The detection of explosives is one of the current pressing concerns in global security. In the past few decades, a large number of emissive sensing materials have been developed for the detection of ...explosives in vapor, solution, and solid states through fluorescence methods. In recent years, great efforts have been devoted to develop new fluorescent materials with various sensing mechanisms for detecting explosives in order to achieve super-sensitivity, ultra-selectivity, as well as fast response time. This review article starts with a brief introduction on various sensing mechanisms for fluorescence based explosive detection, and then summarizes in an exhaustive and systematic way the state-of-the-art of fluorescent materials for explosive detection with a focus on the research in the recent 5 years. A wide range of fluorescent materials, such as conjugated polymers, small fluorophores, supramolecular systems, bio-inspired materials and aggregation induced emission-active materials, and their sensing performance and sensing mechanism are the centerpiece of this review. Finally, conclusions and future outlook are presented and discussed.
The development of high temperature gas sensors for industrial applications such as combustion processes is essential to improve energy efficiency and reduce toxic emissions. However, gas sensors ...operating at high temperatures up to 1000 °C typically encounter many challenging issues, such as thermal and long-term stability, sensitivity, reproducibility and selectivity. This feature article discusses a variety of solid-state gas sensors that can be operated at high temperatures above 600 °C. The basic working principles for each type of solid-state gas sensor are briefly introduced, including potentiometric, amperometric, resistive and impedancemetric sensors. The key results and discussions of previous studies on high temperature O 2 , CO, HCs and NO x sensors are also presented with emphasis on the development of suitable electrolytes and sensing materials with good thermal stability and sensing performance for such high temperature gas sensing applications. Finally, the challenges and scope for future development are discussed.
Glucose detection is of vital importance to diabetes diagnosis and treatment. Optical approaches in glucose sensing have received much attention in recent years due to the relatively low cost, ...portable, and mini-invasive or non-invasive potentials. Surface enhanced Raman spectroscopy (SERS) endows the benefits of extremely high sensitivity because of enhanced signals and specificity due to the fingerprint of molecules of interest. However, the direct detection of glucose through SERS was challenging because of poor adsorption of glucose on bare metals and low cross section of glucose. In order to address these challenges, several approaches were proposed and utilized for glucose detection through SERS. This review article mainly focuses on the development of surface enhanced Raman scattering based glucose sensors in recent 10 years. The sensing mechanisms, rational design and sensing properties to glucose are reviewed. Two strategies are summarized as intrinsic sensing and extrinsic sensing. Four general categories for glucose sensing through SERS are discussed including SERS active platform, partition layer functionalized surface, boronic acid based sensors, and enzymatic reaction based biosensors. Finally, the challenges and outlook for SERS based glucose sensors are also presented.
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•Challenges and rational design of SERS based glucose detection.•Intrinsic and extrinsic glucose sensing.•SERS active platform and partition layer functionalized surface.•Boronic acid and enzymatic reaction based sensors.
Conventional fluorescence microscopy is limited by the optical diffraction of light, which results in a spatial resolution of about half of the light's wavelength, approximately to 250-300 nm. The ...spatial resolution restricts the utilization of microscopes for studying subcellular structures. In order to improve the resolution and to shatter the diffraction limit, two general approaches were developed: a spatially patterned excitation method and a single-molecule localization strategy. The success of super-resolution imaging relies on bright and easily accessible fluorescent probes with special properties. Carbon dots, due to their unique properties, have been used for super-resolution imaging. Considering the importance and fast development of this field, this work focuses on the recent progress and applications of fluorescent carbon dots as probes for super-resolution imaging. The properties of carbon dots for super-resolution microscopy (SRM) are analyzed and discussed. The conclusions and outlook on this topic are also presented.
Fluorescent carbon dots (CDs) are a new class of carbon nanomaterials and have demonstrated excellent optical properties, good biocompatibility, great aqueous solubility, low cost, simple synthesis, ...etc. Since their discovery, various synthesis methods using different precursors have been developed, and are mainly classified as top-down and bottom-up approaches. For the mechanistic origin of CDs photoluminescence, three mechanisms have been proposed such as quantum confinement effect, surface state and molecule state. CDs have presented many applications, and this review article mainly focuses on the development of CDs based fluorescent sensors in recent 5 years. The sensing mechanisms, senor design and sensing properties to various targets are summarized. A broad range of analytes including cations, anions, small molecules, macromolecules, cells and bacteria have been discussed. In addition, the challenges and future directions for CDs as sensing materials are also presented.
Synthesis of carbon dots and their use as sensory materials in recent 5 years are reviewed. The sensing mechanisms, sensor design and sensing properties to various targets and the future directions are also summarized. Display omitted
•Synthesis and mechanistic origin of fluorescent carbon dots.•Sensing mechanisms and sensor design using fluorescent carbon dots as sensory materials.•Sensing applications and properties to various analytes.•Challenges and future directions for fluorescent carbon dots as sensing materials.
The effect of deformation temperature on tensile behavior of Inconel 718 alloy has been studied by a self-developed in-situ high-temperature tensile stage inside a scanning electron microscopy at a ...temperature range from room temperature (RT) to 750 °C. The dynamic microstructure evolution and mechanical properties at different temperatures were performed and compared by the uniaxial tensile tests. The in-situ test results showed that the mechanical properties and fracture mechanisms of Inconel 718 alloy were sensitive to deformation temperatures. From RT to 650 °C, the yield stress and ultimate tensile strength decrease slightly and the tensile ductility is comparable. While up to 750 °C, the yield stress and ultimate tensile strength decrease significantly, the elongation and reduction of cross section also showed a significant decrease from RT to 750 °C. It was found that at RT and 650 °C, tensile cracks tended to initiate around the carbide particles and the triple junctions of grain boundaries, also propagated transgranularly; at 750 °C, the cracks initiated at grain boundaries and propagated intergranularly. In fact, with the increase in deformation temperature, the fracture mechanism transformed from the ductile transgranular fracture to the brittle intergranular fracture.
Fluorescent pyrene–polyethersulfone (Py–PES) nanofibers were prepared through electrospinning technique using mixed solvents. The effects of mixed solvent ratio and polymer/fluorophore concentrations ...on electrospun nanofiber’s morphology and its sensing performance were systematically investigated and optimized. The Py–PES nanofibers prepared under optimized conditions were further applied for highly sensitive detection of explosives, such as picric acid (PA), 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) in aqueous phase with limits of detection (S/N = 3) of 23, 160, 400, and 980 nM, respectively. The Stern–Volmer (S–V) plot for Py excimer fluorescence quenching by PA shows two linear regions at low (0–1 μM) and high concentration range (>1 μM) with a quenching constant of 1.263 × 106 M–1 and 5.08 × 104 M–1, respectively. On the contrary, S–V plots for Py excimer fluorescence quenching by TNT, DNT, and RDX display an overall linearity in the entire tested concentration range. The fluorescence quenching by PA can be attributed to the fact that both photoinduced electron transfer and energy transfer are involved in the quenching process. In addition, pyrene monomer fluorescence is also quenched and exhibits different trends for different explosives. Fluorescence lifetime studies have revealed a dominant static quenching mechanism of the current fluorescent sensors for explosives in aqueous solution. Selectivity study demonstrates that common interferents have an insignificant effect on the emission intensity of the fluorescent nanofibers in aqueous phase, while reusability study indicates that the fluorescent nanofibers can be regenerated. Spiked real river water sample was also tested, and negligible matrix effect on explosives detection was observed. This research provides new insights into the development of fluorescent explosive sensor with high performance.
There have been numerous studies applying iridium oxides in different applications to explore their proton-change-based reactions since the 1980s. Iridium oxide can be fabricated directly by applying ...electrodeposition, sputter-coating method, or oxidation of iridium wire. Generally, there have been currently two approaches in applying iridium oxide to enable its sensing applications. One was to improve or create different electrolytes with (non-)electrodeposition method for better performance of Nernst Constant with the temperature-related system. The mechanism behind the scenes were summarized herein. The other was to change the structure of iridium oxide through different kinds of templates such as photolithography patterns, or template-assisted direct growth methods, etc. to improve the sensing performance. The detection targets varied widely from intracellular cell pH, glucose in an artificial sample or actual urine sample, and the hydrogen peroxide, glutamate or organophosphate pesticides, metal-ions, etc. This review paper has focused on the mechanism of electrodeposition of iridium oxide in aqueous conditions and the sensing applications towards different biomolecules compounds. Finally, we summarize future trends on Iridium oxide based sensing and predict future work that could be further explored.
In this study, two new quasi-three-dimensional Surface Enhanced Raman Scattering (SERS) substrates, namely porous Ag and Ag-NiO nanofibrous mats, were prepared using a simple, ...electrospinning-calcination, two-step synthetic process. AgNO₃/polyvinyl pyrrolidone (PVP) and AgNO₃/Ni(NO₃)₂/PVP composites serving as precursors were electrospun to form corresponding precursory nanofibers. Porous Ag and Ag-NiO nanofibers were successfully obtained after a 3-h calcination at 500 °C under air atmosphere, and analyzed using various material characterization techniques. Synthesized, quasi-three-dimensional porous Ag and Ag-NiO nanofibrous mats were applied as SERS substrates, to measure the model compound Rhodamine 6G (R6G), and investigate the corresponding signal enhancement. Furthermore, porous Ag and Ag-NiO nanofibrous mats were employed as SERS substrates for melamine and methyl parathion respectively. Sensitive detection of melamine and methyl parathion was achieved, indicating their feasibility as an active SERS sensing platform, and potential for food safety and environmental monitoring. All the results suggest that the electrospinning-calcination, two-step method offers a new, low cost, high performance solution in the preparation of SERS substrates.
Pinus armandii, or Chinese white pine, is one of the pine species native to China and plays an important role in ecological conservation and regional socioeconomic development. However, few studies ...have focused on the distribution of its habitat and important environmental factors related to suitability. Therefore, we used a MaxEnt model to represent the current species distribution of P. armandii in China and predicted its future redistribution. The results show that precipitation and temperature are the two major limiting factors that constrain the current distribution of P. armandii. The average temperatures of 24 °C and −14 °C in July and January, respectively, are considered the limits that define the tree-line of P. armandii. Currently, P. armandii is mainly distributed in the Tsinling Mountains, Daba Mountains and terrains in the Yunnan-Kweichow Plateau. Under climate change scenarios, the distribution range of P. armandii is projected to decrease. The response of P. armandii to RCP 8.5 scenario is the most drastic, followed by the RCP 4.5 scenario. The most alarming change is that the suitable habitat in the Wushan Mountains, which connects the Daba Mountains and Yunnan-Kweichow Plateau, is expected to gradually disappear, leading to interruption of the current ecological corridor. The suitable habitat in the Hengduan Mountains is projected to gradually be lost. In the northern part of China, there is no suitable niche for P. armandii. However, the excellent habitat range for P. armandii in both the Tsinling Mountains and Daba Mountains is predicted to enlarge. Our study results can provide timely information for the monitoring of the health of tree populations and the impact of climate change, shedding light on the effectiveness of management responses.
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