Recent advances in fluorescence chemosensors for ammonia sensing in the solution and vapor phases

Panoramic view of artificial fruit ripening agents sensing technologies and the exigency of developing smart, rapid, and portable detection devices: A review

Recently, the availability of point-of-care sensor systems has led to the rapid development of smart and portable devices for the detection of hazardous analytes. The rapid flow of artificially ripened fruits into the market is associated with an elevated risk to human life, agriculture, and the ecosystem due to the use of artificial fruit ripening agents (AFRAs). Accordingly, there is a need for the development of "Point-of-care Sensors" to detect AFRAs due to several advantages, such as simple operation, promising detection mechanism, higher selectivity and sensitivity, compact, and portable. Traditional detection approaches are time-consuming and inappropriate for on-the-spot analyses. Presented comprehensive review aimed to reveal how such technology has systematically evolved over time (through conventional, advanced, and portable smart techniques) detection detect AFRA, till date. Moreover, focuses and highlights a framework of initiatives undertaken for technological advancements in the development of smart the portable detection techniques (kits) for the onsite detection of AFRAs in fruits with in-depth discussion over sensing mechanism and analytical performance of the sensing technology. Notably, colorimetric detection methods have the greatest potential for real-time monitoring of AFRA and its residues because they are easy to assemble, have a high level of selectivity and sensitivity, and can be read by the human eye independently. This study sought to differentiate between traditional credible strategies by presenting new prospects, perceptions, and challenges related to portable devices. This review provides systematic framework of advances in portable field recognition strategies for the on-spot AFRA detection in fruits and critical information for development of new paper-based portable sensors for fruit diagnostic sectors.

Enhanced Fluorescence Based on Slow Light Effect of ZIF-8 Photonic Crystals for Trace 2,4,6-Trinitrophenol Detection

In response to growing concerns about public safety and environmental conservation, it is essential to develop a precise identification method for trace explosives. To improve the stability and detection sensitivity of perovskite quantum dots (PQDs) and address the issue of low porosity in traditional polymer-based photonic crystals (PhCs), this study proposed a PQD photoluminescence (PL) enhancement strategy based on the slow light effect of ZIF-8 PhCs for highly sensitive, selective, and convenient detection of 2,4,6-trinitrophenol (TNP). The slow light effect at the photonic band gap edge is the basis of amplifying the PL signal. PhCs were fabricated by the evaporation-induced self-assembly method. The diffraction wavelength overlapping the whole visible region was designed to match the emission wavelength of PQDs. Results showed that PhCs matching the PBG edge with PQDs' emission peak amplified the PL signal 11.3 times, significantly improving sensitivity for trace TNP detection with a limit as low as 2.52 nM. Moreover, there was a 13.3-fold enhancement of PQDs' fluorescence lifetime when the emission wavelength fell in the PBG range. The hydrophobic surface of ZIF-8 PhCs enhanced the PQDs' stability and moisture resistance. Furthermore, the selective quenching mechanism of TNP by the sensor was photoinduced electron transfer (PET) verified by DFT calculations and time-resolved PL decay dynamics measurements. This study demonstrated great potential for manipulating light emission enhancement by PhCs in developing efficient fluorescent sensors for trace environmental pollutant detection.

AIE paper shred for the detection of evolved amine vapor from putrefaction processes of fish

Seafood plays a major role in the human diet. During transportation, without proper storage and supply chain, its quality deteriorates easily. The post-harvesting processes such as the storage of food play a crucial role in human health. So it is highly imperative to have a technique for identifying food spoilage earlier to ensure the food safety and security of the consumers. Herein we have developed a highly selective and sensitive fluorescent 'Turn-on' probe 2-amino-5-nitrobenzo [d] thiazol-2-yl) imino)methylphenol ANT based on aggregation induced emission (AIE). ANT molecule possesses both restricted intramolecular rotation (RIR) and excited state intramolecular proton transfer (ESIPT) properties leading to fluorescent enhancement rather than aggregation caused quenching (ACQ). The probe shows high selectivity and sensitivity towards the NH3 vapor. This probe with the AIE property is employed for the real-time detection of NH3 in both aqueous and gaseous phases. ANT molecule is deposited on the paper shred by a physical method is utilized to monitor NH3 vapor from red snapper fish as a real-time sample during its degradation processes. After two days there is a ratiometric color change in the paper shred from yellow to orange for the fish stored at room temperature indicating its rotten and unpalatability nature. Paper shred is reused by immersing it into the tetrahydrofuran (THF), in which it retains its initial color due to deprotonation of NH3, keto to enol tautomerism discloses the reusability of the fluorescent probe. Studies carried out using UV-visible and fluorescence spectroscopy infer that the ANT probe has high affinity towards NH3 vapor.

An Encyclopedic Compendium on Chemosensing Supramolecular Metal-Organic Gels

Chemosensing, an interdisciplinary scientific domain, plays a pivotal role ranging from environmental monitoring to healthcare diagnostics and (inter)national security. Metal-organic gels (MOGs) are recognized for their stability, selectivity, and responsiveness, making them valuable for chemosensing applications. Researchers have explored the development of MOGs based on different metal ions and ligands, allowing for tailored properties and sensitivities, and have even demonstrated their applications as portable sensors such as paper-based test strips for practical use. Herein, several studies related to MOGs development and their applications in the chemosensing field via UV-visible or luminance along with electrochemical approach are presented. These papers explored MOGs as versatile materials with their use in sensing bio or environmental analytes. This review provides a foundational understanding of key concepts, methodologies, and recent advancements in this field, fostering the scientific community.

Photoacoustic Spectroscopy Using a Quantum Cascade Laser for Analysis of Ammonia in Water Solutions

Ammonia (NH3) toxicity, stemming from nitrification, can adversely affect aquatic life and influence the taste and odor of drinking water. This underscores the necessity for highly responsive and accurate sensors to continuously monitor NH3 levels in water, especially in complex environments, where reliable sensors have been lacking until this point. Herein, we detail the development of a sensor comprising a compact and selective analyzer with low gas consumption and a timely response based on photoacoustic spectroscopy. This, combined with an automated liquid sampling system, enables the precise detection of ammonia traces in water. The sensor system incorporates a state-of-the art quantum cascade laser as the excitation source emitting at 9 μm in resonance with the absorption line of NH3 located at 1103.46 cm-1. Our instrument demonstrated detection sensitivity at a low ppm level for the ammonia molecule with response times of less than 60 s. For the sampling system, an ammonia stripping solution was designed, resulting in a prompt full measurement cycle (6.35 min). A further evaluation of the sensor within a pilot study showed good reliability and agreement with the reference method for real water samples, confirming the potential of our NH3 analyzer for water quality monitoring applications.

From Body Monitoring to Biomolecular Sensing: Current Progress and Future Perspectives of Triboelectric Nanogenerators in Point-of-Care Diagnostics

In the constantly evolving field of medical diagnostics, triboelectric nanogenerators (TENGs) stand out as a groundbreaking innovation for simultaneously harnessing mechanical energy from micromovements and sensing stimuli from both the human body and the ambient environment. This advancement diminishes the dependence of biosensors on external power sources and paves the way for the application of TENGs in self-powered medical devices, especially in the realm of point-of-care diagnostics. In this review, we delve into the functionality of TENGs in point-of-care diagnostics. First, from the basic principle of how TENGs effectively transform subtle physical movements into electrical energy, thereby promoting the development of self-powered biosensors and medical devices that are particularly advantageous for real-time biological monitoring. Then, the adaptable design of TENGs that facilitate customization to meet individual patient needs is introduced, with a focus on their biocompatibility and safety in medical applications. Our in-depth analysis also covers TENG-based biosensor designs moving toward exceptional sensitivity and specificity in biomarker detection, for accurate and efficient diagnoses. Challenges and future prospects such as the integration of TENGs into wearable and implantable devices are also discussed. We aim for this review to illuminate the burgeoning field of TENG-based intelligent devices for continuous, real-time health monitoring; and to inspire further innovation in this captivating area of research that is in line with patient-centered healthcare.

A three-in-one versatile sensor for concise detecting biogenic amines and beef freshness

Biogenic amines (BAs), as important indicators for evaluating food spoilage caused by fermentation processes or microbial activities, present significant risks of food safety. Consequently, the development of a simple, sensitive, and selective detection method for amines is of great importance. In this study, we proposed a three-in-one sensor 3,6-bis(dimethylamino)-9-(ethylthio)xanthylium (PSE) for high sensitivity and selectivity detecting BAs with multimodal responses, including olfactory, colorimetric, and fluorescent signals, thus facilitating convenient real-time detection of BAs. Mechanism study indicated that the nucleophilic substitution of PSE with BAs induced such rapid multi-responses with a low detection limit (LOD = 0.03 μM). We further fabricated PSE loaded paper for portable detection of BAs vapors. And the accurate determination of BAs levels is achieved through analyzing the RGB color mode. Finally, we successfully applied these test strips for non-destructive assessing meat beef freshness with the assistance of a smartphone in on-site scenarios.

Integrated portable food safety testing pipette based on a color-switchable fluorescence probe for rapid visual discrimination of mild food deterioration

A sensitive, portable, easy-to-operate, directly-readable food freshness monitoring device has been developed for rapid visual identification of mild food spoilage.

Preparation and Characterisation of Acid-Base-Change-Sensitive Binary Biopolymer Films with Olive Oil and Ozonated Olive Oil Nano/Microcapsules and Added Hibiscus Extract

The purpose of this study was to develop and characterise bionanocomposites based on chitosan (CHIT) and alginate (ALG) in two series, which were subsequently functionalised with emulsions based on a combination of water, oil, ozonated oil and hibiscus flower extracts. The structure and morphology of the materials produced were characterised by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and ultraviolet and visible light (UV-Vis) absorption spectroscopy, along with a surface colour analysis and the determination of the mechanical and thermal properties of the resulting composites. Functionalisation did affect the analysed composite parameters. The FTIR spectra indicated that the polysaccharide matrix components were compatible. The SEM images also confirmed the presence of nano/microcapsules in the polysaccharide matrix. The obtained results indicate that the order of adding polysaccharides has a significant impact on the encapsulation capacity. The encapsulation resulted in the improved thermal stability of the composites. The emissions analysis showed that the composites containing nano/microcapsules are characterised by a higher emission intensity and are sensitive to acid or base changes. Significant differences in emission intensity were observed even at low concentrations of acids and bases. A drop in the mechanical properties was observed following functionalisation. The results of this study suggest that these bionanocomposites can be used as active and/or smart packaging materials.

Electrochemical sensing mechanism of ammonium ions over an Ag/TiO2 composite electrode modified by hematite

Here, we demonstrate a new electrochemical sensing mechanism of ammonium ions (NH₄⁺) involving a two-electron oxygen reduction reaction (ORR) and a hydrazine reaction. The NH₄⁺ are electrooxidized to hydrazine by H₂O₂ derived from the ORR over a self-supporting Ag/TiO₂ nanotube array composite electrode modified by hematite (Ag/Fe₂O₃/TNTs). The Ag/Fe₂O₃/TNT sensor exhibits a high sensitivity of 1876 µA mM^-1 cm^-2 with a detection limit of 0.18 µM under non-alkaline conditions, a short response time of 3 s, good reproducibility, and fine selectivity among various interferents, and is also successfully used in real water bodies to display high accuracy. Furthermore, this new mechanism has a certain universality in a range of Ag (main catalyst)/transition metal oxide (cocatalyst)/TNT sensing systems. This work offers a new design basis for the urgently needed electrochemical ammonia nitrogen sensors.