Current Analytical Chemistry - Volume 17, Issue 5, 2021

Background: Photocatalytic hydrogen evolution from water splitting using photocatalyst semiconductors is one of the most promising solutions to satisfy the increasing demands of a rapidly developing society. CdS has emerged as a representative semiconductor photocatalyst due to its suitable band gap and band position. However, the poor stability and rapid charge recombination of CdS restrict its application for hydrogen production. The strategy of using a cocatalyst is typically recognized as an effective approach for improving the activity, stability, and selectivity of photocatalysts. Introduction: Solar-driven photocatalytic hydrogen production from water splitting is one of the most promising solutions to satisfy the increasing demands of a rapidly developing society. CdS has emerged as a representative semiconductor photocatalyst due to its suitable band gap and band position. However, the poor stability and rapid charge recombination of CdS restrict its application for hydrogen production. The strategy of using a cocatalyst is typically recognized as an effective approach for improving the activity, stability, and selectivity of photocatalysts. In this review, recent developments in CdS cocatalysts for hydrogen production from water splitting under visible-light irradiation are summarized. In particular, the factors affecting the photocatalytic performance and new cocatalyst design, as well as the general classification of cocatalysts, are discussed, which includes a single cocatalyst containing noble-metal cocatalysts, non-noble metals, metal-complex cocatalysts, metal-free cocatalysts, and multi-cocatalysts. Finally, future opportunities and challenges with respect to the optimization and theoretical design of cocatalysts toward the CdS photocatalytic hydrogen evolution are described. Methods: This review summarizes the recent developments in CdS cocatalysts for hydrogen production from water splitting under visible-light irradiation. Results: Recent developments in CdS cocatalysts for hydrogen production from water splitting under visible-light irradiation are summarized. The factors affecting the photocatalytic performance and new cocatalyst design, as well as the general classification of cocatalysts, are discussed, which includes a single cocatalyst containing noble-metal cocatalysts, non-noble metals, metal-complex cocatalysts, metal-free cocatalysts, and multi-cocatalysts. Finally, future opportunities and challenges with respect to the optimization and theoretical design of cocatalysts toward the CdS photocatalytic hydrogen evolution are described. Conclusion: The state-of-the-art CdS for producing hydrogen from photocatalytic water splitting under visible light is discussed. The future opportunities and challenges with respect to the optimization and theoretical design of cocatalysts toward the CdS photocatalytic hydrogen evolution are also described.

Background: Many antibiotics were widely used as medication based on their distinctive features. Among them, sulphonamides were commonly and mainly used for bacterial treatment, however, the recalcitrant nature makes them difficult to dispose of. Hence, their interaction with the environment and analytic technique requires considerable attention globally. Objective: Therefore, this review aimed to provide a detailed discussion about environmental as well as human health behavior and analytic techniques corresponding to sulphonamides. Methods: Various results and discussion were extracted from technical journals and books published by different researchers from all over the world. The cited bibliographic references were intentionally investigated in order to extract relevant information related to the proposed work. Results: In this review, the determination techniques such as UV-spectroscopy, Enthalpimetry, Immunosensor, Chromatography, Chemiluminescence, Photoinduced fluorometric determination and Capillary electrophoresis for sulphonamide determination were discussed in detail. Among them, High-performance liquid chromatography (HPLC) and UV-spectroscopy were effective and extensively used for screening sulphonamide. Conclusion: Knowing the quantification and behavior of sulphonamide in aqueous solution is mandatory to opt for the suitable wastewater treatment required. Hence, choosing appropriate high precision and feasible screening techniques is necessary, which can be attained with this review.

Background: Nowadays, effective wastewater treatment has become a hot research topic in the field of environment. A series of novel activated carbon/ titanium dioxide (AC/TiO2) composites at various weight ratio were synthesised using the sol-gel method and were characterised using XRD, SEM-EDX, FT-IR, TGA and surface area analysis. Methods: TiO2 particles were successfully incorporated on the AC surface and were mainly composed of Ti, O and C atoms. The AC/TiO2 composites were made up of spherical TiO2 particles agglomerated on the smooth tubular and porous structure of AC. The photocatalytic efficiency was influenced by the weight proportion of AC:TiO2 and the degradation process was attributed to the adsorption and photocatalytic processes. Results: It was found that 2.5 g/L AC/TiO2 at a weight ratio of 3:1 on an initial Malachite Green concentration of 10 mg/L at 50°C led to a degradation efficiency of 96.3% in 7.5 minutes under a halogen lamp. A chemical oxygen demand (COD) removal of 96.7% was also recorded. Reusability of the AC/TiO2 composite and kinetic study of the photodegradation of Malachite Green were also investigated. The recycled AC/TiO2 composite achieved high catalytic performance (83.1%) after one catalytic cycle. Conclusion: The degradation kinetics of Malachite Green at various solution temperatures were fitted to the pseudo-first-order reactions and the activation energy for the degradation of Malachite Green was 21.48 kJ/mol. This work demonstrated that AC/TiO2 composite is a promising material for photocatalytic degradation of organic dyes.

Background: A simple, low cost and highly sensitive catalytic hydrogen wave (CHW) method has developed for the investigation of Manganese(II) in ammonium 4-phenylpiperazine-1- dithiocarbamate and ammonium 4-benzylpiperidine-1-dithiocarbamate in various environmental and biological samples using D.C. polarography. This procedure was based on the reaction of Mn(II) in APP-DTC/ABP-DTC in the presences of NH4Cl-NH4OH medium at pH 6.6 and 7.2 respectively. The resulting oxidation signals were obtained at -0.78 V and -0.64 V vs SCE, owing to the CHWs. Different experimental conditions such as pH effects, background electrolyte (NH4Cl-NH4OH) effects and DTCs and Mn(II) ion effects have been studied. The current method was effectively employed for the testing of Mn(II) in different environmental and biological samples and attained recovery percentages (95-99%) are comparable to the Atomic Absorption Spectrophotometry (AAS) method. Methods: Direct current polarography, model CL-357 and CL-25 (Elico Private Ltd, Hyderabad, India), Shimadzu AA 6300 spectrometer furnished thru a deuterium background corrector and hollow cathode lamp, at corresponding wavelengths (resonance line) with an air acetylene flame. The experimental guidelines remained those suggested by the makers. Results: The effect of NH4Cl between 0.1 to 0.7 M on the nature of CHW at DME, maintaining the concentrations of Mn(II) at 4.0 ppm and DTC at 3.0 mM (APP-DTC/ABP-DTC) then adjusting the pH to 6.6/7.2 (APP-DTC/ABP-DTC). The polarograms were well-defined in NH4Cl of 0.4/0.5 M for APP-DTC/ABP-DTC. The peak height decreased beyond this concentration and therefore 0.4/0.5 M (APP-DTC/ABP-DTC) concentrations was kept for more analysis. At fixed concentration of DTC, (3.0 mM APP-DTC/ABP-DTC) and (0.4/0.5 M for APP-DTC/ ABP-DTC) NH4Cl adjusting the pH to 6.6/7.2 respectively the metal ion concentration of the Mn(II) was adjusted between 0.05 to 7.0 ppm and results of CHWs were studied. The peak current increased linearly with Mn(II) concentration in the range 0.05 to 4.0 ppm for both DTCs. However, the sensitivity of the method was more with APP-DTC/ABP-DTC because of strong complex of Mn(II) and increased catalytic activity. Conclusion: The developed CHW method is highly sensitive, simple and spontaneous for the analysis of Mn(II) in environmental and biological samples. The polarographic reduction of Mn(II) in aqueous solutions in the attendance of DTC displays a catalytic wave as a role of pH, concentration of supporting electrolyte and metal ion. The graphs of catalytic signals as a role of the concentration of dithiocarbamate shows that the signals do not vary linearly with the concentration of dithiocarbamate which the characteristic of Brdicka CHWs. It is presumed that the dithiocarbamate complexes with metal ions involve adsorption process and can be described by a Langmuir adsorption isotherm and the plot of CL/ip Vs CL should be linear. The CHW method is free from interference effect avoiding the removal stages which made towards placing among utmost sensitive methods for the analysis of Mn(II) in different Environmental and Biological samples.

Background: Environmental pollution has become a worldwide problem. In this regard, decontamination of wastewater and removal of organic pollutants from environment by photocatalysis has emerged as one of the most promising techniques from the last few decades. Objective: In order to degrade the harmful pollutants from wastewater, highly efficient non-toxic Fe2(WO4)3 photocatalyst was synthesized via co precipitation method. The photocatalytic activity of the as-synthesized material was examined by degrading methylene blue (MB) under various conditions. Methods: For this purpose, different experimental parameters such as catalyst load, model compound concentration, H2O2 percentage and pH value were adjusted for excellent degradation of MB, and response surface methodology (RSM) along with central composite design (CCD) as adequate model was employed for optimization process. Results: The experimental results revealed that 1.2 g/L of catalyst load, 10 g/L for dye concentration, 0.5% of H2O2 and pH 7 were found to be the optimized values for the aforesaid parameters. The optimized values led to 93% degradation of MB under UV light exposure. In addition, toxicological studies were analysed using various bioassays for both, untreated and treated samples and a conspicuous reduction (69.12%) in the toxicity level was observed. Conclusion: The study signifies that this method is useful for reclamation of water, making it useful for industry and irrigation.

Background: Empty fruit bunch (EFB) is a type of biomass waste product formed during the production process of palm oil. In the present work, EFB was used to prepare a cellulose-graft-copolymer which can be converted into poly(amidoxime)-poly(hydroxamic acid) ligands suitable for the removal of heavy metals from electroplating wastewater. Methods and Results: Poly(amidoxime)-poly(hydroxamic acid) ligands were synthesized from the poly(acrylonitrile-co-methyl acrylate) grafted palm cellulose and were analyzed via FT-IR and FESEM. The binding capacity (qe) with the metals ions such as copper (Cu²⁺), iron (Fe³⁺), cobalt (Co²⁺), nickel (Ni²⁺) and lead (Pb²⁺) were 341, 290, 284, 204 and 482 mg g^-1, respectively at pH 6. The pseudo-first-order kinetic model is fitted with the results confirming heavy metal adsorption. The isotherm study was conducted using a linear plot of the Langmuir isotherm where results were significantly different from the experimental value (maximum adsorption, qe), indicating that adsorption does not occur on a single layer. However, the coefficient of the correlation values obtained using the Freundlich isotherm model was acceptable (R²>0.99), and it was concluded that adsorption was multilayered with some metal ions. Conclusion: The polymeric ligands synthesized here showed excellent adsorption of heavy metals from electroplating wastewater containing a notable amount of copper and iron metal ions.

Background: Kraton/polyaniline ionomer is synthesized and further characterized by electrochemical studies to check the redox properties of the material. Ion exchange capacity, proton conductivity, and selectivity of the synthesized membrane were determined. And found that the membrane was selective for Cu (II) ions. Methods: The dry Kraton membranes were weighed and kept in 25 mL of 10 % prepared aniline solution in a conical flask for 5, 10, 15, and 20 minutes below 10 0C for socking. The prepared solution of 30 mL of 0.1 M potassium peroxydisulfate was added in a conical flask at constant stirring below 10 0C for half an hour. Finally, the aluminum foil-covered conical flask was kept in the refrigerator for 24 h and modified Kraton membranes were weighed again before carrying out further studies. Results: The membrane was characterized by some physicochemical methods like SEM, TGA, T-IR, IEC, proton conductivity and selectivity sorption studies. An ionomeric membrane of Kraton polymer was developed as reported earlier. Kraton membrane showed the IEC of 1.9 meq·g-1. The FTIR spectrum of Kraton/PANI film reveals that weight loss up to 400°C may be found because of the thermal degradation of composite substances. Conclusion: Ion-selective potentiometric was carried out using the self-prepared ion-selective membrane electrode. The membrane was prepared by solution casting method. The membrane was characterized by some physicochemical methods like SEM, TGA, T-IR, IEC, proton conductivity and selectivity sorption studies. On the basis of selectivity studies, the composite material was found selective for Cu (II) ion. A copper ISME was successfully fabricated using the solution casting method. The ISME possessed good selectivity, linearity, working pH range, and response time which was also used as an indicator electrode for the titration of copper using EDTA.

Background: Nano perovskite-type structures as denoted by ABO3 (A= RE) have been popular targets of fundamental investigations since they exhibit a wide variety of physical properties depending upon the chemical composition, defects and small changes in atomic arrangements. Methods: GdAlO3: Co²⁺ (1, 3 &9 mol %) was synthesized using the solution combustion method by using stoichiometric quantities of gadolinium nitrate [Gd (NO3)3], aluminium nitrate (Al (NO3)2, and cobalt nitrate Co(NO3)2. Results: The morphology, structure and particle size of the prepared GdAlO3: Co²⁺ sample were characterized by transmission electron microscope (TEM) image. The Fourier transform infrared (FT-IR) spectral analysis confirmed that the as-prepared powder was in pure state. Electrochemical impedance measurements (EIS) of different GdAlO3: Co²⁺ samples were measured vs. Ag/AgCl in the frequency range of 1 Hz to 1 MHz with AC amplitude of 5 mV at steady-state which clearly indicated that Co²⁺ dopant is a successful doping material for the fabrication of supercapacitors. Conclusion: Electrochemical impedance measurements (EIS) of different GdAlO3: Co²⁺ samples were measured vs. Ag/AgCl in the frequency range of 1 Hz to 1 MHz with AC amplitude of 5 mV at steady-state which clearly indicated that Co²⁺ dopant is a successful doping material for the fabrication of supercapacitors. From a future perspective, we believe that GdAlO3: Co²⁺ composite material could be a promising electrode material for the fabrication of various sensors, supercapacitors and solar cells.

Background: The organic effluents from industry remain one of the reasons for water contamination. By the natural degradation process, it is difficult to remove this; hence finding an effective solution for this is inevitable. TiO2-based materials have received enormous attention in the area of semiconductor photocatalysis, particularly for the degradation of organic dyes. This work emphasizes on the degradation of two industrial dyes methylene blue and rhodamine blue by visible light irradiation of TiO2 based nanoparticles. Methods: In the present study, pristine and La³⁺ and Ce³⁺ doped nanotitania were synthesized by the sol-gel method. The samples under investigation were characterized using X-ray diffraction, Transmission electron microscopy to study the variation of crystallite size and UV-Visible absorption spectroscopy. Results: The increase in crystallite size for the pristine samples calcined at various temperatures confirms the effect of calcination temperature. Also, the doping reduced the size of the synthesized nanotitania. Visible light extended absorption spectra have been observed for the calcined samples and Ce³⁺ doped nanotitania. The La³⁺ doped sample showed a blue shift in the absorption confirming quantum confinement. The photocatalytic activity in the context of degradation of certain industrial dyes such as methylene blue and rhodamine blue has been investigated for the samples. Conclusion: The studies found that nanotitania consisting of mixed anatase-rutile phase exhibits higher degradation efficiency than that of pure anatase or rutile samples. Besides, photocatalytic dye degradation has been significantly improved for Ce³⁺ doped nanotitania compared to the pristine sample.

Background: Nanomaterials-based cancer therapy plays a significant role in increasing the therapeutic efficiency of anticancer drugs, reducing side effects and targeted delivery of the drug payloads. The present study was aimed to enhance the anticancer effect of a novel dipeptide isolated from marine sponge-associated Bacillus pumilus AMK1 by formulating with Zinc oxide (ZnO) nanoparticles for the effective treatment against HepG2 liver cancer cells. Methods: ZnO nanoparticles were synthesized by chemical method and size of the nanoparticle was characterized by Scanning electron microscope, X-Ray diffraction and Fourier-transform infrared spectroscopy. Furthermore, ZnO nanoparticles were conjugated with the isolated dipeptide and evaluated for anticancer activity. In addition, distinct morphological changes were observed by performing apoptotic staining methods such as propidium iodide staining and acridine orange/ ethidium bromide staining. Furthermore, embryotoxic and teratogenic effects of conjugated dipeptide on the development of zebrafish embryo were investigated in this study. Results: It was observed that conjugated dipeptide showed enhanced cytotoxicity against HepG2 liver cancer cells without any toxic effect on normal liver cells. ZnO with dipeptide showed significant higher apoptosis of liver cancer cells, with around 19% in early apoptosis and 53% in late apoptosis stage. The obtained results suggest that ZnO nanoparticle conjugated dipeptide initiated cytotoxicity through apoptotic death in HepG2 cells. The embryotoxic studies in zebrafish embryos revealed the LC50 197.0 μg/mL. These findings suggest that conjugated dipeptide affected the development of zebrafish embryos only at relatively higher concentrations. Conclusion: The experimental results demonstrate that ZnO nanoparticle conjugated dipeptide has the potential to improve anticancer efficacy against liver cancer cells by inducing apoptosis in cancer cells without any effect on normal liver cells.

Background: Infrared (IR) spectroscopy is a well-established technique for the structural elucidation of simple as well complex molecules. It has wide applications in the qualitative as well as quantitative determination of proteins in different samples. It provides a clear picture of the primary, secondary, or tertiary structure of a protein. Infrared radiations are used to assess different vibrational modes arise from variations in the structural components of a protein. Methods: Various research reports were collected from search engines like Sciencedirect, Pubmed, Researchgate, and Google Scholar. They were further studied thoroughly and important findings/ data were compiled and represented with tables and figures. The procured data, which includes bandwidth, frequency and intensity, have been employed to elucidate the structure of a protein. Results: It was found from various reports that Fourier transforms infrared spectroscopy (FT-IR) has widely been utilized to predict the secondary structure of the protein in the past few years. FTIR has the ability to trace out various structural modifications in the protein structure that originate due to interactions with other materials. It is also evident that it can be utilized to quantify the proteins in a variety of samples. Conclusion: The present review describes the basic principle and the instrumentation of IR spectroscopy and its advancements. Beyond this, various applications of this technique in determining protein structure and quantification in different materials such as food stuffs, biotechnological products and biological fluids have also been summarized.

Background: Dyes have been a blessing to mankind owing to their numerous applications in several industries ranging from textile, food, pharmaceuticals, and paper to leather, and many more. At the same time, these dyes pose a potential threat to mankind, when they are present beyond their permissible limits. This review covers the extraction and determination methods of dyes in different matrices. Introduction: Methylene blue (MB), rhodamine B (RB), and crystal violet (CV) are the three cationic dyes discussed in this review. These dyes can pose a potential threat to biota beyond their permissible limits. Methods: This review article mentions different analytical methods and extraction techniques involved in the determination of dyes. Result: Almost all the analytical methods reported in this article involve proper extraction of the analyte, which finds a place in this review article. Spectrophotometric and electrochemical methods are cost-effective, although the former is less sensitive than the latter. Liquid chromatography (LC) and liquid chromatography coupled with mass spectrometry (LC/MS) are capable of simultaneously determining a number of dyes. Conclusion: This review also offers a compilation of different mobile phase combinations that have been used for the quantitative analysis of these three dyes. The article also contains a list of different solvents for liquid-liquid extraction and different types of sorbent materials used during the solid-phase extraction of the reviewed dyes.