Search

Halide perovskites have emerged as a highly promising class of photoelectric materials. However, the application of lead-based perovskites has been hindered by their toxicity and relatively weak stability. In this work, a composite material comprising a lead-free perovskite cesium copper iodide (CsCu 2 I 3 ) nanocrystal and a metal-organic framework (MOF-801) has been synthesized through an in situ growth approach. The resulting composite material, denoted as CsCu 2 I 3 /MOF-801, demonstrates outstanding stability and exceptional optoelectronic characteristics. MOF-801 may serve a dual role by acting as a protective barrier between CsCu 2 I 3 nanocrystals and the external environment, as well as promoting the efficient transfer of photogenerated charge carriers, thereby mitigating their recombination. Consequently, CsCu 2 I 3 /MOF-801 demonstrates its utility by providing both stability and a notably high initial photocurrent. Leveraging the inherent reactivity between H 2 S and the composite material, which results in the formation of Cu 2 S and structural alteration, an exceptionally sensitive photoelectrochemical sensor for H 2 S detection has been designed. This sensor exhibits a linear detection range spanning from 0.005 to 100 μM with a remarkable detection limit of 1.67 nM, rendering it highly suitable for precise quantification of H 2 S in rat brains. This eco-friendly sensor significantly broadens the application horizon of perovskite materials and lays a robust foundation for their future commercialization.

TiO 2 was grown on both ends of gold nanorods (AuNRs) to form a dumbbell-shaped heterostructure (called AuNRs@end-TiO 2 ) first, and then assembled on the fluorine tin oxide (FTO) electrode surface through hydrophobic interactions to construct a concise photoelectrochemical microRNA-21 (miRNA-21, model target) biosensor using carbon dots (CDs) as photosensitizers. Hairpin probes (HPs) were fixed on the AuNRs@end-TiO 2 -modified FTO electrode surface through the Au-S bond, and CDs-modified complementary DNA (CDs-cDNA) served as photosensitive probes. In the presence of the target, miRNA hybridized with the HP and triggered double-strand-specific nuclease to cleave the complementary part of the HP with miRNA, and miRNA was released, which can trigger another cycle to realize signal amplification. Many HPs were cleaved and the complementary sequence with cDNA was exposed, which can capture the photosensitive probes to the electrode surface and resulted in photocurrent enhancement. The photocurrent intensity system has a linear relationship with the logarithm of the miRNA concentration in the range of 0.1 fM to 100 pM with a low detection limit of 96 aM (S/N = 3). The biosensor has high sensitivity, good selectivity, and good reproducibility and shows satisfactory results in actual sample detection.

The complex synthesis of photoelectric materials and the difficulty of fixing the identification elements on the photoelectrode are long-standing problems in the field of photoelectrochemical (PEC) biosensing. In this work, a simple PEC aptasensor construction strategy based on a sulfur-doped g-C 3 N 4 (SCN)/n-GaN heterostructure photoelectrode was proposed. The SCN/n-GaN heterostructure can be formed through self-assembly in solution since SCN can be uniformly dispersed in solution. In addition, as a dual-function mediate, an aptamer can be fixed on an SCN substrate automatically because of the good adsorption performance of SCN. Therefore, tedious steps of PEC electrode preparation and the fixing of recognition elements were both avoided. Compared with the traditional ones, the construction difficulty and time cost of the prepared PEC aptasensors are greatly reduced. The simplified experimental process improves the stability and reproducibility of the aptasensor. Finally, tetracycline (TET) was used as a model target to verify the sensing performance of the proposed PEC strategy. TET can consume the photogenerated holes of the SCN/n-GaN heterostructure, promote carrier migration, and result in the change in the photocurrent. The linear relationship between the change in the photocurrent intensity and the TET concentration can be used to detect TET. The aptasensor has a linear range of 0.10-10.0 nmol L -1 and the detection limit is 0.030 nmol L -1 (3S/N). The aptasensor was applied to the detection of TET in milk samples with satisfactory results.

An Au/GaN photoelectrode was prepared by sputtering 30 nm thick Au film on the surface of n-type gallium nitride (GaN). When the electrode contacts with multilayered molybdenum disulfide (MoS 2 ), photogenerated electrons and photogenerated holes transfer to MoS 2 because of the band gap matching of MoS 2 and GaN. The presence of Au promotes charge transfer and results in a greater recombination of electrons and holes; by this means, a more significant suppression of photocurrent can be detected. This characteristic has been coupled with the high selectivity of an aptamer and applied to develop a novel photoelectrochemical aptasensor for cancer biomarkers (alpha-fetoprotein (AFP) as a model). The aptamer of AFP was modified on the surface of the Au/GaN photoelectrode by Au-S bonds, which can bind to the target protein with high selectivity. Then, the transfer process of the charge carriers of GaN to MoS 2 can be blocked by the target protein so that the suppression of photocurrent is reduced. The difference of the photocurrent in the presence and absence of AFP ( ΔI ) showed a linear relationship with AFP concentration that ranged from 1.0-150 ng/mL ( R 2 = 0.9995), and the detection limit was 0.3 ng/mL. The standard addition recovery rates ranged from 85.2 to 91.7%. The method possessed good sensitivity and high selectivity for AFP detection. The developed biosensor can be modified to detect other cancer biomarkers by simply replacing the aptamer used.

In recent years, inorganic biomimetic nanozymes that mimic the activity of natural biological enzymes have attracted extensive research interest, and some mimic enzymes have been successfully applied in the fields of biosensing, catalysis, and oncotherapy. Herein, we report the preparation and mechanism study of a novel nanocomposite, Cu 2+ -modified hexagonal boron nitride nanosheets-supported subnanometer gold nanoparticles (Au NPs/Cu 2+ -BNNS). Interestingly, our investigation reveals that Cu 2+ -BNNS exhibits strong peroxidase mimetic nanoenzyme activity, while Au NPs/Cu 2+ -BNNS exhibits excellent oxidase-like activity, that is, it can catalyze the oxidation reaction of the substrate in the absence of an oxidant such as H 2 O 2 . For example, Au NPs/Cu 2+ -BNNS can efficiently and selectively oxidize 3,3',5,5'-tetramethylbenzidine (TMB) and 3,3'-dimethylbiphenyl-4,4'-diamine (OT) coloration without the presence of horseradish peroxidase (HRP) and H 2 O 2 . It is worthy to note that AuNPs/Cu 2+ -BNNS-induced TMB coloration only takes 4 min to reach the platform, while the conventional HRP-H 2 O 2 system takes more than 30 min to reach the platform. Further mechanism study shows that the zeta potential, oxidation potential, and steric hindrance of the oxidative chromogenic substrate determine the selectivity of oxidation coloration, while the oxidase-like properties of Au NPs/Cu 2+ -BNNS are derived from reactive oxygen species generated by the adsorbed oxygen, and Cu 2+ ion can synergistically promote the oxidation process. Compared with conventional biological enzymes, Au NPs/Cu 2+ -BNNS has the advantages of being HRP free and H 2 O 2 free, having high efficiency, low cost, and good stability, and is successfully demonstrated for the detection of carcinoembryonic antigen (a universal cancer biomarker) and H 2 S (the third gaseous signal molecule).

The instability and insolubility of perovskite quantum dots in aqueous solution prohibit applications in polar solvents. As a highly toxic gas pollutant and also an endogenous gaseous signaling molecule existing in a variety of physiological processes, hydrogen sulfide (H 2 S), with high selectivity and high specificity, detection is of great significance. In this study, a simple device has been designed to separate H 2 S from aqueous solution and CsPbBr 3 quantum dots (CsPbBr 3 QDs) have been used as the detection probe to develop a novel fluorescent sensor for rapid H 2 S detection. The addition of hydrogen sulfide to the phosphoric acid solution results in the escape of H 2 S from the aqueous sample and hence it passing into the n -hexane solution containing CsPbBr 3 QDs, resulting in the quenching of the fluorescence of CsPbBr 3 QDs. The fluorescence intensity of the system has a linear relationship with the concentration of H 2 S in the range of 0-100 μM with the detection limit of 0.18 μM. The proposed system has been applied to detection of H 2 S in rat brain microdialysate with satisfying results. The potential mechanism regarding the quenching of fluorescence from CsPbBr 3 QDs by H 2 S has been studied as well.

The electronic balance, one of the most common pieces of equipment in the laboratory, is normally used to directly measure the weight of a target with high accuracy. However, little attention has been paid to the extension of its applications. In this study, an electronic balance was used as a readout to develop a novel aptasensor for protein quantification for the first time. Thrombin was selected as a model target, and its two aptamers recognizing different sites of the protein were used (one aptamer was immobilized on the surface of magnetic microparticles and the other aptamer was functionalized with platinum nanoparticles). The two aptamers were specifically bound with the thrombin to form a sandwich structure; thus, the platinum nanoparticles were linked to the magnetic microparticles, and they were separated by a magnet easily. The captured platinum nanoparticles effectively catalyzed the decomposition of H 2 O 2 , generating a large volume of O 2 to discharge a certain amount of water in a drainage device, because the pressure in the vial is higher than that outside of the vial. The weight of water was accurately measured by an electronic balance. The weight of water increased with the increasing of the thrombin concentration in the range of 0 to 100 nM with a detection limit of 2.8 nM. This is the first time the use of an electronic balance as a signal readout for biomolecule quantitation in bioassay has been reported.