The synthesis of graphene oxide covalently linked with nickel tetraamino phthalocyanine: A photoelectrochemical sensor for the analysis of rifampicin irradiated with blue light

In this article, the fabrication and characterization of a photoelectrochemical (PEC) rifampicin sensor based on graphene oxide grafted with Ni tetraamino phthalocyanine was described, which presents an excellent PEC activity, sensitivity, and material stability. The synthesized graphene oxide grafted with Ni tetraamino phthalocyanine was characterized using ultraviolet–visible (UV–vis), Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. Specifically, detection for rifampicin was based on the reduction of photocurrent caused by binding of the analyte to the sensing electrode surface. The fabricated sensor was characterized in a broad linear response range (0.025–71.3 μM) and with a low detection limit (2.5 nM), outperforming the previously reported sensors and thus being well suited for quality control and other applications, as confirmed by successful real‐life sample testing.     

Phthalocyanine‐Sensitized Graphene–CdS Nanocomposites: An Enhanced Photoelectrochemical Immunosensing Platform

A novel strategy is developed for the fabrication of graphene–CdS (G–CdS) nanocomposites by in situ growth of CdS nanoparticles onto simultaneously reduced graphite oxide, which is noncovalently functionalized by sodium 1‐pyrene sulfonate through strong π–π stacking interactions. Subsequently, cobalt 2,9,16,23‐tetraaminophthalocyanine (CoTAPc) is self‐assembled on the G–CdS nanocomposites through electrostatic interactions to produce phthalocyanine‐sensitized G–CdS nanocomposites. The photoactive superstructure enhances the photocurrent generation capability, and presents an efficient photoelectrochemical immunosensing platform for the ultrasensitive detection of the prostate‐specific antigen (PSA). The quantitative measurement of PSA is based on the decrease in the photocurrent intensity of the phthalocyanine‐sensitized G–CdS nanocomposites, which results from an increase in the steric hindrance due to the formation of the immunocomplex. A linear relationship between the photocurrent decrease and the PSA concentration is obtained in the wide range from 1 pg mL^?1 to 5 μg mL^?1 with a detection limit of 0.63 pg mL^?1. The proposed sensor shows high sensitivity, stability, reproducibility, and can become a promising platform for other biomolecular detection.     

A New Signal‐On Photoelectrochemical Biosensor Based on a Graphene/Quantum‐Dot Nanocomposite Amplified by the Dual‐Quenched Effect of Bipyridinium Relay and AuNPs

A new photoelectrochemical (PEC) biosensor was developed by using carboxyl‐functionalized graphene and CdSe nanoparticles. This sensitive interface was then successfully applied to detection of thrombin based on the dual‐quenched effect of PEC nanoparticle, which relied on the electron transfer of a bipyridinium relay and energy transfer of AuNPs. After recognition with an aptamer, the PEC nanoparticle was removed and a signal‐on PEC biosensor was obtained. Moreover, the bio‐barcode technique used in the preparation of PEC nanoparticle could avoid cross‐reaction and enhances the sensitivity. Taking advantages of the various methods mentioned above, the sensitivity could be easily enhanced. In addition, in this work we also investigated graphene that was modified with different functional groups and AuNPs of different particle sizes. Under optimal conditions, a detection limit of 5.9×10^?15 M was achieved. With its simplicity, selectivity, and sensitivity, this strategy shows great promise for the fabrication of highly efficient PEC biosensors.     

Photoelectrochemical‐assisted Batch Injection Analysis (PEC‐BIA) of Glucose Exploiting Visible LED Light as an Excitation Source

This work describes the development of a novel method for glucose determination exploiting a photoelectrochemical‐assisted batch injection analysis cell designed and constructed with the aid of 3D printer technology. The PEC‐BIA cell was coupled to a LED lamp in order to control the incidence of light on the Cu₂O/Ni(OH)₂/FTO photoelectroactive platform. The electrochemical characteristics of Cu₂O/Ni(OH)₂/FTO photoelectroactive platform were evaluated by cyclic voltammetry, amperometry, and electrochemical impedance spectroscopy. The PEC‐BIA cell presented linear response range, limit of detection based on a signal‐to‐noise ratio of three, and sensitivity of 1–1000 μmol L^?1, 0.76 μmol L^?1 and 0.578 μA L μmol^?1, respectively. The PEC‐BIA method presented a mean value of the recovery values of 97.0 % to 102.0 % when it was applied to glucose determination in artificial blood plasma samples which indicates the promising performance of the proposed system to determine glucose.     

Photoelectrochemistry of free-base-porphyrin-functionalized zinc oxide nanoparticles and their applications in biosensing

The photoelectrochemical properties of free-base-porphyrin-functionalized zinc oxide nanoparticles were studied. A universal photoelectrochemical biosensing platform was constructed on indium tin oxide (ITO) by using the functional nanohybrid. The nanohybrid was synthesized by means of dentate binding of ZnO nanoparticles with carboxylic groups of 4,4',4',4'-(21H,23H-porphine-5,10,15,20-tetrayl)tetrakis(benzoic acid) (TCPP), and characterized with scanning electron microscopy, contact angle measurement, and spectral techniques. The nanohybrid-coated ITO electrode showed an efficient photocurrent response under irradiation at a wavelength of 360 nm, which could be greatly improved upon addition of cysteine by its oxidation at +0.3 V. The possible mechanism was that cysteine acts as a sacrificial electron donor to scavenge the photogenerated holes that locate on the excited state of TCPP, which then injects the photoexcitation electrons into the conduction band of ZnO nanoparticles, thereby transferring photoinduced electrons to the ITO electrode. Based on this enhanced photocurrent signal, a novel method for photoelectrochemical detection of cysteine was developed with a linear range of 0.6 to 157 μmol L(-1) in physiological media. The detection limit was 0.2 μmol L(-1) at a signal-to-noise ratio of 3. The novel strategy of cysteine analysis could provide an alternative method for monitoring biomolecules and extend the application of porphyrin-functionalized semiconductor nanoparticles.     

A Visible‐Light Driven Photoelectrochemical Aptasensor for Endocrine Disrupting Chemicals Bisphenol A with High Sensitivity and Specificity

A visible‐light driven photoelectrochemical (PEC) sensor based on aptamer immobilized TiO₂‐Fe₂O₃ nanotubes was proposed for the first time and highly sensitive and selective bisphenol A determination was realized. Taking advantage of the alloy oxide nanotube structure, high surface area, good biocompatibility, superior photoelectrocatalytic performance, a limit of detection toward BPA as low as 1.8×10^?11 M with linearity in the range from 1.8×10^?11 to 3.2×10^?9 M could be achieved. Specificity was greatly exhibited for this aptasensor under 100‐fold excess concentration of estriol, resorcinol, nonylphenol, 2,4‐D, acetamiprid, chlorpyrifos and omethoate. Simultaneously, satisfactory results were obtained in real water sample investigation from industrial plastics and drinking water. A novel visible‐light driven PEC method for highly sensitive and selective detection of BPA was thus established.     

Current Advances in Quantum‐Dots‐Based Photoelectrochemical Immunoassays

As a newly developed technique, photoelectrochemical (PEC) immunoassays have attracted great attention in recent years because of their low cost and desirable sensitivity. Because the detection signal originates from the photoelectric conversion of photoelectric materials, the appearance and application of quantum dots (QDs), which possess unique photophysical properties and regulated optoelectronic characteristics, has taken the development of PEC immunoassays to new heights. This review concisely introduces the general mechanism of QDs‐based photoelectric conversion for immunoassays and summarizes the current advances in QD applications in immunoassays. Given that signal strategies and photoactive materials are the key elements in PEC biosensor systems, we comprehensively highlight the state‐of‐the‐art signaling strategies and various applications of QDs in PEC immunoassays to introduce advances in QDs‐based PEC immunoassays. Finally, challenges and future developmental trends are briefly discussed     

Optically Transparent Electrodes Modified with Sulfide Ion‐Covered CdS Quantum Dots for Sensitive Photoelectrochemical Detection of Sulfhydryl‐Containing Compounds

A sensitive and selective photoelectrochemical sensor has been developed. Negatively charged, citrate‐capped CdS quantum dots (QDs) are assembled layer‐by‐layer onto indium tin oxide (ITO) electrodes precoated with positively charged poly(diallyldimethylammonium chloride). By exposing the modified photoelectrochemical electrodes to a Na₂S solution, QDs can be covered with excess S^2? ions. The weakly bound S^2? ions are easily replaceable with a sulphydryl‐containing analyte, and the photocurrent decrease is proportional to the analyte concentration. The detection limit is 0.4 nM for cysteine with a linear range of 1.0–100.0 nM. The level of cysteine in human serum samples has been quantified.     

Rationally Design of Near Infrared Light Responsive Micro‐Photoelectrodes for In Vivo Sensing of Neurotransmitter Molecules in Mouse Brain†

The accurate quantification of neurotransmitter molecules is an indispensable means to reveal the physiological mechanisms of neuro movement in molecular level. However, existing detection strategies cannot fully meet practical needs, and the on‐site and in vivo detection of neurotransmitters in brain remains a great challenge. Here, we report the development of a near infrared light responsive photoelectrochemical (PEC) detection method for in vivo quantification of neurotransmitter dopamine in mouse brain. Under guidance of density function theory calculations, a combination strategy of non‐metal cation doping and defect engineering is introduced to rationally design the micro‐photoelectrodes with excellent biocompatibility and stability and implements the in vivo PEC detection of dopamine in mouse brain. It opens up a new way for the accurate in vivo detection of biomolecules and allows researchers to make novel inquiries for long‐standing questions in a new way.     

A Photoelectrochemical Immunosensor for Prostate Specific Antigen Detection Based on Graphdiyne Oxide Conjugated with Horseradish Peroxidase

Graphdiyne (GDY) was a novel flat material with sp and sp² hybridized carbon atoms. It exhibited good biocompatibility. The application of GDY in PEC immunosensor was very limited. Thus, a novel photoelectrochemical sensor for the sensitive detection of prostate specific antigen (PSA) was proposed by using GDY oxide (GDYO) conjugated with horseradish peroxidase (HRP) and secondary antibody for photocurrent signal inhibition. GDYO was prepared by oxidation of honeycomb-like nanotubes composed of numerous GDY nanosheets. It showed high loading capacity for HRP and the catalytic activity of HRP could be remained. With reduced graphene oxide-CdS (rGO-CdS) as photoelectrochemical sensing platform, a sandwich-type photoelectrochemical (PEC) immunosensor was thus fabricated. The immunosensor presented a wide linear concentration range of 10 fg mL⁻¹–20.0 ng mL⁻¹ with a detection limit (LOD) of 3.5 fg mL⁻¹. Moreover, the PEC immunosensor displayed ideal reproducibility, stability, and selectivity, which was a promising platform for the detection of other important tumor targets.     

三苯胺功能染料的合成及在谷胱甘肽超低电位光电检测中的应用

设计合成了一种具有D-π-A结构的三苯胺功能染料(TCA),并通过分子结构中的羧基将其配位于TiO_2纳米粒子修饰的光电极表面,发展了一种可在超低电位下高灵敏检测谷胱甘肽(GSH)的光电传感方法.该TCA分子以三苯胺为电子给体,噻吩为桥连基团,氰基乙酸为电子受体.在可见光的照射下,TCA通过分子内电子转移将光电子由三苯胺经噻吩和羧基注入到TiO_2的导带能级,进而注入基底光电极,产生阳极光电流;同时,TCA被氧化到氧化态.由于氧化态TCA的稳定性好,可循环被生理活性小分子GSH还原,并产生放大的阳极光电流.TCA功能化的TiO_2纳米粒子修饰电极对GSH表现出了极高的催化活性,在波长为480 nm的可见光照射下,在0 V的超低电位下即可实现对GSH的催化氧化.基于这一性质,发展了一种可用于GSH检测的光电传感方法.在最优条件下,该传感器对浓度为2~100μmol/L和0.1~2.4 mmol/L的GSH具有良好的线性响应,检出限低达1μmol/L.此外,该光电传感器具有较好的选择性,可排除13种氨基酸和生理活性物质多巴胺及氢醌的干扰,因此具有一定的实际应用前景.     

α‐Fe2O3 Film with Highly Photoactivity for Non‐enzymatic Photoelectrochemical Detection of Glucose

A non‐enzyme photoelectrochemical (PEC) glucose sensor based on α‐Fe₂O₃ film is investigated. The α‐Fe₂O₃ film was fabricated via a simple spin coating method. The proposed glucose sensor exhibits good selectivity, a fast response time of <5 s, a linear range of 0.05 to 6.0 mM, sensitivity of 17.23 μA mM^?1 cm^?2 and a detection limit of 0.05 μM. Meanwhile, the excellent performances of the α‐Fe₂O₃ sensor were obtained in reproducibility and the long‐term stability under ambient condition. The linear amperometric response of the sensor covers the glucose levels in physiological and clinical for diabetic patients. Therefore, this non‐enzyme PEC sensor based on α‐Fe₂O₃ film has a great potential application in the development of glucose sensors.     

Carbon Nitride Materials for Water Splitting Photoelectrochemical Cells

Graphitic carbon nitride materials (CNs) have emerged as suitable photocatalysts and heterogeneous catalysts for various reactions thanks to their tunable band gap, suitable energy‐band position, high stability under harsh chemical conditions, and low cost. However, the utilization of CN in photoelectrochemical (PEC) and photoelectronic devices is still at an early stage owing to the difficulties in depositing high‐quality and homogenous CN layer on substrates, its wide band gap, poor charge‐separation efficiency, and low electronic conductivity. In this Minireview, we discuss the synthetic pathways for the preparation of various structures of CN on substrates and their underlying photophysical properties and current photoelectrochemical performance. The main challenges for CN incorporation into PEC cell are described, together with possible routes to overcome the standing limitations toward the integration of CN materials in PEC and other photoelectronic devices.     

A photoelectrochemical biosensor using ruthenium complex-reduced graphene oxide hybrid as the photocurrent signal reporter assembled on rhombic TiO2 nanocrystals driven by visible light

An ultrasensitive photoelectrochemical (PEC) immunoassay of cancer biomarker carcinoembryonie antigen (CEA) is proposed that uses rhombic titanium dioxide nanocrystals (TiO₂ NCs) coupled with Ab2–RGO-Ru bioconjugate, which featured CEA signal antibody (Ab2) and ruthenium tris(bipyridine) (Ru complex) labels linked to reduced graphene oxide (RGO) for signal amplification. Herein, the Ru complex acts as an electron donor, while RGO serves as an electron acceptor which facilitates charge separation and suppresses recombination of photoexcited electron–hole pairs in the hybridized species. The rhombic TiO₂ NCs were fabricated through a solvothermal technique in anhydrous ethanol, followed by spin-coating process and calcination, an ITO/TiO₂ electrode was obtained. Chitosan (CS) and glutaraldehyde (GLD) were used to modify the prepared ITO/TiO₂ electrode to covalently immobilize antibodies. With a sandwich-type immunoreaction, CEA and Ab2–RGO-Ru were conjugated successively to form a sandwich-type immunocomplex. Thus, a sandwich-type PEC immunosensor was fabricated for the detection of CEA was developed by monitoring the changes in the photocurrent signals of the electrode resulting from the immunoreaction. The proposed PEC immunosensor showed high sensitivity, selectivity, excellent stability, and good reproducibility, and thus has great potential to be used for other biological assays.     

Electrochemical Preparation of Brilliant‐Blue‐Modified Poly(diallyldimethylammonium Chloride) and Nafion‐Coated Glassy Carbon Electrodes and Their Electrocatalytic Behavior Towards Oxygen and L‐Cysteine

Brilliant blue FCF‐modified glassy carbon electrodes have been prepared by cycling the Nafion (or poly(diallyldimethylammonium chloride) (PDDAC)) coated electrodes repeatedly 15 cycles in brilliant blue FCF (BB FCF) dye solution. The BB FCF molecules are incorporated into Nafion coating by cycling the film‐covered electrode between +0.3 to 1.2 V (vs. Ag/AgCl) in pH 1.5 BB FCF solution while PDDAC‐coated electrode cycled between 0 to ?1.0 V (vs. Ag/AgCl) in pH 6.5 BB FCF solution to immobilize the dye. Electrostatic interaction between dye molecule and PDDAC was predominant in PDDAC coating whereas immobilization of dye in Nafion film attributed to the combined effect of electrostatic and hydrophobic interactions. The voltammetric features of BB FCF‐modified electrodes resemble that of surface‐confined redox couples. The peak potentials of BB FCF‐incorporated PDDAC‐coated electrode were shifted to more positive potential region with decreasing pH of contacting solution. BB FCF‐modified electrodes showed electrocatalytic activity towards reduction of oxygen and oxidation of L ‐cysteine with significant decease of overvoltage compared to unmodified electrode. The BB FCF‐modified Nafion‐coated electrode was tested for its analytical applications toward determination of L ‐cysteine. The linear range of calibration plot at BB FCF‐modified Nafion‐coated electrode is 10 to 100 μM, which coincides with L ‐cysteine levels in biological fluids. Sensitivity and detection limit of the electrode are 111 nA μM^?1 and 0.5 μM, respectively.     

Enhanced Charge Separation Efficiency in Pyridine‐Anchored Phthalocyanine‐Sensitized Solar Cells by Linker Elongation

A series of zinc phthalocyanine sensitizers ( PcS22 – 24 ) having a pyridine anchoring group are designed and synthesized to investigate the structural dependence on performance in dye‐sensitized solar cells. The pyridine‐anchor zinc phthalocyanine sensitizer PcS23 shows 79 % incident‐photon to current‐conversion efficiency (IPCE) and 6.1 % energy conversion efficiency, which are comparable with similar phthalocyanine dyes having a carboxylic acid anchoring group. Based on DFT calculations, the high IPCE is attributed with the mixture of an excited‐state molecular orbital of the sensitizer and the orbitals of TiO₂. Between pyridine and carboxylic acid anchor dyes, opposite trends are observed in the linker‐length dependence of the IPCE. The red‐absorbing PcS23 is applied for co‐sensitization with a carboxyl‐anchor organic dye D131 that has a complementary spectral response. The site‐selective adsorption of PcS23 and D131 on the TiO₂ surface results in a panchromatic photocurrent response for the whole visible‐light region of sun light.     

Organic‐inorganic‐hybrid‐enhancement Electrochemical Sensor for Determination of Cu (II) in River Water

A dual strategy that the L‐cysteine self‐assembling on three‐dimensional network of organic‐hybrid‐materials realized by successive interaction of Au−S bond is employed to construct as the amplified electrochemical sensor for determination Cu (II). Specifically, the sensor combined a rigid three‐dimension inorganic net which provides a higher interfacial area as well as faster adsorption of ions. Accordingly, surface and interfacial‐dominated electro‐catalysis reactivity is used as an ideal test‐bed to verify the reliability of electrochemical sensor that reveal enhancement sensitiveness and selectivity, low detection limit, and stability over a long period of time. Time‐dependent density functional theory (TD‐DFT) were used to calculating the all complexes energies at the B3LYP/LANL2DZ level associated with the polarized continuum model (PCM). The result of calculation indicates that the binding strength of Cu (II), Cd (II), As (III), Hg (II) with L‐cysteine are decrease successively, and this is in well agreement with experimental results. This work not only achieves an unprecedented understanding to L‐cysteine/Au/TiO₂/GCE sensor but also provides a new perspective for application in detection of Cu (II) in real river waters.     

Metal-Organic Framework Glass Catalysts from Melting Glass-Forming Cobalt-Based Zeolitic Imidazolate Framework for Boosting Photoelectrochemical Water Oxidation

Sluggish oxygen evolution kinetics and serious charge recombination restrict the development of photoelectrochemical (PEC) water splitting. The advancement of novel metal–organic frameworks (MOFs) catalysts bears practical significance for improving PEC water splitting performance. Herein, a MOF glass catalyst through melting glass-forming cobalt-based zeolitic imidazolate framework (Co-a_gZIF-62) was introduced on various metal oxide (MO: Fe₂O₃, WO₃ and BiVO₄) semiconductor substrates coupled with NiO hole transport layer, constructing the integrated Co-a_gZIF-62/NiO/MO photoanodes. Owing to the excellent conductivity, stability and open active sites of MOF glass, Co-a_gZIF-62/NiO/MO photoanodes exhibit a significantly enhanced photoelectrochemical water oxidation activity and stability in comparison to pristine MO photoanodes. From experimental analyses and density functional theory calculations, Co-a_gZIF-62 can effectively promote charge transfer and separation, improve carrier mobility, accelerate the kinetics of oxygen evolution reaction (OER), and thus improve PEC performance. This MOF glass not only serves as an excellent OER cocatalyst on tunable photoelectrodes, but also enables promising opportunities for PEC devices for solar energy conversion.     

Hybrid junctions of zinc(II) and magnesium(II) phthalocyanine with wide-band-gap semiconductor nano-oxides: spectroscopic and photoelectrochemical characterization

The optical properties of zinc phthalocyanine (ZnIIPc) and magnesium phthalocyanine (MgIIPc) in DMSO and DMF solutions have been extensively investigated, and the photoelectrochemical behaviors of layer-by-layer hybrid junctions formed of the two metallo(II) phthalocyanines (MIIPcs) and wide-band-gap colloidal semiconductors, namely, ZnO and TiO2 nanocrystals (NCs), have been probed. Different experimental conditions, such as the Pc center metal ion, dye concentration, and solvent identity, were investigated in order to elucidate their effects on the photoelectrochemical performances of the prepared heterojunctions. Finally, thermal treatment of either dye and NC films and control of the NC shape and surface chemistry were also studied and, interestingly, were found to be critical in affecting the performance of photochemical sensitization processes, occurring at the dye/oxide and oxide/solution interfaces.     

Development of a Carbon Paste Electrode Modified with Reduced Graphene Oxide and an Imidazole Derivative for Simultaneous Determination of Biological Species of N‐acetyl‐L‐cysteine,Uric Acid and Dopamine

In this work, the modified carbon paste electrode (CPE) with an imidazole derivative 2‐(2,3 dihydroxy phenyl) 4‐methyl benzimidazole (DHPMB) and reduced graphene oxide (RGO) was used as an electrochemical sensor for electrocatalytic oxidation of N‐acetyl‐L‐cysteine (NAC). The electrocatalytic oxidation of N‐acetyl‐L‐cysteine on the modified electrode surface was then investigated, indicating a reduction in oxidative over voltage and an intensive increase in the current of analyte. The scan rate potential, the percentages of DHPMB and RGO, and the pH solution were optimized. Under the optimum conditions, some parameters such as the electron transfer coefficient (α) between electrode and modifier, and the electron transfer rate constant) k_s) in a 0.1 M phosphate buffer solution (pH=7.0) were obtained by cyclic voltammetry method. The diffusion coefficient of species (D) 3.96×10^?5 cm² s^?1 was calculated by chronoamperometeric technique and the Tafel plot was used to calculate α (0.46) for N‐ acetyl‐L‐cysteine. Also, by using differential pulse voltammetric (DPV) technique, two linear dynamic ranges of 2–18 µM and 18–1000 µM with the detection limit of 61.0 nM for N‐acetyl‐L‐cysteine (NAC) were achieved. In the co‐existence system of N‐acetyl‐L‐cysteine (NAC), uric acid (UA) and dopamine (DA), the linear response ranges for NAC, UA, and DA are 6.0–400.0 µM, 5.0–50.0 µM and 2.0–20.0 µM, respectively and the detection limits based on (C=3s_b/m) are 0.067 µM, 0.246 µM and 0.136 µM, respectively. The obtained results indicated that DHPMB/RGO/CPE is applicable to separate NAC, uric acid (UA) and dopamine (DA) oxidative peaks, simultaneously. For analytic performance, the mentioned modified electrode was used for determination of NAC in the drug samples with acceptable results, and the simultaneous determination of NAC, UA and DA oxidative peaks was investigated in the serum solutions, too.