4.3 THz quantum-well photodetectors with high detection sensitivity

We demonstrate a high performance GaAs/AlGaAs-based quantum-well photodetector(QWP)device with a peak response frequency of 4.3 THz.The negative differential resistance(NDR)phenomenon is found in the dark currentvoltage(I-V)curve in the current sweeping measurement mode,from which the breakdown voltage is determined.The photocurrent spectra and blackbody current responsivities at different voltages are measured.Based on the experimental data,the peak responsivity of 0.3 A/W(at 0.15 V,8 K)is derived,and the detection sensitivity is higher than 10^(11)Jones,which is in the similar level as that of the commercialized liquid-helium-cooled silicon bolometers.We attribute the high detection performance of the device to the small ohmic contact resistance of-2Ωand the big breakdown bias.

Multi-area detection sensitivity calculation model and detection blind areas influence analysis of photoelectric detection target

Multi-element array photoelectric detector is the core devices to form a photoelectric detection target with a large field of view.This photoelectric detection target brings about the problem of uneven detection sensitivity distribution in the detection screen.To improve the uneven detection sensitivity of this photoelectric detection target,this paper analyzes the distribution law of the uneven detection sensitivity of the photoelectric detection target using the multi-element array photoelectric detector,dissects the main factors affecting the detection sensitivity according to the photoelectric detection principle,establishes the calculation model of detection sensitivity of the photoelectric detection target in the different detection areas and proposes a method to improve the detection sensitivity by compensating the gain of each unit photoelectric detector.The analysis of simulation and experimental results show that the proposed method of photoelectric detection target can effectively improve the output signal amplitude of the projectile under the certain detection distance,in particular,the output signal amplitude of the projectile is significantly increased when the projectile passes through the detection blind area.The experimental results are consistent with the simulation results,which verify the effectiveness of the proposed improvement method.

Construction and investigation of all-inone microneedles complexed with functionalized polydiacetylene liposomes for improved in situ detection sensitivity

Polydiacetylene(PDA)liposomes have been widely applied for detection due to their distinctive optical properties.How-ever,the liquid phase in which PDA liposomes are dispersed generates several drawbacks,for instance,instability,compromise of detection sensitivity induced by dilution,and separation of target sampling and detection,making it inconvenient for application.In this paper,various functionalized PDA liposomes for detecting target were prepared,which were also immobilized into swelling microneedles to construct a solid-phase detection system.The PDA lipo-somes-complexed microneedles(PDA/MNs)enable the integration of target sampling and detection in one platform.The effects of the dispersing matrix phase on the detection sensitivity of PDA liposomes were systematically investi-gated from both environmental and chemical perspectives.PDA/MNs exhibited higher sensitivity than their counter-parts in liquid phase.PDA/MNs were optimized and validated for lead ion(Pb2+)and sialic acid(SA)detections.For Pb2+detection,the limit of detection(LOD)of the PDA/MNs was 13.7 mM and 2.5 times lower than the liquid phase.For SA detection,the LOD of the PDA/MNs was 0.83 mM and 1.7 times lower than the liquid phase.The results suggested that such PDA/MNs were validated to provide a label-free,stable,sensitive,and convenient tool in an all-in-one manner for physiologic target detection.

Improvement of Immunoassay Detection Sensitivity by Using Well-Defined Raspberry-Like Magnetic Microbeads as Carriers

Well-defined raspberry-like magnetic microbeads （RMMBs） as immunoassay solid carriers were pre- pared by chemicM covalent binding between Fe304 magnetic microspheres and SiO2 nanoparticles. These RMMBs were not as agglomerative as nano-sized magnetie particles （〈 200 nm）, which was an advangtage for high efficient magnetic separation. When compared to Fe304@SiO2 core-shell magnetic microbeads （CMMBs） with smooth surface, RMMBs exhibited stronger capacity to bind biomolecules. Limit of blank （LOB） and limit of detection （LoD） of HBsAg detection using RMMBs as carriers via chemiluminiscence immunoassay （CLIA） were 0.472 and 1.022 μg/L, respectively, showing a notable improvement compared with CMMBs whose LoB and LoD were 1.017 and 1.988 μg/L, respectively. All these indicated a great potential of RMMBs in immunoassay application.

Sensitivity Detection Technique and Resistance Risk Assessment of Magnaporthe grisea to Tricyclazole

In vitro detection method for the sensitivity of Magnaporthe grisea to tricyclazole was studied, and the potential resistance risk of blast disease to tricyclazole was assessed. Both EC50 of hyphal melanization (EC50-H) and minimum inhibitive concentration of melanization in appressorial (MIC-A) by inhibitor tricyclazole showed positive correlation to the EC50 of tricyclazole against blast disease tested in vivo, with relative co-efficiency (R5) of 0.8995 and 0.8244, respectively. However, stability and reproducibility of EC50-H were better than those of MIC-A, suggesting that it could be used to detect the sensitivity of M. grisea to tricyclazole in vitro. Tricyclazole sensitivity of the progenies derived from single spores of the most sensitive isolate DY2 and the least sensitive isolate GY6 detected in sensitivity monitoring in 2000 was not stable, with mean EC50 values of 4.4968 μg/mL and 5.4010 ug/mL, respectively, indicating that the difference in EC50 between DY2 and GY6 was not caused probably by resistance variation. EC50 of GY6 did not increase significantly when continuously selected for twenty generations under the selection pressure of tricyclazole in vivo. However, the sensitivity of DY2 was decreased by 10-fold after selected for twenty generations. The results suggested that tricyclazole was still low resistance risk for M. grisea in China.

Research of the Phase Sensitive Detection Property of Magnetic Sensor Based on Hall Effect

Aim to detect the characteristic weak magnetic field signal against the strong noises background. Methods In combination with a low-pass-filter, the correlation output of magne-* tic sensors between the magnetic field and reference current was utilized to provide a DC output voltage proportional to the applied magnetic induction, computer simulation was* done to investigate the correlation output of the Hall-effect sensors. Results Some analysis results concerning the noise property, harmonic supppression and the sensitivity were given. Conclsion The minimum detection signal of the equipment evolved from the mentioned cor-* relation theory can be 10-6 T. In addition to the DC output, such sensors can also measure the phase of the detected magnetic induction and has good harmonic suppression as well as* noise elimination.

Generation of broadly tunable picosecond mid-infrared laser and sensitive detection of a mid-infrared signal by parametric frequency up-conversion in MgO:LiNbO_3 optical parametric amplifiers

Picosecond optical parametric generation and amplification in the near-infrared region within 1.361-1.656 μm and the mid-infrared region within 2.976-4.875 μm is constructed on the basis of bulk MgO：LiNbO 3 crystals pumped at 1.064 μm.The maximum pulse energy reaches 1.3 mJ at 1.464 μm and 0.47 mJ at 3.894 μm,corresponding to a pumpto-idler photon conversion efficiency of 25%.By seeding the hard-to-measure mid-infrared radiation as the idler in the optical parametric amplification and measuring the amplified and frequency up-converted signal in the near-infrared or even visible region,one can measure very week mid-infrared radiation with ordinary detectors,which are insensitive to mid-infrared radiation,with a very high gain.A maximum gain factor of about 7 脳 10 7 is achieved at the mid-infrared wavelength of 3.374 μm and the corresponding energy detection limit is as low as about 390 aJ per pulse.

A Surface Plasmon Resonance-based Immunosensors for Sensitive Detection of Heroin

A simple technique for sensitive detection of heroine based on surface- plasmonresonance has been theoretically and experimentally investigated. The experiment was realized by using an anti-MO monoclonal antibody and a morphine (MO)-bovine serum albumin (MOBSA) conjugate (antigen). The reason for using MO-BSA in the detection of heroine was also discussed. MO-BSA was immobilized on a gold thin film of SPR sensor chip by physical adsorption. The configuration of the device is allowed to be further miniaturized, which is required for the construction of a portable SPR device in the application of in-situ analysis.

Highly Sensitive Detection of Deoxyribonucleic Acid Hybridization Using Au-Gated AlInN/GaN High Electron Mobility Transistor-Based Sensors

Gallium nitride- （GaN） based high electron mobility transistors （HEMTs） provide a good platform for biological detection. In this work, both Au-gated AlInN/GaN HEMT and AlGaN/GaN HEMT biosensors are fabricated for the detection of deoxyribonucleic acid （DNA） hybridization. The Au-gated AIInN/GaN HEMT biosensor exhibits higher sensitivity in comparison with the AlGaN/GaN HEMT biosensor. For the former, the drain-source current （VDS = 0.5 V） shows a clear decrease of 69μA upon the introduction of 1μmolL^-1 （μM） complimentary DNA to the probe DNA at the sensor area, while for the latter it is only 38 μA. This current reduction is a notable indication of the hybridization. The high sensitivity can be attributed to the thinner barrier of the AlInN/GaN heterostructure, which makes the two-dimensional electron gas channel more susceptible to a slight change of the surface charge.

Record-Breaking Frequency of 44 GHz Based on the Higher Order Mode of Surface Acoustic Waves with LiNbO_(3)/SiO_(2)/SiC Heterostructures

Surface acoustic wave (SAW) technology has been extensively explored for wireless communication, sensors, microfluidics, photonics, and quantum information processing. However, due to fabrication issues, the frequencies of SAW devices are typically limited to within a few gigahertz, which severely restricts their applications in 5G communication, precision sensing, photonics, and quantum control. To solve this critical problem, we propose a hybrid strategy that integrates a nanomanufacturing process (i.e., nanolithography) with a LiNbO_(3)/SiO_(2)/SiC heterostructure and successfully achieve a record-breaking frequency of about 44 GHz for SAW devices, in addition to large electromechanical coupling coefficients of up to 15.7%. We perform a theoretical analysis and identify the guided higher order wave modes generated on these slow-on-fast SAW platforms. To demonstrate the superior sensing performance of the proposed ultra-high-frequency SAW platforms, we perform micro-mass sensing and obtain an extremely high sensitivity of approximately 33151.9 MHz·mm2·μg−1, which is about 1011 times higher than that of a conventional quartz crystal microbalance (QCM) and about 4000 times higher than that of a conventional SAW device with a frequency of 978 MHz.

Bioinspired anti-freezing 3D-printable conductive hydrogel microfibers for highly-sensitive and wide-range detection of ultralow and high strains

Soft strain sensors that can transduce stretch stimuli into electrical readouts are promising as sustainable wearable electronics.However,most strain sensors cannot achieve highly-sensitive and wide-range detection of ultralow and high strains.Inspired by bamboo structures,anti-freezing microfibers made of conductive poly(vinyl alcohol)hydrogel with poly(3,4-ethylenedioxythiphene)-poly(styrenesulfonate)are developed via continuous microfluidic spinning.The microfibers provide unique bamboo-like structures with enhanced local stress to improve both their length change and resistance change upon stretching for efficient signal conversion.The microfibers allow highlysensitive(detection limit:0.05%strain)and wide-range(0%-400%strain)detection of ultralow and high strains,as well as features of good stretchability(485%strain)and anti-freezing property(freezing temperature:-41.1°C),fast response(200 ms),and good repeatability.The experimental results,together with theoretical foundation analysis and finite element analysis,prove their enhanced length and resistance changes upon stretching for efficient signal conversion.By integrating microfluidic spinning with 3D-printing technique,the textiles of the microfibers can be flexibly constructed.The microfibers and their 3D-printed textiles enable highperformance monitoring of human motions including finger bending and throat vibrating during phonation.This work provides an efficient and general strategy for developing advanced conductive hydrogel microfibers as highperformance wearable strain sensors.

A sensitive one-pot ROA assay for rapid miRNA detection

MicroRNAs(miRNAs)and short RNA fragments(18–25 nt)are crucial biomarkers in biological research and disease diagnostics.However,their accurate and rapid detection remains a challenge,largely due to their low abundance,short length,and sequence similarities.In this study,we report on a highly sensitive,one-step RNA O-circle amplification(ROA)assay for rapid and accurate miRNA detection.The ROA assay commences with the hybridization of a circular probe with the test RNA,followed by a linear rolling circle amplification(RCA)using dUTP.This amplification process is facilitated by U-nick reactions,which lead to an exponential amplification for readout.Under optimized conditions,assays can be completed within an hour,producing an amplification yield up to the microgram level,with a detection limit as low as 0.15 fmol(6 pM).Notably,the ROA assay requires only one step,and the results can be easily read visually,making it user-friendly.This ROA assay has proven effective in detecting various miRNAs and phage ssRNA.Overall,the ROA assay offers a user-friendly,rapid,and accurate solution for miRNA detection.

High-Sensitivity Detection of Fruit Tree Viruses UsingBacterial Magnetic Particles

Prunus necrotic ring spot virus （PNRSV） and grapevine fanleaf virus （GFLV） were detected by fluoroimmunoassay using bacterial magnetic particles （BMPs）, and a double antibody sandwich enzyme linked immunosorbent assay （DAS-ELISA）. For the fluoroimmunoassay, fluorescein isothiocyanate labeled anti-PNRSV antibody or anti-GFLV antibody was conjugated onto BMPs of Magnetospirillum gryphiswaldense MSR-1. With this method, a very low minimum antigen concentration （1×10^6 dilution of the original sample concentration） could be detected. Using DAS-ELISA, the minimum antigen detection concentration was the original sample concentration. Thus, comparing these two methods, a BMP-based method could increase the sensitivity up to six orders of magnitude （10^6） higher than an ELISA-based method of detection PNRSV and GFLV.

Number of COVID-19 cases required in a population to detect SARS-CoV-2 RNA in wastewater in the province of Alberta, Canada:Sensitivity assessment

With a unique and large size of testing results of 1,842 samples collected from 12 wastewater treatment plants (WWTP) for 14 months through from low to high prevalence of COVID-19,the sensitivity of RT-qPCR detection of SARS-CoV-2 RNA in wastewater that correspond to the communities was computed by using Probit analysis.This study determined the number of new COVID-19 cases per 100,000 population required to detect SARS-CoV-2RNA in wastewater at defined probabilities and provided an evidence-based framework of wastewater-based epidemiology surveillance (WBE).Input data were positive and negative test results of SARS-CoV-2 RNA in wastewater samples and the corresponding new COVID-19 case rates per 100,000 population served by each WWTP.The analyses determined that RT-qPCR-based SARS-CoV-2 RNA detection threshold at 50%,80%and 99%probability required a median of 8 (range:4-19),18 (9-43),and 38 (17-97) of new COVID-19 cases/100,000,respectively.Namely,the positive detection rate at 50%,80%and 99%probability were 0.01%,0.02%,and 0.04%averagely for new cases in the population.This study improves understanding of the performance of WBE SARS-CoV-2 RNA detection using the large datasets and prolonged study period.Estimated COVID-19 burden at a community level that would result in a positive detection of SARS-CoV-2 in wastewater is critical to support WBE application as a supplementary warning/monitoring system for COVID-19 prevention and control.

PMOXA/PAA Brushes toward on-Line Preconcentration for BSA in Capillary Electrophoresis

In this work, a binary-mixed-brushes-coated (BBC) capillary with switchable protein adsorption/desorption properties was developed and applied for on-line preconcentration of proteins. Firstly, amine-terminated poly(2-methyl-2-oxazoline)(PMOXA-NH2) and thiolterminated poly(acrylic acid)(PAA-SH) were synthesized by using cationic ring-opening polymerization (CROP) and reversible addition fragmentation chain transfer (RAFT) polymerization, respectively. Then, the BBC capillary based on poly(2-methyl-2-oxazoline)(PMOXA) and poly(acrylic acid)(PAA) was prepared by sequentially grafting of PMOXA-NH2 and PAA-SH onto fused-silica capillary inner surface through poly(dopamine)(PDA) as an anchor. The obtained PMOXA/PAA coating formed on the capillary or capillary's raw material was characterized in terms of the thickness, surface chemical composition by using scanning electron microscope (SEM) and X-ray photoelectron spectrum (XPS). The switchable protein adsorption/desorption performance of the BBC capillary was investigated by using fluorescence microscope under di erent solutions with certain pH and ionic strength(I). The results showed that bovine serum albumin (BSA) could be adsorbed on BBC capillary at pH=5.0 (I=10^-5 mol/L), and then the adsorbed BSA could be released at pH=9.0 (I=0.1 mol/L). This switchable protein adsorption/desorption property of coated capillary was then used to preconcentrate proteins on-line for increasing the detection sensitivity of BSA in capillary electrophoresis (CE). With this method, a sensitivity enhancement factor (SEF) more than 5000 for BSA detection was obtained.

Novel conductive metallo-supramolecular polymer AIE gel for multi-channel highly sensitive detection of hydrazine hydrate

Hydrazine hydrate(DH)is an important fine chemical intermediate and as fuel for rockets,however,it also has serious toxic for humans and environment.Developing novel materials and methods for sensitive detection of DH in water and air is an important task.In order to effectively detect DH,a novel conductive supramolecular polymer metallogel(PQ-Ag)has been constructed by the coordination of bis-5-hydroxyquinoline functionalized pillar[5]arene(PQ5)with Ag+.The metallogel PQ-Ag could realize the multi-channel sensitive detection of DH through naked-eye,fluorescence,and electrochemical methods.The lowest limit of detection(LOD)is 0.1 mg/m^(3)in air and 2.68×10^(−8)mol/L in water,which is lower than the standard of the US Environmental Protection Agency(EPA)for DH of maximum allowable concentration in drinking water.More importantly,an electronic device for DH detection based on the metallogel PQ-Ag was designed and prepared,which can realize conveniently and efficiently multi-channel detection and alert of DH through sound and light alarms not only in water but also in air.

A high-sensitivity H2S gas sensor based on optimized ZnO-ZnS nano-heterojunction sensing material

This paper reports a high-performance H2S gas sensing material that is made of ZnO nanowires(NWs)modified by an optimal amount of ZnS to form nano-hete rojunctions.Compared with the intrinsic ZnONWs,the three differently modified nano-heterostructure material ZnO-ZnS-x(x=5,10,15)shows significant improvement in sensing performance to H2S at the working temperatures of 100-400℃,especially in the low temperature range(<300℃).The chemiresistive sensor with ZnO-ZnS-10 sensingmaterial exhibits the largest response signal to H2S among all the other ZnO-ZnS-x(x=5,10,15,20)sensors.Its response signal to 5 ppm H2S at 150℃is about 2.7 times to that of the ZnO-NWs sensor.Besides,the ZnO-ZnS-10 sensor also features satisfactory selectivity and repeatability at 150℃.With the technical advantage attributed to the reduction of the redesigned band gap at the interface between ZnO and ZnS,the ZnO-ZnS hete ro structure sensor rather than the traditional ZnO-NWs sensor can be used for high-sensitivity application at low working temperature.

Highly sensitive detection of NT-proBNP by molecular motor

FoF1-ATPase is an active rotary motor,and generates three-ATP for each rotation.At saturated substrate concentration,the motor can achieve about 103 r.p.m,which means one motor can generate about 105 ATP molecules during 30 min.Here,we constituted a novel nanodevice with a molecular rotary motor and a“battery”,FoF1-ATPase and chromatophore,and presented a novel method of sandwich type rotary biosensor based on εsubunit with one target-to-one motor,in which one target corresponds 105 ATP molecules as detection signals during 30 min.The target such as NT-proBNP detection demonstrated that this novel nanodevice has potential to be developed into an ultrasensitive biosensor to detect low expressed targets.

Detection of low-concentration EGFR with a highly sensitive optofluidic resonator

A hollow-core metal-cladding waveguide（HCMW） optofluidic resonator that works based on a free-space coupling technique is designed. An HCMW can excite ultra-high-order modes（UOMs） at the coupled angle, which can be used as an optofluidic resonator to detect alterations of the epidermal growth factor receptor（EGFR）concentration. Theoretical analysis shows that the UOMs excited in the HCMW have a highly sensitive response to the refractive index（RI） variation of the guiding layer. An EGFR solution with a 0.2 ng/mL alteration is detected, and the RI variation caused by the concentration alteration is about 2.5 × 10^（-3）.

A CMOS high resolution, process/temperature variation tolerant RSSI for WIA-PA transceiver

This paper presents a high resolution, process/temperature variation tolerant received signal strength indicator （RSSI） for wireless networks for industrial automation process automation （WIA-PA） transceiver fabri- cated in 0.18μm CMOS technology. The active area of the RSSI is 0.24 mm2. Measurement results show that the proposed RSSI has a dynamic range more than 70 dB and the linearity error is within ±0.5 dB for an input power from -70 to 0 dBm （dBm to 50 Ω）, the corresponding output voltage is from 0.81 to 1.657 V and the RSSI slope is 12.1 mV/dB while consuming all of 2 mA from a 1.8 V power supply. Furthermore, by the help of the integrated compensation circuit, the proposed RSSI shows the temperature error within ± 1.5 dB from -40 to 85 ℃, and process variation error within ±0.25 dB, which exhibits good temperature-independence and excellent robustness against process variation characteristics.