Field Of Environmental Monitoring Research Articles

Dual-core-enhanced surface plasmon resonance for sensing high refractive index liquid based on photonic crystal fiber

A dual-core photonic crystal fiber sensor based on surface plasmon resonance is theoretically proposed for the high-sensitive detection of high refractive index liquid analytes. Dual-core construction can effectively enhance the coupling effect between the fiber-core mode and the surface plasmon polariton modes, leading to sharp loss peaks at the resonance wavelengths. As the refractive index of the targeted analyte varies, the resonance condition will change as well and cause a certain shift of loss peak. Numeric results show that this dual-core fiber sensor exhibits an average linear sensitivity 9538 nm/RIU and a maximum sensitivity is 11400 nm/RIU with a resolution 8.77 × 10−6 RIU. The detected range is broad and covers the high refractive index range from 1.45 to 1.58 with an average figure of merit 284.5 RIU−1. The dependence of structure parameters and the thickness of coated-metal thin-film on sensing performance is performed systemically and suggests different responses. The proposed sensor is highly promising in detecting high refractive index liquid analytes in the fields of biological detection, environmental monitoring and chemical analysis.

High performance acetone sensor based on yttria stabilized-zirconia and NiGaxAl2-xO4 (x = 0, 0.6, 1 and 1.4) sensing electrode

In this paper, YSZ-based high performance acetone sensor was successfully developed for intelligent medical service, environmental monitoring, and safety production of smart city. New type spinel electrode sensing materials NiGaxAl2-xO4 (x = 0, 0.6, 1 and 1.4) were synthesized by a sol-gel method. Compared to the other sensing electrode materials, NiGa0.6Al1.4O4 had the highest electrochemical catalytic activity to acetone, and the sensor based on NiGa0.6Al1.4O4-SE performed the best sensing performance of −48 mV to 10 ppm acetone. Moreover, the present acetone sensor has a wide detection range of 0.2–1000 ppm, with sensitivity of −45 mV/decade, meeting the field of diabetic non-invasive diagnosis and real-time in-situ environmental monitoring. In addition, the device also performs excellent repeatability, acceptable selectivity, terrific humidity resistance and marvelous long-term stability during continuous measurements over 30 days. Overall, based on its excellent sensing performance, the developed sensor has marvelous application prospects for acetone detection in intelligent medical service, environmental monitoring, and safety production fields of smart city.

DNAzyme amplified dispersion state change of gold nanoparticles and its dual optical channels for ultrasensitive and facile detection of lead ion in preserved eggs

A dual-mode sensing platform for Pb2+ was constructed based on the dual optical channels of Au NPs system with the amplification of DNAzyme, and it was successfully applied for Pb2+ determination in preserved egg with satisfactory results. The presence of Pb2+ activated the DNAzyme and induced the dispersion change of Au NPs in high salt concentration. The sequent absorption change of Au NPs was translated to the fluorescence change of carbon dots through FRET, and the scattering change was transferred to grey value of images involving the Tyndall effect. Thus, a sensing platform based on fluorescence and colorimetric dual-technique was achieved for Pb2+ detection, under the optimized conditions. With the assistance of DNAzyme, the linear range of fluorometric and colorimetric method were 2.0 × 10-14 ∼ 8.0 × 10-10 mol/L and 2.4 × 10-13 ∼ 9.5 × 10-9 mol/L, respectively. The dual-mode sensing platform demonstrated its promising application in the environmental monitoring and food safety field.

A-367 Development of a Novel Handheld Platform for Real-time Fluorescence-based Nucleic Acid Detection

Abstract Background Real-time fluorescent nucleic acid detection systems are usually large and complex to operate. In the past three years, the pandemic outbreak of COVID-19 has sparked a variety of point-of-care testing (POCT) nucleic acid detection platforms. However, most of these platforms need to be paired with specific reagents, and many detection reagents on the market cannot be applied to these POCT platforms. Methods In this research, a novel handheld real-time nucleic acid detection device was invented. The device uses a heating element to adjust the temperature in time with a sensor to ensure accuracy. The optical detection module is highly scalable and can be extended up to 6 fluorescence channels. The FAM and HEX fluorescence channels were utilized in this experiment. This platform is open and can adjust temperature for various types of isothermal nucleic acid detection, such as LAMP, RPA, and RCA. Results We used a commercial COVID-19 reagent kit with our device to get results in just 30 minutes, detecting SARS-CoV-2 virus as little as 500 copies/mL. Our system provides a reliable and efficient tool for COVID-19 testing in a variety of settings. Conclusion The handheld device was also used to test for flu A and mycobacterium tuberculosis, with good results. This device can be used not only for pathogen detection of human diseases, but also in pathogen detection for animals and plants, food safety, environmental monitoring, and other fields, thus expanding the application range of nucleic acid detection and making it simpler and more convenient to use.

Near-zero-power infrared relay based on microfluidic switch and metamaterial absorber

Internet of Things sensor nodes, which integrate information acquisition, processing, exchange, and execution modules, have widely been used for unattended industrial production, environmental monitoring, and other fields. However, limited battery power constrains the lifespan of the sensor nodes. In this paper, we propose a near-zero-power infrared relay consists of microfluidic switches and a metamaterial absorber (MA). When target appears, the MA absorbs the infrared energy emitted from the target and uses it to turn on the microfluidic switch. When valid information is not present, the microfluidic switch is in “off” state with a high resistance of over 109 Ω. The infrared relay with a pair of microfluidic switches shows common mode suppression capability against environmental temperature variation. We further demonstrate a sensor node consists of the infrared relay and a MoS2 photodetector. In a standby mode, the sensor node shows near-zero power consumption. As target infrared signal occurs, the photodetector is wakened by the infrared relay and illustrates excellent optical sensing performance. The simplicity of this approach provides a route for significantly extending the lifespan of sensor nodes powered by batteries, especially the sensor nodes for detecting infrequent but critical events.

Gas Sensor Array Fault Diagnosis Based on Multi-Dimensional Fusion, an Attention Mechanism, and Multi-Task Learning.

With the development of gas sensor arrays and computational technology, machine olfactory systems have been widely used in environmental monitoring, medical diagnosis, and other fields. The reliable and stable operation of gas sensing systems depends heavily on the accuracy of the sensors outputs. Therefore, the realization of accurate gas sensor array fault diagnosis is essential to monitor the working status of sensor arrays and ensure the normal operation of the whole system. The existing methods extract features from a single dimension and require the separate training of models for multiple diagnosis tasks, which limits diagnostic accuracy and efficiency. To address these limitations, for this study, a novel fault diagnosis network based on multi-dimensional feature fusion, an attention mechanism, and multi-task learning, MAM-Net, was developed and applied to gas sensor arrays. First, feature fusion models were applied to extract deep and comprehensive features from the original data in multiple dimensions. A residual network equipped with convolutional block attention modules and a Bi-LSTM network were designed for two-dimensional and one-dimensional signals to capture spatial and temporal features simultaneously. Subsequently, a concatenation layer was constructed using feature stitching to integrate the fault details of different dimensions and avoid ignoring useful information. Finally, a multi-task learning module was designed for the parallel learning of the sensor fault diagnosis to effectively improve the diagnosis capability. The experimental results derived from using the proposed framework on gas sensor datasets across different amounts of data, balanced and unbalanced datasets, and different experimental settings show that the proposed framework outperforms the other available methods and demonstrates good recognition accuracy and robustness.

High storage and operational stability self-powered UV photodetector based on p-CuI/n-GaN heterojunction prepared by thermal evaporation method

Self-powered ultraviolet (UV) photodetectors play an important role in environmental monitoring, aerospace and other fields because of the advantage of effective light response without an external power supply. Herein, a p-CuI/n-GaN heterojunction UV photodetector with self-powered function is constructed by vacuum thermal evaporation method. At 365 nm UV irradiation, the photodetector has an on/off ratio of 7536, a large photocurrent (∼35 mA) and a fast response time (rise/decay time of 10.46/10.35 ms) at zero bias. There was no significant decrease in photocurrent during the 100 on/off cycles of the continuous test, and the photocurrent of the photodetector can maintain 93.17% of the initial value after continuous operation for 15 h without bias voltage. The rise in ambient temperature exhibits a negative effect on the UV photodetector, but when it is naturally cooled from 80℃ to room temperature (RT), the photocurrent can restore to 95% of the original level. Furthermore, the photodetector maintains superior stability even after being stored in air for 3 months of without package. This work not only proves the controllable preparation strategy of CuI thin films, but also provides an efficient structure for self-powered UV photodetectors with high operational and storage stability.

Whole-genome detection using multivalent DNA-coated colloids

To minimize the incorrect use of antibiotics, there is a great need for rapid and inexpensive tests to identify the pathogens that cause an infection. The gold standard of pathogen identification is based on the recognition of DNA sequences that are unique for a given pathogen. Here, we propose and test a strategy to develop simple, fast, and highly sensitive biosensors that make use of multivalency. Our approach uses DNA-functionalized polystyrene colloids that distinguish pathogens on the basis of the frequency of selected short DNA sequences in their genome. Importantly, our method uses entire genomes and does not require nucleic acid amplification. Polystyrene colloids grafted with specially designed surface DNA probes can bind cooperatively to frequently repeated sequences along the entire genome of the target bacteria, resulting in the formation of large and easily detectable colloidal aggregates. Our detection strategy allows "mix and read" detection of the target analyte; it is robust and highly sensitive over a wide concentration range covering, in the case of our test target genome Escherichia coli bl21-de3, 10 orders of magnitude from [Formula: see text] to [Formula: see text] copies/mL. The sensitivity compares well with state-of-the-art sensing techniques and has excellent specificity against nontarget bacteria. When applied to real samples, the proposed technique shows an excellent recovery rate. Our detection strategy opens the way to developing a robust platform for pathogen detection in the fields of food safety, disease control, and environmental monitoring.

Recent Development of Polymer Nanofibers in the Field of Optical Sensing.

In recent years, owing to the continuous development of polymer nanofiber manufacturing technology, various nanofibers with different structural characteristics have emerged, allowing their application in the field of sensing to continually expand. Integrating polymer nanofibers with optical sensors takes advantage of the high sensitivity, fast response, and strong immunity to electromagnetic interference of optical sensors, enabling widespread use in biomedical science, environmental monitoring, food safety, and other fields. This paper summarizes the research progress of polymer nanofibers in optical sensors, classifies and analyzes polymer nanofiber optical sensors according to different functions (fluorescence, Raman, polarization, surface plasmon resonance, and photoelectrochemistry), and introduces the principles, structures, and properties of each type of sensor and application examples in different fields. This paper also looks forward to the future development directions and challenges of polymer nanofiber optical sensors, and provides a reference for in-depth research of sensors and industrial applications of polymer nanofibers.

An improved dissipative particle dynamics method for the liquid-particle two-phase flow in microchannels

Liquid-particle two-phase flow in microchannel widely exists in the fields of biomedical and environmental monitoring, such as the lab-chip device for disease diagnosis. The standard dissipative particle dynamics (DPD) method has been previously employed to study the liquid-particle two-phase flow in microchannel, but it cannot accurately simulate the real process because of the unsuitable DPD parameters. In the present study, an improved DPD method was developed by changing the system energy and fitting the characteristic curve between the random force coefficient and the Schmidt number. In addition, a new logarithmic relationship between the conservative force coefficient and the particle size was found. The result demonstrated that the improved DPD method enabled more accurate simulation on the liquid-particle two-phase flow in microchannels than the standard DPD method. For instance, in the simulation of particle sedimentation, the relative deviation between the value obtained by the improved DPD method and the theoretical value was less than 6% while the relative deviation was more than 20% for the standard DPD method. The simulated result of the particle migration in microchannel was in good agreement with the result obtained by Matas et al, and the relative deviation was less than 1.5%. Therefore, the improved DPD method would have great potentials in the study on the liquid-particle two-phase flow in microchannels.

Amorphous/Crystal Heterostructure Coupled Oxygen Vacancies‐Sensitized TiO2 with Conspicuous Charge‐Transfer Resonance for Efficient SERS Detection of Chloramphenicol

AbstractAntibiotic environmental pollutants, such as chloramphenicol (CAP), have attracted global attention. They usually show a complex background, low concentration, and weak chemical activity in water bodies, making their rapid and on‐site detection a scientific challenge. Surface‐enhanced Raman spectroscopy (SERS) technology can facilitate the practical application of CAP detection; however, it is important to match substrate materials with excellent SERS properties. The most challenging aspect of SERS substrate design is the realization of energy level matching and charge‐transfer resonance. Herein, a crystal‐amorphous TiO2 substrate material rich in oxygen vacancies, CA‐V‐TiO2, is proposed. Through the cooperative regulation of vacancies and amorphous state, the bandgap structure can be optimized, the charge‐transfer efficiency can be improved, and finally the energy level matching between CA‐V‐TiO2 substrate and molecules can be realized and the conspicuous charge‐transfer resonance phenomenon can be generated, effectively optimizing the performance of SERS substrate. In addition, CA‐V‐TiO2 substrate is used for sensitive detection of CAP, showing multiple advantages such as low detection limit, good reproducibility, and high stability, which can realize trace CAP detection in actual water environments. This work provides a reliable platform for SERS on‐site detection of CAP in the field of food and environmental monitoring.

Highly sensitive digital detection of SARS-CoV-2 nucleocapsid protein through single-molecule counting.

Nucleocapsid protein (NP) is one of the structural proteins of SARS-CoV-2 which is stable, well-conserved, highly immunogenic, and abundantly expressed due to the host's adaptive immune response, making it a promising antigenic biomarker for the early and rapid identification and diagnosis of SARS-CoV-2. Traditional antigen analytical methods with NP as the detection marker often have insufficient sensitivity. To achieve rapid and highly sensitive detection of NP, we constructed a novel single-molecule (digital) fluorescence-linked immunosorbent assay (FLISA) based on streptavidin-modified transparent 96-well microplates. Streptavidin was immobilized on the microplate under optimized conditions with a 15mM carbonate buffer solution (pH 9.6) as the coating solution, biotinylated antibodies conjugated with streptavidin as capture probes, and carboxylated fluorescent microsphere-conjugated monoclonal antibodies (FMs-mAbs) as fluorescent probes. Individual sandwich immunolabeled complexes of the SARS-CoV-2 diagnostic marker NP were detected and counted though wide-field inverted fluorescence microscopy (1.1 × 1.4 mm2). FLISA had a linear detection range of 0.2pg/mL to 200ng/mL and a limit of detection (LOD) of 0.73fg/mL and 8fg/mL for NP in phosphate buffer saline and spiked nasal swab samples, respectively. The sensitivity was much higher than commercial antigen detection kits, providing wide detection prospects in future clinical diagnosis, environmental monitoring, and other fields.

Navigable DNA walker coupled with exonucleases-assisted signal amplification for sensitive fluorescent detection of Staphylococcus aureus

A fluorescent aptasensor for Staphylococcus aureus (S. aureus) was constructed by integrating the mechanisms of fluorescence signal regulation and exonucleases-assisted two-step signal amplification into a navigable DNA walker. After the recognition of S. aureus, the first signal amplification step converts the aptamer-cDNA1 duplex to the hydrolysate of cDNA1 by exonuclease I (Exo I). Then the second signal amplification step converts the hydrolysate to the fuel chain of the navigable DNA walker with the help of exonuclease III (Exo III) reaction system containing hairpin probe and cDNA2. Driven by the fuel chain, the movement of the DNA walker triggers the fluorescence resonance energy transfer (FRET) to obtain an amplified fluorescent signal that correlates to the target concentration. The movement track is ingeniously designed and constructed by DNA self-assembly technology, which controls the motion direction and stride of the DNA walker. In addition, the movement triggers FRET, which effectively enhances the detection signal. The biosensor has a wide detection concentration range of 1 × 102-2 × 107 CFU/mL, and the detection limit is 9 CFU/mL. This biosensor provides a reference method for customization of signal amplification strategy in DNA circuit machinery. And has potential applications in the fields of environmental and food safety monitoring.

VII congress of biophysicists of Russia

The problems and results of research in biophysics, which were devoted to the VII Congress of Biophysicists of Russia (Krasnodar, April 17-23, 2023, http://rusbiophysics.ru/db/conf.pl), are discussed. The results of fundamental and applied research in the field of molecular biophysics, cell biophysics, biophysics of complex multicomponent systems were presented at plenary, sectional and poster sessions. The structure and dynamics of biopolymers, the fundamental mechanisms underlying the impact of physicochemical factors on biological systems, membrane and transport processes were actively discussed. Much attention was paid to new experimental methods of biophysical research, methods of bioinformatics, computer and mathematical modeling as essential research tools at all levels of organization of living systems. Along with the fundamental problems of studying the biophysical mechanisms of regulation of processes at the molecular, subcellular and cellular levels, much attention was paid to applied research in the field of biotechnology and environmental monitoring. Works in the field of medical biophysics were especially widely represented. During the Congress, the National Council for Biophysics was formed.

Surface Plasmon Resonance Sensor Based on Waveguides Inscribed in No-Core Fiber

We present a surface plasmon resonance (SPR) refractive index sensor based on femtosecond laser inscribed waveguides in a no-core fiber sandwiched between two sections of single mode fibers. The waveguides inscribed have a trapezoidal structure which consists of three sections: two slant waveguides to direct light out and back into the core of single mode fiber and a straight waveguide close to and in parallel with the surface of no-core fiber. A thin layer of Cr+Ag is coated on the surface of NCF to cover the straight waveguide region. The device is compact and has good mechanical robustness. The experimental results obtained show that the device has a refractive index sensitivity of ~3234 nm/RIU in the refractive index range of 1.34-1.37, and is expected to have practical applications in the fields of bio-medicine and environmental monitoring.

Efficient detection of hydrogen peroxide based on hollow SiO2 photonic crystals and Rhodamine 6G

Hydrogen peroxide (H2O2) is an important oxidant that exists widely in biological systems and the environment, and has been extensively used in medical, environmental, food, and industrial fields. Accurate, rapid, and sensitive detection of H2O2 content is of great significance in the fields of biomedicine, environmental monitoring, food safety, and public safety. In this study, a probe was developed by utilizing Rhodamine 6G (Rh6G), a readily available commercial fluorescent dye, within hollow SiO2 photonic crystals (HSPCs) to produce an amplified fluorescent signal. Furthermore, I- were incorporated into the system, which can be oxidized to I2 in the presence of H2O2. The I3- produced can react with Rh6G to form a complex that quenches the fluorescence signal, enabling highly efficient detection of H2O2. The method does not require complex organic synthesis or modification of fluorescent groups. Additionally, the sensors exhibit good performance in terms of repeated use and can also potentially detect different concentrations of ethanol solutions.

A three-dimensional boron-doped diamond mesh aptasensor for the sensitive determination of cefquinome

Aptamer can specifically identify the target and combine with surface functionalized electrodes to construct highly selective electrochemical aptasensor, so it has a wide range of applications in environmental monitoring, medical diagnosis and other fields. In this study, we designed and fabricated a boron-doped diamond (BDD) electrochemical aptasensor based on three-dimensional mesh structure for the detection of trace cefquinome (CFQ). The low detection limit of 9.29 × 10−16 mol L−1 as well as broad linear relationship ranging from 1.0 × 10−15 to 1.0 × 10−9 mol L−1 were achieved through a modification to the surface of BDD mesh using gold nanoparticle (Au-NPs), aptamers and 6-mercapto-1-ethanol (MCH). The experimental findings demonstrate that the aptasensor is of significant sensitivity, specificity and stability, and it has broad application prospects in the field of trace detection.

CNT/PDMS conductive foam-based piezoresistive sensors with low detection limits, excellent durability, and multifunctional sensing capability

In this paper, a carbon nanotube (CNT)/polydimethylsiloxane (PDMS) conductive composite foam (CCF) was fabricated via a dual-solvent ice template (DSIT) process, whose structure features the conductive filler CNT "embedded" in the cell wall surface, and this CCF was applied to the field of flexible piezoresistive sensing. Benefiting from the sensitive conductive network constructed by the DSIT process, the CNT/PDMS CCF-based piezoresistive sensor can effectively detect compression strains down to 0.1% and exhibits excellent and stable response at compression strains up to 90%. In addition, the CCF shows fast response and recovery times (54 ms and 65 ms), as well as excellent durability and stability (2000 cycles). An electronic skin assembled from the CCF into 5 × 5 pixels was applied to detect the magnitude and spatial distribution of forces and strains. The CCF was also applied for roughness recognition, optical and thermal sensing responses, which shows its potential applications in personalized medical monitoring, electronic smart skin fabrication, external environment monitoring and other fields.

A tunable water antenna

AbstractThis paper presents a pure water antenna with frequency reconfigurability, which is composed of a water resonator, L‐shaped feeder, and metal ground pad. An L‐shaped feeding structure is designed so that the working frequency can be adjusted by changing the water level of the resonator. The cross‐stack periodic water radiator structure improves the radiation efficiency by 2–4 dB compared with simple rectangular structure. The working frequency of this antenna is around 1 GHz, and will decrease by 17 MHz for every 5 mm increase in water level, which proves the feasibility of this antenna for water level monitoring. It has the potential for application in the field of wireless environmental monitoring for the Internet of Things.

Global Path Planning of Unmanned Surface Vehicle Based on Improved A-Star Algorithm.

To make unmanned surface vehicles that are better applied to the field of environmental monitoring in inland rivers, reservoirs, or coasts, we propose a global path-planning algorithm based on the improved A-star algorithm. The path search is carried out using the raster method for environment modeling and the 8-neighborhood search method: a bidirectional search strategy and an evaluation function improvement method are used to reduce the total number of traversing nodes; the planned path is smoothed to remove the inflection points and solve the path folding problem. The simulation results reveal that the improved A-star algorithm is more efficient in path planning, with fewer inflection points and traversing nodes, and the smoothed paths are more to meet the actual navigation demands of unmanned surface vehicles than the conventional A-star algorithm.