Inkjet-printed disposable metal complexing indicator-displacement assay for sulphide determination in water

Optical Chemosensors Synthesis and Appplication for Trace Level Metal Ions Detection in Aqueous Media: A Review

In recent years, the development of optical chemosensors for the sensitive and selective detection of trace level metal ions in aqueous media has garnered significant attention within the scientific community. This review article provides a comprehensive overview of the synthesis strategies and applications of optical chemosensors dedicated to the detection of metal ions at low concentrations in water-based environments. The discussion encompasses a wide range of metal ions, including but not limited to heavy metals, transition metals, and rare earth elements, emphasizing their significance in environmental monitoring, industrial processes, and biological systems. The review explores into the synthesis methodologies employed for designing optical chemosensors, discovering diverse materials like organic dyes, nanoparticles, polymers, and hybrid materials. Special attention is given to the design principles that enable the selective recognition of specific metal ions, highlighting the role of ligand chemistry, coordination interactions, and structural modifications. Furthermore, the article thoroughly surveys the analytical performance of optical chemosensors in terms of sensitivity, selectivity, response time, and detection limits. Real-world applications, including water quality assessment, environmental monitoring, and biomedical diagnostics, are extensively covered to underscore the practical relevance of these sensing platforms. Additionally, the review sheds light on emerging trends, challenges, and future prospects in the field, providing insights into potential advancements and innovations. By synthesizing the current state of knowledge on optical chemosensors for trace level metal ions detection. The collective information presented herein not only offers a comprehensive understanding of the existing technologies but also inspires future research endeavors to address the evolving demands in the realm of trace metal ion detection.

Ag0 decorated Cr2S3 NPs embedded on PVP matrix: A colorimetric probe for selective and rapid detection of sulphide ions from environmental samples

Globally, the environmental pollution is one of the major issues causing toxicity towards human and aquatic life. We have developed a facile and innovative sensing approach for detection of sulphide ions (S^2-) present in the aqueous media using Ag⁰ decorated Cr₂S₃ NPs embedded on PVP matrix (Ag/Cr₂S₃-PVP). Based on the SPR phenomena, the detection of S^2- ions was established. The nanohybrid was characterized using various techniques such as UV-vis spectrophotometer, High-Resolution Transmission Electron Microscopy (HR-TEM), Thermal Gravimetric Analysis (TGA), X-ray diffraction analysis(XRD), Energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The yellowish colour of Ag/Cr₂S₃-PVP nanohybrid turned to brown colour in presence of S^2- ions. The selectivity and sensitivity of the prepared probe was studied against the other interfering metal ions. In addition, the effect of different concentration of S^2- ions in the nanohybrid solution was investigated and the Limit of detection (LOD) was found to be 6.6 nM. The good linearity was found over the range of 10 nM to 100 μM with R² value of 0.981. The paper strip based probe was developed for rapid onsite monitoring of S^2- ions. The proposed method is found to be cost-effective, rapid, and simple. We have validated the practical applicability of the prepared probe for determining the concentration of S^2- ions in real water samples.

Synthesis optimization of rich-urea carbon-dots and application in the determination of H2S in rich- and barren-liquids of desulphurizing solutions

In the research of carbon dots (CDs) containing various nitrogen sources, it was first found that urea/citric acid-CDs showed a selective discolouration reaction with sulphide ions. Therefore, by optimizing various synthesis and detection conditions of the CDs determining sulfur ions, such as the raw material ratio, temperature, time, pH, and oxidation atmosphere in the CD synthesis, a discolour CD-probe method for trace-level sulphide ions was developed. The method is environmentally friendly, shows two linear-response ranges in 0.050-1.0 mg L^-1 (A = -0.0827c + 0.8366) and 1.0-15 mg L^-1 S^2- (A = -0.0209c + 0.7587) and can be used for the high and low concentration quantification of sulphide in various wastewaters. Subsequently, in order to realize the separation and detection of sulphide ions in wastewaters or rich- and barren-liquids containing N-methyldiethanolamine and other substances in desulphurizing solutions, an automatic pretreatment system was also established.

Indicator displacement assays: from concept to recent developments

Overcoming the synthetic burden related to covalently connected receptors with appropriate indicators for sensing various analytes via an indicator spacer receptor (ISR) approach, the indicator displacement assay (IDA) seems to be a very sophisticated and versatile supramolecular sensing paradigm, and it has taken the phenomenon of molecular recognition to the next level in the realm of host-guest chemistry. Due to the unavailability of a comprehensive report on what has been done in the last decade in relation to IDAs, we decided to set down this account illustrating diverse indicator displacement assays (IDAs) in detail from the concept stage to recent developments relating to the detection of cationic, anionic, and neutral analytes. The authors conclude this account with future perspectives and highlight the limitations and challenges relating to IDAs which need to be overcome in order to realize the full potential of this popular sensing phenomenon. While we were finalizing our account for publication, a tutorial review by the research groups of Anslyn, Sessler, and Sun was published, which focuses mainly on diverse aspects of the chemistry related to IDAs. As can be seen, our review, besides discussing various basic IDA concepts, has a vast collection of information published in the past decade and hence, hopefully, will be very informative for the supramolecular community. We believe that this work will offer new insights for the construction of novel sensors operating through the IDA approach.

Optimization of clinically applied orthodontic archwire electrothermal treatment conditions by heat tint and mechanical properties: An experimental study

OBJECTIVE

Electric resistance heat treatment procedures are performed by most orthodontists; however, the effects of electrothermal treatment on the mechanical properties, surface morphology, phase transition, colour and arch width of stainless steel archwires remain controversial and are worthy of investigation.

MATERIALS AND METHODS

Stainless steel archwires (0.017×0.025 and 0.019×0.025 inches) were heat-treated using a spot-welder machine at a power setting of 3 for 5, 10, 15 or 20s and were then cooled in air. After the heat treatment, we analysed the surface morphology of the samples by scanning electron microscopy (SEM) and the flexural modulus with a universal testing machine. The changes in phase and the austenite content after heat treatment were determined by X-ray diffraction (XRD). The changes in the colour of the sample were analysed by a digital single-lens reflex (DSLR) camera, and the arch width changes were measured with Vernier calippers.

RESULTS

The flexural modulus and austenite content of the orthodontic stainless steel archwires increased after heat treatment (P<0.05). The colour changed from silver to yellow-brown-blue. Heat treatment of the stainless steel wires increased the inter-canine and inter-molar widths only when the amount of heat received was low.

CONCLUSION

Heat treatment of stainless steel orthodontic archwires using an electric resistance device is an effective and convenient method to improve their flexural modulus. The colour of the wire surface after heat treatment can help determine the heating conditions, and the maximum flexural modulus of the stainless steel wires was obtained when the colour changed to brownish yellow.

Screen-Printed Sensors for Colorimetric Detection of Hydrogen Sulfide in Ambient Air

A fast and sensitive method to monitor hydrogen sulfide (H₂S) in ambient air based on a visible color change of a printed disposable sensor has been developed. As gas-sensitive material, an immobilized copper(II) complex of the azo dye 1-(2-pyridylazo)-2-naphtol (H-PAN) was synthesized and prepared in an ethyl cellulose matrix for screen printing. If H₂S is present in ambient air, the gas sensitive layer changes its color from purple to yellow. A pre-primed polyethylene (PE) foil and a coated offset paper served as the printing substrate. The colorimetric response to the target gas was measured by UV/Vis spectroscopy in reflection at H₂S concentrations between 1 to 20 ppm. Possible cross-sensitivities of the printed sensors towards methane (CH₄), formaldehyde (CH₂O), carbon monoxide (CO), ammonia (NH₃), and nitrogen dioxide (NO₂), as well as the long-term stability was investigated. Furthermore, reflection measurements of the Cu-PAN complex on an amorphous silica powder under gas admission served as preliminary test for the subsequent paste development.

An AIE-based metallo-supramolecular assembly enabling an indicator displacement assay inside living cells

We report a novel metallo-supramolecular assembly (Z/E-TPE2CyZn-PV), which consists of a tetraphenylethene (TPE)-based dinuclear Zn2+-cyclen complex and pyrocatechol violet (PV). The assembly is developed for indicator-displacement assays (IDAs) inside living cells.

Technical aspects and challenges of colorimetric detection with microfluidic paper-based analytical devices (μPADs) - A review

Paper-based devices are a leading alternative among the main analytical tools for point-of-care testing, due to their portability, low-cost, and ease-of-use. Colorimetric readouts are the most common method of detection in these microfluidic devices, enabling qualitative, semi-quantitative and fully quantitative analysis of multiple analytes. There is a multitude of ways to obtain a colorimetric output in such devices, including nanoparticles, dyes, redox and pH indicators, and each has unique drawbacks and benefits. There are also multiple variables that impact the analysis of colorimetric reactions in microfluidic paper-based systems, including color homogeneity, image capture methods, and the data handling itself. Here, we present a critical review of recent developments and challenges of colorimetric detection on microfluidic paper-based analytical devices (μPADs), and present thoughts and insights towards future perspectives in the area to improve the use of colorimetric readouts in conjunction with μPADs.

Silver nanoparticle anchored carbon dots for improved sensing, catalytic and intriguing antimicrobial activity

Catalytic, sensing and efficient antimicrobial activity of silver nanoparticle anchored hybrid carbon dots.