Silver nanoprism-mediated colourimetric sensing probe for efficient detection of Pd(II) and Pt(II) ions in water and reuse of formed bimetallic nanoprisms

Sensitive and selective methods for detecting Pd(II) and Pt(II) ions in water are crucial for environmental monitoring and remediation. Although traditional methods for detection of Pd(II) and Pt(II) ions are accurate and sensitive, they face substantial challenges due to high costs, reliance on specialised equipment and limited field applicability, thereby presenting notable limitations. In this study, we introduce a novel colourimetric sensing probe designed specifically to identify Pd(II) and Pt(II) ions in aqueous solutions. This probe utilises the enhanced chemical stability of Ag nanoprisms achieved through Pd or Pt deposition on their surfaces. Our approach features exceptionally low limits of detection of 2.6 nM for Pd(II) and 0.3 nM for Pt(II), indicating an impressive detection range. Furthermore, the probe's ease of use, cost-effectiveness and compatibility with both naked eye and UV-Vis spectrophotometric detection make it a selective, reliable and affordable option for point-of-care analysis. Beyond its impressive sensitivity for ion detection, this methodology offers the additional benefit of enabling the on-demand synthesis of customised bimetallic catalysts. The synthesised Ag/Pd and Ag/Pt bimetallic nanoprisms demonstrate promising catalytic potential for environmental remediation. This advancement paves the way for efficient recycling and reuse of valuable Pd(II) and Pt(II) ions in various catalytic applications.

Sensor development for multiple simultaneous classifications using genetically engineered M13 bacteriophages

Sensors for detecting infinitesimal amounts of chemicals in air have been widely developed because they can identify the origin of chemicals. These sensing technologies are also used to determine the variety and freshness of fresh food and detect explosives, hazardous chemicals, environmental hormones, and diseases using exhaled gases. However, there is still a need to rapidly develop portable and highly sensitive sensors that respond to complex environments. Here, we show an efficient method for optimising an M13 bacteriophage-based multi-array colourimetric sensor for multiple simultaneous classifications. Apples, which are difficult to classify due to many varieties in distribution, were selected for classifying targets. M13 was adopted to fabricate a multi-array colourimetric sensor using the self-templating process since a chemical property of major coat protein p8 consisting of the M13 body can be manipulated by genetic engineering to respond to various target substances. The twenty sensor units, which consisted of different types of manipulated M13, exhibited colour changes because of the change of photonic crystal-like nanostructure when they were exposed to target substances associated with apples. The classification success rate of the optimal sensor combinations was achieved with high accuracy for the apple variety (100%), four standard fragrances (100%), and aging (84.5%) simultaneously. We expect that this optimisation technique can be used for rapid sensor development capable of multiple simultaneous classifications in various fields, such as medical diagnosis, hazardous environment monitoring, and the food industry, where sensors need to be developed in response to complex environments consisting of various targets.

The development progress of multi-array colourimetric sensors based on the M13 bacteriophage

Techniques for detecting chemicals dispersed at low concentrations in air continue to evolve. These techniques can be applied not only to manage the quality of agricultural products using a post-ripening process but also to establish a safety prevention system by detecting harmful gases and diagnosing diseases. Recently, techniques for rapid response to various chemicals and detection in complex and noisy environments have been developed using M13 bacteriophage-based sensors. In this review, M13 bacteriophage-based multi-array colourimetric sensors for the development of an electronic nose is discussed. The self-templating process was adapted to fabricate a colour band structure consisting of an M13 bacteriophage. To detect diverse target chemicals, the colour band was utilised with wild and genetically engineered M13 bacteriophages to enhance their sensing abilities. Multi-array colourimetric sensors were optimised for application in complex and noisy environments based on simulation and deep learning analysis. The development of a multi-array colourimetric sensor platform based on the M13 bacteriophage is likely to result in significant advances in the detection of various harmful gases and the diagnosis of various diseases based on exhaled gas in the future.

Digitalization of colourimetric sensor arrays for volatile fatty acid detection in anaerobic digestion

During the process of converting the organic matter into methane, many volatile fatty acids (VFAs) are produced during acidogenesis and acetogenesis phases of the process. The main VFAs of interest are acetic acid, butyric acid and propionic acid. Although the production of these VFAs are essential for the production of methane, they also play an inhibitory role for many of the organisms involved in the production of biogas. As a consequence, the levels of VFAs produced in an anaerobic digester must be monitored. Current methodologies for VFA monitoring are either unspecific, or costly. Therefore, the development of a sensor method that is specific to the different VFAs, while maintaining a low cost, will facilitate the lowering of biogas production, as well as avoiding the costly biological collapse of the whole biogas production process. Here, an array of coloured dyes (colourimetric array) has been assessed for their ability to detect low concentrations of VFAs within the digestate during biogas production. This methodology lays the foundation for the development of a sensor system for use in biogas plants and could also be expanded to detect many other parameters within the biogas production process.

•

Easy to establish.

•

Low user input.

•

Accurate measurement.

Benzimidazole based ratiometric and colourimetric chemosensor for Ni(II)

A highly sensitive and selective benzimidazole based colourimetric chemosensor (HL) for the efficient detection of Ni(2+) has been reported. The synthesized chemosensor HL is highly efficient in detecting Ni(2+) over other metal ions that commonly coexist with Ni(2+) in physiological and environmental samples. HL also shows distinct color change from orange yellow to blue visible under the naked eye due to specific binding with Ni(2+). This color change corresponds to a large red shift of the UV-Vis spectrum from 403 nm to 600 nm with a distinct isosbestic point at around 500 nm. The cation sensing property of the receptor HL has been examined by UV-Vis spectroscopy. Electronic structure of the HL-Ni(2+) complex and sensing mechanism has been interpreted by DFT and TDDFT calculations.