Current Analytical Chemistry - Volume 19, Issue 1, 2023

Background: Water is polluted daily with biological and chemical toxins that can seriously threaten human health, animals and ecosystems. The regular identification and monitoring of biological and chemical toxins in water resources are the first steps of the preventive method. The devices used in traditional detection methods such as adsorption and chromatography combined with mass spectrometry are not easy to transport for analysis and involve laborious preliminary sample preparation steps. However, the developments in nanosensors prepared with nanomaterials provide solutions to these challenges. Nanomaterials such as gold nanoparticles, graphene and quantum dots are often preferred for the surface preparation of plasmonic nanosensors for the selective, sensitive and label-free detection of very low concentrations of pollutants in water. Methods: There are different plasmonic nanosensors such as electrochemical, colorimetric and optical sensors prepared using different nanomaterials for the determination of environmental pollutants. These serious nanosensors have many advantages and disadvantages. In this review, the use of different nanomaterials in different types of plasmonic nanosensors for the determination of environmental pollutants, their modifications and their effects on performance in terms of signal enhancement will also be discussed. Results: When the studies in the literature are examined, although many articles have been published on the detection of pollutants in water, the number of publications specific to nanomaterial based plasmonic nanosensors for detection is quite limited. In this review, we focused on using different nanomaterials to prepare nanosensor surfaces for the detection of environmental pollutants and the preparation, optimization, experimental analysis and application areas of different plasmonic nanosensors made in the literature for detection methods. Conclusion: Recently, nanomaterials such as gold nanoparticles, graphene and quantum dots have been preferred for the preparation of surfaces in plasmonic nanosensors. Nanomaterials have important plasmonic properties and are preferred for the selective, sensitive and label-free detection of trace pollutants in water. In studies conducted in the literature, it has been observed that environmental pollutants such as toxins, bacteria, heavy metal ions, and pesticides, especially in water, are determined and analyzed. In this review, it was observed that the low detection limit and sensitive and selective analyses were performed with nanomaterial-based nanosensors. The current review includes the preparation and application studies of nanomaterial based plasmonic nanosensors, especially for the detection and quantification of various trace pollutants in water.

Availing diseases as warfare began before humans learned that microorganisms are involved in the dissemination of infections. In the past, war brigades had the intention to weaken rival groups by using festering corpses with the premeditated purpose of causing disease. Nowadays, the unfortunate improvement of biowarfare is indubitably linked to our extensive collaborative work in exploring the use of microorganisms and their derivatives to create products and services that are beneficial to society. Natural defense barriers such as innate immunity and the immune specific adaptive response come to mind when thinking of bacteria and virus potentially being operated as tools for biological warfare. On the other hand, some bacterial toxins disrupt the immune cell functions and others do not trigger sufficient immune response, thus being not suitable for immunotherapy applications. As an alternative to these drawbacks, the systematic evolution of ligands by exponential enrichment (SELEX) develops specific nucleic acid or peptides for a variety of targets, including toxins. These aptamers are efficiently produced in vitro using enzymes or synthetical synthesis within days, low cost, and reproducibility. Oligonucleotide aptamers are a nanotechnological high spot because of their physicochemical characteristics such as resilience, pH responsiveness, and addressability at the nanoscale. Additionally, they induce no immunogenicity and can be modified by association with nanoparticles to increase their stability in biological environments. In this review, we explore the recent trends and perspectives on biosensor construction based on oligonucleotide aptamer-conjugated nanomaterials as effective biosecurity devices and their relevance to the development of risk-assessment protocols that could be used as intelligent barriers to provide continuous, cheap, and easy monitoring to prevent unexpected attacks.

Background: Hydrazine is a well-known hepatotoxic, mutagen, and carcinogen. It adversely affects not only the liver, DNA, and kidney but the central nervous system also. As per the record of the Environmental Protection Agency (EPA), the United States, the optimum concentration of it has been permitted in sewage and industrial and agricultural effluents is 0.1 ppm. Therefore, monitoring hydrazine concentration is essential at the trace level. This review focuses on the preparation, characterization, and application of graphene-based nanomaterials for the development of electrochemical sensors for hydrazine sensing. Methods: Several literature reports over the last decade, i.e., 2010 to 2021, have been tried to summarize the development of different electrochemical sensors using graphene-based nanomaterials for the detection of hydrazine in water and other environmental samples. The performance of several reported modified electrodes has been reviewed in terms of limit of detection, linear range, selectivity, etc. Results: Graphene-based nanomaterials/nanocomposites offer a new path toward the development of high-performance electrochemical sensors due to their greater active surface area and good electron transference property. Furthermore, these nanostructures have defects in edges, and they can be expected to show more reactivity towards chemical species compared to pristine graphene. However, these novel graphene nanostructures have been scantily explored in the development of electrochemical sensors. Conclusion: The review presents that graphene-based nanomaterials offer excellent electrocatalytic and electrochemical behavior toward hydrazine detection. The performance of fabricated electrochemical sensors has been compared in terms of linear range, limit of detection, stability, and sensitivity. Still, no commercialized electrochemical sensor is available and there is enough scope to synthesize an efficient graphene-based nanomaterial to develop a portable and on-site electrochemical sensor for hydrazine detection.

Background: Nanomaterials derived from sustainable and biodegradable polymers are currently the most attractive materials. Polymeric nano-biocomposites (PNBCs) are a specific class of materials derived by combining nanosized fillers with polymer materials, and the most commonly used nano-fillers are hydroxyapatite, organic or inorganic metal nanoparticles, clays, etc. Methods: Many recent research works have focused on utilizing biopolymer-based hydrogel materials for the fabrication of analyte sensors and electrode modifiers due to their high permeability and faster mobilization of electrons. Such biopolymer hydrogels utilize newer printing methods in electrode prototyping, which renders portable, flexible, and advanced bioelectronics sensors with high-performance characteristics. Few researchers have also stated the use of polyaniline reinforced biocomposites for fabricating electrochemical sensors and actuators because of their unique properties, making them a potential material choice for electronics applications. Results: Nanoparticles of polyaniline improve the detection limit and sensitivity of the sensor even when used for recognizing a single molecule. Bionanocomposites possess excellent thermo-mechanical properties in the designed nanocomposite, even at low nanoparticle concentrations. These materials possess higher hardness and stability, giving rise to excellent mechanical characteristics. Furthermore, incorporating nanoparticles into a biopolymeric matrix can enhance its electrical conductivity, barrier properties, and consistency. Also, the powerful interaction between biopolymers and functional groups of nanoparticles increases the strength of bionanocomposites. Conclusion: Nano-biocomposites-based biosensors were found to possess high specificity, sensitivity, and a wider target spectrum. The current review discusses the use of sustainable and renewable biocomposites for the preparation of biosensors and actuators, their properties like sensitivity, the limit of detection, advantages over the synthetic material, and environmental hazards.

Background: In this study, Carbon Nanotubes (CNT) were synthesized by the CVD method at 950°C. CNT and metal ZnO nanocomposites synthesized by ball mill procedure were examined. Stability of nanocomposite was attained by cationic Ion Liquid (IL), 1-tetradecyl-3 methylimidazolium chloride, structural morphology material characterized by Fourier Transform Infrared (FTIR) spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), and Ultraviolet- Visible (UV-Vis) spectroscopy. Furthermore, these materials were analyzed by Energy Dispersive X-ray spectroscopy (EDX) to examine the percentage of elemental composition. It was found that Current-Voltage (I-V), characterized by electrical properties, was highly responsive to resistance variation, and easy recoverable high sensitivity was the main feature of the CO2 gas sensing properties. Objective: This study aimed at combining carbon nanotube and zinc oxide nanoparticles in different ratios and optimizing coating methods used for sensor applications. Methods: CNT was synthesized by the chemical vapor deposition method, and zinc nanoparticle was developed by the ball mill method. Moreover, spin coating and dip coating methods were optimized on a glass surface. Results: FTIR spectrum results revealed that the existing hydroxyl group and C group of CNT-ZnO nanoparticles were covered by the surface-active site of ZnO. The size and composition of the CNTZnO were confirmed by FESEM EDAX studies. The absorption and transmittance wavelengths of CNT-ZnO nanoparticles were recorded by UV-Visible spectroscopy. The I-V property showed that the drain current and voltages were varied by gas, implying that materials were suitable for applications. Conclusion: This module can be used to monitor CO2 gas application instruments with the help of software. In the future, this module and techniques could be used to study stress sensors and piezoelectric applications.

Background: Capillary electrophoresis (CE) has found a wide range of applications because of its high separation efficiency, low expense, short analysis time and minimal sample volume requirement. The tobacco quality depends on the nature and quantity of numerous substances. CE has been applied in the constituent analysis of tobacco and tobacco products for quality control and research. Methods: The advances in the applications of CE to tobacco analysis are reviewed. The main subjects cover the separation modes of CE, the detection techniques of CE, sample preparations and the applications of CE in the measurements of various constituents in tobacco samples. In addition, the CE-based metabonomic investigation of tobacco is also introduced. Results: Capillary zone electrophoresis, micellar electrokinetic chromatography, capillary isotachophoresis, capillary gel electrophoresis, capillary electrochromatography and non-aqueous CE have been applied in the determination of a variety of constituents in tobacco and tobacco products. The assayed substances include alkaloids, amines, saccharides, organic acids, inorganic ions, phenols, phenolic acids, flavonoids, amino acids, peptides, proteins, hormones, agricultural chemicals, etc. Conclusion: This review demonstrates that CE is a promising analytical technique in tobacco analysis. It is anticipated that CE will find more applications in tobacco investigations.