Preparation of Graphene/MoS2 Composite for Detection of Dopamine

A new composite of graphene/MoS2 is synthesized by co-exfoliation of graphite and MoS2 in isopropanol (IPA) using the organic salt potassium sodium tartrate as the assistant. The composite is characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectra. The results of TEM, XPS, and Raman spectra all illustrate that the graphene/MoS2 composite has been synthesized successfully. Furthermore, the composite is modified on glassy carbon electrode to fabricate a sensor to detect dopamine (DA). The sensor shows two linear detection ranges for DA. One is 1-45 μM and the other is 45-120 μΜ. The detection limit of the sensor (S/N=3) is 0.76 μM.

Crystal-Reconstructed BiVO4 Semiconductor Photoelectrochemical Sensor for Ultra-Sensitive Tumor Biomarkers Detection

In this work, we develop a crystal-reconstructed-BiVO4 aptamer photoelectrochemical (PEC) biosensor by high-energy laser treatment technique. This biosensor achieves a limit of detection (LOD) (0.82 ag/mL), linear detection range (1...

Multiformity of Photoelectron Storages in Functionalized Carbon Nitrides Enabling Reversible and Adaptable Colorimetric Sensing

Colorimetric sensing has been widely used for centuries across diverse fields, thanks to easy operation with no electricity and uncompromised high sensitivity. However, the limited number of chromogenic systems hampers its broader applications. Here, we reported that carbon nitride (CN), the raw materials-abundant and cheap semiconductors with photoelectron storage capability, can be developed as a new chromogenic platform for colorimetric sensing. Beyond most photoelectron storage materials that only demonstrated blue color in the excited state, CN could also exhibit brown color by terminal group functionalization. The experiments and DFT theoretical calculation revealed the origin of the unusual two types of color switches. Cyano and carbonyl terminal groups in CN elongated the centroids distance of electron/hole and stabilized the excited states through a physical and electrochemical pathway, respectively; meanwhile, the counter cations strengthened these processes. As a result, the CN-derived colorimetric O2 sensors demonstrated excellent reversibility in recycling hundreds of times for detection, and exhibited adaptable limit of detection and linear detection range, which was superior to commercial O2 sensors, especially for complex systems with broad variable concentrations.

Trimetallic metal-organic frameworks (Fe,Co,Ni-MOF) derived as efficient electrochemical determination for ultra-micro imidacloprid in vegetables

The excessive use of imidacloprid in agricultural production leads to a large number of residues that seriously threaten human health. Therefore, the detection of imidacloprid has become very important. But how to quantitatively detect imidacloprid at ultra-low levels is the main challenges. In this work, trimetallic metal-organic frameworks Fe, Co, Ni-MOF (FCN-MOF) is in situ prepared on nickel foam (NF) and then used to make an electrochemical sensor in the detection of imidacloprid. FCN-MOF exhibits the characteristics of ultra-micro concentration detection for imidacloprid with high specific surface area and rich active metal centers. The high conductivity and 3D skeleton structure of the NF electrode enhance the contact site with imidacloprid and promote the transmission of electrons efficiently. All results show that the prepared electrochemical sensor has the advantages of ultra-low detection limits (0.1 pM), wide linear detection ranges (1-5×107 pM) and good sensitivity (132.91 μA pM‒1 cm‒2), as well as good reproducibility, excellent anti-interference ability, and fantastic stability. Meanwhile, the electrochemical sensor is used to determine imidacloprid in lettuce, tomato, and cucumber samples with excellent recovery (90-102.7%). The novel electrochemical sensor is successfully applied to the ultra-micro detection of imidacloprid in vegetables, which provides a new way for the efficient monitoring of imidacloprid in agriculture.

Photoluminescence-Based Bioassay With Cysteamine-Capped TiO2 Nanoparticles for the Selective Recognition of N-Acyl Homoserine Lactones

Currently available diagnostic procedures for infections are laborious and time-consuming, resulting in a substantial financial burden by increasing morbidity, increased costs of hospitalization, and mortality. Therefore, innovative approaches to design diagnostic biomarkers are imperative to assist in the rapid and sensitive diagnosis of microbial infections. Acyl homoserine lactones (AHLs) are ubiquitous bacterial signaling molecules that are found to be significantly upregulated in infected sites. In this pioneering work, we have developed a simple photoluminescence-based assay using cysteamine-capped titanium oxide (TiO2) nanoparticles for AHL detection. The PL intensity variation of the oxygen defect state of TiO2 was used for the biosensing measurements. The bioassays were validated using two well-studied AHL molecules (C4-HSL and 3-oxo-C12 HSL) of an important human pathogen, Pseudomonas aeruginosa. The developed system has a maximum relative response of 98%. Furthermore, the efficacy of the system in simulated host urine using an artificial urine medium showed a linear detection range of 10–160 nM. Also, we confirmed the relative response and specificity of the system in detecting AHLs produced by P. aeruginosa in a temporal manner.

FPGA-Based Linear Detection Algorithm of an Underground Inspection Robot

Conveyor belts are key pieces of equipment for bulk material transport, and they are of great significance to ensure safe operation. With the development of belt conveyors in the direction of long distances, large volumes, high speeds, and high reliability, the use of inspection robots to perform full inspections of belt conveyors has not only improved the efficiency and scope of the inspections but has also eliminated the dependence of the traditional method on the density of sensor arrangement. In this paper, relying on the wireless-power-supply orbital inspection robot independently developed by the laboratory, aimed at the problem of the deviation of the belt conveyor, the methods for the diagnosis of the deviation of the conveyor belt and FPGA (field-programmable gate array) parallel computing technology are studied. Based on the traditional LSD (line segment detection) algorithm, a straight-line extraction IP core, suitable for an FPGA computing platform, was constructed. This new hardware linear detection algorithm improves the real-time performance and flexibility of the belt conveyor diagnosis mechanism.

Determination of Prostate-Specific Antigen Via The Assembly of a Two-Dimensional Nanoplatform

Two-dimensional platforms with favorable features are highly expected for diverse application. In this work, we report a highly sensitive and selective “turn-on” fluorescent nanoprobe for prostate-specific antigen (PSA) detection base on cobalt oxyhydroxide nanosheets (CoOOH NSs). CoOOH NSs are employed as the suitable sensing hosts, in which fluorescein amidite-(abbreviated as FAM) labeled aptamer probe (PA) has been adsorbed on nanosheets. Energy transfer between substrate and optical species has switched off the fluorescence of PA. The strong affinity of PA to the target PSA induces the formation of a rigid aptamer structure and the integration with the CoOOH NSs has been drastically affected. The recognition process has been followed by the release of the aptamer probe PA from the nanosheet surface and the green luminescence has been recovered. The dynamic nano-sensor exhibits highly sensitive and accurate analytical performance toward PSA with a linear detection range from 0.1 to 5 nM and a detection limit of 56.1 pM. Therefore, a simple and efficient sensing platform for the detection of prostate cancer can be established.

Novel and Selective Photoelectrochemical Sensing of Levofloxacin Based on BiOI Microflower Spheres Modified with Bi-Metal and BiPO4

This paper reports the design of a photoelectrochemical (PEC) sensing method for detecting levofloxacin (LEVX) in tablets. In this paper, a three-dimensional plasma Bi/BiPO4/BiOI heterojunction was fabricated by a two-step method, in which Bi-metal and BiPO4 were fixed on the surface of BiOI with beads. The composites were characterized by a variety of analytical methods. Bi/BiPO4/BiOI-5% showed better photocatalytic activity than BiPO4/BiOI. Indium tin oxide (ITO) modified with the Bi/BiPO4/BiOI-5% composites was used to determine LEVX and achieved linear detection ranges of 0.2–2 [Formula: see text]M and 2–7 [Formula: see text]M. These composites present alternative materials for the analysis of antibiotics.

A Sensitive SERS Method for Determination of Pymetrozine in Apple and Cabbage Based on an Easily Prepared Substrate

Residual pesticides are one of the major food safety concerns around the world. There is a demand for simple and reliable methods to monitor pesticide residues in foods. In this study, a sensitive method for determination of pymetrozine in apple and cabbage samples using surface-enhanced Raman spectroscopy (SERS) based on decanethiol functionalized silver nanoparticles was established. The proposed method performed satisfactorily with the linear detection range of 0.01–1.00 mg/L and limit of detection (LOD) of 0.01 mg/L in methanol. In addition, it was successfully used to detect pymetrozine in apple and cabbage samples, the LOD was 0.02 and 0.03 mg/L, respectively, and the recoveries of spiked cabbage and apple ranged 70.40–104.00%, with relative standard deviations below 12.18% and 10.33% for intra-day and inter-day tests. Moreover, the results of the correlation test with real cabbage samples of liquid chromatography-tandem mass spectrometry showed that they were highly correlated (slope = 0.9895, R2 = 0.9953). This study provides a sensitive approach for detection of pymetrozine in apple and cabbage, which has great potential for determination of pymetrozine residues in food products.

Quantitative Analysis of Polymetallic Ions in Industrial Wastewater Based on Ultraviolet-Visible Spectroscopy

In order to detect and control the concentration of polymetallic ions in industrial wastewater in real time, a spectrophotometric method combining wavelet transform (WT) and partial least squares regression (PLSR) is proposed for the simultaneous determination of zinc, cobalt and nickel in industrial wastewater by ultraviolet-visible spectrometry, without a separation step. WT was found to be suitable for spectral preprocessing, which effectively eliminated the noise, enhanced spectral feature information, improved the linearity of the detected ions and increased the number of selectable modeling wavelengths. PLSR was used to study the simultaneous detection of zinc, cobalt and nickel. The linear detection ranges were 10–100 mg/L for zinc, 0.6–6.0 mg/L for nickel and 0.3–3.0 mg/L for cobalt. The average relative deviation for zinc, nickel and cobalt was 2.85%, 3.05% and 2.24%, respectively. The results indicated that the WT–PLSR method is suitable for the online detection of polymetallic ions by ultraviolet-visible spectroscopy in zinc industrial wastewater.