO4/FeVO4 nanocomposite for applications in environmental disciplines as well as in biosensing.

A Mini Review: Antireflective Coatings ProcessingTechniques, Applications and Future Perspective

Antireflective coatings (AR) are widely applied to eliminate the unwanted surface reflections from the AR coated substrate. In different optoelectronic devices, AR coatings have potential usage in photovoltaic solar cells, sensors, display devices, automobile industries to reduce reflectance, glare and enhance light transmittance. Natural phenomenon inspires researchers, and they generate bionic AR coatings copying the nature such as moth eyes, or cicada wings to fabricate efficient light harvesting AR coatings. In the current review article, we analyse and evaluate critically the progress and recent development in the fabrication of AR thin films comprising organic coatings, inorganic coatings, polymer AR coatings and bionic AR coatings. We predominantly emphasise the AR coatings fabrication by different methods and pinpoints the technological challenges in their real-world reliability. Finally, we address the future challenges and potential strategies for their upcoming prospect.

Al2O3 Encapsulated Teflon Nanostructures with High Thermal Stability and Efficient Antireflective Performance

Scientific advancement is highly inspired and imitative of natural phenomenons, which exhibits extremely developed and well-organized nanostructures to cope with challenges under different environmental circumstances, such as moth eyes protuberances for efficient antireflective (AR) performance. Innovative researches have been performed in the past to exterminate the undesirable reflectance in common optical components and optoelectronic industrial applications by biomimetic and replicating moth eye nanostructures creating gradient effect using metal oxides, composites, or polymers in multilayer AR coatings. However, in few multilayer AR designs, the properties mismatch at interfaces, high cost, low mechanical durability, wetting issues, or thermal stability bounds their practical applicability. Herein, we develop an approach for fabricating efficient, high-performance Teflon (polytetrafluoroethylene [PTFE]) AR nanostructures for glass-based supporting materials. Nanotailoring, the morphology and structure of PTFE, have been efficaciously carried out for fabricating high-performance AR coatings according to predicted optical simulation. The total reflectance from polymer AR coating lessens to <0.05% in a visible wavelength range which according to our best knowledge seems to be the superior AR performance by a polymer coating ever reported. Furthermore, the fabricated polymer AR coatings are omnidirectional, mechanically durable, and thermally stable up to 200 °C. Moreover, we modify and tune the refractive index of PTFE from 1.34 to 1.156 by inducing porosity and changing deposition angle.