Effect of perylene assembly shapes on photoelectrochemical properties and ultrasensitive biosensing behaviors toward dopamine.

In this study, a photoelectrochemical (PEC) sensor based on perylene diimide derivatives (PDIs) was developed for the ultrasensitive quantification of dopamine (DA). PDIs were able to form self-assembled semiconductor nanostructures by strong π-π stacking, suitable for photoactive substances. Moreover, the shape of the PDI significantly affected the PEC properties of these nanostructures. The results showed that amino PDI with two-dimensional (2D) wrinkled layered nanostructures exhibited superior PEC properties relative to one-dimensional (1D) nanorods and fiber-based nanostructures (methyl and carboxyl PDIs). Based on these results, a mechanism for PEC sensor action was then proposed. The presence of 2D amino-PDI resulted in accelerated charge separation and transport. Furthermore, dopamine acted as effective electron donor to cause an increase in photocurrent. The as-obtained sensor was then used to detect small molecules like DA. A blue light optimized sensor at an applied potential of 0.7 V showed a detection limit of 1.67 nM with a wide linear range of 5 nM to 10 µM. On the other hand, the sensor presented acceptable reliability in determining DA in real samples. A recovery rate between 97.99 and 101.0% was obtained. Overall, controlling the morphology of semiconductors can influence PEC performance, which is a useful finding for the future development of PEC sensors.

SARS-CoV-2 detection enabled by a portable and label-free photoelectrochemical genosensor using graphitic carbon nitride and gold nanoparticles.

Fast, sensitive, simple, and cheap sensors are highly desirable to be applied in the health system because they improve point-of-care diagnostics, which can reduce the number of cases of infection or even deaths. In this context, here we report the development of a label-free genosensor using a screen-printed electrode modified with 2D-carbonylated graphitic carbon nitride (c-g-C3N4), poly(diallyldimethylammonium) chloride (PDDA), and glutathione-protected gold nanoparticles (GSH-AuNPs) for photoelectrochemical (PEC) detection of SARS-CoV-2. We also made use of Arduino and 3D printing to miniaturize the sensor device. The electrode surface was characterized by AFM and SEM techniques, and the gold nanoparticles by UV-Vis spectrophotometry. For SARS-CoV-2 detection, capture probe DNA was immobilized on the electrode surface. The hybridization of the final genosensor was tested with a synthetic single-strand DNA target and with natural saliva samples using the photoelectrochemistry method. The device presented a linear range from 1 to 10,000 fmol L-1 and a limit of detection of 2.2 and 3.4 fmol L-1 using cpDNA 1A and 3A respectively. The sensibility and accuracy found for the genosensor using cpDNA 1A using biological samples were 93.3 and 80% respectively, indicating the potential of the label-free and portable genosensor to detect SARS-CoV-2 RNA in saliva samples.

A novel photoelectrochemical immunosensor based on TiO2@Bi2WO6 hollow microspheres and Ag2S for sensitive detection of SARS-COV-2 nucleocapsid protein.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV-2) is a cluster of ß coronaviruses. The 2019 coronavirus disease (COVID-19) caused by SARS-COV-2 is emerging as a global pandemic. Thus, early diagnosis of SARS-COV-2 is essential to prevent severe outbreaks of the disease. In this experiment, a novel label-free photoelectrochemical (PEC) immunosensor was obtained based on silver sulfide (Ag2S) sensitized titanium dioxide@bismuth tungstate (TiO2@Bi2WO6) nanocomposite for quantitative detection of SARS-COV-2 nucleocapsid protein. The constructed TiO2@Bi2WO6 hollow microspheres had large specific surface area and could produce high photocurrent intensity under visible light illumination. Ag2S was in-situ grown on the surface of thioglycolic acid (TGA) modified TiO2@Bi2WO6. In particular, TiO2@Bi2WO6 and Ag2S formed a good energy level match, which could effectively enhance the photocurrent conversion efficiency and strength the photocurrent response. Ascorbic acid (AA) acted as an effective electron donor to effectively eliminate photogenerated holes. Under optimal experimental conditions, the constructed immunosensor presented a supersensitive response to SARS-COV-2 nucleocapsid protein, with a desirable linear relationship ranged from 0.001 to 50 ng/mL for nucleocapsid protein and a lower detection limit of 0.38 pg/mL. The fabricated sensor exhibited a wide linear range, excellent selectivity, specificity and stability, which provided a valuable referential idea for the detection of SARS-COV-2.

A sandwich-type photoelectrochemical sensor constructed with a signal amplification strategy based on the upconversion luminescence characteristics of Ag@N-CQDs for sensitive detection of neuron specific enolase.

In this paper, Bi2S3/AgBiS2 composite nanomaterials and PDA@Ag@N-CQDs were synthesized, and used as substrates and second antibody label respectively to construct a sandwich photoelectrochemical (PEC) sensor. The upconversion luminescence effect of N-CQDs can convert long wavelength light into short wavelength light that can be utilized by the substrate material, which can provide additional excitation light energy for the substrate material and further enhance the photoelectric response. Besides, Ag has SPR effect and can also promote electron transfer. The proposed sandwich immunosensor achieves detection of NSE in the concentration range of 0.001 ng mL-1 to 100 ng mL-1, with a detection limit of 0.28 pg mL-1 (S/N = 3). What's more, the proposed sensor also exhibits good stability, selectivity, as well as reproducibility, indicating its promising application prospects.

Molecularly imprinted photoelectrochemical sensor for ultrasensitive and selective detection of hydroquinone using 0D CdS nanoparticle/3D flower-like ZnIn2S4 microsphere nanocomposite.

A novel photoelectrochemical (PEC) sensor was developed for the ultra-sensitive and highly selective detection of hydroquinone (HQ), featuring a composite structure that combines 0D CdS nanoparticles with a 3D flower-like ZnIn2S4 microsphere. The sensor, termed rMIP/CdS/ZnIn2S4, employed molecularly imprinted polymers (MIPs) to achieve specific recognition of HQ. An p-phenylenediamine (pPD) polymer film was electrochemically polymerized onto the surface of the CdS/ZnIn2S4 composite-coated glassy carbon electrode (GCE). Through hydrogen bonding, HQ molecules were imprinted onto the polymer film. Subsequent elution removed these molecules, leaving behind specific recognition sites, enabling selective detection of HQ. The unique spatial structure and heterojunction properties of the 0D CdS nanoparticle/3D flower-like ZnIn2S4 composite, combined with molecular imprinting, significantly enhanced the photocurrent response and increased the selectivity and sensitivity for HQ detection. Under optimal conditions, the rMIP/CdS/ZnIn2S4 sensor demonstrated a low detection limit (0.7 nmol·L-1, S/N=3) over a wide linear range of 1-1200 nmol·L-1. The sensor was successfully applied to detect HQ in real water samples, showing promise for environmental pollution control applications.

Dual-mode self-powered photoelectrochemical and colorimetric determination of procalcitonin accomplished by multienzyme-expressed Ni4Cu2 bimetallic hollow nanospheres and spherical nanoflower-MoS2/Cu2ZnSnS4/Bi2S3.

Bacterial infections, viral infections and autoimmune diseases pose a considerable threat to human health. Procalcitonin (PCT) has emerged as a biomarker for the detection of these diseases. To ensure accurate and reliable results, we propose a dual-mode approach that incorporates self-validation and self-correction mechanisms. Herein, we develop a dual-mode self-powered photoelectrochemical (PEC) and colorimetric sensor to determine PCT. The self-powered PEC sensor was constructed with a photoanode of spherical nanoflower-MoS2/Cu2ZnSnS4/Bi2S3 material and a photocathode of CuInS2 material. Ni4Cu2 bimetallic hollow nanospheres (BHNs) possess superoxide dismutase and catalase performance, which facilitate superoxide anion radical (·O2-) and H2O2 circulating generation, promoting the separation of photogenerated electrons and holes to amplify photocurrent signal. Thus Ni4Cu2 BHNs is used as a marker material for PEC sensor. Meanwhile, in colorimetric mode, Ni4Cu2 BHNs converts blue oxTMB to a colourless TMB for colorimetric detection of PCT. Based on this principle, dual-mode determination of PCT with high sensitivity is achieved. The dual-mode method not only demonstrates outstanding properties and practicability, but also presents an effective, highly efficient and reliable method for detecting PCT.

ZnO/C nanocomposite grafted molecularly imprinted polymers as photoelectrochemical sensing interface for ultrasensitive and selective detection of chloramphenicol.

Nanomaterials-based photoelectrochemical (PEC) detection is becoming a rapidly-developing analytical technique in chemical and biological assays due to its unique advantages of easy miniaturization, high sensitivity, and rapid turnaround time. Herein, a molecularly imprinted polymer-assisted PEC sensor based on ZnO/C nanocomposite was successfully fabricated for the highly sensitive and selective determination of chloramphenicol (CAP). Benefiting from the hydrophilic functional groups (-OH, -COOH) and large surface area of bio-templated ZnO/C nanocomposite, the tight grafting of MIP with excellent recognition ability on substrate is easier and more stable than traditional PEC sensor, thus significantly increasing the performance. Under optimal conditions, the PEC sensor exhibited significant CAP detection performance in the range of 0.01-5000 ng mL-1 with a detection LOD of 5.08 pg mL-1 (S/N = 3) and successfully applied to the detection of CAP in milk sample. Our results show that ZnO/C nanocomposite and MIP can act as an efficient photo-responsible matrix to fabricate PEC sensor, providing important application potentials for pollutants control in food and environment.

C-doped ZnO nanocomposites molecularly imprinted photoelectrochemical sensor for ultrasensitive and selective detection of oxytetracycline in milk.

Antibiotic monitoring remains vital to ensure human health and safety in the environment and foods. As the most popular detection method, photoelectrochemical (PEC) sensor can achieve rapid and accurate detection of antibiotics with the advantages of high sensitivity, easy-to-preparation process, as well as high selectivity. Herein, an extremely-efficient visible-light responsible ZnO/C nanocomposite was prepared and combined with acetylene black (as an enhanced conductive matrix), and the electron migration efficiency was greatly accelerated. Meanwhile, a molecularly imprinted polymer obtained by electrical agglomeration was conjugated as a specific recognizing site for target. Furthermore, the as-prepared rMIP-PEC sensor showed a low detection limit (8.75 pmol L-1, S/N = 3) in a wide linear detection range of 0.01-1000 nmol L-1 for oxytetracycline (OTC), with excellent selectivity and long-term stability. Our work shed light on applying C-doped ZnO semiconductor and molecularly imprinted polymer as photoelectric active sensing materials for rapid and accurate analysis of antibiotics in foods and environment.

ß-Bi2O3 Nanosheets Functionalized with Bisphenol A Synthetic Receptors: A Novel Material for Sensitive Photoelectrochemical Platform Construction.

In this study, ß-Bi2O3 nanosheets functionalized with bisphenol A (BPA) synthetic receptors were developed by a simple molecular imprinting technology and applied as the photoelectric active material for the construction of a BPA photoelectrochemical (PEC) sensor. BPA was anchored on the surface of ß-Bi2O3 nanosheets via the self-polymerization of dopamine monomer in the presence of a BPA template. After the elution of BPA, the BPA molecular imprinted polymer (BPA synthetic receptors)-functionalized ß-Bi2O3 nanosheets (MIP/ß-Bi2O3) were obtained. Scanning electron microscopy (SEM) of MIP/ß-Bi2O3 revealed that the surface of ß-Bi2O3 nanosheets was covered with spherical particles, indicating the successful polymerization of the BPA imprinted layer. Under the best experimental conditions, the PEC sensor response was linearly proportional to the logarithm of BPA concentration in the range of 1.0 nM to 1.0 µM, and the detection limit was 0.179 nM. The method had high stability and good repeatability, and could be applied to the determination of BPA in standard water samples.

A self-powered photoelectrochemical cathodic molecular imprinting sensor based on Au@TiO2 nanorods photoanode and Cu2O photocathode for sensitive detection of sarcosine.

Quantitative determination of sarcosine (SAR) in biological liquids is of great importance, as SAR has been recently suggested as a promising biomarker for prostate cancer diagnostics. Herein, a self-powered photoelectrochemical (PEC) molecular imprinted sensor integrated with photoanode (Au@TiO2 nanorods) and photocathode (Cu2O) is proposed for the first time towards the specific and sensitive detection of SAR. With the benefits of strong photocurrent driving force attributed to a large inherent deviation between the Fermi levels of photoanode and photocathode in this system, the photogenerated electrons of Au@TiO2 can rapidly transferred along the outer circuit and attracted by the holes in the valence band of the photocathode, forming a self-powered PEC system and improve the photocurrent of the cathode. Under the optimal conditions, the constructed cathode imprinted sensor has a linear range of 10 nM - 10 µM, and the limitation of detection is 0.19 nM. This work proved that the PEC sensing platform has great potential in the field of miniaturized biosensing without external power supply.

Surface Plasmon-Enhanced Photoelectrochemical Sensor Based on Au Modified TiO2 Nanotubes.

Based on the enhanced charge separation efficiency of the one-dimensional structure and strong surface plasmon resonance (SPR) of gold, a gold modified TiO2 nanotube (Au/TiO2NTs) glucose photoelectrochemical (PEC) sensor was prepared. It could be activated by visible red light (625 nm). Under optimal conditions, the Au/TiO2NTs sensor exhibited a good sensitivity of 170.37 µA·mM-1·cm-2 in the range of 1-90 µM (R2 = 0.9993), and a detection limit of 1.3 µM (S/N = 3). Due to its high selectivity, good anti-interference ability, and long-term stability, the fabricated Au/TiO2NTs sensor provides practical detection of glucose. It is expected to be used in the construction of non-invasive PEC biosensors.

A label-free photoelectrochemical immunosensor for prostate specific antigen detection based on Ag2S sensitized Ag/AgBr/BiOBr heterojunction by in-situ growth method.

Prostate cancer is one of the most common cancers in the world, and its early detection is vital to saving the lives of patients. In this research, a novel label-free photoelectrochemical immunosensor was designed for sensitive detection of prostate specific antigen (PSA). Ag2S sensitized on Ag/AgBr/BiOBr heterojunction could effectively inhibit photogenic holes recombination and improve photocurrent response and sensitivity. Ascorbic acid was an effective electron donor, which can effectively eliminate photo-generated holes. The photocurrent reduced linearly with the logarithm of PSA concentration ranged from 0.001 to 50 ng·mL-1 and the limit of detection was 0.25 pg·mL-1. The designed sensor had the advantages of wide linear range, good stability, high reproducibility, and good selectivity. This study not only provided a method for efficient and sensitive detection of PSA, but also provided valuable reference ideas for the detection of other tumor markers.

A label-free photoelectrochemical immunosensor for detection of the milk allergen ß-lactoglobulin based on Ag2S -sensitized spindle-shaped BiVO4/BiOBr heterojunction by an in situ growth method.

Food allergies have become a nonnegligible food safety issue, and milk allergies are one of the most common food allergies, that has attracted large consumer attention. In this work, a novel label-free photoelectrochemical (PEC) immunosensor for the detection of the allergen ß-lactoglobulin (ß-LG) in dairy products was designed that used the specific recognition of allergen ß-LG and antibodies in dairy products in combination with biosensing technology. Here, Ag2S-sensitized spindle-shaped BiVO4/BiOBr heterojunction was fixed on the surface of the ITO electrode as an excellent photoactive substrate and effectively improved the photocurrent responses and sensitivity. Thioglycolic acid (TGA) was used as a linker to immobilize the ß-LG antibody on the surface of the electrode. The photocurrent was detected at different antigen concentrations, which realized the quantitative testing of ß-LG. Under the optimal experimental conditions, the PEC immunosensor proved an ideal linear relationship ranging from 10 pg/mL to 100 ng/mL, with a low detection limit of 3.7 pg/mL. The designed immunosensor showed good stability, a wide linear range, high sensitivity and good reproducibility and could be used for the detection of actual samples. The PEC immunosensor had a strong ability to specifically recognize ß-LG, which was not affected by other proteins in the milk without pretreatment. Meanwhile, the developed immunosensor provided a promising PEC detection platform and reference idea for the detection of other proteins in milk.

Hollow ZnS-CdS nanocage based photoelectrochemical sensor combined with molecularly imprinting technology for sensitive detection of oxytetracycline.

A novel hollow ZnS-CdS nanocage-based molecularly imprinted photoelectrochemical (ZnS-CdS/rMIP PEC) sensor was designed for sensitive detection of oxytetracycline (OTC). O-phenylenediamine was electropolymerized onto hollow ZnS-CdS nanocages to form a polymer film, and then OTC molecules were imprinted on the polymer film through hydrogen bonding. When OTC was eluted, many specific recognition sites were formed on the polymer membrane for detecting OTC in samples. It is worth noting that the rhombohedral dodecahedral structure of hollow ZnS-CdS nanocage can provide large specific surface area, allowing more OTC molecules to be imprinted into the polymer film. Moreover, the unique hollow structure and the heterojunction formed by ZnS and CdS can significantly enhance the photocurrent response. Furthermore, molecular imprint polymer (MIP) technology greatly improves the selectivity and sensitivity of the constructed PEC sensor for detection of OTC. Under optimal conditions, the ZnS-CdS/rMIP PEC sensor has prominent linear relationship in the range of OTC concentration from 1 nmol L-1 to 3 µmol L-1, and the detection limit is 0.10 nmol L-1 (S/N = 3). It is gratifying that the fabricated ZnS-CdS/rMIP PEC sensor displays excellent selectivity for OTC detection when interferences with similar structure exist. It also exhibits superior reproducibility and stability as well as high recovery in the investigation of actual water samples. The combination of PEC and MIP technology will provide significant reference value for effective and rapid detection of other pollutants in the environment.

Photoelectrochemical Strategy for Discrimination of Microbial Pathogens Using Conjugated Polymers.

A photoelectrochemical (PEC) biosensor for facile and sensitive identification of pathogenic microorganisms was developed. Cationic poly(phenylene vinylene) derivative (PPV) as photoelectrochemical active species was modified on the electrode. Under light irradiation, PPV could be excited and generate efficient photocurrent. PPV also had the ability to bind with negatively charged membrane of pathogenic microorganisms, which hindered the electron transfer between electrode and electrolyte. As a result, the photocurrent would decrease obviously. For E. coli, B. subtilis and C. albicans, the photocurrent density was reduced by 18, 33 and 59 %, respectively. Based on the reduction degree of the photocurrent after capturing different types of species of pathogenic microorganisms, a PEC sensor for discrimination of pathogenic microorganisms was realized.