Complete surface coverage of ZnO nanorod arrays by pulsed electrodeposited CuInS2 for visible light energy conversion

Well-aligned ZnO nanorods were uniformly coated with a layer of CuInS2 nanoparticle photosensitizers using a tailored sequential pulsed electrodeposition. The formation of CuInS2-ZnO heterojunction with well-matched band energy alignment and the superior electron mobility in ZnO nanorods led to a remarkable 3.75 times improved photoelectrochemical performance of the electrode under visible light irradiation

Restoration of Liquid Effluent from Oil Palm Agroindustry in Malaysia using UV/TiO2 and UV/ZnO Photocatalytic Systems: A Comparative Study

In this study, we have employed a photocatalytic method to restore the liquid effluent from a palm oil mill in Malaysia. Specifically, the performance of both TiO2 and ZnO was compared for the photocatalytic polishing of palm oil mill effluent (POME). The ZnO photocatalyst has irregular shape, bigger in particle size but smaller BET specific surface area (9.71 m2/g) compared to the spherical TiO2 photocatalysts (11.34 m2/g). Both scavenging study and post-reaction FTIR analysis suggest that the degradation of organic pollutant in the TiO2 system has occurred in the bulk solution. In contrast, it is necessary for organic pollutant to adsorb onto the surface of ZnO photocatalyst, before the degradation took place. In addition, the reactivity of both photocatalysts differed in terms of mechanisms, photocatalyst loading and also the density of photocatalysts. From the stability test, TiO2 was found to offer higher stability, as no significant deterioration in activity was observed after three consecutive cycles. On the other hand, ZnO lost around 30% of its activity after the 1st-cycle of photoreaction. The pH studies showed that acidic environment did not improve the photocatalytic degradation of the POME, whilst in the basic environment, the reaction media became cloudy. In addition, longevity study also showed that the TiO2 was a better photocatalyst compared to the ZnO (74.12%), with more than 80.0% organic removal after 22 h of UV irradiation

One-dimensional TiO2 nanostructured photoanodes: from dye-sensitised solar cells to perovskite solar cells

This review presents one dimensional (1D) TiO nanostructured photoanodes for next generation solar cells such as dye-sensitised solar cells (DSCs) and perovskite solar cells (PSCs). Due to the unique morphological properties, 1D TiO nanostructures can act as express electron channels as well as light scattering layer, leading to improved charge transport properties, such as charge separation, electron injection, and electron lifetime, and light harvesting efficiency. As 1D TiO nanostructures are applied to solar cells, 1D TiO nanostructures should be further modified to overcome some drawbacks. In this review, we have described some solutions by introducing various 1D TiO synthetic methods and device fabrication processes for solar cell applications, where we have described some important surface engineering and hierarchical device design strategies that facilitate charge transport and light utilisation in 1D TiO nanostructured photoanode system

Resolve deep-rooted challenges of halide perovskite for sustainable energy development and environmental remediation

Metal halide perovskite (ABX3) has become a new class of fascinating nanomaterial that has attracted extensive interdisciplinary attention as a low-cost and easy to manufacture photocatalyst in the platform of solar energy conversion and environmental remediation. This is due to its appealing optimal band gaps, long carrier diffusion length, high carrier mobility, defect tolerance, unique chemical and optoelectronic properties. Nevertheless, their ionic crystal structures are unstable, therefore hindering practical application. In this review, we first introduce the unique structural and physical properties of metal halide perovskites. Subsequently, we examine the critical challenges faced by present halide perovskites, including (1) material instability, (2) Pb-toxicity, and (3) material defective structures. Next, we highlight the practical approaches being taken to resolve the bottlenecks of metal halide perovskites, particularly the adoption of (1) protonic solvents (i.e., HX; X = I or Br) for water splitting reaction, (2) mild protonic solvents for CO2 photoreduction, (3) functionalizing and encapsulation of perovskites, (4) engineering Pb-less/Pb-free material, and (5) defect remediation, followed by several methods to evaluate and quantify defect states. Then, we summarize a panorama of the latest progression of halide perovskites either in its pristine formed or hybridized formed used in photocatalysis, photoelectrochemical, and photovoltaic-photoelectrochemical systems. Lastly, this review is ended with a summary and some revitalized perspectives on the future directions for stable and efficient metal halide perovskite-based photocatalysis research. It is anticipated that this review provides a new research direction for future metal halide perovskite-based photocatalysis development

Green synthesis of gamma-valerolactone (GVL) through hydrogenation of biomass-derived levulinic acid using non-noble metal catalysts : A critical review

The distinct physicochemical properties and renewable origin of gamma-valerolactone (GVL) have provided opportunities for diversifying its applications, particularly as a green solvent, excellent fuel additive, and precursor to valuable chemicals. Among the related publications found in the SCOPUS database (≈172 in the last 10 years), we focused our effort to review the conversion of levulinic acid (LA) to GVL over non-noble metal catalysts and the corresponding mechanisms (≈30 publications) as well as the applications of GVL as a solvent, fuel additive, and platform chemical (≈30 publications) mostly in the last five years (some preceding publications have also been included due to their relevance and importance in the field). The use of non-noble metals (e.g., Cu and Zr) presents a greener route of GVL synthesis than the conventional practice employing noble metals (e.g., Pd and Ru), in view of their higher abundance and milder reaction conditions needed (e.g., low pressure and temperature without H 2 involved). The significance of the catalyst characteristics in promoting catalytic transfer hydrogenation of LA to GVL is critically discussed. Structural features and acid-base properties are found to influence the activity and selectivity of catalysts. Furthermore, metal leaching in the presence of water in catalytic systems is an important issue, resulting in catalyst deactivation. Various endeavors for developing catalysts using well-dispersed metal particles along with a combination of Lewis acid and base sites are suggested for efficiently synthesizing GVL from LA

Utilization of reduced graphene oxide/cadmium sulfide-modified carbon cloth for visible-light-prompt photoelectrochemical sensor for copper (II) ions

A newly developed CdS/rGO/CC electrode was prepared based on a flexible carbon cloth (CC) substrate with cadmium sulfide (CdS) nanoparticles and reduced graphene oxide (rGO). The CdS was synthesized using an aerosol-assisted chemical vapor deposition (AACVD) method, and the graphene oxide was thermally reduced on the modified electrode surface. The existence of rGO in the CdS-modified electrode increased the photocurrent intensity of the CdS/rGO/CC-modified electrode by three orders of magnitude, compared to that of the CdS/ITO electrode and two orders of magnitude higher than the CdS/CC electrode. A new visible-light-prompt photoelectrochemical sensor was developed based on the competitive binding reaction of Cu2+ and CdS on the electrode surface. The results showed that the effect of the Cu2+ on the photocurrent response was concentration-dependent over the linear ranges of 0.1–1.0 μM and 1.0–40.0 μM with a detection limit of 0.05 μM. The results of a selectivity test showed that this modified electrode has a high response toward Cu2+ compared to other heavy metal ions. The proposed CdS/rGO/CC electrode provided a significantly high potential current compared to other reported values, and could be a practical tool for the fast, sensitive, and selective determination of Cu2+

GaP-ZnS Multilayer Films:Visible-Light Photoelectrodes by Interface Engineering

In the field of solar water splitting, searching for and modifying bulk compositions have been the conventional approaches to enhancing visible-light activity. In this work, manipulation of heterointerfaces in ZnS-GaP multilayer films is demonstrated as a successful alternative approach to achieving visible-light-active photoelectrodes. The photocurrent measured under visible light increases with the increasing number of interfaces for ZnS-GaP multilayer films with the same total thickness, indicating it to be a predominantly interface-driven effect. The activity extends to long wavelengths (650 nm), much longer than those expected for pure ZnS and also longer than those previously reported for GaP. Density functional theory calculations of ZnS-GaP multilayers predict the presence of electronic states associated with atoms at the interfaces between ZnS and GaP that are different from those found within the layers away from the interfaces; these states, formed due to unique bonding environments found at the interfaces, lead to a lowering of the band gap and hence the observed visible-light activity. The presence of these electronic states attributed to the interfaces is confirmed by depth-resolved X-ray photoelectron spectroscopy. Thus, we show that interface engineering is a promising route for overcoming common deficiencies of individual bulk materials caused by both wide band gaps and indirect band gaps and hence enhancing visible-light absorption and photoelectrochemical performance

Gold-silver@TiO2 nanocomposite-modified plasmonic photoanodes for higher efficiency dye-sensitized solar cells

In the present investigation, gold–silver@titania (Au–Ag@TiO2) plasmonic nanocomposite materials with different Au and Ag compositions were prepared using a simple one-step chemical reduction method and used as photoanodes in high-efficiency dye-sensitized solar cells (DSSCs). The Au–Ag incorporated TiO2 photoanode demonstrated an enhanced solar-to-electrical energy conversion efficiency of 7.33%, which is ∼230% higher than the unmodified TiO2 photoanode (2.22%) under full sunlight illumination (100 mW cm−2, AM 1.5G). This superior solar energy conversion efficiency was mainly due to the synergistic effect between the Au and Ag, and their surface plasmon resonance effect, which improved the optical absorption and interfacial charge transfer by minimizing the charge recombination process. The influence of the Au–Ag composition on the overall energy conversion efficiency was also explored, and the optimized composition with TiO2 was found to be Au75–Ag25. This was reflected in the femtosecond transient absorption dynamics in which the electron–phonon interaction in the Au nanoparticles was measured to be 6.14 ps in TiO2/Au75:Ag25, compared to 2.38 ps for free Au and 4.02 ps for TiO2/Au100:Ag0. The slower dynamics indicates a more efficient electron–hole separation in TiO2/Au75:Ag25 that is attributed to the formation of a Schottky barrier at the interface between TiO2 and the noble metal(s) that acts as an electron sink. The significant boost in the solar energy conversion efficiency with the Au–Ag@TiO2 plasmonic nanocomposite showed its potential as a photoanode for high-efficiency DSSCs

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data