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

Integrating detection and degradation of bisphenol A by photocatalytic fuel cell-driven photoelectrochemical sensor

To ensure food safety and environmental protection, it is crucial to rapidly identify and remove bisphenol A (BPA), a plasticizer commonly used in the inner lining of food containers and beverage packaging. Here, a photocatalytic fuel cell (PFC)-integrated self-powered photoelectrochemical (PEC) sensor is constructed. Unlike conventional single PEC or PFC sensors, this PFC-integrated PEC sensor relies on not only the difference in Fermi energy levels between photoanode and photocathode but also charge accumulation resulted from the oxidation of BPA by photogenerated holes. Consequently, this sensor achieved a remarkable maximum output power (Pmax) of 8.58 μW cm-2, as well as a high sensitivity, wide linear detection range (0.1-200 μM), low detection limit (0.05 μM), great stability, reproducibility, and real sample detection capability. This work integrates PFC and PEC technologies successfully for the rapid identification and efficient removal of BPA.

Photoelectrochemical sensor for the detection of Escherichia coli O157:H7 based on TPA-NO2 and dual-functional polythiophene films

The detection of Escherichia coli (E. coli) is of great significance for the environment and human health. Herein, a photoelectrochemical (PEC) detection strategy based on molecularly imprinted polymers (MIPs) was proposed for the sensitive detection of E. coli. 4,4',4″-Trinitrotriphenylamine (TPA-NO2) was prepared using a simple nitration reaction. Subsequently, MIP films were polymerized on the surface of TPA-NO2 using 1,3-dihydrothieno[3,2-d]pyrimidine-2,4-dione as the functional monomer with the dual functions of specific recognition and sensitization. The linear range was 10-108 CFU/mL and the limit of detection was 10 CFU/mL. It showed favorable recoveries in real sample tests of milk, orange juice and tomato. Additionally, the ability of functional monomers to bind excellently with E. coli was verified using molecular docking techniques. This research provided broader possibilities for constructing MIPs-PEC sensors and analyzing the interaction mechanism between E. coli and functional monomers.

A molecularly imprinted photoelectrochemical sensor based on an rGO/MoSSe heterojunction for the detection of chlortetracycline

A reduced graphene oxide/molybdenum selenosulfide (rGO/MoSSe) heterojunction was synthesized, and a molecularly imprinted photoelectrochemical sensor for the detection of chlortetracycline was prepared. MoSSe was grown in situ on rGO by a hydrothermal method to form an rGO/MoSSe heterojunction, which acts as the sensitive film of the sensor. Since rGO can promote electron transfer and effectively inhibit electron-hole recombination, it effectively reduces the recombination probability of electrons and holes and improves the photoelectric efficiency, thus enhancing the detection sensitivity of the PEC sensor. The rGO/MoSSe was immobilized on an FTO electrode, and molecularly imprinted polymers (MIPs) were prepared by electropolymerization on the rGO/MoSSe-modified FTO electrode with chlortetracycline as the template molecule and o-phenylenediamine as the functional monomer, so as to construct a molecularly imprinted photoelectrochemical (MIP-PEC) sensor. The determination of chlortetracycline was realized by the strategy of a "gate-controlled effect", and the detection range of the chlortetracycline concentration was 5.0 × 10-13-5 × 10-9 mol L-1 with a detection limit of 1.57 × 10-13 mol L-1. The sensor has been applied to the determination of chlortetracycline in animal-derived food samples.

Metal-organic-framework-confined quantum dots enhance photocurrent signals: A molecularly imprinted photoelectrochemical cathodic sensor for rapid and sensitive tetracycline detection

BACKGROUND

Tetracycline (TC), a cost-effective broad-spectrum antibacterial drug, has been excessively utilized in the livestock and poultry industry, leading to a serious overabundance of TC in livestock wastewater. However, conventional analytical methods such as liquid chromatography and gas chromatography face challenges in achieving sensitive detection of trace amounts of TC in complex substrates. Therefore, it is imperative to develop a highly sensitive and anti-interference analytical method for the detection of tetracycline in livestock wastewater.

RESULTS

A porphyrin-based MOF (PCN-224)-confined carbon dots (CDs) material (CDs@PCN-224) was synthesized by a "bottle-around-ship" strategy. The reduced carrier migration distance is conducive to the separation of electron-hole pairs and enhanced the photocurrent signal due to the tight coupling of CDs and PCN-224. Further, molecularly imprinted polymer (MIP) was synthesized by rapid in-situ UV-polymerization and employed as a recognition element. The specific recognition of the target by imprinted cavities blocks electron transfer, resulting in a "turn off" response signal, thus realizing the selective detection of TC. Under optimal conditions, the constructed MIP-PEC cathodic sensor detected 1.00 × 10-12 M to 1.00 × 10-7 M of TC sensitively, with a limit of detection of 3.72 × 10-13 M. In addition, the proposed MIP-PEC sensor demonstrated good TC detection performance in actual livestock wastewater.

SIGNIFICANCE

The strategy based on MOF pore-confined quantum dots can effectively enhance the photocurrent response of the photosensitive substrate. Simultaneously, the MIP constructed by in-situ rapid UV-polymerization showed excellent anti-interference and reusable properties. This work provides a promising MIP-PEC cathodic sensing method for the rapid and sensitive detection of antibiotics in complex-matrix environmental samples.

Emerging trends in sensors based on molecular imprinting technology: Harnessing smartphones for portable detection and recognition

Molecular imprinting technology (MIT) has become a promising recognition technology in various fields due to its specificity, high efficiency, stability and eco-friendliness in the recognition of target. Molecularly imprinted polymers (MIPs), known as 'artificial receptors', are shown similar properties to natural receptors as a biomimetic material. The selectivity of recognition for targets can be greatly improved when MIPs are introduced into sensors, as known that MIPs, are suitable for the pretreatment and analysis of trace substances in complex matrix samples. At present, various sensors has been developed by the combination with MIPs for detecting and identifying trace compounds, biological macromolecules or other substances, such as optical, electrochemical and piezoelectric sensors. Smart phones, with their built-in sensors and powerful digital imaging capabilities, provide a unique platform for the needs of portability and instant detection. MIP sensors based on smart phones are expected to become a new research direction in the future. This review discusses the latest applications of MIP sensors in the field of detection and recognition in recent years, summarizes the frontier progress of MIP sensor research based on smart phones in the past two years, and points out the challenges, limitations and future development prospects.

Computational simulation-assisted design and experimental verification of molecularly imprinted polymers for selective extraction of chlorogenic acid

Chlorogenic acid (CGA) is an active ingredient in honeysuckle with a broad-spectrum of antibacterial activity, suppressing tumor growth and other pharmacological effects. However, it is susceptible to damage during traditional extraction and separation processes. Therefore, developing selective and efficient extraction methods of CGA is essential. Based on computational molecular simulations, a reliable and efficient molecularly imprinted polymers (MIPs) were successfully developed for selective extraction of CGA. MIPs and non-molecularly imprinted polymers (NIPs) were synthesized using a precipitation polymerization method, employing three different functional monomers: [methacrylic acid (MAA), 4-vinylpyridine (4-VP), and methyl methacrylate (MMA)], with CGA serving as the template molecule. To simulate the polymers and predict the optimal ratio between the template and functional monomer, the computational studies and adsorption performance experiments were carried out. The adsorption characteristics and thermal stability of polymers were evaluated by isothermal adsorption, adsorption kinetics, selective adsorption and thermogravimetric analysis, aiming to obtain the MIPs with specific recognition and selectivity for CGA. When the molar ratio of template CGA to functional monomer 4-VP was 1:8, the prepared MIPs was found to have the maximum adsorption capacity (14.85 mg g-1) and the highest imprinting factor (1.74) at the CGA concentration of 100 mg L-1. These results were consistent with those obtained by computational molecular simulation. This study not only provides good guidance for developing separation materials for extracting CGA from natural plants but also inspires the application of computer simulation and molecular docking techniques in the preparation of specific MIPs materials.

Triple-Mode Sensor Coupled by Photoelectrochemical, Electrochromic, and Spectral Signals for Sensitive Visualized Detection of Nonylphenol

Conventional photoelectrochemical (PEC) biosensors suffer from the difficulty of visualizing rapid detection and limited accuracy due to a single-signal output. Here, we develop a PEC, electrochromic (EC), and spectral (ST) triple-mode platform for the sensitive visualized detection of nonylphenol (NP). First, the reasonably stepped Fermi energy level arrangement between the defective TiO2 anode and MoO3 cathode enables a remarkable photocurrent response (Mode 1). Then, MoO3 itself is a widely used EC candidate, which can react with free Li-ions to form a LixMoO3 intermediate, and its color will change from white to blue accordingly (Mode 2). More importantly, MoO3 is also a Li-ion host and the potential of LixMoO3 depends on the inserted Li-ion quantity deduced by spectral analysis on residual Li-ions in the electrolyte (Mode 3). The EC signal endows fast visual detection, and triple-mode cross-validation improves reliability and accuracy. As a result, this PEC-EC-ST triple-mode molecularly imprinted sensor has a wide linear range (1-5000 μg L-1), a low detection limit (0.18 μg L-1), selectivity, stability, reproducibility, and actual sample detection capability. This innovative multimode platform not only improves detection reliability but also broadens applications of electrochromic/energy storage materials in biosensors.

A highly sensitive TiO2-based molecularly imprinted photoelectrochemical sensor with regulation of imprinted sites by Photo-deposition

Molecularly imprinted photoelectrochemical sensors (MIPES) have gained significant attention in the detection field due to their high selectivity and accuracy. However, their sensitivity still needs improvement. Here we developed a TiO2-based MIPES (TiO2 NRs/NiOOH/rMIP) to detect ciprofloxacin (CIP). We identified the photoactive sites of TiO2 by NiOOH photo-deposition and anchored the imprinted sites on the photoactive sites by complexation between CIP and NiOOH. By regulating the imprinted sites, the photocurrent difference before and after the addition of CIP increases and the detection sensitivity of CIP is improved. Moreover, a PN heterojunction is formed between TiO2 and NiOOH, which enables rapid transfer of photoexcited holes and electrons to different semiconductors under the built-in electric field. This leads to improved photoactivity of TiO2 and further increases the sensitivity of MIPES. Compared with sensors prepared by the traditional electro-polymerization CIP and Molecularly imprinted polymers (TiO2 NRs/NiOOH/eMIP), TiO2 NRs/NiOOH/rMIP as constructed in this work displays higher sensitivity, wider linear detection range, and lower limit of detection (LOD). Additionally, TiO2 NRs/NiOOH/rMIP shows good selectivity, stability, and recovery rate, and has a promising application prospect in the actual detection of antibiotics.

Research progress of sensors based on molecularly imprinted polymers in analytical and biomedical analysis

Molecularly imprinted polymers (MIPs) have had tremendous impact on biomimetic recognition due to their precise specificity and high affinity comparable to that of antibodies, which has shown the great advantages of easy preparation, good stability and low cost. The combination of MIPs with other analytical technologies can not only achieve rapid extraction and sensitive detection of target compounds, improving the level of analysis, but also achieve precise targeted delivery, in-vivo imaging and other applications. Among them, the recognition mechanism plays a vital role in chemical and biological sensing, while the improvement of the recognition element, such as the addition of new nanomaterials, can greatly improve the analytical performance of the sensor, especially in terms of selectivity. Currently, due to the need for rapid diagnosis and improved sensing properties (such as selectivity, stability, and cost-effectiveness), researchers are investigating new recognition elements and their combinations to improve the recognition capabilities of chemical sensing and bio-sensing. Therefore, this review mainly discusses the design strategies of optical sensors, electrochemical sensors and photoelectric sensors with molecular imprinting technology and their applications in environmental systems, food fields, drug detection and biology including bacteria and viruses.

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.

Hydrophilic ZnO/C nanocomposites with superior adsorption, photocatalytic, and photo-enhanced antibacterial properties for synergistic water purification

Owing to the numerous potential applications of ZnO nanomaterials, the development of ZnO-based nanocomposites has become of great scientific interest in various fields. In this paper, we are reporting the fabrication of a series of ZnO/C nanocomposites through a simple "one-pot" calcination method under three different temperatures, 500 ℃, 600 ℃, and 700 ℃, with samples labeled as ZnO/C-500, -600, and -700, respectively. All samples exhibited adsorption capabilities and photon-activated catalytic and antibacterial properties, with the ZnO/C-700 sample showing superior performance among the three. The carbonaceous material in ZnO/C is key to expanding the optical absorption range and improving the charge separation efficiency of ZnO. The remarkable adsorption property of the ZnO/C-700 sample was demonstrated using Congo red dye, and is credited to its good hydrophilicity. It was also found to exhibit the most notable photocatalysis effect due to its high charge transfer efficiency. The hydrophilic ZnO/C-700 sample was also examined for antibacterial effects both in vitro (against Escherichia coli and Staphylococcus aureus) and in vivo (against MSRA-infected rat wound model), and it was observed to exhibit synergistic killing performance under visible-light irradiation. A possible cleaning mechanism is proposed on the basis of our experimental results. Overall, this work presents a facile way of synthesizing ZnO/C nanocomposites with outstanding adsorption, photocatalysis, and antibacterial properties for the efficient treatment of organic and bacterial contaminants in wastewater.

A Turn-Off Fluorescent Biomimetic Sensor Based on a Molecularly Imprinted Polymer-Coated Amino-Functionalized Zirconium (IV) Metal-Organic Framework for the Ultrasensitive and Selective Detection of Trace Oxytetracycline in Milk

Developing sensitive and effective methods to monitor oxytetracycline residues in food is of great significance for maintaining public health. Herein, a fluorescent sensor (NH₂-UIO-66 (Zr)@MIP) based on a molecularly imprinted polymer-coated amino-functionalized zirconium (IV) metal-organic framework was successfully constructed and first used for the ultrasensitive determination of oxytetracycline. NH₂-UIO-66 (Zr), with a maximum emission wavelength of 455 nm under 350 nm excitation, was prepared using a microwave-assisted heating method. The NH₂-UIO-66 (Zr)@MIP sensor with specific recognition sites for oxytetracycline was then acquired by modifying a molecularly imprinted polymer on the surface of NH₂-UIO-66 (Zr). The introduction of NH₂-UIO-66 (Zr) as both a signal tag and supporter can strengthen the sensitivity of the fluorescence sensor. Thanks to the combination of the unique characteristics of the molecularly imprinted polymer and NH₂-UIO-66 (Zr), the prepared sensor not only exhibited a sensitive fluorescence response, specific identification capabilities and a high selectivity for oxytetracycline, but also showed good fluorescence stability, satisfactory precision and reproducibility. The fabricated sensor displayed a fluorescent linear quenching in the OTC concentration range of 0.05-40 μg mL^-1, with a detection limit of 0.012 μg mL^-1. More importantly, the fluorescence sensor was finally applied for the detection of oxytetracycline in milk, and the results were comparable to those obtained using the HPLC approach. Hence, the NH₂-UIO-66 (Zr)@MIP sensor possesses great application potential for the accurate evaluation of trace oxytetracycline in dairy products.

Integration of CuS/ZnIn2S4 flower-like heterojunctions and (MnCo)Fe2O4 nanozyme for signal amplification and their application to ultrasensitive PEC aptasensing of cancer biomarker

Vascular endothelial growth factor 165 (VEGF₁₆₅) is a crucial regulator of angiogenesis and works as a major protein biomarker of cancer metastasis. Therefore, its quantitative detection is pivotal in clinic. In this work, CuS/ZnIn₂S₄ flower-like heterojunctions had strong and stable photocurrents, which behaved as photoactive material to construct a photoelectrochemical (PEC) aptasensor for detecting VEGF₁₆₅, combined by home-prepared (MnCo)Fe₂O₄ nanozyme-mediated signal amplification. The interfacial photo-induced electron transfer mechanism was chiefly discussed by UV-vis diffuse reflectance spectroscopy in details. Specifically, the (MnCo)Fe₂O₄ modified VEGF₁₆₅ aptamer was released from the PEC aptasensing platform for its highly specific affinity to target VEGF₁₆₅, which terminated the color precipitation reaction, ultimately recovering the PEC signals. The developed sensor displayed a wider linear range from 1 × 10^-2 to 1 × 10⁴ pg mL^-1 with a smaller limit of detection (LOD) of 0.1 fg mL^-1. This study provides some valuable insights for building other ultrasensitive aptasensors for clinical assays of cancer biomarkers in practice.

MOF/COF heterostructure hybrid composite-based molecularly imprinted photoelectrochemical sensing platform for determination of dibutyl phthalate: A further expansion for MOF/COF application

A novel metal-organic framework (MOF)/covalent-organic framework (COF) heterostructure hybrid composite (NH₂-UiO-66/TpPa-1-COF) with excellent photoactivity was developed, which further acted as the photoelectrochemical sensitized layer of a molecularly imprinted photoelectrochemical (MIP-PEC) sensor for extremely sensitive and selective determination of dibutyl phthalate (DBP). The NH₂-UiO-66/TpPa-1-COF was synthesized using a simple one-step solvothermal method, which showed improved photocurrent response owing to heterojunction formation, favorable energy-band configuration and strong light absorption capacity. To improve the sensing performance, molecularly imprinted polymer (MIP) was developed by sol-gel polymerization method as the recognition component of PEC sensor. The specific binding of imprinting sites towards DBP could block the electron transfer, causing decreased photocurrent response of the MIP-PEC sensor. The MIP-PEC sensor showed a wide detection range from 0.1 nmol L^-1 to 100 μmol L^-1 with a limit of detection of 3.0 × 10^-11 mol L^-1 under optimal conditions. Meanwhile, the proposed MIP-PEC sensor showed good stability, selectivity, reproducibility, and applicability in real samples. This is the first attempt to apply MOF/COF heterostructure hybrid composite for MIP-PEC sensor construction, providing new insight into the potential applications of microporous crystalline framework heterostructure hybrid composite in the sensing field.

Self-powered molecular imprinted photoelectrochemical sensing platform of sialic acid employing WO3/Bi2S3 photoanode and CuInS2 photocathode

A dual-photoelectrode molecular imprinted photoelectrochemical (PEC) sensor is first built for the determination of sialic acid (SA) without additional energy supply. Specifically, WO₃/Bi₂S₃ heterojunction behaves as a photoanode to provide amplified and stable photocurrent for the PEC sensing platform, which is attributed to the matched energy levels of WO₃ and Bi₂S₃ promoting the electron transfer and improving photoelectric conversion properties. CuInS₂ micro-flowers functionalized by molecularly imprinted polymers (MIPs) are served as photocathode to recognize SA, avoiding the deficiency of high production cost and poor stability from biological enzymes, aptamers, or antigen-antibodies. The inherent deviation between the Fermi level of the photoanode and the photocathode guarantees a spontaneous power supply for the PEC system. Benefiting from the photoanode and recognition elements, the as-fabricated PEC sensing platform has a strong anti-interference ability and high selectivity. Moreover, the PEC sensor displays a wide linear range of 1 nM-100 μM and a low detection limit of 7.1 × 10^-10 M (S/N = 3) based on the relationship between photocurrent signal and SA concentration. Accordingly, this research provides a new and valuable approach to detecting various molecules.

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.

A novel photoelectrochemical sensor based on flower-like SnS2, sea urchin-like AgBiS2 and graphene oxide nanocomposite film for efficient and sensitive detection of acetaminophen in lake water samples

As an emerging detection technology, photoelectrochemical sensors have been widely noticed for their unique technical features. Among others, the technology has been widely used in the fields of drug, biological antibody or antigen and contaminant detection. Secondly, acetaminophen, as a novel environmental pollutant, is difficult to be degraded in the ecosystem, which in turn causes serious impacts on the ecosystem. Therefore, in this work, we designed a photoelectrochemical sensor based on a composite film of flower-like SnS₂, sea urchin-like AgBiS₂ and graphene oxide for the detection of acetaminophen in water samples. Among them, graphene oxide, as a two-dimensional carbon-based material, can immobilize other photoelectric materials well. In addition, the flower-like SnS₂ and sea urchin-like AgBiS₂ can enhance the intensity of the photoelectric response due to their synergistic effect. Notably, the combination of graphene oxide with SnS₂ and AgBiS₂ revealed an exponential increase in the photoresponse intensity, indicating that SnS₂/AgBiS₂/GO has a satisfactory photoresponse intensity. At the same time, the photoelectrochemical sensor exhibited sensitive detection performance (LOD = 4 nM) and a wide detection range (0.01-50 μM) for acetaminophen under optimal detection conditions. Moreover, it also showed excellent detection performance in the detection of actual water samples, indicating that it can be applied to the detection of acetaminophen in lakes.

A Sensitive Photoelectrochemical Sensor for Levodopa Detection Using Benzothiadiazole-Based Conjugated Microporous Polymer-Coated Graphene Heterostructures

Since the 1960s, levodopa (LDA) has been the standard drug for treating of Parkinson's disease. In this study, a novel benzothiadiazole-based conjugated microporous polymer-coated graphene heterostructure (CMP-rGO) was synthesized and used to construct a sensitive photoelectrochemical (PEC) sensor capable of detecting LDA. Under optimal experimental conditions, the intensity of the photocurrent produced by the sensor was linear from 0.005 to 40 μM, and the limit of detection of the sensor was 0.0027 μM. The sensor showed good repeatability, stability, and selectivity for LDA detection. Finally, the constructed sensor was used to detect LDA in levodopa tablets, human serum samples, and urine samples and satisfactory results were obtained. Therefore, the PEC sensor provides a novel platform for the detection of LDA in real samples and broadens the applications of conjugated microporous polymers in PEC sensing.

Ultrathin Covalent Organic Framework Nanosheets/Ti3C2Tx-Based Photoelectrochemical Biosensor for Efficient Detection of Prostate-Specific Antigen

Designable and ultrathin covalent organic framework nanosheets (CONs) with good photoelectric activity are promising candidates for the construction of photoelectrochemical (PEC) biosensors for the detection of low-abundance biological substrates. However, achieving highly sensitive PEC properties by using emerging covalent organic framework nanosheets (CONs) remains a great challenge due to the polymeric nature and poor photoelectric activity of CONs. Herein, we report for the first time the preparation of novel composites and their PEC sensing properties by electrostatic self-assembly of ultrathin CONs (called TTPA-CONs) with Ti₃C₂T_x. The prepared TTPA-CONs/Ti₃C₂T_x composites can be used as photocathodes for PEC detection of prostate-specific antigen (PSA) with high sensitivity, low detection limit, and good stability. This work not only expands the application of CONs but also opens new avenues for the development of efficient PEC sensing platforms.

Kill two birds with one stone: Selective and fast removal and sensitive determination of oxytetracycline using surface molecularly imprinted polymer based on ionic liquid and ATRP polymerization

Oxytetracycline (OTC) residue in food and environment has potential threats to ecosystem and human health, thus its sensitive monitoring and effective elimination are very important. In this work, a new molecularly imprinted polymer (MIP) composite was prepared through atom transfer radical polymerization by using OTC as template, gold nanoparticles modified carbon nanospheres (Au-CNS) as supporter, ionic liquids (IL) as functional monomer and cross-linking agent. The obtained MIP-IL@Au-CNS composite was characterized by Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. It displayed high imprinting factor (5.50) and adsorption capacity (56.7 mg g^-1), and could achieved the adsorption equilibrium in short time (about 15 min). Results also illustrated that the adsorption process basically conformed to the quasi-second-order kinetic model and Freundlich model, and MIP-IL@Au-CNS could be recycled at least 5 times. Furthermore, a sensitive OTC electrochemical sensor was developed by combining MIP-IL@Au-CNS with IL-modified carbon nanocomposites (IL@N-rGO-MWCNT). The resulting sensor demonstrated a linear response to OTC in the wide range of 0.02-20 μM, and the detection limit was down to 5 nM. It also had the advantages of high selectivity, fast elution/regeneration and simple construction procedure. The sensor had been applied to the detection of real samples, and acceptable recovery (96.4%-106%) and RSD (3.2%-6.2%) were obtained. This work expands the application of IL-based MIP in pollutant monitoring and enriching.

Advances in Detection of Antibiotic Pollutants in Aqueous Media Using Molecular Imprinting Technique-A Review

Antibiotics constitute one of the emerging categories of persistent organic pollutants, characterised by their expansion of resistant pathogens. Antibiotic pollutants create a major public health challenge, with already identifiable detrimental effects on human and animal health. A fundamental aspect of controlling and preventing the spread of pollutants is the continuous screening and monitoring of environmental samples. Molecular imprinting is a state-of-the-art technique for designing robust biomimetic receptors called molecularly imprinted polymers (MIPs), which mimic natural biomolecules in target-selective recognition. When integrated with an appropriate sensor transducer, MIP demonstrates a potential for the needed environmental monitoring, thus justifying the observed rise in interest in this field of research. This review examines scientific interventions within the last decade on the determination of antibiotic water pollutants using MIP receptors interfaced with label-free sensing platforms, with an expanded focus on optical, piezoelectric, and electrochemical systems. Following these, the review evaluates the analytical performance of outstanding MIP-based sensors for environmentally significant antibiotics, while highlighting the importance of computational chemistry in functional monomer selection and the strategies for signal amplification and performance improvement. Lastly, the review points out the future trends in antibiotic MIP research, as it transits from a proof of concept to the much demanded commercially available entity.

Chitosan-based molecularly imprinted photoelectric sensor with ZnO/Bi2O3/Bi2S3 sensing layer for thiamethoxam determination

A molecularly imprinted photoelectrochemical sensor with high sensitivity and stable structure was constructed and applied to detect thiamethoxam pesticide. ZnO/Bi₂O₃/Bi₂S₃ heterojunction photoelectric material was formed on the fluorine-doped tin oxide (FTO) electrode by seed layer growth, drip coating, and in situ ion exchange. A chitosan-imprinted polymer membrane was prepared using chitosan as the functional monomer, glutaraldehyde as the cross-linking agent, and thiamethoxam as the template molecule. The photoelectric material was characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy analyses. The electron transfer mechanism of Z-type heterojunction was verified by ultraviolet-visible curve and Mott-Schottky curve. When thiamethoxam was re-adsorbed on the imprinted membrane, the current recorded at 0 V (vs. Ag/AgCl) was reduced because the thiamethoxam molecule blocked the electron transfer. The molecularly imprinted sensor exhibited a linear relationship to thiamethoxam concentration in the range from 7.0 × 10^-13 mol/L to 7.0 × 10^-10 mol/L and the detection limit was 3.32 × 10^-13 mol/L, which is lower than the values reported by other detection methods. Most pesticides, such as propoxur and isoprocarband carbaryl, do not interfere with the determination. The sensor also showed good practicability and suitability for the determination of trace thiamethoxam in environmental water and soil leaching solutions, with a recovery of 99.6-102.1% (RSD < 3.74%). A novel molecularly imprinted photoelectrochemical (MI-PEC) sensor with high sensitivity and selectivity for the determination of thiamethoxam (TMX) was developed. A Z-type heterojunction ZnO/Bi₂O₃/Bi₂S₃ photoelectric material was synthesized for the first time. The MI-PEC sensor was prepared with ZnO/Bi₂O₃/Bi₂S₃ as the sensitive material and MI membrane as the recognition element. The sensor exhibits an extremely sensitive response to thiamethoxam with a detection limit of 3.32 × 10^-13 mol/L due to the excellent photoelectrochemical properties of ZnO/Bi₂O₃/Bi₂S₃.

Construction of a photoelectrochemical immunosensor based on CuInS2 photocathode and BiVO4/BiOI/Ag2S photoanode and sensitive detection of NSE

In this paper, a photoelectrochemical (PEC) immunosensor was constructed to detect neuron-specific enolase (NSE) with ITO/BiVO₄/BiOI/Ag₂S as photoanode and ITO/CuInS₂ as photocathode. Due to its excellent photocurrent response, Ag₂S sensitized BiVO₄/BiOI composite was selected to provide stable photocurrent in place of the traditional Pt electrode. ITO/CuInS₂ electrode was used to immobilize biomolecules, which solved the deficiency of poor anti-interference ability of single photoanode. Under the optimal experimental conditions, the PEC immunosensor had outstanding linear relationship within the range of NSE concentration from 5 pg/mL-200 ng/mL, and the detection limit was 1.2 pg/mL. The constructed PEC immunosensor had two advantages. On the one hand, the PEC immunosensor was built on the photocathode, which had better anti-interference ability because of the separation of light capture and biomolecular recognition process. On the other hand, the introduction of photoanode increased the photocurrent response and reduced the detection limit of target antigen. The PEC immunosensor had good stability, reproducibility and specificity, and provided a broad prospect for the detection of other molecules.

Organic-Inorganic Hybrid Flower-Shaped Microspheres Applied in Photoelectrochemical Sensing

Organic-inorganic hybrid materials are rarely applied in photoelectrochemical (PEC) sensing because of the serious charge-carrier recombination in organic conjugated polymers. In this work, a series of poly(3,4-ethylenedioxythiophene) (PEDOT)/ZnIn2S4 hybrid flower-shaped microspheres were synthesized using ionic liquids (ILs) as the supporting electrolyte for EDOT electropolymerization and as the regulating reagent for controlling ZnIn2S4 growth, respectively. It was found that the hybrid material [HOEMIM]NTf2-PEDOT/[HOEMIM]BF4-ZnIn2S4 ([HOEMIM]+: 1-hydroxyethyl-3-methylimidazolium cation; NTf2-: bis(trifluoromethanesulfonyl)amide) was the optimal one, with a smooth, transparent, and continuous polymer film covering the uniform and ordered cross-linked nanosheet arrays. The hybrid material could produce a high anodic photocurrent, which was about 78 times as high as that produced by the [HOEMIM]BF4-ZnIn2S4. The enhancement effect should be the highest among all the organic-inorganic hybrid materials reported so far. This was related to its unique micromorphology structure, p-n heterojunction, and the coexisting ILs, which restrained the charge-carrier recombination in PEDOT and enhanced PEDOT sensitization to ZnIn2S4. Then, a carcinoembryonic antigen PEC immunosensor was constructed based on the photoanodic sensing platform, and it exhibited good performance. Furthermore, the [HOEMIM]BF4-ZnIn2S4 was treated with NaClO solution to create the [HOEMIM]NTf2-PEDOT/[HOEMIM]BF4-S-ZnwInxSyOz general platform for both photoanodic and photocathodic sensing. As a proof of concept, L-cysteine and dissolved oxygen were used as models for photoanodic and photocathodic sensing, respectively. The results demonstrated that the general PEC platform was quite competent. This work opens up a window for the design of organic-inorganic hybrid PEC materials and will promote the application of such hybrid materials in PEC biosensing.

Self-powered photoelectrochemical aptasensor based on MIL-68(In) derived In2O3 hollow nanotubes and Ag doped ZnIn2S4 quantum dots for oxytetracycline detection

A self-powered photoelectrochemical (PEC) aptasensor was constructed based on MIL-68(In) derived indium oxide hollow nanotubes (In₂O₃ HNs) and Ag-doped ZnIn₂S₄ quantum dots (QDs) as sensing matrix for the ultrasensitive detection of oxytetracycline (OTC). The hollow tube structure of the designed photoelectric active platform provided abundant active sites and a larger specific surface area for the immobilization of target recognition unit. The coupling of Ag:ZnIn₂S₄ QDs and In₂O₃ HNs can accelerate the transmit and separation of photoinduced charge, and thus greatly increasing the intensity of photocurrent signal. Then, the well-constructed OTC-aptamer was anchored on the modified photoelectrode as an accurate capturing element, achieving the specific detection of analyte. Under optimal conditions, the photocurrent intensity of the PEC aptasensor decreases linearly, with a linear response range of 10^-4 -10 nmol/L, and a limit of detection (LOD) of 3.3 × 10^-5 nmol/L (S/N = 3). The developed self-powered aptasensor with excellent reproducibility, stability, and selectivity, provides a potential way to detect antibiotic residues in environmental media.

Detection of NSE by a photoelectrochemical self-powered immunosensor integrating RGO photocathode and WO3/Mn:CdS nanomaterial photoanode

Generally, the photoanodic photoelectrochemical (PEC) immunoassay method has an outstanding photocurrent and low detection limit, but its poor anti-interference ability in the detection of real samples restricts its performance. The photocathode immunoassay method has an excellent ability to see interference in actual sample detection, but it has its own defect in that the photocurrent is not obvious. Here, a promising new cathodic PEC immunosensing platform is reported, which integrates a photocathode and photoanode. The photoanode and photocathode are WO₃/Mn:CdS composite modified and reduced graphene oxide (RGO) modified indium tin oxide (ITO) electrodes, respectively. In addition to an excellent PEC response, the immunosensor constructed by the integrating the photoanode and photocathode also has good anti-interference ability in actual sample analysis. The constructed immunosensor achieves accurate detection of NSE with a range from 5.0 pg/mL to 20 ng/mL, and the limit of detection (LOD) is 1.2 pg/mL. The proposed immunoassay method has good stability, selectivity and reproducibility. Moreover, it introduces new ideas for the construction of PEC immunosensors.

A dual-response ratiometric fluorescence imprinted sensor based on metal-organic frameworks for ultrasensitive visual detection of 4-nitrophenol in environments

A dual-response ratiometric fluorescence imprinted sensor based on visible/near-infrared emission was established for ultrasensitive, selective and visual detection 4-nitrophenol (4-NP). The molecularly imprinted polymer was incorporated in the ratiometric sensing system consisting of visible emission carbon dots@zeolitic imidazolate framework-8 (CDs@ZIF-8) and near-infrared emission cadmium telluride (CdTe) quantum dots. The CDs@ZIF-8 enhanced the emission of CDs and the fluorescence sensing performance. Compared to short wavelength of fluorophore, the near-infrared emission CdTe is less interference caused by auto-fluorescence of sample. The ratiometric fluorescence imprinted sensor exhibited dual response for 4-NP at 420 nm and 703 nm and a wide concentration response range. Moreover, a good linear response was existed in the two concentration ranges of 0.1 pM-3.0 pM and 0.05 μM-30 μM with the detection limit of 0.08 pM and 0.05 μΜ, respectively. Significantly, the fluorescence color changes can be observed from purple to pink to red with the naked eye. The fluorescence quenching mechanism of the ratimetric fluorescence imprinted sensor was discussed in detail. The ratiometric fluorescence imprinted sensor was used to detect 4-NP in various real samples with satisfactory recoveries of 97.5-106.3%, which provided an interesting avenue for the rapid detection of pollutant with high sensitivity, high selectivity and visualization in real environment.

A simple paper-based ratiometric luminescent sensor for tetracyclines using copper nanocluster-europium hybrid nanoprobes

Tetracyclines (TCs), as one of the broad-spectrum antibiotics, are widely used to treat bacterial infections. The residues of TCs in animal-origin foods and drinking water have raised safety concerns and affected the public health. Thus, there is a high demand to develop a simple and rapid method for the detection of TCs. In this work, we developed a ratiometric luminescence probe for the sensitive and visualized detection of TCs. Specifically, tannic acid-stabilized copper nanoclusters (TA-CuNCs) with blue emission at 433 nm were synthesized. The luminescence of TA-CuNCs attenuated partially by the europium ions (Eu³⁺) due to the aggregation-induced quenching. When TCs were added to the TA-CuNCs-Eu³⁺ system, the luminescence of TA-CuNCs at 433 nm can be further quenched by the inner-filter effect, and the characteristic luminescence of Eu³⁺ at 617 nm emerged due to the formation of Eu³⁺-TCs complex. The ratio of the luminescence at 617 nm-433 nm increased linearly to the concentration of TCs. Additionally, we demonstrated the detection of oxytetracycline in real samples such as tap and lake water, milk, pharmaceutical industry wastewater, honey and soil extract with high recovery rate (97.25%-103.44%). Furthermore, a portable paper device is fabricated by the luminescent probe to conduct the on-site analysis of TCs.

Rapid electrochemical detection of domoic acid based on polydopamine/reduced graphene oxide coupled with in-situ imprinted polyacrylamide

Domoic acid, namely amnesic shellfish toxin, is a highly neurotoxic substance to marine animals and humankind. To reduce the incidence of poisoning accidents, the exploitation of specific and rapid detection method for domoic acid monitoring is highly required. Herein, an electrochemical molecularly imprinted polymer (MIP) sensor based on polydopamine-reduced graphene oxide/polyacrylamide composite (PDA-rGO/PAM) was constructed successfully to detect domoic acid. The domoic acid molecule could be recognized in imprinted cavities of PAM reversibly through hydrogen bonding. PDA-rGO promoted the loading capacity of PAM and improved the charge transfer rate, which amplified the electrical signal response of the MIP sensor. The screen-printed electrode (SPE) modified with PDA-rGO/PAM displayed satisfactory response toward toxin contaminated sample at a linear range from 1 to 600 nM and a low detection limit of 0.31 nM, demonstrating the prospective application of the transducer as a portable sensing platform for the on-site detection of hazardous marine biotoxin. Moreover, benefiting from the superior specificity and stability of MIP, the fabricated sensor could be utilized to detect the domoic acid content in mussel extracts directly without complex pretreatment operation.

A descriptive and comparative analysis on the adsorption of PPCPs by molecularly imprinted polymers

Molecularly imprinted polymers (MIPs) have aroused great attention as a new material for the removal or detection of pharmaceuticals and personal care products (PPCPs). However, it is not clear about the superiority and deficiency of MIPs in the process of removing or detecting PPCPs. Herein, we evaluated the performance of MIPs in the aspects of adsorption capacity, binding affinity, adsorption rate, and compatibility to other techniques, and proposed ways to improve its performance. Without regard to the selectivity of MIPs, for the PPCPs adsorption, MIPs surprisingly did not always perform better than the conventional adsorbents (non-imprinted polymers, biochar, activated carbon and resin), indicating that MIPs should be used where selectivity is crucial, for example recovery of specific PPCPs in an environmental sample extraction process. Compared to the traditional solid-phase extraction for PPCPs detection pretreatment, the usage of MIPs as substitute extraction agents could obtain high selectivity of specific substance, due to the uniformity and effectiveness of the specific sites. A promising development in the future would be to combine other simple and rapid quantitative technologies, such as electro/photochemical sensor and catalytic degradation, to realize rapid and sensitive detection of trace PPCPs.

MOF@COF Heterostructure Hybrid for Dual-Mode Photoelectrochemical-Electrochemical HIV-1 DNA Sensing

We developed a novel metal-organic framework (MOF)@covalent-organic framework (COF) hybrid with a hierarchical nanostructure and excellent photoactivity, which further acted as the bifunctional platform of a dual-mode photoelectrochemical (PEC) and electrochemical (EC) biosensor for detecting HIV-1 DNA via immobilizing the HIV-1 DNA probe. First, the presynthesized Cu-MOF nanoellipsoids were used as the template for the in situ growth of the COF network, which was synthesized using copper-phthalocyanine tetra-amine (CoPc-TA) and 2,9-bis[p-(formyl)phenyl]-1,10-phenanthroline as building blocks through the Schiff base condensation. In view of the large specific surface area, abundant reserved amino group, excellent electrochemical activity, and high photoactivity, the obtained Cu-MOF@CuPc-TA-COF heterostructure not only can serve as the sensitive platform for anchoring the HIV-1 DNA probe strands but also can be utilized as the signal transducers for PEC and EC biosensors. Thereby, the constructed biosensor shows the sensitive and selective analysis ability toward the HIV-1 target DNA via the complementary hybridization between probe and target DNA strands. The dual-mode PEC and EC measurements revealed that the Cu-MOF@CuPc-TA-COF-based biosensor displayed a wide linear detection range from 1 fM to 1 nM and an extremely low limit of detection (LOD) of 0.07 and 0.18 fM, respectively. In addition, the dual-mode PEC-EC biosensor also demonstrated remarkable selectivity, high stability, good reproducibility, and preferable regeneration ability, as well as acceptable applicability, for which the detected HIV-1 DNA in human serum showed good consistency with real concentrations. Thereby, the present work can open a new dual-mode PEC-EC platform for detecting HIV-1 DNA based on the porous-organic framework heterostructure.

Molecularly imprinted polypyrrole nanotubes based electrochemical sensor for glyphosate detection

An electrochemical sensor based on molecularly imprinted polypyrrole nanotubes (MIPNs) has been developed for the detection of glyphosate (Gly) with high sensitivity and specificity. Herein, the MIPNs are prepared by imprinting Gly sites on the surface of polypyrrole (PPy) nanotubes. The synthesized MIPNs have high electrical conductivity and exhibit rapid adsorption rate, enhanced affinity and specificity to Gly. An electrochemical sensor for Gly detection is fabricated by assembling MIPNs-modified screen-printed electrodes with a 3D-printed electrode holder, which is highly portable and suitable for real-time detection. The results demonstrate that the MIPNs-based electrochemical sensor for Gly exhibits a wide detection range of 2.5-350 ng/mL with a limit of detection (LOD) of 1.94 ng/mL. Besides, the Gly sensor possessed good stability, reproducibility, and excellent selectivity against other interferents. The practicability of the sensor is verified by detecting Gly in orange juice and rice beverages, indicating that the sensor is suitable for monitoring pesticides in actual food and environmental samples.

Cobalt-Iron Double Ion-Bovine Serum Albumin Chelation-Assisted Thermo-Sensitive Surface-Imprinted Nanocage with High Specificity

To develop multifunctional protein imprinted materials, a cobalt-iron double ion-BSA directional chelation-assisted thermo-sensitive surface-imprinted hollow nanocage (Co-Fe@CBMA-MIPs) with excellent specificity is developed on the surface of ZIF-67@Co-Fe in this study by synergizing the advantages of surface imprinting, metal ion chelation, anti-protein adsorption segments, and thermo-sensitive components. Beyond previous research, well-designed multifunctional protein-imprinted materials possess high binding capacity, fast adsorption kinetics, and outstanding selectivity. When the adsorption is carried out at 32 °C, the adsorption capacity of Co-Fe@CBMA-MIPs for BSA reaches 520.35 mg/g within 50 min. The imprinting factor is 8.55. The selectivity factors of Co-Fe@CBMA-MIPs for HSA, Bhb, OVA, and Lyz are 3.72, 6.09, 4.10, and 8.41, respectively. More significantly, Co-Fe@CBMA-MIPs could specifically recognize BSA from mixed proteins and actual samples and exhibit excellent repeated use stability. Based on the above advantages, the development of this research provides an effective means to improve the recognition specificity of molecularly imprinted polymers.

A novel small molecular liquid crystal catalytic amplification-nanogold SPR aptamer absorption assay for trace oxytetracycline

Liquid crystals (LCs) have been applied for a long time in the field of analytical chemistry. To date, there are no reports about utilization of LCs as the catalyst to amplification analytical signal. In this article, three small molecules LCs in water aqueous solutions were characterized using molecular spectra and particle size analysis. The characterization indicated that there are nanoparticles in the system. Among the them, 4-heptylbenzoic acid (HPB) exhibits the most sensitive performance in the analytical system based on the reduction of HAuCl₄ to gold nanoparticles (AuNPs) by NaH₂PO₂ by the spectrophotometric slope evaluation procedure. As the concentration of LCs catalyst increases, the AuNPs surface plasmon resonance (SPR) absorption peak at 550 nm increases linearly, that can be utilized to amply the absorption signal. Based on the LCs catalytic amplification reaction and immunoreaction, a new SPR spectrophotometric analysis method was developed for the label-free detection of oxytetracycline, with a detection limit of 0.50 ng/mL. The method was also successfully applied for the detection of oxytetracycline-spiked environmental water samples to demonstrate its practical usefulness.

A photoelectrochemical sensor based on Z-Scheme TiO2@Au@CdS and molecularly imprinted polymer for uric acid detection

A novel photoelectrochemical (PEC) sensor based on "Z-scheme" TiO₂@Au@CdS and molecularly imprinted polymer (MIP) was developed for the non-invasive detection of uric acid (UA). The "Z-scheme" material, consisting of an electron-transfer system (Au) and two isolated photochemical systems (CdS, TiO₂), was synthesized by chemical deposition method and it worked as a substrate for electro-polymerization of MIP. Due to the high photoelectric conversion efficiency provided by TiO₂@Au@CdS and specific imprinting effect afforded by MIP, the sensor displayed desirable sensing performance with the merits of sensitivity, selectivity, repeatability, and stability. The linear range for UA detection is from 1 nM to 9 μM with the detection limit of 0.3 nM (S/N = 3). Moreover, the assay was successfully utilized to measure UA in human tears and offered a reliable result. The incorporation of MIP and "Z-scheme" material into a PEC sensor system is expected to provide a promising strategy for detecting other small molecules.

Development of a molecularly imprinted photoelectrochemical sensing platform based on NH2-MIL-125(Ti)-TiO2 composite for the sensitive and selective determination of oxtetracycline

In this work, a molecularly imprinted photoelectrochemical (MIP-PEC) sensor based on a novel PEC composite of metal-organic frameworks (MOFs) and TiO₂ (NH₂-MIL-125(Ti)-TiO₂) was established for the ultrasensitive and selective detection of oxytetracycline (OTC). This is the first attempt of applying MOFs in the construction of MIP-PEC sensor. The NH₂-MIL-125(Ti)-TiO₂ was synthesized by a simple one-step solvothermal method and modified onto the surface of indium tin oxide (ITO) electrode as the photosensitive layer. Subsequently, molecularly imprinted polymer (MIP) was modified as recognition element by electropolymerization. The NH₂-MIL-125(Ti)-TiO₂ showed an enhanced photocurrent response due to stronger light absorption capacity and matched energy band. Furthermore, MIP greatly improved the selectivity and sensitivity of the constructed PEC sensor. The photocurrent response of the MIP-PEC sensor was reduced after OTC recognition because the specific binding of OTC to the imprinted cavities blocked the electron transfer of the electrode. Under optimal experimental conditions, the MIP-PEC sensor exhibited a wide detection range from 0.1 nM to 10 μM with a low limit of detection (LOD) of 60 pM, as well as certain reproducibility, stability and good applicability in real samples. The proposed sensor provides ideas for the application of MOFs in the construction of PEC sensors and will offer an alternative method for the detection of other pollutants in the field of food safety.