Advances in Optical Sensors for Persistent Organic Pollutant Environmental Monitoring

Self-Powered Acceleration Sensor for Distance Prediction via Triboelectrification

Accurately predicting the distance an object will travel to its destination is very important in various sports. Acceleration sensors as a means of real-time monitoring are gaining increasing attention in sports. Due to the low energy output and power density of Triboelectric Nanogenerators (TENGs), recent efforts have focused on developing various acceleration sensors. However, these sensors suffer from significant drawbacks, including large size, high complexity, high power input requirements, and high cost. Here, we described a portable and cost-effective real-time refreshable strategy design comprising a series of individually addressable and controllable units based on TENGs embedded in a flexible substrate. This results in a highly sensitive, low-cost, and self-powered acceleration sensor. Putting, which accounts for nearly half of all strokes played, is obviously an important component of the golf game. The developed acceleration sensor has an accuracy controlled within 5%. The initial velocity and acceleration of the forward movement of a rolling golf ball after it is hit by a putter can be displayed, and the stopping distance is quickly calculated and predicted in about 7 s. This research demonstrates the application of the portable TENG-based acceleration sensor while paving the way for designing portable, cost-effective, scalable, and harmless ubiquitous self-powered acceleration sensors.

Chemresistive Detection of NO2 of ppb Level in Humid Air at 350 K Using Azo-Spaced Polycroconamide

Organic molecules are of great interest for gas sensing applications. However, achieving high-performance gas sensors with high sensitivity, fast response, low consumption, and workability in humid conditions is still challenging. Herein, we report the rational design and synthesis of an ion-in-conjugation polymer, PADC (poly-4,4'-azodianiline-croconamide), obtained by the condensation of croconic acid with 4-4'diaminoazobenzene for gas sensing under humid conditions. The as-fabricated PADC-based gas sensor exhibits ultrahigh sensitivity (802.7 ppm-1 at 1 ppm), subppb detection limit, and high selectivity under humid air with an 80% humidity effect at a temperature down to 350 K. PADC shows good planarity, excellent thermostability, and a narrow band gap of 1.2 eV because of azobenzene fragments spacing previously repulsed biphenyl rings. Compared to previous humidity immunity works, PADC-based sensors realized humidity immunity at a relatively lower temperature, resulting in lower energy consumption.

Optical Chemical Sensors: Design and Applications

More than ever, optical chemical sensing is a thriving research field with a strong outlook in terms of future development and penetration into growing industrial markets [...].

Towards miniaturized electrochemical sensors for monitoring of polychlorinated biphenyls

Pollution of our environment as a result of industrialization and other human activities is a growing concern due to the harmful effects of most chemicals that are released into the environment. Of particular interest are the persistent organic pollutants (POPs) that are reported to be toxic and build up in the environment due to their persistence. Among the POPs are polychlorinated biphenyls (PCBs), which were widely used in the past in various applications ranging from additives in pesticides to dielectric fluids in electrical equipment. As a way of protecting the one health trilogy (environment, human and animal health), their determination in the environment is a paramount call that has seen researchers continue to provide advanced technologies towards achieving this goal. These technologies involve the conventional gold standard gas chromatography systems coupled to sensitive detectors that can detect trace level concentrations. They have come in handy in monitoring of PCBs but their application for routing monitoring may not be sustainable because of the cost of operation associated with them and the need for experts to run the equipment. As a result, there is need for affordable systems that are still able to achieve the required sensitivity for routine monitoring and real-time data acquisition. Sensor systems fit very well in this category since they can be miniaturized for affordability and portray many other desirable features. PCBs as environmentally relevant environmental pollutants have received minimal attention with regards to sensor development and this review highlights the efforts that have been made so far. It provides in-depth discussions on electrochemical sensors and the various modifications that have been employed to date to achieve detection of PCBs at low concentrations as well as the future prospects in remote and routine monitoring.

Chiral H-aggregation-induced large stokes shift with CPL generation assisted by α-helical poly(L-lysine) substructure

Fluorescent materials with large Stokes shifts have significant potential for use in optical applications. Typically, a synthetic design strategy is utilized for this purpose. In this study, we demonstrated a novel method by binding a chiral template to a nonchiral fluorescent agent without chemical modification. Specifically, α-helical poly(L-lysine) was employed as the chiral template, which interacted with a disulfonic fluorescent dye, such as NK2751. The dye caused excimer luminescence by inducing the formation of a chirally H-aggregated dimer only when poly(L-lysine) was in an α-helical shape. The result was a Stokes shift of 230 nm. Similar effects were not observed when the chiral template was in a random coil condition and the Stokes shift was less than 40 nm. These findings imply that H-aggregated dimerization, which often results in quenching, permits the electronic transitions necessary for fluorescence events by the formation of the chirally twisted state. In addition, we introduce for the first time the generation of circularly polarized luminescence using the chirality induction phenomena in a dye supported by poly(L-lysine).

Fluorescent sensing of non-steroidal anti-inflammatory drugs naproxen and ketoprofen by dansylated squaramide-based receptors

Bis-squaramide receptors L1-L4 bearing a dansyl moiety were synthesised and their potential applications as fluorescent probes towards non steroidal anti-inflammatory drugs naproxen and ketoprofen was investigated. A detailed photophysical characterization in CH₃CN/DMSO solution (9 : 1 v/v) was conducted and demonstrated that the two macrocyclic receptors L1 and L2 show good sensitivity towards ketoprofen with an ON-OFF fluorescent response, while the two open chain receptors L3 and L4 behave similarly with the three guests considered. DFT theoretical calculations carried out on L2 and L4 as model receptors allowed to propose a possible coordination mode towards the guests. Finally, ¹H-NMR spectroscopy in DMSO-d₆/0.5% water solution demonstrated that the four receptors interact with the considered guests via H-bonds.

Recent advances in the analysis of polycyclic aromatic hydrocarbons in food and water

Polycyclic aromatic hydrocarbons (PAHs), a class of harmful and persistent organic contaminant, are widely distributed in the environment and eventually accumulated in water and food. Also, they are formed in different varieties and varying amounts during processing of food depending on the food composition, cooking method and processing condition. According to the International Agency for Research on Cancer (IARC), various PAHs are classified under Group 1 to 3 category, with Group 1 designated as carcinogenic to humans, Group 2A as probable carcinogen, Group 2B as possible carcinogen and Group 3 as noncarcinogenic. Therefore, it is imperative to develop rapid and highly sensitive analytical methods for determination of PAHs in food and water. This article aims to overview the recent advances of various chromatographic methods as well as electrochemical and SERS-based optical sensing methods for analysis of PAHs in food and water. Initially, several conventional sample preparation methods along with the advanced extraction for isolation of PAHs were summarized, followed by reviewing various gas chromatographic methods coupled with various detection techniques for PAHs analysis in various food products including meat/meat products, seafood, oil, milk/milk products, baby foods, honey, vegetable, cocoa products, tea/coffee, juice, rice, flour, noodle and cake. In addition, high performance liquid chromatographic methods coupled with fluorescence, diode array or mass/tandem mass detection techniques as well as an emerging supercritical fluid chromatographic technique employed for determination of PAHs in different food and water matrices were also overviewed. Finally, various electrochemical sensors and SERS-based optical sensors developed recently for onsite detection of PAHs were tabulated and discussed. Thus, this review article can provide a research update on chromatography and sensor-based analytical methods for PAH analysis as well as enable elucidation of research gaps for future studies.