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Hydrogen (H2) is a clean energy carrier and its cost-effective separation is important for future H2 energy deployment. Currently, H2 is mainly produced from high temperature methane steam reforming reactions and thus the availability of membrane separation technology that can work at elevated temperatures can reduce the production cost. In this work, a cross-linked polybenzimidazole (PBI)-triglycidylisocyanurate (TGIC) and sulfonated graphene (SG) composite membrane was developed using a mixed proton–electron conducting concept. In such a membrane, protons diffuse by hopping along the cross-linking sites between the sulfonic groups of SG and the pyrrole rings of PBI, while electrons are transported via highly electron conductive SG. Following the addition of SG, the membrane became more compact, given the reduced interlayer spacing and swelling ratio. The thermal stability and oxidative resistance are comparable to those of other PBI-based membranes. For H2/CO2 separation, H2 can permeate through a 132 μm-thick membrane with 99.99% selectivity and a high flux of up to 0.22 mL min−1 cm−2 at 300 °C. The stable operation at 280 °C for 160 hours proves the membrane robustness at such an elevated temperature. Compared to the previously reported mixed conducting ceramic membranes exhibiting equivalent H2 fluxes requiring operation temperatures above 800 °C, the polymer and graphene composite membrane presented herein can reduce the operation temperature by 500 °C. This is an important requirement to ensure a more practical integration of membrane technology into industrial processes.

The kinetics of the ultraviolet light-induced solution atom transfer radical polymerization (ATRP) of methyl acrylate using titanium oxide (TiO2) was investigated through experiments and modeling b...

In this study, an ultramicro interdigital electrode array chip (UIEA) was designed and fabricated by using Micro-Electro-Mechanical systems (MEMS) technology, and a portable detection system, using the chip for determination of heavy-metal ions in water, was developed. The working electrode of the UIEA was modified with gold nanoparticles by electrodeposition. The detection sensitivity of the UIEA chip for copper ions was 0.0138 μA·L·μg−1, with the linear range of 0–400 μg/L and the detection limit of 18.89 μg/L (3σ), which was better than that of the compared columnar glassy carbon electrode. The results of the interference experiment verified that the UIEA chip has a certain anti-interference ability against common heavy-metal ions in water, such as Pb2+, Zn2+, and Mg2+ ions. The standard addition method was used to investigate the performance of the developed s ystem for copper ion determination in real water. The recovery range from 87.5% to 94.7% was achieved.

For investigating the fractional crystallization process of high-saline wastewater from coal chemical industry, the primary nucleation kinetics of NaNO3 during cooling crystallization was studied. 20 g NaCl/100 g H2O was added to simulate the high-saline environment, which resulted in a ternary NaCl-NaNO3-H2O mixture system. Based on the measured solubility and supersolubility in the temperature range from 288.09 to 311.70 K by using ultrasonic velocity sensor, the effects of stirring rate, cooling rate and presence of seed crystals on the metastable zone width (MSZW) were analyzed. The results showed that increasing the saturation temperature as well as increasing the stirring rate will make the MSZW of NaNO3 narrow. This is mainly attributed to the intensification of mass transfer and diffusion, which promotes the crystal nucleation. By contrast, the change in the size of solute molecular clusters in the solution may lag behind the transformation of the solution state, so that the MSZW of NaNO3 becomes wide when increasing the cooling rate. Meanwhile, because the addition of seed crystals is beneficial to induce the solution to start crystallization at a lower supersaturation, it always leads to the narrowing of MSZW, whereas the dosage has a relatively weak effect in the scope of experimental research. Furthermore, self-consistent Nývlt-like equation and classical 3D nucleation theory were used to study the primary nucleation kinetics of NaNO3 during cooling crystallization process. Corresponding nucleation kinetic equations were regressed based on the experimental data. The activation energies Esat of NaNO3 nucleation process fitted by these two models were 28.97 and 26.08 kJ/mol, respectively.

Significant efforts have been devoted to developing trace-level quantification of Hg2+. In this work, a novel fluorescence detection (FD) approach combined with preconcentration of Hg2+ in ionic liquid (IL), N-octylpyridinium tetrafluoroborate ([OPy]+[BF4]−), was developed for the determination of trace Hg2+ in water. The temperature-controlled ionic liquid dispersive liquid–liquid microextraction (TC-IL-DLLME) technique was used to improve the enrichment factor. After extraction and centrifugal separation, precipitated IL was diluted with water and acetonitrile containing the fluorescent probe. Under optimum conditions, the photoluminescence intensity of the fluorescence emission peak was found to be linear with the concentration of Hg2+ in the range from 0.1 to 0.5 μg L−1. The limit of detection for the TC-IL-DLLME-FD method was calculated to be 0.0342 μg L−1 (S/N = 3). Further, the selectivity of the sensor was measured by evaluating its response to other heavy-metal ions and was shown to be excellent. Recoveries were assessed by spiking water samples with different Hg2+ standard stock solutions, giving satisfactory recoveries from 80 to 110%.

This study reports a novel electrochemical sensor to detect trace mercury based on an electrode coated by chitosan/graphene oxide/MoS 2 /AuNPs and thymine-Hg2+-thymine base pair. This method effectively utilizes the biocompatibility of molybdenum disulfide to DNA and constructs a detection platform for mercury ions. The electrocatalytic activity of MoS 2 and the specific binding of thymine-Hg2+-thymine base pair significantly reduce the detection limit of mercury and improve the sensitivity of the electrode. When there exists Hg2+, the voltammetric current signal of redox peak decreases after the interaction between mercury and DNA. The sensor showed good linearity from $0.01\mu\mathrm{g}/\mathrm{L}$ to $4\mu\mathrm{g}/\mathrm{L}$ with a correlation coefficient of 0.991 and the limit of detection was found to be 5.8ng/L. This simple, sensitive, low cost and easy preparation electrochemical sensor has the potential application in trace mercury detection.

The accurate detection of SO 2 F 2 and SOF 2 of SF 6 decomposition components plays a very important role in the state assessment and fault diagnosis of SF 6 electrical equipment. The gas detection based on spectroscopy has the characteristics of high sensitivity, good reliability and strong anti-cross interference ability. It is a suitable detection scheme for applications in the power industry. In this paper, theoretical and experimental researches on the infrared characteristics of SO 2 F 2 and SOF 2 are carried out. The detection bands that can be used for the detection of the two decomposition components are analyzed. It provides technical reference and support for the future development of SO 2 F 2 and SOF 2 detection devices based on spectroscopic technology.

Mercury ions (Hg2+) pollution in the water environment can cause serious harm to human health. Trace Hg2+ detection is of vital importance for environmental monitoring. Herein, we report a novel design of Ru-MOFs modified gold microelectrode for Hg2+ determination. Ru-MOFs are synthesized directly by the cathodic method on gold microelectrode, with the covered area accurately controlled. Cathodic synthesized Ru-MOFs show good conductivity and are suitable to be used as the electrode surface material directly. The synergy of the pre-deposition process and the adsorption process of Ru-MOFs can effectively improves the performance of the sensor. The results show good linearity (R2 = 0.996) from 0.1 ppb to 5 ppb, with a high sensitivity of 0.583 &mu, A ppb&minus, 1 mm&minus, 2. The limit of detection is found to be 0.08 ppb and the test process is within 6 min. Most importantly, the senor has a good anti-interference ability and the recoveries are satisfactory. This miniature electrochemical sensor has the potential for on-site detection of trace mercury in the field.

Hexavalent chromium (Cr (VI)) has strong oxidizing properties and can result in strong carcinogenic effects on human bodies. Therefore, it is necessary to detect hexavalent chromium sensitively and accurately. This article proposes the gold nanoparticles (AuNPs)&ndash, boron-doped diamond (BDD) electrode for the direct determination of chromium with a green and simple detection process by cathodic stripping voltammetry. Gold nanoparticles are used to enhance the detection performance toward Cr (VI). The effect of different pretreatment methods on electrode modification has been studied, and the detection parameters have been optimized. With the optimized conditions, the AuNPs&ndash, BDD electrode presents a good linear behavior in a Cr (VI) concentration range of 10 to 1000 &mu, g/L. A low limit of detection of 1.19 &mu, g/L is achieved. The detection process is simple and environmentally friendly. The sensor has been tested for the detection of Cr (VI) in a real water sample with satisfactory results, which indicates potential application of the AuNPs&ndash, BDD electrode for the sensitive and onsite detection of Cr (VI).

A dual laser cantilever enhanced photoacoustic spectroscopy detection system is proposed to simultaneously detect H 2 S and CO. A beam combiner is used to combine the laser sources for the two gases detection into the photoacoustic cell, and distinguish the photoacoustic signals corresponding to the gas detection according to the different modulation frequencies, and finally simultaneous detection of two SF 6 decomposition components is realized. Under the condition of single component and mixed component, the linear relationship between the different concentration of each component and the photoacoustic signal under its detection wavelength and frequency is studied through experiments, which proved the effectiveness of the detection method.

this paper demonstrated a smartphone- controlled electrochemical sensor for copper ions (Cu2+) detection in waters. The electrochemical sensor is composed of a three-electrode-system and a detecting circuit module. The three-electrode-system is configured as an Au working- electrode, a Pt counter-electrode and an Ag/AgCl reference electrode. Configured under the square wave impulse voltammetry (SWV), the detecting circuit utilizes low-power consuming MCU to carry out constant potential control and weak current detection. Smartphone installed with the customized App can be used to control the operation of the sensor and implement data management in the detection process. The App was developed to realize the function of man-machine interaction and display testing curves of the electroanalytical measurements. Data exchange between the sensor and the smartphone is based on the Bluetooth protocol. A series of standard copper samples were tested to evaluate performance of the sensor, and the experimental results reveal that the sensor exhibits better sensitivity (4.064 μA/μgL-1) to Cu2+ than the original prototype from 0 μg/L to 1000 μg/L.

As an important means to protect water resources, water quality detection is of great social and economic significance. Water quality detection sensors processed by micro-electro-mechanical system (MEMS) technology have the advantages of low-cost, small size, and high sensitivity. In this paper, a multi-parameter water quality detection integrated sensor chip is further studied, and a portable detection system using this chip is developed. Temperature, pH, oxidation-reduction potential (ORP), conductivity and concentration of copper ions (Cu2+) are selected as typical water quality parameters. Experiments of sensor calibrations using this portable detection system were performed in standard solutions. The sensor has a sensitivity of &minus, 57.34 mV/pH in pH detection and 5.95 &Omega, /&deg, C in temperature response. ORP is directly detected by Pt microelectrode on the chip and the relative error is less than 3%. The electrode constant of the sensor is 1.416 cm&minus, 1 and the linearity is 0.9995 in conductivity detection. With the gold nanoparticles deposited on the electrode, the detection peak of Cu2+ appears at 280 mV and the sensor shows good linearity to the concentration of Cu2+ in the range of 0&ndash, 0.6 mg/L. The detection limit of Cu2+ concentration is 2.33 &mu, g/L. Through measurement and calculation, the accuracy of the portable system is within 4%. This portable multi-parameter water quality detection system with the MEMS-based integrated chip shows great potential in the field and fast detection.

One of the hottest topics in the field of selective catalytic reduction (SCR) of nitrogen oxide is to develop a catalyst with low cost, low toxicity, high activity, and good selectivity for N2 to replace high-cost and high-toxic vanadium catalyst. In this work, low-cost spinel MFe2O4 (M = Cu, Mn, and Zn) were synthesized, and applied in SCR. MnFe2O4 exhibited the best activity (99.9%) and selectivity (95.7%) at 100 °C. In comparison, CuFe2O4 was more suitable for SCR above 150 °C, and removed 94.3% of NO (950 ppm) together with a selectivity of 97.5% at the same time (150 °C). Detailed characterizations showed that the spinels were similar to each other in crystal structure, textural property, and micro-topography. Diffuse Reflection Fourier Transform Infrared spectrum indicated that the spinels all reduced nitric oxide by an Eley-Rideal mechanism. Mass spectrometry and density-functional-theory calculations revealed that different cation substitutions resulted in different abilities of NH3 dehydrogenation and over oxidization. MnFe2O4 had the lowest energy barrier (1.21 eV) for NH3 dehydrogenation, resulting in the best activity. ZnFe2O4 had a highest energy barrier (0.22 eV) for over oxidization of NH3, resulting in the best selectivity. After all, main result of this work is in favor of developing cleaner catalyst, and further works should be focused on coating the catalysts on monolithic support.

It is of great importance to measure tetrabromobisphenol A (TBBPA) owing to its high toxicity and wide existence in the environment. In this paper, an electrochemical sensor based on boron-doped diamond (BDD) thin film was developed for the detection of TBBPA. The diamond thin film was deposited on Si substrate via filament-assisted chemical vapor deposition. Due to the great electrochemical properties, the BDD electrode could be reactivated after a pretreatment process after each measurement, which realized a continuous detection of TBBPA and solved the problem of renewal. The electrochemical pretreatment procedure was studied in order to achieve better performance. The peak current of the BDD electrode displayed a good linearity toward TBBPA concentrations ranging from 50 nM to $10~\mu \text{M}$ , and the detection limit was 27 nM (S/N = 3).

Biochemical oxygen demand (BOD) is an international regulatory index for evaluating organic water pollution, which requires to be rapidly detected. In this paper, a microbial electrode for rapid BOD sensing has been developed. Carboxyl graphene (GN-COOH) and Au nanoparticles (AuNPs) have been co-electrodeposited on the electrode and microorganisms (Bacillus subtilis) have been immobilized onto the modified electrode through covalent bonding. The modification process has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), fluorescence microscope and Fourier transform infrared spectroscopy (FT-IR). The AuNPs with an average particle size of 30 nm are dispersed in the GN-COOH film. The co-electrodeposited film not only facilitates the electron transfer between electrode and reagents, but also creates a biocompatible microenvironment and a rough surface with more sites for cell immobilization. Compared with the traditional BOD electrode including immobilized microbial film and oxygen permselective membrane, the B. subtilis/rGN-COOH-AuNPs/Au electrode simplifies the structure for more effective mass transfer. After modification parameters’ optimization, the response time for detection has been shortened to 3 min. The proposed BOD electrode shows a linear range from 2 to 15 mg/L, indicating its potential in BOD rapid detection.

Tetrabromobisphenol A (TBBPA) is an extensively used flame retardant in printed circuit boards. It is toxic and widely spread in the environment, which needs sensitive detection. Cationic surfactants were utilized to enhance the response of TBBPA on boron-doped diamond (BDD) electrode. Among four kinds of surfactants, stearyltrimethylammonium bromide (STAB) showed the greatest enhancement to the electrochemical signal. TBBPA got better response on BDD electrode with doping level of 1000 ppm. The linear range of the system was from 10μg/L to 500 μg/L, and the limit of detection reduced from 27 nM to 2.5 nM (1.34 μg/L) owing to the enhancement of STAB.

Mercury ions (Hg2+) pollution in water environment can cause serious harm to human health. Trace Hg2+ detection is of vital importance for environment monitoring. This paper reports a novel approach for rapid detection of trace mercury by microelectrode with the immobilization of Ru-based metal-organic frameworks (Ru-MOFs). Ru-MOFs are synthesized by cathodic electrochemical method on the gold microelectrode, which significantly enlarges electrochemical active surface area. This method offers the advantages of short synthesis time and needless for high temperature and high pressure that required by solvothermal synthesis. Differential pulse stripping voltammetry is used to determine mercury ions (Hg2+). The results show a good linearity (R2=0.996) from 0.1ppb to 5ppb, with a high sensitivity of 0.583μA ppb−1 mm−2. The limit of detection is found to be 0.08ppb and the test process is within 6min. This miniature electrochemical sensor has the potential for on-site rapid detection of trace mercury.

This paper demonstrates a portable electrochemical sensor system for the detection of copper ions (Cu2+) in water samples. The hardware of the sensor is based on a customized electrochemical electrode and a miniaturized detecting circuit module. An application (APP) running on an Android PAD is developed to functionalize the hardware into a sensor system. The electrochemical electrode is configured with a gold disk working-electrode (WE), a platinum disk counter-electrode (CE) and a commercial Ag/AgCl reference electrode (RE). The detecting circuit module use an ARM chip to realize the key operations, such as precise control of multichannel potentiostat and weak current detection, in electrochemical detection based on anodic stripping voltammetric method. The APP is used to manage the Bluetooth wireless communication between the sensor and the Android PAD, and implement data management and graphic display of the detecting results. The developed sensor system was verified with standard copper salt samples. The testing result shows that it performes high sensitivity (0.0075 μA/μgL−1) to Cu2+ within the concentrations ranging from 0 μg/L to 400 μg/L by the square wave voltammetry (SWV). The standard substance tests also exhibit a good precision of the sensor system for simultaneous determination of Cu2+ and Pd2+, which indicates it can also be used to implement multi-parameters detection in water quality monitoring.

Developing a sensitive, simple and fast sensing system for 3,3',5,5'-tetrabromobisphenol A (TBBPA) is important because of its ubiquitousness and high toxicity. In this work, a gold nanoparticles (AuNPs) and poly(sulfosalicylic acid) (PSSA) composite film (AuNPs-PSSA) is fabricated in-situ on an electrode surface via cyclic voltammetry scanning. The characterization via scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray (EDX) analysis and Fourier transform infrared (FTIR) spectroscopy indicate that the PSSA film is homogeneously decorated with AuNPs, and a highly uniform and thin composite film is obtained. Electrochemical tests reveal that the AuNPs-PSSA film exhibits larger active surface area, lower charge transfer resistance and higher accumulation efficiency toward TBBPA than single AuNPs and PSSA film. As a result, the oxidation signals and sensing sensitivity of TBBPA are significantly enhanced on the surface of the AuNPs-PSSA. The developed TBBPA sensing platform using AuNPs-PSSA composite film, with low detection limit (25 pM) and wide linear range (0.1-10 nM), is successfully utilized to measure TBBPA level in wastewater samples. The results are highly consistent with those that obtained from high-performance liquid chromatography. The preparation and reusability of the TBBPA sensor can be automatically achieved through CV scanning, providing a promising on-line monitoring system for wastewater samples.

Based on anodic stripping voltammetric (ASV) method, this paper demonstrated a portable sensor system for copper ions (Cu2+) detection in water samples. The proposed sensor system is composed of a customized electrochemical probe, a detecting circuit module and an application (APP) running on an Android device. The electrochemical probe is based on an environment-friendly three-electrode system that is configured with a gold disk working-electrode (WE), a platinum disk counter-electrode (CE) and a commercial Ag/AgCl reference electrode (RE). The detecting circuit module utilizes ARM Context-M4 platform to carry out constant potential control, weak current detection and Bluetooth wireless transmission. The Android application is used to manage the wireless communication between the hardware module and the Android device, and implement data management and graphic display of the testing results. The developed sensor system was verified with both standard copper salt reagents and real water samples. The testing result shows that it performes high sensitivity (0.0075 μA/μgL−1) to Cu2+ within the concentrations ranging from 0 μg/L to 400 μg/L by the square wave voltammetry (SWV). The recovery tests exhibit a good precision of the sensor system for copper determination. It can also be used to detect other heavy metal ions such as lead at the same time.

Gold nanoparticles (AuNPs) embedded in chitosan (CHI) film, well-dispersed and smaller in size (about 10 nm), were fabricated by one-step electrodeposion on Au microelectrode in solution containing chitosan and chloride trihydrate. The nano-structure CHI-AuNPs composite film offers abundant amine groups, good conductivity, excellent biocompatibility and stability for antibody immobilization. The combination of aflatoxin B1 (AFB1) with immobilized antibody introduces a barrier to electron transfer, resulting in current decreasement. The morphologies and characterizations of modified microelectrodes were investigated by scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FT-IR). The proposed non-enzyme and label-free immunosensor exhibited high sensitive amperometric response to AFB1 concentration in two linear ranges of 0.1 to 1 ng mL(-1) and 1 to 30 ng mL(-1), with the detection limit of 0.06 ng mL(-1) (S/N=3). The immunoassay was also applied for analysis of maize samples spiked with AFB1. Considering the sample extraction procedure, the linear range and limit of detection were assessed to be 1.6-16 ng mL(-1) and 0.19 ng mL(-1) respectively. The simple method showed good fabrication controllability and reproducibility for immunosensor design.

A localized surface plasmon resonance (LSPR) biosensor was prepared with gold nanospheres (AuNSs) coated on the tip face of the optical silica fiber. AuNSs with the sizes of 20 nm and 80 nm were used. The sensitivities of AuNS20 nm and AuNS80 nm modified sensors to bulk refractive index (RI) variation are 82.86 nm/RIU and 218.98 nm/RIU, respectively. The AuNS80 nm modified sensor was used for the detection of 40 bases DNA hybridization and the limit of detection is 50 nmol/L, where the 40-bases DNA probe was covalently linked with AuNS80 nm. The complementary DNA sequence in tris-acetate-EDTA (TAE) buffer solution was detected as the target DNA. This fiber sensor has the advantages of small sample consumption, easy fabrication and high sensitivity.

A facile method of measuring electrical conductivity was developed to characterize the formation of rGO network in polymer matrix. The electrical conductivity, barrier and anticorrosion of PVP@rGO/epoxy nanocomposite coating were investigated as function of rGO’ loading. When the electrical conductivity sharply increased to be seven orders, it indicated the formation of rGO network in polymer matrix in the loading of 0.75wt%. Furthermore, it also confirmed that although a conducting rGO network could effectively hinder the diffusion of electrolytes, yet it also accelerated corrosion at the interface. This strategy dose not only provide a facile method to determine the formation of rGO network in polymer matrix, but also proposes a new insight about effect of rGO’ loading on anticorrosion of polymer coating.

This paper presents the fabrication, characterization and application of a miniaturized electrochemical sensor for nitrate detection in potable water. The miniaturized sensor employed in the electrochemical measurements was fabricated by standard MEMS techniques. As the sensitive material, copper nanoparticles were prepared using electrodeposition method and characterized by scanning electron microscope. The electrodeposition process was completed with a controlled-potential reduction in acidic copper sulphate electrolyte directly. The electrocatalytic reduction of nitrate on copper surface under acidic condition $(\mathbf{pH}=2.0)$ was measured by linear sweep voltammetry (LSV) scan to implement the ion recognition and quantification process. The experimental results reveal that the deposited copper film was porous and exhibits a larger surface areas compared with average copper film. The sensor performed high sensitivity of $0.0332 \ \mu \text{A}/\mu \text{molL}^{-1}$ for nitrate detection with the concentration range from $6.25 \ \mu \text{molL}^{-1}$ to $1000 \ \mu \text{molL}^{-1}$. Concentrations of five standard nitrate samples and two real water samples were measured. The results given by the sensors were in good agreement with the data obtained by standard ultraviolet (UV) spectrophotometric method for nitrate measurement. The maximum deviation between two methods is of 16.2%.

A simple, high performance Localized Surface Plasmon Resonance(LSPR) sensor was prepared by depositing gold nanospheres(AuNS) on the side wall of the optical silica fiber through electrostatic self-assembly method. The size and density of AuNS were optimized to investigate the best refractive index(RI) sensitivity. The results indicated that the RI sensitivities were increased with the increasing of size and density. The best RI sensitivity was about 2016.224 nm/RIU which was the highest in current LSPR fiber sensor study in visible wavelength range. Additionally, the high density AuNS monolayer was suitable for using as the Surface Enhanced Raman Scattering (SERS) substrate by measuring Raman signal of crystal violet. This fiber sensor will be expected to apply in the biochemistry detection.

Heavy metal ion pollution problems have had a terrible influence on human health and the environment. Therefore, the monitoring of heavy metal ions is of great practical significance. In this paper, an electrochemical three-electrode system was fabricated and integrated on nitrocellulose membrane (NC) by the use of magnetron sputtering technology, which exhibited a uniform arrangement of porous structure without further film modification. This paper-based sensor chip was used for Cu2+ detection by square-wave stripping voltammetry (SWSV). Within the ranges of 5~200 μg·L−1 and 200~1000 μg·L−1, it showed good linearity of 99.58% and 98.87%, respectively. The limit of detection was 2 μg·L−1. On the basis of satisfying the detection requirements (10 μg·L−1), the integrated sensor was small in size and inexpensive in cost. Zn2+, Cd2+, Pb2+ and Bi3+ were also detected by this paper-based sensor chip with good linearity.

The study presented herein investigated an easy preparation, high performance, wavelength-modulated LSPR optical fiber chemosensor coated by gold nanospheres(AuNS) for Hg2+ detection based on thymine-Hg2+-thymine base pair mismatches and the coupled plasmonic resonance effect.Utilizing electrostatic self-assembly method, the high density and dispersivity monolayer AuNS coated LSPR fiber sensor had the near field refractive index sensitivity up to 2016 nm/RIU. The single-strand probe DNA served as a binding element for free AuNS labelled-target DNA conjugates was attached to the monolayer AuNS by Au-S bond. In the present of Hg2+, the coupled plasmonic resonance band between monolayer AuNS and free AuNS was produced by thymine-Hg2+-thymine structure and leaded to red-shift of LSPR peak. Under the optimal conditions, the enlarged red-shift in peak of LSPR spectroscopy was linearly with the concentration of Hg2+ in the range from 1.0 × 10-9 to 5.0 × 10-8 M with the coefficient of 0.976. The limit of detection was 0.7 nM(S/N = 3). The specificity of the sensor was proved high by evaluating the response to other heavy metal ions. The proposed fiber sensor provided a label-free, miniature, low-cost approach for the Hg2+ detection and had potential in real environmental evaluations.

This paper describes the fabrication, characterization and the application of the photocatalytic TiO2nanofiber as the photocatalyst for the digestion of total phosphorus (TP). The nanoTiO2fibers were fabricated by the electro-spinning technique on silicon substrate. Under the conditions of room temperature (25 degrees Celsius) and humidity less than 40%, the TiO2fabricated by the electro-spinning presents a silky coagulation appearance, which can be converted to the nanofiber appearance by annealed in the muffle furnace at 450 degrees Celsius for 10 hours. X-ray diffraction (XRD) examination shows that the silky coagulation can be converted to anatase-type TiO2. The absorbance values of different phosphate concentrations after exposure in UV light at the intensity of 7000μW/cm2were tested in this paper. Sodium tripolyphosphate solutions serve as the water sample of TP, and five standard concentrations (by weight of P) are 0.0mg/L, 1.0mg/L, 2.0mg/L,3.0mg/L and 4.0mg/L, respectively. The digestion rate exhibits satisfied linearity ranges from 0.0mg/L to 4.0mg/L with acceptable linearity R2of calibration curve, in both digestion temperature of 25 degrees Celsius and 50 degrees Celsius.

The fabrication and characterisation of an integrated microfluidic chip for phosphate detection are described. A micro three-electrode-system embedded in a microfluidic channel was used for the analysis of samples. Working electrodes and counter electrodes were arranged as an interdigitated array to increase the current response. Owing to the nonlinear diffusion effect of ultra-microelectrodes and the high generation-collection mode of interdigitated electrode arrays, the current density and sensitivity of phosphate detection were improved effectively compared with normal disk microelectrodes. The current density sensitivity for phosphate detection is −0.00537 μA/mm2·(μmol/l)−1, which is three times that of the disk microelectrode. The current density was averagely 6.5 times that of the disk microelectrode. The microfluidic chip was then used for total phosphorus (TP) detection. The TP detection results showed good consistency with nominal values of standard solutions.

This paper investigated two different modification methods of graphene (GN) on ultramicroelectrode array (UMEA) and applied the GN modified UMEA for the determination of dissolved oxygen (DO). The UMEAs were fabricated by Micro Electro-Mechanical System (MEMS) technique and the radius of each ultramicroelectrode is 10 μm. GN-NH2 and GN-COOH were modified on UMEA by using self-assembling method. Compared with GN-NH2 modified UMEA, the GN-COOH modified UMEA showed better electrochemical reduction to DO, owing to better dispersing and more active sites. The GN-COOH on UMEA was electroreduced to reduced GN-COOH (rGN-COOH) to increase the conductivity and the catalysis performance. Finally, the palladium nanoparticles/rGN-COOH composite was incorporated into DO microsensor for the detection of DO.

This work describes the fabrication, characterization, and application of a gold microband array electrode (MAE) for the determination of phosphate in fresh water samples. The working principle of this MAE is based on the reduction of a molybdophosphate complex using the linear sweep voltammetric (LSV) method. The calibration of this microsensor was performed with standard phosphate solutions prepared with KH2PO4 and pH adjusted to 1.0. The microsensor consists of a platinum counter electrode, a gold MAE as working electrode, and an Ag/AgCl electrode as reference electrode. The microelectrode chips were fabricated by the Micro Electro-Mechanical System (MEMS) technique. To improve the sensitivity, gold nanoparticles (AuNPs) were electrodeposited on the working electrode. With a linear range from 0.02 to 0.50 mg P/L, the sensitivity of the unmodified microsensor is 2.40 µA per (mg P/L) (R2 = 0.99) and that of the AuNPs-modified microsensor is 7.66 µA per (mg P/L) (R2 = 0.99). The experimental results showed that AuNPs-modified microelectrode had better sensitivity and a larger current response than the unmodified microelectrode.

This work presents a bulk electrode and a microband electrode array for electrochemical nitrate sensing in acidic medium. The microelectrode array is fabricated on silicon wafer by micro electro-mechanical system technique. Electrodepostion was carried out to modify tin onto the bulk palladium electrode and thus formed Pd-Sn bimetallic composite. On the microelectrode array, Pd and Sn were successively deposited to obtain a double-layer composite. The performance of the two kinds of electrodes towards nitrate sensing was investigated and compared. The microelectrode array showed better sensitivity and repeatability than the bulk electrode. The results are consistent with the unique properties of the microelectrode array in electrochemical analysis such as high current density and low background noise.

The electrochemical detection of tetrabromobis-phenol A (TBBPA) with boron-doped diamond (BDD) thin film electrode is demonstrated. The electrode is synthesized by filament-assisted chemical vapor deposition. An irreversible oxidation peak is observed for TBBPA in phosphate buffer on BDD surface. A method to renew the electrode is developed by sweeping in H2SO4 at 3V for 100s first and at −3V for 100s afterwards. The electrode gets higher oxidation peak current in phosphate buffer of pH 8. The linear range is from 500nM to 10µM.

This paper presents an electrochemical microsensor based on ultramicroelectrode array modified with copper nanoparticles to perform trace nitrate detection in potable water. The microsensor is fabricated with standard micromachining technology. As the working-electrode, an ultramicroelectrode array constructed of 421 disk-shaped ultramicroelectrodes provides enhanced electrochemical performance for the microsensor, with faster response time and higher current density than conventional plate electrodes with the same area. Copper nanoparticles with an average diameter of 20 nm are electrodeposited onto the surface of disk-shaped ultramicroelectrodes as the sensing material for nitrate ions. The copper nanoparticles increase the sensitive surface area of the ultramicroelectrode array and further improve the current response. The developed microsensor is examined with the method of linear sweep voltammetry, and displays a linear range from 12.5 µmol/L to 200 µmol/L of nitrate concentrations in the acidic sodium sulfate buffer solutions. Compared with the conventional copper modified disk electrode, our proposed ultramicroelectrode array shows a higher sensitivity of 0.0892 µA/µmolL−1 for nitrate ions. The microsensor is also used to detect nitrate in running water samples. The results are consistent with the data obtained by the standard ultraviolet spectrophotometric method, and the maximal difference is 13.1%.

This paper presents the fabrication, characterization and application of PEDOT-ionic liquid composite films modified Au microelectrodes. Here only one-step electropolymerization was required for the preparation of PEDOT-BMIMBF4 and PEDOT-BMIMPF 6 composite films, which were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS), respectively. Our experiments displayed the uniform formation of ionic liquids within the conducting polymer films. With regard to their synergistically enhanced effect for the determination of nitrite, two types of composites show excellent and similar sensitivity (638 mA M−1·cm−2) along with high correlation coefficients (over 0.99).

Biochemical oxygen demand (BOD) is an important index for the assessment of organic water pollution, which needs to be detected rapidly and sensitively. In this paper, a BOD biosensor has been developed based on the direct immobilization of microorganisms around carboxyl graphene (GN-COOH) modified ultramicroelectrode array (UMEA). UMEA is designed in ring shape and hexagon distribution, which shows nonlinear diffusion in electrochemical tests, indicating fast mass transfer. The modification of UMEA comprises the electrodeposition of GN-COOH and the covalent bonding bacteria immobilization. The potential and time for electrodeposition have been optimized. The deposited GN-COOH facilitates the electron transfer and increases the current responses. The response time of the detection has been shortened to 3 min. The proposed biosensor shows a linear range from 2 to 15 mg/L with the sensitivity of 3.04 nA/(mg/L), which is about 3-times to that of our previous study without GN-COOH.

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were prepared by electro-oxidation on Au microelectrodes in an aqueous solution. Electrolyte solutions and polymerization parameters were optimized prior to overoxidation. The effect of overoxidation time has been optimized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which results in the film overoxidized for 45 s at 1.35 V presenting a strong adsorption. The other one-step overoxidation film prepared by direct CV ranging from -0.6 V to 1.35 V was polymerized for comparison. Scanning electron microscope (SEM) analysis and Fourier transform infrared (FTIR) spectroscopy were used for monitoring morphological changes and the evolution of functional groups. Both of them indicate increased abundant oxygen functional groups and roughness, yet the products exhibit dendritic morphology and piles of spherical protrusions, respectively. Moreover, double-step overoxidized film showed better electrochemical performance toward lead ion sensing. These characterizations highlight some novel properties that may be beneficial for specific sensing applications.

The sensitive detection of trace levels of heavy metal ions such as Pb2+ is of significant importance due to the health hazard they pose. In this paper, we present a polypyrrole (PPy)/multiwalled carbon nanotube (MWCNT)-modified Au microelectrode. The PPy/MWCNT composite film was electrochemically deposited on the microelectrode by cyclic voltammetry (CV). The composite film was investigated by scanning electron microscope (SEM), CV, and electrochemical impedance spectroscopy (EIS), and the results show that this film presents a uniformly distributed and web-like entangled structure and good conductivity. Differential pulse stripping voltammetry (DPSV) was applied to determine trace levels of Pb2+. Experimental conditions including accumulation time and deposition potential were optimized. In optimal conditions, the PPy/MWCNT-modified microelectrode performed sensitive detection of Pb2+ within a concentration range from 1 to 100 μg·L−1, and the limit of detection was 0.65 μg·L−1 at the signal-to-noise ratio of three.

In this paper, reduced carboxylic graphene/palladium nanoparticles (rGN-COOH/PdNPs) modified ultramicroelectrode array (UMEA) was investigated and applied in electrochemical determination of biochemical oxygen demand (BOD). The UMEAs were fabricated by micro electro-mechanical system technique. The sensitive film of rGN-COOH/PdNPs was prepared by self-assembling of carboxylic graphene (GN-COOH), electroreducing the GN-COOH and electrodepositing the palladium nanoparticles on UMEA. This modification method is suitable to UMEA, which can immobilize the sensitive film on the designed sites and maintain the unique characteristics of UMEA. Compared with the sensitive film of GN-COOH, rGN-COOH and PdNPs, the sensitive film of rGN-COOH/PdNPs showed satisfied electroreduction performance to dissolved oxygen (DO). A BOD microsensor was fabricated based on the rGN-COOH/PdNPs modified UMEA. A good linear range from 1 to 30 mg/L for BOD determination was displayed.

An ultramicro interdigital array electrode modified by palladium-gold was developed for nitrate detection in neutral water. The ultramicro interdigital array electrode was fabricated based on silicon substrate by Micro Electro-Mechanical System (MEMS) technique. The nanostructured palladium-gold (Pd-AuNPs) composite sensing film was electrodeposited on the surface of a working electrode by electrochemical method. The synergistic effect of Pd-AuNPs composite was investigated and its enhancement of the catalytic activity and stability was revealed. The Pd-AuNPs modified electrode showed good linearity (R2 = 0.99) from 1 mg/L to 15 mg/L (as N) for nitrate determination in a neutral water environment (pH = 7.2), with a sensitivity of 4.7 &mu, A&middot, mg&minus, 1&middot, L. The results showed that the developed Pd-AuNPs-modified ultramicro interdigital array electrode chip can achieve sensitive and environmentally-friendly detection for nitrate in neutral water.

Thermal-assisted ultraviolet (UV) and H2O2-assisted UV photocatalytic oxidation methods utilizing nano-TiO2 photocatalyst are presented for the digestion of total phosphorus (TP) in water. The photocatalytic experiments for TP digestion were conducted using a 365 nm wavelength UV light, and TiO2 nanoparticles immobilized on a silicon wafer as the photocatalyst. The effects of H2O2 and temperature on the UV photocatalytic oxidation process are explained. The pseudo-first-order rate constants k of two phosphorus compounds for the UV digestion processes were obtained according to the pseudo-first-order equation. Both H2O2 and heating could improve the efficiency of the UV photocatalytic oxidation method. But by comparison, the enhancement of heating on the UV photocatalysis process is more distinctly than H2O2. In addition, the thermal-assisted UV digestion process will not lead to secondary pollution since no oxidant is needed in this digestion process, which makes it more compatible with electrochemical detection of TP. The thermal-assisted UV digestion method was employed for the digestion of real water samples. Compared with the conventional thermal digestion method for TP detection, this thermal-assisted UV digestion process decreased the digestion temperature from 120°C to 60°C within the same time, which enable the digestion process work at normal pressure.

This article demonstrates a novel chemical vapor deposition strategy of tin oxide (SnO2) by vapor phase material reaction at room temperature and presents the applications to hydrogen detection using this material. Tin chloride anhydrate was used as the precursor, and it reacted with NH3 to form Sn(OH)4 nanospheres. The samples with Sn(OH)4 nanospheres were subject to drying up at 80 °C, and then they transformed to polycrystalline SnO2 nanospheres. The X-ray diffraction measurement was carried out to investigate the structural properties of the SnO2 films annealed at various temperatures. The morphology of the samples was investigated by field-emission scanning electron microscopy. Micropellistor was fabricated based on the SnO2 catalyst for hydrogen detection. Compared with the traditional method to make SnO2 sensing material (hydrolysis of SnCl4·5H2O in basic solutions), the SnO2 nanospheres prepared by this method have a higher relative sensitivity and a good linearity for the concentration of H2 ranging from 0% v/v to 4% v/v. A short response time about 6 s was achieved.

This work presents a novel thermal assisted ultra-violet (UV) photocatalysis oxidation method for total phosphorus (TP) detection. A 365nm wavelength UV light was used as the UV light source, and the TiO2 particles, immobilized on silicon wafer, were used as the catalyst. The sodium glycerophosphate was digested as the typical compound of TP. The digested samples were determined by spectrophotometry after the phosphomolybdenum blue reaction. The catalyst can be used repetitively with long-term stability in this work. For the photocatalysis digestion process under room-temperature, when the reaction time reached 120min, the conversion rates were 92.31% and 93.66% for 1mg/L and 4mg/L of C3H7Na2O6P solutions, respectively. And conversion rates were 95.48% and 99.37% respectively for thermal assisted ultra-violet (UV) photocatalysis digestion process at the condition of 30min and 60°C. Compared with the conventional thermal digestion method and photocatalysis digestion method for TP detection, this thermal assisted UV digestion method can greatly decrease the digestion time and enhance the efficiency.

This paper describes the fabrication, characterization and application of an environment-friendly tin film/gold nanoparticles (Sn/AuNPs) modified gold microelectrode for square wave stripping voltammetric (SWSV) determination of copper, lead and zinc. The microelectrode chips were fabricated by Micro Electro-Mechanical System (MEMS) technique. The sensitivity of the modified microelectrode was largely improved due to the large surface area of AuNPs and the formation of alloys between target metals and Sn. The influence of hydrogen overflow was reduced and the current response was enhanced because AuNPs made the stripping potential shift positively and Sn extended the stripping potential range. Combining AuNPs with Sn, the obtained microelectrode exhibited satisfied linearity ranges from 5 to 500 μg L-1 for copper and lead, from 10 to 500 μg L-1 for zinc, with a limit of detection of 2 μg L-1 for copper, 3 μg L-1 for lead and 5 μg L-1 for zinc. The Sn/AuNPs/gold microelectrode was successfully applied for simultaneous detection of copper, lead and zinc in tap water sample.

This paper presents a microsensor chip integrated with a gold nanoparticles-modified ultramicroelectrode array (UMEA) as the working electrode for the detection of copper ions in water. The microsensor chip was fabricated with Micro-Electromechanical System technique. Gold nanoparticles were electrodeposited onto the surface of UMEA at a constant potential of −0.3 V. The ratio d/Rb of interelectrode spacing (d) over the individual electrode’s radius (Rb) was investigated to improve the electrochemical performance. The UMEA with a d/Rb of 20 showed the best hemispherical diffusion mode, resulted in fast response time and high current response. The gold nanoparticles increased the active surface area of UMEA by not changing the geometries of UMEA, and the current response was increased further. Incorporating the optimized characteristic of UMEA and gold nanoparticles, the microsensor showed a good linear range from 0.5 to 200 µg L−1 of copper ions in the acetate buffer solutions with the method of square wave stripping voltammetry. Compared with the gold nanoparticles-modified disk electrode, the gold nanoparticles-modified UMEA showed higher sensitivity (0.024 µA mm−2 µg−1 L) and lower limit of detection (0.2 µg L−1). Water samples from river water and tap water were analyzed by the microsensor chip with recovery ranging from 100.7 % to 107.8 %.

In this work, electrospray technique combined sol-gel method was used to prepare porous TiO2 film. X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD), and Scanning Electron Microscope (SEM) analyses were conducted to examine the chemical composition, phase structure, and surface morphology of the sprayed TiO2 film. After calcined at 450 °C in air atmosphere for 2 h, mesoporous TiO2 nano-spheres clusters were formed on the surface of silicon wafer and the average size of nano-spheres was 250 nm. Ti presented as Ti4+ oxidation state in TiO2 film, and the TiO2 film exhibited the anatase phase. The sprayed porous TiO2 films were employed as photocatalyst to degrade organic phosphorus in water samples. Compared with the TiO2 film prepared by Sol-Gel spin-coating method, the porous TiO2 film deposited by electrospray combined sol-gel method showed higher photocatalytic activity.

A 3D dendritic nanostructure of silver-array (DSA) was prepared via electrodeposition on an interdigitated array (IDA) microelectrode. For preparation of this nanostructure, the optimal parameters such as deposition potential, deposition time, the electrode bandwidth and gap size were systematically investigated. It was found that the edge effect of the IDA microelectrode is a key factor for controlling the 3D dendritic growth of silver. Furthermore, the formation of the 3D dendritic morphology was discussed from the aspect of electrochemical nucleation theory and nonequilibrium growth dynamics to give a deep understanding of its growth mechanism. For its potential practical application, we showed that the as-prepared 3D DSA nanomaterial exhibited high electrocatalytic reduction ability to nitrate in neutral solution and excellent performance for nitrate determination. An amperometric nitrate microsensor based on the 3D DSA was obtained.