Aptamer molecular gate functionalized mesoporous SiO2@MB controlled-release system for pollutant detection using Ti(â ¢) self-doped TiO2 NTs as active photoanode coupled with electrostatic modulation.

Atrazine (ATZ) is a widely used herbicide that can cause serious harm to organisms and ecosystems. An immobilization-free photoelectrochemical (PEC) aptasensor has been herein developed for ATZ based on aptamer molecular gate functionalized mesoporous SiO2@MB controlled release system. Compared with traditional immobilization-based sensors, immobilization-free sensors (IFSs) avoid the modification of the recognition element on the electrode surface. Mesoporous SiO2 with large surface area and good biocompatibility can be used as nanocontainers to stably encapsulate the signal shuttle molecule methylene blue (MB). The bifunctional aptamer (APT) is used not only as the recognition element for ATZ but also as the signal switch to block or release MB. In the presence of ATZ, the specific recognition between ATZ and APT will cause the detachment of APT from the surface of SiO2, thus the molecular gate will open and release MB. Due to pH modulation, the positively charged MB can reach the surface of the negatively charged Ti(III) self-doped TiO2 NTs (Ti(III)-TiO2 NTs) electrode to act as an electron donor, which increases the photocurrent. The immobilization-free aptasensor has shown ultrasensitive detection of ATZ with a wide linear range from 1.0 pM to 100.0 nM and a low detection limit of 0.1 pM. In addition, the sensor has excellent selectivity, stability and anti-interference ability, and has been used in real water sample analysis successfully. This strategy has provided a new idea for the design of advanced immobilization-free PEC sensors for environmental pollutant detection.

Enhanced Label-Free Photoelectrochemical Strategy for Pollutant Detection: Using Surface Oxygen Vacancies-Enriched BiVO4 Photoanode.

Label-free photoelectrochemical sensors have the advantages of high sensitivity and a simple electrode structure. However, its performance is greatly limited due to the photoactive materials' weak photoactivity and poor stability. Herein, a robust homogeneous photoelectrochemical (PEC) aptasensor has been constructed for atrazine (ATZ) based on photoetching (PE) surface oxygen vacancies (Ov)-enriched Bismuth vanadate (BiVO4) (PE-BVO). The surface of the Ov improves the carrier separation ability of BiVO4, thus providing a superior signal substrate for the sensor. A thiol molecular layer self-assembled on PE-BVO acts as a blocker, while 2D graphene acts as a signal-on probe after release from the aptamer-graphene complex. The fabricated sensor has a wide linear detection range of 0.5 pM to 10.0 nM and a low detection limit of 0.34 pM (S/N = 3) for ATZ. In addition, it can efficiently work in a wide pH range (3-13) and high ionic strength (∼6 M Na+), which provides promising opportunities for detecting environmental pollutants under complex conditions.

Glucose oxidase-like Co-MOF nanozyme-catalyzed self-powered sensor for sensitive detection of trace atrazine in complex environments.

The self-powered sensor (SPS) is a sensor method that does not require the external power source and has the potential for portable detection of environmental contaminants. In this work, for the first time, a biomolecule-free SPS for detection of ultra-trace triazine endocrine disruptor atrazine (ATZ) with high sensitivity and selectivity is constructed using a glucose oxidase (GOD)-like cobalt metal-organic framework (Co-MOF) nanozyme-modified high-performance anode and a molecularly imprinted cathode. By modulating the size and morphology of the prepared materials, Co-MOF nanozyme with superior GOD-like property (Michaelis constant Km = 15.8 mM) has been obtained and modified at the anode to catalyze glucose oxidation with high efficiency and provide energy continuously and stably for the SPS. The separation mode of anodic energy supply-cathodic recognition ensures the recognition effect without affecting the catalytic characteristic of Co-MOF and the output signal of the SPS. The designed SPS has a wide linear range of 1 pM-100 nM and a detection limit as low as 0.65 pM, as well as superior selectivity and good stability. The present work provides a promising approach for the design of self-powered sensors which can be extended to detection of a wider range of environmental pollutants.

Immobilization-Free Photoelectrochemical Aptasensor for Atrazine Based on Bifunctional Graphene Signal Amplification and a Controllable Sulfhydryl-Assembled BiOBr/Ag NP Microinterface.

Immobilization-free sensors (IFSs), with no requirement of fixing the recognition element to the electrode surface, have received increasing attention due to their unique advantages of reusable electrodes, not being limited by the load of the recognition element, and not being easily changed to the structure of the probe. In the present work, an effective visible light-driven immobilization-free photoelectric aptasensor for ultrasensitive detection of atrazine (ATZ) was proposed based on a reusable BiOBr/Ag NP substrate electrode with ultrafast charge transfer. Controllable thiols were used as conditioning agents for the photoelectric signal. The ingeniously designed bifunctional graphene can act as not only a molecular "bridge" for the ATZ aptamer through a strong π-π stacking effect, obtaining a graphene-aptamer complex, serving as a homogeneous recognition element, but also a switch for signal modulation for quantitative detection of target substances. Benefiting from the synergistic effect of the above-mentioned factors, the proposed sensor is capable of ultrasensitive and highly selective detection of ATZ in real water samples with a low detection limit of 1.2 pM and a wide linear range from 5.0 pM to 10.0 nM. Furthermore, it shows high stability, good selectivity, and strong anti-interference ability. Thus, this work has provided a fresh perspective for designing advanced immobilization-free photoelectric sensors and convenient detection of environmental pollutants.

Dual-Photoelectrode Fuel Cell Based Self-Powered Sensor for a Picomole Level Pollutant: Using an In Situ Molecularly Imprinted p-Type Organic Photocathode.

Developing a dual-photoelectrode fuel cell based self-powered sensor (DPFC-SPS) with an ideal signal output capability and high sensitivity performance for the detection of environmental pollutant atrazine (ATZ) has an important value. In this work, the in situ molecularly imprinting functionalized p-type organic semiconductor polyterthiophene (MI-pTTh) is used as a photocathode to construct a DPFC-SPS toward the typical environmental pollutant ATZ for the first time. Due to its excellent photoactivity, higher stability, and superior oxygen reduction reaction activity, pTTh serves as the photocathode material for constructing a self-powered sensing platform with a stable signal output and high photoelectric activity. Based on the sensitive light-triggered large self-bias of the DPFC-SPS, the open circuit potential (EOCV) of the device reaches 1.21 V and the maximum power density (Pmax) reaches 121.5 µW·cm-2, which is much higher than most reported PFC-SPSs. Simultaneously, in situ molecularly imprinted (MI) functionization of pTTh can further endow it with specific recognition ability, helping the constructed SPS achieve high sensitivity, selectivity, and effective recognition of the important environmental pollutants ATZ in complex systems. It exhibits a broad linear relationship from 0.002 to 100 nM and a low detection limit (estimated by S/N > 3) of 0.21 pM toward ATZ. The mechanism of the binding kinetics of the MI-pTTh with the target ATZ is further studied via in situ infrared spectroscopy. This work provides theoretical guidance for sensing strategies using dual-photoelectrode devices and offers a rational device design for cost-effective electricity generation from renewable resources.

A highly sensitive and selective photoelectrochemical aptasensor for atrazine based on Au NPs/3DOM TiO2 photonic crystal electrode.

A photoelectrochemical (PEC) sensing platform with high sensitivity and selectivity has been fabricated based on Au nanoparticles (Au NPs) modified three dimensionally ordered macroporous (3DOM) TiO2 nanostructure frame for trace detection of an endocrine disrupting pesticide, atrazine (ATZ). The resultant photoanode (Au NPs/3DOM TiO2) shows enhanced PEC performance under visible light due to multi signal amplification of the unique structure of 3DOM TiO2 and surface plasmon resonance (SPR) of Au NPs. ATZ aptamers are used as recognition elements and immobilized on Au NPs/3DOM TiO2 by Au-S bond in large packing density and dominant spatial orientation. The specific recognition and high binding affinity between aptamer and ATZ provides the PEC aptasensor with excellent sensitivity. The detection limit is 0.167 ng/L. Besides, this PEC aptasensor exhibits outstanding anti-interference ability in 100-fold concentration of other endocrine disrupting compounds and has been applied successfully to analyze ATZ in real water samples. A simple but efficient PEC aptasensing platform has therefore been successfully developed with high sensitivity, selectivity and repeatability for pollutant monitoring and potential risk evaluation in the environment with great application prospect.

Self-powered aptasensor for picomole level pollutants based on a novel enzyme-free photofuel cell.

Atrazine (ATZ) is a highly toxic chlorine-containing aromatic structural triazine endocrine disruptor. Due to its chemical stability and electrochemical inertness, it is of great challenge and significance to establish a simple, portable, and in situ electrochemical sensor for ATZ. In the present work, a self-powered aptasensor (SPA) based on a novel enzyme-free photofuel cell (PFC) is successfully developed for ATZ for the first time. The designed SPA is constructed by the Ti-Fe-O nanotubes/nickel hydroxide (Ti-Fe-O NTs/Ni(OH)2) photoanode and Au/aptamer (Au/Apt) cathode, responsible for the spontaneous generation of electrons and specific recognition of ATZ, respectively. It is worth noting that Ti-Fe-O NTs on the photoanode can exhibit good visible-light absorption property, and modified Ni(OH)2 further enhances the photo-generated carrier separation and improves the output power generation of the SPA. The recognition is set at the cathode to ensure the detection of ATZ and the anti-interference ability. Under the separation mode, the constructed SPA has a high output power (390 µW cm-2), much better than most previous reports. It can further show specific recognition of ATZ with prominent sensitivity and a limit of detection (LOD) as low as 5.4 pM. Moreover, it has been applied to the real water sample analysis with satisfactory results. A promising self-powered sensing platform based on an enzyme-free PFC has therefore been provided for picomole level pollutants with high sensitivity and outstanding selectivity.

Enzyme-Free Molecularly Imprinted and Graphene-Functionalized Photoelectrochemical Sensor Platform for Pollutants.

In this work, a label-free nonenzymatic photoelectrochemical (PEC) sensor is successfully developed for the detection of a typical pollutant, microcystin-LR (MC-LR), based on a visible-light-responsive alloy oxide, with highly ordered and vertically aligned Ti-Fe-O nanotubes (NTs) as substrates. Ti-Fe-O NTs consisting mainly of TiO2 and atomically doped Fe2O3 are in situ prepared on a Ti-Fe alloy by electrochemical anodic oxidation. Using a simple electrochemical deposition technique, reduced graphene oxide (RGO) could be grown onto Ti-Fe-O NTs, exhibiting significant bifunctions. It not only provides an ideal microenvironment for functionalization of molecularly imprinted polymers (MIPs) on the surface but also serves as the PEC signal amplification element because of its outstanding conductivity for photons and electrons. The designed MIP/RGO/Ti-Fe-O NT PEC sensor exhibits high sensitivity toward MC-LR with a limit of detection as low as 10 pM. High selectivity toward MC-LR is also proven for the sensor. A promising detection platform not only for MC-LR but also for other pollutants has therefore been provided.

In situ monitoring of the selective adsorption mechanism of small environmental pollutant molecules on aptasensor interface by attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS).

In situ monitoring of the interactions and properties of pollutant molecules at the aptasensor interface is being a very hot and interesting topic in environmental analysis since its charming molecule level understanding of the mechanism of environmental biosensors. Attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) provides a unique and convenient technique for the in situ analysis, but is not easy for small molecules. Herein, an ATR-SEIRAS platform has been successfully developed to in situ monitor the selective adsorption mechanism of small pollutant molecule atrazine (ATZ) on the aptasensor interface by characteristic N‒H peak of ATZ for the first time. Based on the constructed ATR-SEIRAS platform, a thermodynamics model is established for the selective adsorption of ATZ on the aptasensor interface, described with Langmuir adsorption with a dissociation constant of 1.1 nM. The adsorption kinetics parameters are further obtained with a binding rate constant of 8.08×105 M-1 s-1. A promising and feasible platform has therefore successfully provided for the study of the selective sensing mechanism of small pollutant molecules on biosensors interfaces, further broadening the application of ATR-SEIRAS technology in the field of small pollutant molecules.

Enhanced trichloroethylene dechlorination by carbon-modified zero-valent iron: Revisiting the role of carbon additives.

Given that there are still some debates on the influence of carbon modification on zerovalent iron (ZVI) decontamination process, the roles of carbon on trichloroethylene (TCE) reduction by ZVI were re-investigated in this work. Compared to activated carbons (AC) with high adsorption ability, carbon fibers (CF) with good electronic conductivity performed much better in enhancing ZVI performance in terms of both reactivity and selectivity. Moreover, it was interesting to observe that a low carbon loading is sufficient to effectively improve TCE reduction and this promoting effect would decline with further increasing the carbon amounts from 1.0 wt.% to 50 wt.%. Regarding to the ZVI selectivity, a relatively high carbon loading (especially for CF, it may be as high as 50 wt.%) was needed to protect ZVI from non-productive reactions with H2O/H+ effectively. However, a mixture of 10 wt.% AC and 1.0 wt.% CF could combine their respective merits of inhibiting side reactions and enhancing TCE reduction, and thus simultaneously enhanced the reactivity and selectivity of ZVI. Mechanistic investigations revealed that carbon modification could enhance the ZVI performance through improving TCE adsorption and/or accelerating electron transfer, while the latter one may play a more important role especially at high carbon loadings.

Immobilization-free photoelectrochemical aptasensor for environmental pollutants: Design, fabrication and mechanism.

Atrazine (ATZ) is one of the most widely used and highly toxic triazine herbicides in the world. Photoelectrochemical (PEC) method is an attractive and sensitive alternate for ATZ. However, for conventional PEC sensors, recognition elements usually need to immobilize on electrode surface, where a complex procedure is unavoidable and the reproducibility of sensors fabrication is usually poor. Therefore, we herein proposed a new and feasible strategy for developing a signal-on immobilization-free PEC aptasensor to ATZ. Aptamer for ATZ is combined with graphene to obtain APT-GN complex, serving as the recognition element in solution. TiO2 nanotubes (NTs) electrode deposited with Au nanoparticles (NPs) is used as the substrate electrode. After further self-assembled with 1-Mercaptooctane (MCT), the photo-generated carriers transfer between the resultant electrode and the electrolyte will be blocked, leading to a signal-off of the photocurrent. But when sensing ATZ, aptamers on APT-GN will be grasped by ATZ, leaving free graphene to assemble onto MCT/Au NPs/TiO2 NTs, which will largely "turn on" the photocurrent response of the substrate electrode due to the efficient carrier transport efficiency of graphene. Meanwhile, simultaneous addition of deoxyribonuclease I (DNase I) can bring about further cycling amplification of the signal enhancement. The as-designed PEC aptasensor exhibits a linear range from 50.0 fM to 0.3 nM with detection limit of 12.0 fM for ATZ. Since the reaction of recognition elements and targets ATZ occurs in homogeneous solution rather than on the photoelectrode surface, this PEC aptasensor exhibits advantages of high stability, anti-interference ability, reproducibility, and wide pH and ion strength feasibility range. A promising immobilization-free aptasensing platform has thus been provided not only for ATZ but also for other kinds of environmental pollutants.

Light-driven water oxidation by a dye-sensitized photoanode with a chromophore/catalyst assembly on a mesoporous double-shell electrode.

A mesoporous atomic layer deposition (ALD) double-shell electrode, Al2O3 (insulating core)//ALD ZnO|ALD TiO2, on a fluorine-doped tin oxide (FTO) conducting substrate was explored for a photoanode assembly, FTO//Al2O3 (insulating core)//ALD ZnO|ALD TiO2|-chromophore-catalyst, for light-driven water oxidation. Photocurrent densities at photoanodes based on mesoporous ALD double-shell (ALD ZnO|ALD TiO2|) and ALD single-shell (ALD ZnO|, ALD TiO2|) electrodes were investigated for O2 evaluation by a generator-collector dual working electrode configuration. The high photocurrent densities obtained based on the mesoporous ALD ZnO|ALD TiO2 photoanode for O2 evolution arise from a significant barrier to back electron transfer (BET) by the optimized tunneling barrier in the structure with the built-in electric field at the ALD ZnO|ALD TiO2 interface. The charge recombination is thus largely decreased. In the films, BET following injection has been investigated through kinetic nanosecond transient absorption spectra, and the results of energy band analysis are used to derive insight into the internal electronic structure of the electrodes.

A simple and highly selective electrochemical label-free aptasensor of 17ß-estradiol based on signal amplification of bi-functional graphene.

In the present work, a convenient signal-on electrochemical label-free aptasensor for 17ß-estradiol (E2), a typical steroidal hormones endocrine disrupting chemicals, was proposed. 6-mercapto-1-hexanol (MCH) self-assembled monolayer (SAM) modified Au (MCH/Au) electrode was used as the substrate electrode. Graphene is used with bi-functions, not only to adsorb E2 binding aptamer, serving as the recognition element to E2, but also to be assembled onto MCH/Au electrode when sensing E2, to controllably turn on the electron transfer (eT), and further indicate the signal to E2 concentration. With the synergistic effect of DNase I enzyme, highly sensitive detection of E2 was achieved at this aptasensing system, with a linear range from 0.07 to 10 pM and a detection limit of 50 fM. An outstanding selectivity towards E2 was proven for the sensing system by simultaneously detecting 100-fold potential co-existing interferences. The stability and reproducibility were also evaluated to be satisfactory. Spiked real water analysis further indicated its reliability and potential in practical environmental monitoring.

Controlling Vertical and Lateral Electron Migration Using a Bifunctional Chromophore Assembly in Dye-Sensitized Photoelectrosynthesis Cells.

Integration of photoresponsive chromophores that initiate multistep catalysis is essential in dye-sensitized photoelectrosynthesis cells and related devices. We describe here an approach that incorporates a chromophore assembly surface-bound to metal oxide electrodes for light absorption with an overlayer of catalysts for driving the half-reactions of water splitting. The assembly is a combination of a core-twisted perylene diimide and a ruthenium polypyridyl complex. By altering the connection sequence of the two subunits in the assembly, in their surface-binding to either TiO2 or NiO, the assembly can be tuned to convert visible light into strongly oxidizing equivalents for activation of an electrodeposited water oxidation catalyst (NiCo2O x) at the photoanode, or reducing equivalents for activation of an electrodeposited water reduction catalyst (NiMo0.05S x) at the photocathode. A key element in the design of the photoelectrodes comes from the synergistic roles of the vertical (interlayer) charge transfer and lateral (intralayer) charge hopping in determining overall cell efficiencies for photoelectrocatalysis.

Enhanced Reactivity and Electron Selectivity of Sulfidated Zerovalent Iron toward Chromate under Aerobic Conditions.

When zerovalent iron (ZVI) is used in reductive removal of contaminants from industrial wastewater, where dissolved oxygen (DO) competes with target contaminant for the electrons donated by ZVI, both the reactivity and the electron selectivity (ES) of ZVI toward target contaminant are critical. Thus, the reactivity and ES of two sulfidated ZVI (S-ZVI) samples, synthesized by ball-milling with elemental sulfur (S-ZVIbm) and reacting with Na2S (S-ZVINa2S), toward Cr(VI) under aerobic conditions were investigated. Sulfidation appreciably increased the reactivity of ZVI and the ratio of the rate constants for Cr(VI) removal by S-ZVIbm or S-ZVINa2S to their counterparts without sulfur fell in the range of 1.4-29.9. ES of S-ZVIbm and S-ZVINa2S toward Cr(VI) were determined to be 14.6% and 13.3%, which were 10.7- and 7.5-fold greater than that without sulfidation, respectively. This was mainly ascribed to the greater improving effect of sulfidation on the reduction rate of Cr(VI) than that of DO by ZVI. The improving effects of sulfidation on the performance of ZVI were mainly due to the following mechanisms: sulfidation increased the specific surface area of ZVI, the FeS x layer facilitated the enrichment of Cr(VI) anions on S-ZVI surface because of its anions selective property and favored the electron transfer from Fe0 core to Cr(VI) at the surface because of its role as efficient electron conductor.

Selective Electrocatalytic Degradation of Odorous Mercaptans Derived from S-Au Bond Recongnition on a Dendritic Gold/Boron-Doped Diamond Composite Electrode.

To improve selectivity of electrocatalytic degradation of toxic, odorous mercaptans, the fractal-structured dendritic Au/BDD (boron-doped diamond) anode with molecular recognition is fabricated through a facile replacement method. SEM and TEM characterizations show that the gold dendrites are single crystals and have high population of the Au (111) facet. The distinctive structure endows the electrode with advantages of low resistivity, high active surface area, and prominent electrocatalytic activity. To evaluate selectivity, the dendritic Au/BDD is applied in degrading two groups of synthetic wastewater containing thiophenol/2-mercaptobenzimidazole (targets) and phenol/2-hydroxybenzimidazole (interferences), respectively. Results show that targets removals reach 91%/94%, while interferences removals are only 58%/48% in a short time. The corresponding degradation kinetic constants of targets are 3.25 times and 4.1 times that of interferences in the same group, demonstrating modification of dendritic gold on BDD could effectively enhance electrocatalytic target-selectivity. XPS and EXAFS further reveal that the selective electrocatalytic degradation derives from preferential recognition and fast adsorption to thiophenol depending on strong Au-S bond. The efficient, selective degradation is attributed to the synergetic effects between accumulative behavior and outstanding electrochemical performances. This work provides a new strategy for selective electrochemical degradation of contaminants for actual wastewater treatment.

A pM leveled photoelectrochemical sensor for microcystin-LR based on surface molecularly imprinted TiO2@CNTs nanostructure.

A simple and highly sensitive photoelectrochemical (PEC) sensor towards Microcystin-LR (MC-LR), a kind of typical cyanobacterial toxin in water samples, was developed on a surface molecular imprinted TiO2 coated multiwalled carbon nanotubes (MI-TiO2@CNTs) hybrid nanostructure. It was synthesized using a feasible two-step sol-gel method combining with in situ surface molecular imprinting technique (MIT). With a controllable core-shell tube casing structure, the resultant MI-TiO2@CNTs are enhanced greatly in visible-light driven response capacity. In comparison with the traditional TiO2 (P25) and non-imprinted (NI-)TiO2@CNTs, the MI-TiO2@CNTs based PEC sensor showed a much higher photoelectric oxidation capacity towards MC-LR. Using this sensor, the determination of MC-LR was doable in a wide linear range from 1.0pM to 3.0nM with a high photocurrent response sensitivity. An outstanding selectivity towards MC-LR was further achieved with this sensor, proven by simultaneously monitoring 100-fold potential co-existing interferences. The superiority of the obtained MC-LR sensor in sensitivity and selectivity is mainly attributed to the high specific surface area and excellent photoelectric activity of TiO2@CNTs heterojunction structure, as well as the abundant active recognition sites on its functionalized molecular imprinting surface. A promising PEC analysis platform with high sensitivity and selectivity for MC-LR has thus been provided.

High-Yield and Selective Photoelectrocatalytic Reduction of CO2 to Formate by Metallic Copper Decorated Co3O4 Nanotube Arrays.

Carbon dioxide (CO2) reduction to useful chemicals is of great significance to global climate and energy supply. In this study, CO2 has been photoelectrocatalytically reduced to formate at metallic Cu nanoparticles (Cu NPs) decorated Co3O4 nanotube arrays (NTs) with high yield and high selectivity of nearly 100%. Noticeably, up to 6.75 mmol·L(­1)·cm(­2) of formate was produced in an 8 h photoelectrochemical process, representing one of the highest yields among those in the literature. The results of scanning electron microscopy, transmission electron microscopy and photoelectrochemical characterization demonstrated that the enhanced production of formate was attributable to the self-supported Co3O4 NTs/Co structure and the interface band structure of Co3O4 NTs and metallic Cu NPs. Furthermore, a possible two-electron reduction mechanism on the selective PEC CO2 reduction to formate at the Cu­Co3O4 NTs was explored. The first electron reduction intermediate, CO2 ads•­, was adsorbed on Cu in the form of Cu­O. With the carbon atom suspended in solution, CO2 ads•­ is readily protonated to form the HCOO­ radical. And HCOO­ as a product rapidly desorbs from the copper surface with a second electron transfer to the adsorbed species.

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

Driven by the urgent demand of determining low level of 17ß-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.

A highly sensitive and wide-ranged electrochemical zinc(II) aptasensor fabricated on core-shell SiO2-Pt@meso-SiO2.

In this work, bi-functional SiO2-Pt@meso-SiO2 core-shell nanoparticles were designed to prepare a highly sensitive and selective electrochemical zinc(II) aptasensor. This core-shell structure boasts its SiO2 mesoporous shell and the inside Pt nanoparticles. SiO2 mesoporous shell can fix aptamer without affecting its configuration and can admit electrolyte through the shell. SiO2 core inside can be the substrate of larger amount of Pt nanoparticles that improve the conductivity of the modified electrode dramatically. Due to the application of such a special bi-functional structure and the aptamer's strong combination capacity with Zn(2+), Zn(2+) is pre-enriched onto the electrode effectively and specifically, so that it can be determined sensitively and selectively. Results have shown that the zinc(II) aptasensor can be utilized at a wide linear working range from 100 pM to 50 µM and a low detection limit of 65 pM, which makes it practical in both biological samples and environment monitoring. This method has been successfully applied in Zn(2+) monitoring in human blood and disrupted human cells (MCF-7).