Photoactive catalysts for treatment of air pollutants: a bibliometric analysis.

In recent years, photocatalysts are becoming attractive to researchers in exploring their application for treatment of air pollutants. Exposure to ultra-violet visible (UV-VIS) light on photocatalysts often makes them active in decomposing various toxic materials into less or environment-friendly products. Thus, identification, as well as simple synthesis and processing of photocatalysts, could ultimately lead to technologies for the cost-effective mitigation of environmental hazards. A bibliometric analysis has been carried out here to understand and assess the development in photocatalyst research. The data retrieved from the Scopus database on the topic for 2000-2020 were analyzed to investigate the research activities of the past to foresight the future. Various facets of bibliometry were investigated to produce this holistic article. The contribution of various countries, institutions, and authors were investigated. Numerous facets of photocatalyst such as types of photocatalysts, their modification through metal and non-metal doping, their pollutants treatment potency, types of reactors for photocatalysis, factors influencing treatment performance, and models used for designing reactors were examined. In brevity, substantial growth was observed in the last two decades. Contribution of China, the USA, Japan, and India were notable. Chinese universities contributed majorly to the research. Applied Catalysis B: Environmental Journal was the topic's main journal and Titanium dioxide was the hotspot in photocatalytic research. The research development, problem disclosure, adopted strategies, and materials explored on the photocatalysis for air pollution treatment over recent years across the world could be insightful to the researchers and eventually will be beneficial to formulate new research strategies.

Case study on the use of image analysis for the simple and inexpensive colorimetric detection of Fe(iii) in water.

In the present work, we have reported a simple and cost effective colorimetric method for the detection of Fe(iii) in water. The method is based on the color change through the formation of an Fe(iii)-glycine complex at room temperature. This type of complex formation produces an intense color due to the ligand to metal charge transfer (LMCT). The rate of this type of complex formation depends appreciably on the Fe(iii) concentrations. An important aspect of the present work is that here the image analysis technique has been used successfully for the discrimination of the color obtained by the variation of the Fe(iii) concentration. The fundamental spectro-photochemical studies on the colorimetric detection of Fe(iii) by forming a metal ligand complex and thereafter the discrimination of the complex through image analysis can provide effective insight into the development of cost effective devices for the detection of liquid phase analytes.

Miniaturized nanohole array based plasmonic sensor for the detection of acetone and ethanol with insights into the kinetics of adsorptive plasmonic sensing.

The present work demonstrates development of a miniaturized plasmonic platform comprised of a Au nanohole array (NHA) on a Si/Si3N4 substrate. Plasmonic responses of the NHA platform, which is coated with Cu-benzenetricarboxylate metal organic framework (MOF), are found to be promising even towards 500 nmol mol-1 (ppb) of acetone or ethanol vapors at room temperature. The sensing characteristics are further investigated by varying the operating temperature (296 K to 318 K) of the sensor and the concentrations of vapors (500 nmol mol-1 to 320 µmol mol-1). The plasmonic responses for the sensors are correlated with the adsorption of vapors on the MOF surface and modeled in accordance to Langmuir-type adsorption. Kinetic parameters are estimated for the adsorption of fixed concentrations of acetone and ethanol vapors within the studied operating temperature range. The linear variation of characteristic response time constants with the operating temperature provides Arrhenius activation energies for the adsorption of acetone and ethanol vapors. The comparatively lower activation energy estimated for the adsorption of ethanol results in faster and more sensitive response of the sensor towards that analyte. The plasmonic sensor for the detection of nmol mol-1 level acetone and ethanol vapors at room temperature along with the kinetic correlation on plasmonic response with the adsorption of the analytes described herein offer new insights to existing reports on surface modification and plasmonic detection.

Discrimination of 1- and 2-Propanol by Using the Transient Current Change of a Semiconducting ZnFe2 O4 Chemiresistor.

A semiconducting metal oxide (SMO) chemiresistor (ZnFe2 O4 ) is used for discriminating two isomeric volatile organic compounds (VOCs), namely 1- and 2-propanol. The transient current of the SMO chemiresistor is correlated with the aerobic oxidation of organic vapors on its surface. The changes in transient current of the ZnFe2 O4 chemiresistor are measured at different temperatures (260-320 °C) for detecting equal concentrations (200 ppm) of the two structural isomers of propanol. The transient current of ZnFe2 O4 reflects a faster oxidation of 2-propanol than 1-propanol on the surface. First-principles calculations and kinetic studies on the interaction of 1- and 2-propanol over ZnFe2 O4 provide further insight in support of the experimental evidence. The calculations predict more spontaneous adsorption of 2-propanol on the (111) surface of ZnFe2 O4 than 1-propanol. Kinetic parameters for the oxidation of isomeric vapors are estimated by modelling the transient current of ZnFe2 O4 using the Langmuir-Hinshelwood reaction mechanism. The faster oxidation of 2-propanol and comparatively lower activation energy for the respective process over ZnFe2 O4 is justified in accordance to the chemical structures of vapors. The findings have strong implications in exploring a new technique for discriminating isomeric VOCs, which is significant for environmental monitoring and medical applications.