Good Photocurrent Response Research Articles

Studying and fabricating optical, electrical, and structural properties of p-type Al- and N- co-doped SnO2 (ANTO) films and investigating the photo-electro effect of p-ANTO/n-Si heterojunctions

P-type SnO2 films co-doping Al and N increased the high solubility N in the SnO2 host lattice without degrading the crystal structure of the film. The solubility N in the SnO2 host lattice increased with the Al2O3 content in the ATO (Al2O3 doped SnO2) target, and the optimum Al2O3 content was found to be 6 %wt, which corresponds with the best film crystal quality. The optimum optical, electrical, and structural properties of films were achieved at a deposition temperature of 300 °C in a mixture of 50 % Ar and 50 % N2 gas from 6 %wt Al2O3-doped SnO2 target. The Al3+–Sn4+ and N3−–O2− substitution was verified using measurements, such as X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and XRD patterns. Data regarding the tetragonal rutile to cubic phase transformation indicated the N3−–O2− substitution, while the Al3+–Sn4+ replacement was also verified by the appearance of an additional (101) lattice reflection. The resistivity, hole concentration, and hole mobility of the ANTO-6-50 film achieved the best values were 7.1 × 10−3 Ω cm, 6.24 × 1019 cm−3, and 14.1 cm2 V−1 s−1, respectively. The I–V characteristics of p-ANTO-x-50/n-Si heterojunctions under illumination showed p-type conductive properties of the ANTO-x-50 films and a good reproducible photocurrent response of the p-ANTO-x-50/n-Si heterojunction diodes.

Precise and Wide-Ranged Band-Gap Tuning of Ti6-Core-Based Titanium Oxo Clusters by the Type and Number of Chromophore Ligands.

Sensitization with dyes is the most promising option to narrow the band gap and improve visible-light absorption of TiO2. As ideal structure and reaction models of TiO2, titanium oxo clusters (TOCs) with exact crystal structure are beneficial for further understanding the structure-property relationship of TiO2. Most reports mainly focus on the synthesis and properties of TOCs, but research on the band-gap tuning of TOCs at the large range of 3.7-2.0 eV by chromophore ligands (CLs) has been lacking. Herein, six new Ti6-core-based TOCs (Ti6-TOCs) were successfully synthesized by using CLs in a simple and general approach. Each Ti6-TOC structure contains two Ti3(μ3-O) units featuring a flat or pyramidal mode as building blocks. Five Ti6-core structure types were present among the six Ti6-TOCs, which enriched the family of hexanuclear TOCs. To be noted, the band-gap values were tuned at a wide range of 3.41-1.98 eV by controlling the type and number of the CLs 2-hydroxypyridine, salicylaldoxime, and catechol in the structure. Density functional theory calculation revealed that the lowest-energy bands of these Ti6-TOCs are attributed to the CL-to-TiO core charge-transfer bands. This work provides a precise and wide-ranged band-gap tuning method for TOCs. Additionally, the six Ti6-TOCs exhibit good photocurrent response.

Highly Responsive Ultraviolet Sensor Based on ZnS Quantum Dot Solid with Enhanced Photocurrent

Detection of visible blind UV radiation is not only interesting but also of technologically important. Herein, we demonstrate the efficient detection of UV radiation by using cluster like ZnS quantum dot solid nanostructures prepared by simple reflux condensation technique. The short-chain ligand 3-mercaptopropionic acid (MPA) involved in the synthesis lead to the cluster like formation of ZnS quantum dots into solids upon prolonged synthesis conditions. The ZnS QD solid formation resulted in the strong delocalization of electronic wave function between the neighboring quantum dots. It increases the photocurrent value, which can be further confirmed by the decrease in the average lifetime values from 64 to 4.6 ns upon ZnS cluster like QD solid formation from ZnS QDs. The ZnS quantum dot solid based UV sensor shows good photocurrent response and a maximum responsivity of 0.31 (A/W) at a wavelength of 390 nm, is not only competitive when compared with previous reports but also better than ZnS and metal oxide-based photodetectors. The device exhibits a high current value under low-intensity UV light source and an on/off ratio of IUV/Idark = 413 at zero biasing voltage with a fast response. Further, photocurrent device has been constructed using ZnS quantum dot solid nanostructures with graphene hybrids as an active layer to improve the enhancement of photoresponsivity.

Mo-doped porous BiVO4/Bi2S3 nanoarray to enhance photoelectrochemical efficiency for quantitative detection of 17β-estradiol

A new porous nanoarray is constructed as sensing platform of photoelectrochemical (PEC) biosensor for detection of 17β-estradiol (E2) by using aptamer. The molybdenum (Mo) ions doped into porous bismuth vanadate (Mo-p BiVO4) nanoarray by electrodeposition of BiOI nanoarray. Then, the bismuth sulfide (Bi2S3) nanoparticles are grown in-situ on the surface of Mo-p BiVO4 by the self-sacrificial synthesis method to form novel Mo-p BiVO4/Bi2S3 heterojunction. Herein, the Mo-p BiVO4/Bi2S3 heterojunction presents a high PEC signal because of Mo-p BiVO4 could increase electron-hole separation yield by supplying additional free electrons, furthermore the heterojunction of Mo-p BiVO4/Bi2S3 could promote ultrafast transfer of charge and inhibit the recombination of e−/h+ pairs by presenting cascade band-edge levels under irradiation of the visible light. Moreover, the nanoarray structure has large specific surface area, which could accelerate electron transfer and provide large number of binding sites to immobilize aptamer. This PEC aptamer sensor exhibits high sensitivity with a detection limit 3.2 × 10-4 pM and a good photocurrent response toward target E2 in the range of 1 × 10-3 - 5 × 102 pM. Good specificity and stability are acquired for analysis of E2 in human urine. Importantly, this designed sensor platform of Mo-p BiVO4/Bi2S3 heterojunction provides a new promising application for other environmental estrogen analysis.

Encapsulating Halometallates into 3-D Lanthanide-Viologen Frameworks: Controllable Emissions, Reversible Thermochromism, Photocurrent Responses, and Electrical Bistability Behaviors.

The encapsulation of guests into metal-organic frameworks (MOF) is an efficient strategy to generate novel multifunctional materials with enhanced properties. Herein, four halometallate@MOF composites with formulas of {(Pb2I4Br3)[(Pr(bpdo)4(H2O)2]·(H2O)}n (1), {[Pb3I10(H2O)2][Y2(bpdo)5(OH)2]·4(H2O)}n (2), {(Bi2I9)[(Pr(bpdo)3(H2O)]}n (3), {(Bi4I18)[(La(bpdo)4(H2O)2]2}n (4) (bpdo = 4,4'-bipyridine N,N'-dioxide) were prepared. In these composites, lanthanide-viologen MOF act as matrices, whose cavities were penetrated by halometallates. Consequently, the insertion of electron-rich halometallates into electron-deficient lanthanide-viologen matrices leads to the presence of strong room temperature charge transfer (CT) interactions. Importantly, these composites exhibit enhanced photo/thermal stabilities, controllable white emissions, reversible thermochromisms, and good photocurrent response performances. Specially, the memory devices based on these composites illustrate reversible electrical bistability behaviors, which can be assigned to ohmic and space-charge-limited conduction (SCLC) mechanisms. This kind of composite can be utilized as a multifunctional platform with enhanced stability.

Synthesis, Characterization, Optical, Electrochemical and Current-Voltage Characteristics of Coumarin Dyes.

A series of coumarin dyes having common acceptor and pi spacer with different donors were synthesized and characterized by spectroscopic techniques. The TiO2 nanoparticle has been synthesized by sol-gel method and characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Photophysical and electrochemical properties have been investigated. The band gap, molar absorption coefficient and energies of frontier molecular orbitals (FMO) have been calculated. The results showed that an electron releasing group helps in tuning the band gap. The geometry optimization and energies of FMO were obtained by density functional theory calculations. The calculated global chemical parameters help in understanding the intrinsic donor-acceptor properties of the synthesized dye molecules. The result of current-voltage characteristics showed good photocurrent response under illumination condition.

Preciously Determining Energy Levels and Screening Extraction Medium to Design Highly Efficient Carriers Transport Pathways for Zn‐CuInS2 Quantum Dots Based H2 Generation Application

AbstractWith the creation of long‐lived defect states‐related donor‐acceptor pair (DAP) recombination pathway, the Zn doped CuInS2 quantum dots (CIZS QDs) sensitized TiO2 photoelectrode displayed a good photocurrent response ability with a density of 2.7 mA/cm2. Further introduction Au nanoparticles (NPs) between CIZS and TiO2, and the outermost layer CdS, the photocurrent of CdS‐CIZS−Au‐TiO2 reached 7.5 mA/cm2 with an increase of 75% and 175%, respectively. The enhancements both in photo‐conversion ability and photoelectrochemical hydrogen generation reactivity can be mainly attributed to the functions of Au NPs acting as electron traps to help separate the long‐lived carriers of CIZS QDs and subsequently improve interfacial charge transfer, as well as CdS's ability to enhance holes extraction.

Ultrafine M-doped TiO2 (M = Fe, Ce, La) nanosphere photoanodes for photoelectrochemical water-splitting applications

In this study, Fe-, Ce-, and La-doped TiO2 ultrafine nanospheres were synthesized via low-temperature solvothermal method. The structural and morphological variations of bare and M (Fe, Ce, La)- doped TiO2 were confirmed by X-ray photoelectron spectroscopy and transmission electron microscopy images. The fabricated photoanodes were tested using 1 M KOH electrolyte and demonstrated that they can be used for eco-friendly photoelectrochemical solar water-splitting application. Compared to bare TiO2 photoanodes, foreign cations (Fe, Ce, La)-doped TiO2-based photoanodes exhibited higher photocurrent response without bias. In nutshell, the rare-earth element La-doped TiO2 nanosphere photoanode showed good photocurrent response to approximately 0.48 mA/cm2 under illumination, with lower flat band potential shift of −0.83 V. The highest photostability of 96% was achieved over 2 h for 10% La-doped TiO2 nanosphere photoanode and was suitable for solar water-splitting applications.

Fabrication of ultraviolet photodetector with aluminum nitride nanowire networks via direct transfer method

This paper presents the fabrication of an ultraviolet (UV) photodetector based on Aluminum nitride nanowire (AlNNW) networks on a flexible polyvinyl chloride (PVC) substrate. The device was fabricated via a direct transfer method through a very low-cost non-lithographic fabrication scheme. The device has demonstrated very fast photoresponse rise and decay times of 0.27 s and 0.41 s to UV light illumination at 15 V, respectively. Moreover, the device exhibited a good photocurrent response at 2 V bias enabling very high sensitivity and capability of the AlNNW device operating at low voltages. Furthermore, the facile fabrication scheme is very cost-effective, readily scalable; and offers broad integration capabilities, with further optimization, in various flexible electronic and photonic applications.

An ultrasensitive photoelectrochemical biosensor for glucose based on bio-derived nitrogen-doped carbon sheets wrapped titanium dioxide nanoparticles

In this work, an ultra-sensing photoelectrochemical (PEC) glucose biosensor has been constructed from the bio-derived nitrogen-doped carbon sheets (NDC) wrapped titanium dioxide nanoparticles (NDC-TiO2 NPs) followed by the covalent immobilization of glucose oxidase (GODx) on them (designated as a GODx/NDC-TiO2NPs/ITO biosensor). Initially, the TiO2 NPs was synthesized by sol-gel method and then NDC-TiO2 NPs was synthesized utilizing a green source of Prunus persica (peach fruit) through a simple hydrothermal process. The synthesized NDC-TiO2 NPs composite was characterized by FESEM, HRTEM, Raman spectroscopy, XRD, ATR-FTIR spectroscopy and XPS to determine composition and phase purity. These fabricated GODx/NDC-TiO2NPs/ITO biosensor exhibited a good charge separation, highly enhanced and stable photocurrent responses with switching PEC behavior under the light (λ > 400 nm). As a result, GODx/NDC-TiO2NPs/ITO PEC glucose sensor exhibits a good photocurrent response to detection of glucose concentrations (0.05–10 μM) with an ultra-low detection limit of 13 nM under optimized PEC experimental conditions. Also, the PEC glucose sensor revealed a high selectivity, good stability, long time durability, and capability to analyze the glucose levels in real human serum. Also, the further development of this work may provide new insights into preparing other bio-derived carbon nanostructure-based photocatalysts for PEC applications.

Photoelectrochemical immunoassay of lipoprotein-associated phospholipase A2 via plasmon-enhanced energy transfer between gold nanoparticles and CdS QDs/g-C3N4.

A facile and feasible photoelectrochemical (PEC) immunoassay based on plasmon-enhanced energy transfer between gold nanoparticles (AuNPs) and CdS quantum dots (QDs)/g-C3N4 nanosheets was developed for the ultrasensitive detection of lipoprotein-associated phospholipase A2 (Lp-PLA2). To construct such a sensing platform, the immunosensor was prepared by immobilizing Lp-PLA2 on a CdS QDs/g-C3N4-modified electrode. A competitive-type immunoreaction was utilized for Lp-PLA2 detection, with AuNP-labeled anti-Lp-PLA2 antibody used as the competitor. Introducing AuNPs with the specific antibody for the antigen target Lp-PLA2 led to heavy quenching of the photocurrent of CdS QDs/g-C3N4 due to the plasmon-enhanced energy transfer between AuNPs and CdS QDs. The quenching efficiency decreased with increasing target Lp-PLA2 concentration. Under optimal conditions, the PEC immunosensor presented a good photocurrent response to the target Lp-PLA2 in the dynamic linear range of 0.01-300ngmL-1, with a low detection limit of 5.3pgmL-1. Other biomarkers and natural enzymes did not interfere with response of this system. The reproducibility and accuracy of this method for the analysis of human serum specimens were evaluated, and the results given by the method developed here were found to closely correspond to the results obtained with commercial Lp-PLA2 ELISA kits. Importantly, this protocol offers promise for the development of exciton-plasmon interaction-based PEC detection systems. Graphical abstract ᅟ.

Lead(II) ion detection in purified drinking water by nickel hexacyanoferrate-modified n-Si electrode in presence of dihydroxybenzene

To develop feasible probes for heavy metal ions has been considered as one of the most important research topics, due to the significance in monitoring and evaluating the toxicity of environmental water system, especially for the drinking water. This work provided a probe for Pb(II) ion detection in purified drinking water. Nickel hexacyanoferrate (NiHCF) films were prepared by vacuum evaporating nickel fine wire and transforming in a potassium ferricyanide solution on the front surface of platinum coated n-silicon. The transformed NiHCF film shows a reversible insertion electrochemistry and possesses electrocatalytic activity under illumination. The NiHCF-modified electrode was used as photoelectrode and dihydroxybenzene as photocurrent mediators to make up photoelectrochemical (PEC) sensor for Pb(II) ion detection in purified drinking water based on a two-electrode cell in absence of reference electrode and operated at zero working voltage. We have investigated the effects of Pb(II) ions on the photocurrent of hydroquinone or catechol in the purified water. The assay demonstrated good photocurrent responses by adding different concentrations of Pb(II) ion into purified drinking water with a linear range of 20–1560 nM and the limit of determination (based on S/N = 3) is 4.8 nM and 5.3 nM for the presence of hydroquinone and catechol, respectively.

Double Photosystems-Based 'Z-Scheme' Photoelectrochemical Sensing Mode for Ultrasensitive Detection of Disease Biomarker Accompanying Three-Dimensional DNA Walker.

A new double photosystems-based 'Z-scheme' photoelectrochemical (PEC) sensing platform is designed for ultrasensitive detection of prostate-specific antigen (PSA) by coupling with a three-dimensional (3D) DNA walker. Two photosystems consist of CdS quantum dots (photosystem I; PS I) and BiVO4 photoactive materials (photosystem II; PS II), whereas gold nanoparticles (AuNPs) photodeposited on high-active {010} facets of BiVO4 are used as the electron mediators to promote electron transfer from conduction band of PS II to valence band of PS I. 3D DNA walker-based amplification strategy is carried out between hairpin DNA1 conjugated onto the AuNP, hairpin DNA2 labeled with CdS quantum dot (QD-H2), and DNA walker complementary with the PSA aptamer modified to a magnetic bead (Apt-MB). Upon addition of target, DNA walker strand is displaced from DNA walker/Apt-MB to open hairpin DNA1 on AuNP@BiVO4. In the presence of QD-H2, DNA walker induces the hybridization of DNA1 with DNA2 on the gold nanoparticles step by step, thereby resulting in the assembly of CdS QDs on the AuNP@BiVO4 to form Z-scheme double photosystems with strong photocurrent. Under optimum conditions, the Z-scheme PEC sensing system exhibits good photocurrent responses toward target PSA within the working range of 0.01-50 ng mL-1 at a low detection limit of 1.5 pg mL-1. Good reproducibility and accuracy are acquired for analysis of target PSA and human serum specimens relative to the commercial PSA ELISA kit. Importantly, our strategy provides a new horizon for photoelectrochemical in vitro diagnostics.

π-π nanoassembly of water-soluble metalloporphyrin of ZnTCPP on RGO/AuNPs/CS nanocomposites for photoelectrochemical sensing of hydroquinone

The RGO/AuNPs/CS/ZnTCPP nanocomposites were successfully prepared with reduced graphene oxide (RGO) loaded with Au nanoparticles (AuNPs) existed in chitosan (CS) and water-soluble zinc meso-tetra (4-carboxylphenyl) porphyrin (ZnTCPP) by π-π nanoassembly method and were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), 1H NMR spectra and UV–vis absorption spectroscopy. The most important advantage of the RGO/AuNPs/CS/ZnTCPP nanocomposites was environmentally friendly. Indium tin oxide (ITO) electrode surface was modified with the RGO/AuNPs/CS/ZnTCPP nanocomposites exhibited a good photocurrent response at −0.2 V under whitelight of Xenon lamp illumination. The photocurrent response could be greatly increased by adding hydroquinone (HQ) to the solution. Electrons of ZnTCPP were excited from HOMO to LUMO by irradiating light. The photoexcited electrons injected into the RGO, and then transferred to AuNPs further to the ITO. Addition of HQ resulted in the enhanced photocurrent signal by acting as a sacrificial electron donor; Thereby scavenged the photogenerated holes of the excited ZnTCPP and oxidized to benzoquinone (BQ). Based on the above interaction, detection of HQ was developed by a novel photoelectrochemical (PEC) sensor (S/N = 3) with a linear range from 5 to 300 nmol/L (r = 0.997) and detection limit of 0.5 nmol/L. Proposed biosensor is simple, rapid and this was successfully applied for the quantification HQ in the real sample matrices.

Carbon Dots/g-C3N4 Nanoheterostructures-Based Signal-Generation Tags for Photoelectrochemical Immunoassay of Cancer Biomarkers Coupling with Copper Nanoclusters.

A class of 0-dimensional/2-dimensional (0D/2D) nanoheterostructures based on carbon quantum dots (CQDs) and graphitic carbon nitride (g-C3N4) was designed as the signal-generation tags for the sensitive photoelectrochemical (PEC) immunoassay of prostate-specific antigen (PSA) coupling with the copper nanoclusters (CuNCs). Combination of CQDs with g-C3N4 promoted the photoexcited electron/hole separation and largely increased the photocurrents of the nanoheterostructures. Initially, a sandwich-type immunoreaction was carried out on monoclonal anti-PSA antibody-coated microplate by using PSA aptamer linked with CuNCs as the tracer. Accompanying the immunocomplex, the carried CuNCs were dissolved under acidic conditions. The as-released copper ions from the CuNCs could be captured onto the CQDs/g-C3N4 nanoheterostructures via the amino-group on the CQD surface as well as the -NHx (x = 1, 2, 3) of g-C3N4 nanosheets. The strong coordination of the Lewis basic sites on the CQDs/g-C3N4 with Cu2+ decreased the photocurrent of the nanoheterostructures. Under optimal conditions, CQDs/g-C3N4 nanoheterostructures displayed good photocurrent responses for the detection of PSA within the dynamic linear range of 0.02-100 ng mL-1 and a limit of detection (LOD) of 5.0 pg mL-1. This method was also evaluated for quantitative screening of human PSA serum specimens by using the referenced electrochemiluminescent enzyme-linked immunoassay (ECL-ELIA) and gave good matched results between two methods. Additionally, this system was beneficial to explore the charge-separation and photoinduced electron transfer mechanism in the photoelectrochemical sensing protocols.

Reduced graphene oxide/BiFeO3 nanohybrids-based signal-on photoelectrochemical sensing system for prostate-specific antigen detection coupling with magnetic microfluidic device

A novel magnetic controlled photoelectrochemical (PEC) sensing system was designed for sensitive detection of prostate-specific antigen (PSA) using reduced graphene oxide-functionalized BiFeO3 (rGO-BiFeO3) as the photoactive material and target-triggered hybridization chain reaction (HCR) for signal amplification. Remarkably enhanced PEC performance could be obtained by using rGO-BiFeO3 as the photoelectrode material due to its accelerated charge transfer and improved the visible light absorption. Additionally, efficient and simple operation could be achieved by introducing magnetic controlled flow-through device. The assay mainly involved in anchor DNA-conjugated magnetic bead (MB-aDNA), PSA aptamer/trigger DNA (Apt-tDNA) and two glucose oxidase-labeled hairpins (H1-GOx and H2-GOx). Upon addition of target PSA, the analyte initially reacted with the aptamer to release the trigger DNA, which partially hybridized with the anchor DNA on the MB. Thereafter, the unpaired trigger DNA on the MB opened the hairpin DNA structures in sequence and propagated a chain reaction of hybridization events between two alternating hairpins to form a long nicked double-helix with numerous GOx enzymes on it. Subsequently, the enzymatic product (H2O2) generated and consumed the photo-excited electrons from rGO-BiFeO3 under visible light irradiation to enhance the photocurrent. Under optimal conditions, the magnetic controlled PEC sensing system exhibited good photocurrent responses toward target PSA within the linear range of 0.001 − 100ng/mL with a detection limit of 0.31pg/mL. Moreover, favorable selectivity, good stability and satisfactory accuracy were obtained. The excellent analytical performance suggested that the rGO-BiFeO3-based PEC sensing platform could be a promising tool for sensitive, efficient and low cost detection of PSA in disease diagnostics.

Preparation of GO-COOH/AuNPs/ZnAPTPP nanocomposites based on the π–π conjugation: Efficient interface for low-potential photoelectrochemical sensing of 4-nitrophenol

The GO-COOH/AuNPs/ZnAPTPP nanocomposites were constructed using zinc monoamino porphyrin (ZnAPTPP) through π–π conjugation with carboxylated graphene oxide (GO-COOH) loaded with Au nanoparticles (AuNPs). Prepared materials were characterized by 1H NMR spectra, UV–vis absorption spectroscopy and electrochemical impedance spectroscopy. ITO electrode surface was modified with the prepared nanocomposites showed a good photocurrent response when the bias potential, −0.1V was applied. Nanocomposites modified ITO electrode exhibited good photo-response to the 4-nitrophenol (4-NP). ZnAPTPP were excited from HOMO to LUMO under light irradiation, the photoexcited electrons injected into the conduction band of GO-COOH, and then transferred to AuNPs further to the ITO. The presence of GO-COOH and AuNPs improved the separation of photogenerated charges due to their synergetic effect and excellent conductivity. Externally added 4-NP scavenges the photogenerated holes i.e. it acts as a sacrificial electron donor thereby it enhances the photocurrent of the system. Based on this interaction, a novel method for photoelectrochemical detection of 4-NP was developed with a linear range from 0.1 to 15nmol/L (r = 0.996) and detection limit of 0.04nmol/L (S/N = 3). Proposed method is simple and sensitive and this was successfully applied for the quantification 4-NP in river water sample matrices.

LAPS and SPIM Imaging Using ITO-Coated Glass as the Substrate Material.

Light-addressable potentiometric sensors (LAPS) and scanning photo-induced impedance microscopy (SPIM) use photocurrent measurements for spatiotemporal imaging of ion concentrations, electrical potentials, and impedance. In this work, ITO-coated glass was confirmed to produce photocurrents at anodic potentials with 405 nm diode laser illumination. Therefore, it was developed as a low cost and robust substrate material for LAPS and SPIM imaging compared to traditional expensive ultrathin Si substrates. ITO showed good ac photocurrent and pH response without surface modification and insulator. Local photocurrents were produced by scanning a focused laser beam across the sample, which proved the light addressability of ITO-coated glass. With a high-impedance PMMA dot deposited onto the ITO as a model system, a lateral resolution of about 2.3 μm was achieved.

CdS:Mn quantum dot-functionalized g-C3N4 nanohybrids as signal-generation tags for photoelectrochemical immunoassay of prostate specific antigen coupling DNAzyme concatamer with enzymatic biocatalytic precipitation

A new photoelectrochemical (PEC) immunosensor based on Mn-doped CdS quantum dots (CdS:Mn QDs) on g-C3N4 nanosheets was developed for the sensitive detection of prostate specific antibody (PSA) in biological fluids. The signal derived from the as-synthesized Cd:Mn QDs-functionalized g-C3N4 nanohybrids via a hydrothermal method and was amplified through DNAzyme concatamers on gold nanoparticles accompanying enzymatic biocatalytic precipitation. Experimental results by UV–vis absorption spectra and photoluminescence revealed that CdS:Mn QDs/g-C3N4 nanohybrids exhibited higher photocurrent than those of CdS:Mn QDs and g-C3N4 alone. Upon addition of target PSA, a sandwich-type immunoreaction was carried out between capture antibodies and the labeled detection antibodies. Accompanying introduction of gold nanoparticles, the labeled initiator strands on the AuNPs triggered hybridization chain reaction and the formation of DNAzyme concatamers in the presence of hemin. The formed DNAzyme catalyzed 4-chloro-1-naphthol (4-CN) to produce an insoluble/insulating precipitate on the Mn:CdS QDs/g-C3N4, and blocked the light harvesting of Mn:CdS QDs/g-C3N4, thus resulting in the decreasing photocurrent. Under optimal conditions, the immunosensor exhibited good photocurrent responses for determination of target PSA, and allowed detection of PSA at a concentration as low as 3.8pgmL−1. The specificity, reproducibility and precision of this system were acceptable. Significantly, this methodology was further evaluated for analyzing human serum samples, giving well-matched results with referenced PSA enzyme-linked immunosorbent assay (ELISA) method.

Confinement Effects of Metal-Organic Framework on the Formation of Charge-Transfer Tetrathiafulvalene Dimers.

Three transition metal coordination polymers (CPs) based on the redox-active dimethylthio-tetrathiafulvalene-bicarboxylate (L) and 1,3-bi(4-pyridyl)propane (bpp) ligands, formulated as [MnL(bpp)]n (1), [CdL(bpp)]n (2), and [Cd2L(bpp)2(H2O)(C2O4)0.5]n·n(ClO4)·n(H2O) (3), are crystallographically characterized. Complexes 1 and 2 are isostructural 2-D polymers, and 3 features an unusual 3-D metal-organic framework (MOF). The 3-D MOF is constructed from tetranuclear cluster nodes built through the μ2-O bridge of the TTF ligand, which is first found for TTF coordination polymers. It is found that the channel generated by the 3-D MOF exerts a confinement effect on the formation of TTF dimers. The TTF dimers show strong intradimer interaction with partial electron transfer or charge transfer, and hence, the Cd compound 3 has relatively good photocurrent response property in comparison with that of 2-D Cd compound 2.