Building Feedback-Regulation System Through Atomic Design for Highly Active SO_(2)Sensing

Reasonably constructing an atomic interface is pronouncedly essential for surface-related gas-sensing reaction.Herein,we present an ingen-ious feedback-regulation system by changing the interactional mode between single Pt atoms and adjacent S species for high-efficiency SO_(2)sensing.We found that the single Pt sites on the MoS_(2)surface can induce easier volatiliza-tion of adjacent S species to activate the whole inert S plane.Reversely,the activated S species can provide a feedback role in tailoring the antibonding-orbital electronic occupancy state of Pt atoms,thus creating a combined system involving S vacancy-assisted single Pt sites(Pt-Vs)to synergistically improve the adsorption ability of SO_(2)gas molecules.Further-more,in situ Raman,ex situ X-ray photoelectron spectroscopy testing and density functional theory analysis demonstrate the intact feedback-regulation system can expand the electron transfer path from single Pt sites to whole Pt-MoS_(2)supports in SO_(2)gas atmosphere.Equipped with wireless-sensing modules,the final Pt1-MoS_(2)-def sensors array can further realize real-time monitoring of SO_(2)levels and cloud-data storage for plant growth.Such a fundamental understanding of the intrinsic link between atomic interface and sensing mechanism is thus expected to broaden the rational design of highly effective gas sensors.

Preparation of single atom catalysts for high sensitive gas sensing

Single atom catalysts(SACs)have garnered significant attention in the field of catalysis over the past decade due to their exceptional atom utilization efficiency and distinct physical and chemical properties.For the semiconductor-based electrical gas sensor,the core is the catalysis process of target gas molecules on the sensitive materials.In this context,the SACs offer great potential for highly sensitive and selective gas sensing,however,only some of the bubbles come to the surface.To facilitate practical applications,we present a comprehensive review of the preparation strategies for SACs,with a focus on overcoming the challenges of aggregation and low loading.Extensive research efforts have been devoted to investigating the gas sensing mechanism,exploring sensitive materials,optimizing device structures,and refining signal post-processing techniques.Finally,the challenges and future perspectives on the SACs based gas sensing are presented.

Mechanical regulation of lipid and sugar absorption by Piezo1 in enterocytes

Obesity is primarily caused by excessive intake as well as absorption of sugar and lipid.Postprandial surge in distention pressure and intestinal motility accelerates the absorption of nutrients.The response of intestinal epithelial cells to mechanical stimulation is not fully understood.Piezo1,a mechanosensitive ion channel,is widely expressed throughout the digestive tract.However,its function in intestinal nutrient absorption is not yet clear.In our study,excessive lipid deposition was observed in the duodenum of obese patients,while duodenal Piezo1-CaMKK2-AMPKa was decreased when compared to normal-weight individuals.Under high-fat diet condition,the Piezo1iKO mice exhibited abnormally elevated sugar and lipid absorption as well as severe lipid deposition in the duodenum and liver.These phenotypes were mainly caused by the inhibition of duodenal CaMKK2-AMPKa and the upregulation of SGLT1 and DGAT2.In contrast,Yoda1,a Piezo1 agonist,was found to reduce intestinal lipid absorption in diet induced obese mice.Overexpression of Piezo1,stretch and Yoda1 inhibited lipid accumulation and the expression of DGAT2 and SGLT1,whereas knockdown of Piezo1 stimulated lipid accumulation and DGAT2 in Caco-2 cells.Our study reveals a previously unexplored mechanical regulation of nutrient absorption in intestinal epithelial cells,which may shed new light on the therapy of obesity.

TDDFT Study on Different Sensing Mechanisms of Similar Cyanide Sensors Based on Michael Addition Reaction

The solvents and substituents of two similar fluorescent sensors for cyanide, 7-diethylamino- 3-formylcoumarin （sensor a） and 7-diethylamino-3-（2-nitrovinyl）coumarin （sensor b）, are proposed to account for their distinct sensing mechanisms and experimental phenomena. The time-dependent density functional theory has been applied to investigate the ground states and the first singlet excited electronic states of the sensor as well as their possible Michael reaction products with cyanide, with a view to monitoring their geometries and photophysieal properties. The theoretical study indicates that the protic water solvent could lead to final Michael addition product of sensor a in the ground state, while the aprotic acetonitrile solvent could lead to carbanion as the final product of sensor b. Furthermore, the Michael reaction product of sensor a has been proved to have a torsion structure in its first singlet excited state. Correspondingly, sensor b also has a torsion structure around the nitrovinyl moiety in its first singlet excited state, while not in its carbanion structure. This could explain the observed strong fluorescence for sensor a and the quenching fluorescence for the sensor b upon the addition of the cyanide anions in the relevant sensing mechanisms.

Biogreen Synthesis of Carbon Dots for Biotechnology and Nanomedicine Applications

Over the past decade, carbon dots have ignited a burst of interest in many different fields, including nanomedicine, solar energy, optoelectronics, energy storage,and sensing applications, owing to their excellent photoluminescence properties and the easiness to modify their optical properties through doping and functionalization. In this review, the synthesis, structural and optical properties,as well as photoluminescence mechanisms of carbon dots are first reviewed and summarized. Then, we describe a series of designs for carbon dot-based sensors and the different sensing mechanisms associated with them.Thereafter, we elaborate on recent research advances on carbon dot-based sensors for the selective and sensitive detection of a wide range of analytes, including heavy metals, cations, anions, biomolecules, biomarkers,nitroaromatic explosives, pollutants, vitamins, and drugs.Lastly, we provide a concluding perspective on the overall status, challenges, and future directions for the use of carbon dots in real-life sensing.

Quantitative description of infrared radiation characteristics of preflawed sandstone during fracturing process

Previous studies show that infrared radiation temperature(IRT)abnormalities are always accompanied by the crack development in rocks under external loads.In this context,experiments were conducted on preflawed sandstone to investigate the infrared radiation characteristics during failure process.Two indicators were defined herein,i.e.coefficient of variation of IRT(CVIRT)and skewness of IRT(SIRT).The regression analysis shows that the IRT probability distributions during loading process fit the Gaussian model.The variations in the CVIRT are characterized by four stages:primary stage,steady stage,accelerating stage and post-peak stage.Besides,the variations in the SIRT are divided into three stages:primary stage,steady stage and failure and post-peak stage.The precursor point for preflawed rock failure is identified based on the CVIRTetime curve,with average precursor point of 83%of the peak stress.Compared with other IRT indicators,the proposed two IRT indicators have higher sensitivity to IRT abnormalities during failure process.Furthermore,the connection between the IRT indicators and the rock fracturing was investigated to interpret the IRT indicator abnormalities.Based on the Verhulst inverse function,a new quantitative model was presented to describe the primary stage,steady stage and accelerating stage of the CVIRTetime curve.The results obtained in this study can provide early-warning information for rock failure prediction.

Twisting mode of supercoil leucine-rich domain mediates peptide sensing in FLS2–flg22–BAK1 complex

Plants and animals recognize microbial invaders by detecting pathogen-associated molecular patterns (PAMPs) through pattern-recognition receptors (PRRs). This recognition plays a crucial role in plant immunity. The newly discovered protein in plants that responds to bacterial flagellin, i.e., flagellin-sensitive 2 (FLS2), is ubiquitously expressed and present in many plants. The association of FLS2 and BAK1, facilitated by a highly conserved epitope flg22 of flagellin, triggers such downstream immune responses as activated MAPK pathway and elevated reactive oxygen species (ROS) for bacterial defense and plant immunity. Here we study the intrinsic dynamics and conformational change of FLS2 upon the formation of the FLS2–flg22–BAK1 complex. The top intrinsic normal modes and principal structural fluctuation components are very similar, showing two bending modes and one twisting mode. The twisting mode alone, however, accounts for most of the conformational change of FLS2 induced by binding with flg22 and BAK1. This study indicates that flg22 binding suppresses FLS2 conformational fluctuation, especially on the twisting motion, thus facilitating FLS2–BAK1 interaction. A detailed analysis of this sensing mechanism may aid better design on both PRR and peptide mimetics for plant immunity.

Rapid detection of nanoplastic particles by a luminescent Tb-based coordination polymer

Nanoplastics(NPs)in aqueous environment have become a category of emerging pollutants on account of their potential risks to both human health and environment.The detection of NPs is a great challenge due to the lack of sensitive and selective sensing materials with fast response time and wide sensing range of particle sizes.Herein,a Tb-based coordination polymer has been synthesized for luminescent detection of nanopolystyrene with different particle sizes in aqueous solutions,showing a low limit of detection,fast response time within 10 s and high selectivity in the presence of other plastics.The“turn-on”sensing mechanism is studied in detail.This work provides a facile method for the fast detection of NPs.

Multimode sensing based on optical microcavities

Optical microcavities have the ability to confne photons in small mode volumes for long periods of time,greatly enhancing light-matter interactions,and have become one of the research hotspots in international academia.In recent years,sensing applications in complex environments have inspired the development of multimode optical microcavity sensors.These multimode sensors can be used not only for multi-parameter detection but also to improve measurement precision.In this review,we introduce multimode sensing methods based on optical microcavities and present an overview of the multimode single/multi-parameter optical microcavities sensors.Expected further research activities are also put forward.

Ultra-thin CoAl layered double hydroxide nanosheets for the construction of highly sensitive and selective QCM humidity sensor

To achieve real-time monitoring of humidity in various applications,we prepared facile and ultra-thin CoAl layered double hydroxide(CoAl LDH)nanosheets to engineer quartz crystal microbalances(QCM).The characteristics of CoAl LDH were investigated by transmission electron microscopy(TEM),X-ray diffraction(XRD),X-ray photoelectric spectroscopy(XPS),Brunauer–Emmett–Telle(BET),atomic force microscopy(AFM)and zeta potential.Due to their large specific surface area and abundant hydroxyl groups,CoAl LDH nanosheets exhibit good humidity sensing performance.In a range of 11.3%and 97.6%relative humidity(RH),the sensor behaved an ultrahigh sensitivity(127.8 Hz/%RH),fast response(9.1 s)and recovery time(3.1 s),low hysteresis(3.1%RH),good linearity(R^(2)=0.9993),stability and selectivity.Besides,the sensor can recover the initial response frequency after being wetted by deionized water,revealing superior self-recovery ability under high humidity.Based on in-situ Fourier transform infrared spectroscopy(FT-IR),the adsorption mechanism of CoAl LDH toward water molecules was explored.The QCM sensor can distinguish different respiratory states of people and wetting degree of fingers,as well as monitor the humidity in vegetable packaging,suggesting excellent properties and a promising application in humidity sensing.

Advanced flexible humidity sensors:structures,techniques,mechanisms and performances

Flexible humidity sensors are widely used in many fields,such as environmental monitoring,agricultural soil moisture content determination,food quality monitoring and healthcare services.Therefore,it is essential to measure humidity accurately and reliably in different conditions.Flexible materials have been the focusing substrates of humidity sensors because of their rich surface chemical properties and structural designability.In addition,flexible materials have superior ductility for different conditions.In this review,we have summarized several sensing mechanisms,processing techniques,sensing layers and substrates for specific humidity sensing requirements.Aadditionally,we have sorted out some cases of flexible humidity sensors based on different functional materials.We hope this paper can contribute to the development of flexible humidity sensors in the future.

Recent advances in formaldehyde-responsive fluorescent probes

Formaldehyde, as one of the simplest reactive carbonyl species（RCS）, is regarded as a potential carcinogen and a sick house syndrome gas. Recent studies have shown that abnormally high levels of formaldehyde may result in cognitive decline and spatial memory deficits, asthmatic symptoms,Alzheimer＇s disease, and cancer. Due to the harmfulness of high levels of formaldehyde in nature and humans, it is of great significance to further elucidate the roles and functions of formaldehyde by a noninvasive detection approach. Fluorescence imaging has become a powerful and popular tool in monitoring bio-species owing to their high sensitivity and selectivity, excellent spatiotemporal resolution and non-invasion nature. Therefore, fluorescent probes are widely applied to track and detect formaldehyde in vitro and in vivo which have attracted more and more interest recently. This review focuses on various strategies to design the fluorescent probes for detecting formaldehyde based on different recognition groups.

Recent Progress on Smart Fiber and Textile Based Wearable Strain Sensors:Materials,Fabrications and Applications

With the rapid development of smart products,fexible and stretchable smart wearable electronic devices gradually play an important role,and they are considered as the pioneers of the new generation of fexible electronic devices.Among these intelligent devices,fexible and stretchable strain sensors have been widely studied for their good fexibility,high sensitivity,high repeatability and huge potential for application in personal healthcare and motion detection.Moreover,unlike traditional rigid bulky sensors,the high-performance fexible strain sensors are lightweight portable devices with excellent mechanical and electrical performance,which can meet personalized needs and become more popular.Herein,the research progress of fexible strain sensors in recent years are reviewed,which mainly introducing the sensing principles and key parameters of strain sensors,commonly used conductive materials and fexible substrates and common preparation methods,and fnally proposes the future application and prospects of strain sensors.

Primary cilia in hard tissue development and diseases

Bone and teeth are hard tissues.Hard tissue diseases have a serious effect on human survival and quality of life.Primary cilia are protrusions on the surfaces of cells.As antennas,they are distributed on the membrane surfaces of almost all mammalian cell types and participate in the development of organs and the maintenance of homeostasis.Mutations in cilium-related genes result in a variety of developmental and even lethal diseases.Patients with multiple ciliary gene mutations present overt changes in the skeletal system,suggesting that primary cilia are involved in hard tissue development and reconstruction.Furthermore,primary cilia act as sensors of external stimuli and regulate bone homeostasis.Specifically,substances are trafficked through primary cilia by intraflagellar transport,which affects key signaling pathways during hard tissue development.In this review,we summarize the roles of primary cilia in long bone development and remodeling from two perspectives:primary cilia signaling and sensory mechanisms.In addition,the cilium-related diseases of hard tissue and the manifestations of mutant cilia in the skeleton and teeth are described.We believe that all the findings will help with the intervention and treatment of related hard tissue genetic diseases.

Recent Progresses in Lanthanide Metal-Organic Frameworks(Ln-MOFs) as Chemical Sensors for Ions, Antibiotics and Amino Acids

Various ions and antibiotics,widely used in industry and clinical medicine,respectively,are massively discharged to atmosphere and water,resulting in severe pollutions on environment and potential threats to human health.Besides,amino acids,the primary substances for the establishment of proteins,cells and tissues,are crucial to human health.Therefore,seeking effective and practicable materials to detect aforesaid analytes is vitally meaningful.Metal-organic frameworks centered with lanthanide ions(Ln-MOFs),also known as lanthanide coordination polymers,are considered as a charming category of multi-functional hybrid crystalline materials with fascinating structures and incomparable luminescent characteristics.Benefited from their unique merits,Ln-MOFs have been largely developed as excellent luminescent sensors for fast and efficient sensing various analytes.In this review,we aim to introduce some of the recent researches between 2018 to 2022 on Ln-MOFs applied as chemical sensors for ions,antibiotics and amino acids based on luminescent quenching and enhancing effects,and provide an update and summary for the latest progresses in this field.

Sensing mechanism of Ag/α-MoO_(3) nanobelts for H_(2)S gas sensor

Sensing mechanism is still a big problem in the field of gas sensor.In-depth study of the sensing mechanism can provide better ideas for the design of sensing materials,and it is also more conducive to the improvement in gas-sensing performance.In this work,Ag/α-MoO_(3) material was obtained by loading Ag in α-MoO_(3) nanobelts prepared by hydrothermal method.The material was characterized by field electron scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS).Comparing the gas sensing properties of α-MoO_(3) and Ag/α-MoO_(3),it is found that Ag effectively improves the selectivity of the material to H_(2)S at 133℃.The response of the 5 wt% Ag/α-MoO_(3) sensor to 100 × 10-6 hydrogen sulfide(H_(2)S) is 225 and the detection limit is 100 ×10^(-9).The sensing mechanism was verified by gas chromatography and mass spectrometer(GC-MS),XPS and Fourier transform infrared spectroscopy(FTIR).

β-Ga_(2)O_(3) nanowires and thin films for metal oxide semiconductor gas sensors:Sensing mechanisms and performance enhancement strategies

The reliable,selective,and fast detection of the inorganic and organic gases in indoor and outdoor air and industrial processes is a huge challenge for environmental sustainability,healthier life,and disease control and diagnosis.Metal oxides have been frequently explored as highly sensitive receptor elements in the electronic gas sensors since the 1960s.Gallium oxide(Ga_(2)O_(3)),often recognized as one of the widest-bandgap semiconductors,has shown tremendous potential as the inorganic gas receptor because of its extraordinary chemical and thermal stability,and excellent electronic properties.This article presents a comprehensive reference on the electrical properties,historical developments,detection mechanisms,and gas sensing performance of Ga_(2)O_(3) nanowires and composite nanostructures.In particular,the relationships between composition,nanostructure,and gas sensing properties of galliumcontaining oxidic nanomaterials such as β-Ga_(2)O_(3) nanowires,surface-modified Ga_(2)O_(3),metal-doped Ga_(2)O_(3) or Ga-doped metal oxides,and Ga_(2)O_(3)/metal oxide composite heterostructures are studied.The applications of Ga_(2)O_(3) gas sensors are discussed with an emphasis on their practical limitations such as high-temperature operation,power consumption,and miniaturization issues.Finally,future research directions and potential developments are suggested.

Enhanced positive humidity sensitive behavior of p-reduced graphene oxide decorated with n-WS_(2) nanoparticles

Most resistance-type humidity sensors exhibit negative humidity sensitivity,i.e.,their resistance decreases with a corresponding increase in humidity.This is primarily attributed to the dominant role of ionic conduction in adsorbed water.In this work,a humidity sensor based on a p-type reduced graphene oxide(p-rGO)with positive humidity sensitivity is proposed.Moreover,its positive humidity sensing response is further enhanced by n-type WS_(2) nanoparticles modification.The results show that both rGO and r GO/WS_(2) humidity sensors have good linear response in the relative humidity(RH)range of0%-91.5%.The sensitivity of the rGO/WS_(2) humidity sensor is 1.87 times that of rGO humidity sensor,which is mainly attributed to p-n heterojunction between rGO and WS_(2).Besides,the r GO/WS_(2) humidity sensor has small humidity hysteresis(-3%RH)and good repeatability.This work demonstrates a humidity sensor based on rGO/WS_(2) composite film and provides a facile route for fabricating humidity sensor with positive humidity sensing properties.

Adjustment of oxygen vacancy states in ZnO and its application in ppb-level NO2 gas sensor

Oxygen vacancy(VO)is long believed as a key factor influencing the gas sensing properties.However,the concentration of VO is generally focused while the VOstate is neglected,which masks the inherent mechanism of gas sensor.Using a post annealing process,the influence of VO states on the response of ZnO nanofilm to NO2 gas is investigated in this study.The systematical analysis of the results obtained by different methods indicates a transformation of VO from the neutral to the doubly ionized state during post annealing treatment.The results also imply that the gas sensing properties is not directly correlated with the VO concentration.And due to the competitive adsorption of ambient O2,the neutral VO is majorly occupied by the adsorbed O2 while the VO in doubly ionized state can promote the adsorption of NO2.Consequently,the transition of VO from the neutral to the doubly ionized state can lead to a dramatic increase of the response to NO2,from 733 to 3.34×10^4 for 100 ppm NO2.Guided by this mechanism,NO2 gas sensing in ppb-level is also achieved:the response reaches 165%to 25 ppb(0.025 ppm)NO2 with a good repeatability.

Small-molecule fluorescent probes for the detection of carbon dioxide

During the last few years, the preparation of novel fluorescent probes for the detection of carbon dioxide has attracted considerable attention since carbon dioxide plays extremely important roles in widespread fields including chemical, environmental, clinical analysis, and agri-food industry. This review focuses on the recent advances in the design principles, recognition mechanisms, and preparation of small-molecule fluorescent probes for the selective detection and monitoring of CO;. Moreover, their properties and functions will be discussed detailedly as well.