Huijie Shi

A highly selective electrochemical impedance spectroscopy-based aptasensor for sensitive detection of acetamiprid

A simple aptasensor for sensitive and selective detection of acetamiprid has been developed based on electrochemical impedance spectroscopy (EIS). To improve sensitivity of the aptasensor, gold nanoparticles (AuNPs) were electrodeposited on the bare gold electrode surface by cycle voltammetry (CV), which was employed as a platform for aptamer immobilization. With the addition of acetamiprid, the formation of acetamiprid-aptamer complex on the AuNPs-deposited electrode surface resulted in an increase of electron transfer resistance (Ret). The change of Ret strongly depends on acetamiprid concentration, which is applied for acetamiprid quantification. A wide linear range was obtained from 5 to 600nM with a low detection limit of 1nM. The control experiments performed by employing the pesticides that may coexist or have similar structure with acetamiprid demonstrate that the aptasensor has only specific recognition to acetamiprid, resulting in high selectivity of the aptasensor. The dissociation constant, Kd of 23.41nM for acetamiprid-aptamer complex has been determined from the differential capacitance (Cd) by assuming a Langmuir isotherm, which indicates strong interaction between acetamiprid and aptamer, further proving high selectivity of the aptasensor. Besides, the applicability of the developed aptasensor has been successfully evaluated by determining acetamiprid in the real samples, wastewater and tomatoes.

Design of a Novel Cu2O/TiO2/Carbon Aerogel Electrode and Its Efficient Electrosorption-Assisted Visible Light Photocatalytic Degradation of 2,4,6-Trichlorophenol

Cu(2)O/TiO(2) heterojunction photocatalyst is built on carbon aerogel (CA) substrate with good adsorption properties by sol impregnation and seed-mediated synthesis approach. The Cu(2)O/TiO(2)/CA electrode has excellent electrosorptive and high efficient photocatalytic properties. Its morphology and surface chemical composition are characterized with SEM, TEM, X-ray diffraction (XRD) and Raman spectra. The UV-vis diffuse reflectance spectra show that the optical absorption edge for Cu(2)O/TiO(2)/CA appears at 636 nm. Under visible-light (λ > 420 nm) irradiation, the photocurrent density increment on Cu(2)O/TiO(2)/CA is 60 times of that on Cu(2)O/TiO(2)/FTO. The electrochemical characteristic is investigated with electrochemical impedance spectrum (EIS). The Cu(2)O/TiO(2)/CA electrode is further applied in the electrosorptive photodegradation of the 2,4,6-trichlorophenol (2,4,6-TCP) wastewater. The result shows that the removal ratio of 2,4,6-TCP in 5.5 h on Cu(2)O/TiO(2)/CA is 96.3% and the TOC removal is 91.3%. The intermediates generated in the degradation process are analyzed by GC-MS and HPLC. The possible mechanism of visible light photocatalytic degradation of 2,4,6-TCP on Cu(2)O/TiO(2)/CA is also studied.

A femtomolar level and highly selective 17β-estradiol photoelectrochemical aptasensor applied in environmental water samples analysis.

Driven by the urgent demand of determining low level of 17β-estradiol (E2) present in environment, a novel and ultrasensitive photoelectrochemical (PEC) sensing platform based on anti-E2 aptamer as the biorecognition element was developed onto CdSe nanoparticles-modified TiO2 nanotube arrays. The designed PEC aptasensor exhibits excellent performances in determination of E2 with a wide linear range of 0.05-15 pM. The detection limit of 33 fM is lower than the previous reports. The aptasensor manifests outstanding selectivity to E2 while used to detect seven other endocrine disrupting compounds that have similar structure or coexist with E2. The superior sensing behavior toward E2 can be attributed to the appropriate PEC sensing interface resulting from the preponderant tubular microstructure and excellent photoelectrical activity, the large packing density of aptamer on the sensing interface, as well as the high affinity of the aptamer to E2. The PEC aptasensor was applied successfully to determine E2 in environmental water samples without complicate sample pretreatments, and the analytical results showed good agreement with that determined by HPLC. Thus, a simple and rapid PEC technique for detection low level of E2 was established, having promising potential in monitoring environmental water pollution.

Fabrication of a Novel and Simple Microcystin-LR Photoelectrochemical Sensor with High Sensitivity and Selectivity

Microcystin-LR (MC-LR), an inert electrochemical species, is difficult to be detected by a simple and direct electrochemical method. In the present work, a novel photoelectrochemical sensor is developed on highly ordered and vertically aligned TiO(2) nanotubes (TiO(2) NTs) with convenient surface modification of molecularly imprinted polymer (MIP) (denoted as MIP@TiO(2) NTs) for highly sensitive and selective determination of MC-LR in solutions. Molecularly imprinted polypyrrole (PPy) of MC-LR is chosen as the recognition element. The designed MIP@TiO(2) NTs photoelectrochemical sensor presents excellent applicability in MC-LR determination, with linear range from 0.5 to 100 μg L(-1) and limit of detection of 0.1 μg L(-1). Moreover, the sensor exhibits outstanding selectivity while used in coexisting systems containing 2,4-dichorophenoxyacetic acid, atrazine, paraquat, or monosultap with high concentration, 100 times that of MC-LR. The sensor presents good photoelectric conversion efficiency and detection sensitivity, as well as broad linear detection range, mainly because of the high specific surface area and photoelectric activity of TiO(2) NTs and the π bond delocalized electron system of PPy that promotes the separation of electron-holes. The prominent selectivity is from the MIP by forming multiple hydrogen bonds between PPy and MC-LR. Mechanisms for photoelectrochemical analysis and selective recognition are also discussed.

A solar-driven photocatalytic fuel cell with dual photoelectrode for simultaneous wastewater treatment and hydrogen production

A solar-driven dual photoelectrode photocatalytic fuel cell (PFC) based on n-type semiconductor photoanode and p-type semiconductor photocathode is reported for wastewater treatment with simultaneous hydrogen production. The PFC shows a superior performance for phenol degradation and hydrogen production with a maximum TOC removal rate of 84.2% and a total hydrogen production rate of 86.8 μmol cm−2 in 8 hours which is much higher than other similar researches. Compared to the system comprised of a photoanode (photocathode) and Pt for phenol degradation (hydrogen production), the results prove that there is a synergistic effect between the two photoelectrodes. This is because the electrons are preferentially stored on the photocathode for hydrogen production and holes on the photoanode for pollutant degradation. Several semiconductors are chosen as photoelectrodes to investigate the factors influencing the performance of the PFC system. The VOC value of the PFC increases with the difference of Fermi level between the two photoelectrodes. This PFC system provides a new approach for efficient energy recovery from wastewater.

Glucose oxidation over ultrathin carbon-coated perovskite modified TiO2 nanotube photonic crystals with high-efficiency electron generation and transfer for photoelectrocatalytic hydrogen production

Photoelectrocatalytic (PEC) hydrogen production from renewable energy sources (e.g. water, biomass, etc.) has become attractive in the field of renewable energy technology. The potential improvement of hydrogen production processes involves the reduction of the oxidation reaction overpotential, as well as the prohibition of photo-generated electron–hole combination in the photoelectrocatalytic process. Herein, we present high efficiency hydrogen production from PEC glucose oxidation by employing the ultrathin carbon-coated perovskite (Cr-doped SrTiO3) modified TiO2 nanotube photonic crystal (C@Cr-SrTiO3/TiO2 NTPC) as a photoanode material. The photocurrent density of the C@Cr-SrTiO3/TiO2 NTPC photoanode reached as high as 0.43 mA cm−2 at the bias potential of 0.6 V (vs. SCE) and in glucose electrolyte, which is about 4.8 and 3.3 times higher than that of TiO2 NTPC and C@Cr-SrTiO3/TiO2 NTPC photoanode in pure KOH electrolyte, respectively. The excellent PEC activity and photoelectrochemical performance can be attributed to the less endergonic process of glucose oxidation compared to water oxidation. Additionally, the rational design and fabrication of C@Cr-SrTiO3/TiO2 NTPC is favorable towards the high-efficiency generation and transfer of photo-generated electrons, due to the high electrical conductivity and fast transport characteristics of the ultrathin carbon layer, the superior visible light absorption properties of Cr-SrTiO3 and the independently modulating carrier diffusion length of TiO2 NTPC. A probable mechanism for PEC hydrogen production from glucose oxidation over the ultrathin carbon-coated heterostructure photoanode is proposed and discussed.

A simple highly sensitive and selective aptamer-based colorimetric sensor for environmental toxins microcystin-LR in water samples

A simple and highly sensitive aptamer-based colorimetric sensor was developed for selective detection of Microcystin-LR (MC-LR). The aptamer (ABA) was employed as recognition element which could bind MC-LR with high-affinity, while gold nanoparticles (AuNPs) worked as sensing materials whose plasma resonance absorption peaks red shifted upon binding of the targets at a high concentration of sodium chloride. With the addition of MC-LR, the random coil aptamer adsorbed on Au NPs altered into regulated structure to form MC-LR-aptamer complexes and broke away from the surface of Au NPs, leading to the aggregation of AuNPs, and the color converted from red to blue due to the interparticle plasmon coupling. Results showed that our aptamer-based colorimetric sensor exhibited rapid and sensitive detection performance for MC-LR with linear range from 0.5 nM to 7.5 μM and the detection limit reached 0.37 nM. Meanwhile, the pollutants usually coexisting with MC-LR in pollutant water samples had not demonstrated disturbance for detecting of MC-LR. The mechanism was also proposed suggesting that high affinity interaction between aptamer and MC-LR significantly enhanced the sensitivity and selectivity for MC-LR detection. Besides, the established method was utilized in analyzing real water samples and splendid sensitivity and selectivity were obtained as well.

A simple and label-free aptasensor based on nickel hexacyanoferrate nanoparticles as signal probe for highly sensitive detection of 17β-estradiol.

A simple and label-free electrochemical aptasensor was developed for detecting 17β-estradiol (E2). To translate the binding events between aptamer and E2 into the measurable electrochemical signal, the nickel hexacyanoferrate nanoparticles (NiHCF NPs) as signal probe was in situ introduced on the electrode by a simple two-step deposition method, exhibiting well-defined peaks with good stability and reproducibility. Subsequently, Au nanoparticles (Au NPs) was covered on the NiHCF NPs, which not only provided a platform for immobilizing the aptamer by S-Au interaction, but further enhanced the conductivity and stability of the signal probe. With the addition of E2, the formation of E2-aptamer complexes on the sensing interface retarded the interfacial electron transfer reaction of the probe, resulting in the decrease of the electrochemical signal. E2 could be readily examined by measuring the signal change. A linear range of 1×10(-12)-6×10(-10) M was obtained with a low detection limit of 0.8×10(-12) M. The aptasensor also exhibited high specificity to E2 in control experiments employing seven endocrine disrupting compounds as the interferents that had similar structure or coexisted with E2 in the environment. Besides, the applicability of the aptasensor was successfully evaluated by determining E2 in the real samples.

Double-Layer 3D Macro-Mesoporous Metal Oxide Modified Boron-Doped Diamond with Enhanced Photoelectrochemical Performance.

In this work, a TiO2/Sb-doped SnO2 electrode was prepared on the boron-doped diamond (BDD) substrate with double-layer three-dimensional macro-mesoporous (DL3DOM-m) structure, using the polystyrene sphere (PS) vertical deposition method. The as-prepared DL3DOM-m TiO2/SnO2/BDD was employed for organic contaminant removal, showing excellent photoelectrocatalytic performance. SEM, XRD and XPS indicated that DL3DOM-m electrode possessed a 3D macroporous layered framework with uniform pore size (about 400 nm), nanosized particles (4.5-5.8 nm), and high electroactive surface area (3-fold more than that of BDD). SA-XRD indicated the backbone of DL3DOM-m electrode had mesoporous structure. It was found that the as-prepared electrode exhibited remarkable electrocatalytic activity, high photocurrent and outstanding absorption capability (91.0 μg cm-2). Furthermore, bisphenol A (BPA) was completely decomposed after 3 h of reaction applying DL3DOM-m electrode as photoanode, and that on BDD was only 58.9%. It indicated that the modified electrode had great potential to be used in practical water treatment with high photoelectrochemical performance.

A highly selective and picomolar level photoelectrochemical sensor for PCB 101 detection in environmental water samples.

A highly selective and sensitive photoelectrochemical (PEC) sensor was fabricated for fast and convenient detection of PCB 101 in environmental water samples with a low detection limit of 1.0×10(-14)molL(-1) based on single crystalline TiO2 nanorods (NRs). By integration with molecular imprinting (MI) technique, the PEC sensors selectivity towards PCB 101 was significantly improved, so that the interference caused by 100-fold excess of PCB 126 and PCB 77 which had similar structure with PCB 101 was below 37%, not to mention other coexisted pollutants. This high selectivity could be attributed to the high-quality expression of the molecular imprinting sites on the rigid and smooth surface of single crystalline TiO2 NRs on which PCB 101 could be selectively and preferentially adsorbed. The oriented and multiple halogen bonds formed between PCB 101 and the molecular imprinting sites played a critical role in improving the recognition ability of the PEC sensor. Meanwhile, the one dimensional nanorods structure of TiO2 was beneficial for the efficient separation of photogenerated electrons and holes, leading to enhanced photocurrent response and further improving the sensitivity of the PEC sensor.