Highly Efficient Visual Detection of Trace Copper(II) and Protein by the Quantum Photoelectric Effect

Target-Modulated Hydrophobic Precipitation in Photocatalytic Nanochannels for Sensitive Detection of Alpha Fetoprotein

It is important to detect cancer biomarkers at an early stage of tumor development for the effective diagnosis and treatment of cancer. As a well-known probe for detecting superoxide (·O₂^-) radicals, nitro blue tetrazolium (NBT) can rapidly react with ·O₂^- to form a hydrophobic formazan precipitate. In this study, by deliberately utilizing this reaction, Pt asymmetrically decorated on a TiO₂ nanochannel membrane (Pt/TiNM) is explored to fabricate an electrochemical immunosensing platform with outstanding selectivity and ultrahigh sensitivity. Using NBT as the substrate, hydrophobic formazan precipitation induces a substantial block of ionic diffusion flux in nanochannels. Using alpha fetoprotein (AFP) as the target analyte, the established immunorecognition event was used to induce MoS₂-Ab₂ conjugates. Thanks to the excellent light-shielding ability of MoS₂ nanosheets, the production of ·O₂^- radicals from the photocatalysis of Pt/TiNM is effectively depressed because of the attenuated arrival of light. The reduced formazan precipitation results in ionic transport changes in nanochannels, which in turn enables the selective recognition of AFP down to 2 ng mL^-1. This target-modulated sensing strategy is also capable of sensing other immune targets, thus paving a new way for designing nanochannel-based sensing platforms.

Ultrasensitive photoelectrochemical sensor enabled by a target-induced signal quencher release strategy

In this work, a target-induced signal quencher release strategy was proposed to construct a sensitive photoelectrochemical (PEC) sensor.

A Cu2+-doped two-dimensional material-based heterojunction photoelectrode: application for highly sensitive photoelectrochemical detection of hydrogen sulfide

In this work, on the basis of a Cu2+-doped two-dimensional material-based heterojunction photoelectrode, a novel anodic photoelectrochemical (PEC) sensing platform was constructed for highly sensitive detection of endogenous H2S. Briefly, with g-C3N4 and TiO2 as representative materials, the sensor was fabricated by modifying g-C3N4/TiO2 nanorod arrays (NAs) onto the surface of fluorine-doped tin oxide (FTO) and then doping Cu2+ as a Cu x S (x = 1, 2) precursor. After the binding of S2- with surface-attached Cu2+, the signal was quenched owing to the in situ generation of Cu x S which offers trapping sites to hinder generation of photocurrent signals. Since the photocurrent inhibition was intimately associated with the concentration of S2-, a highly sensitive PEC biosensor was fabricated for H2S detection. More importantly, the proposed sensing platform showed the enormous potential of g-C3N4/TiO2 NAs for further development of PEC bioanalysis, which may serve as a common basis for other semiconductor applications and stimulates the exploration of numerous high-performance nanocomposites.

Photovoltage-triggered electrochromic tablet for visualized photoelectrochemical sensing

In this work, we designed an integrated photoelectrochemical (PEC) analytical system with photovoltage-regulated electrochromic tablet for visualized sensing. The electrochromic tablet consisted of electron-injector (EI) part and colorimetric system, which was functionalized with dye-sensitized titanium dioxide and nickel oxide nanosheet film as the recognition element and signal readout, respectively. Under irradiation of home-built white light, the EI part provided sufficient and stable photovoltage and injected the photoexcited electrons to nickel oxide nanosheet through the conductive inner side of indium tin oxide slide. Thus, the different color states of nickel oxide nanosheet were observed, resulting in a detectable signal by naked eyes for visual analysis. More importantly, the color change was identified to be dependent on the photovoltages generated from EI part. Using copper ions as a model analyte, the electrochromic tablet was successfully applied to visually detect copper ions based on its quenching effect on photovoltage due to the formation of exciton trapping. As a result, the copper ions could be simultaneously determined over a wide range through photovoltage record, average RGB value, and naked eyes. Furthermore, the device exhibited considerable stability and could be reused through simple washing steps. The smart tablet PEC system provides a new avenue to design practical PEC sensor in point-of-care diagnosis.

Quantum dot-DNA aptamer conjugates coupled with capillary electrophoresis: A universal strategy for ratiometric detection of organophosphorus pesticides

Based on the highly sensitivity and stable-fluorescence of water-soluble CdTe/CdS core-shell quantum dots (QDs) with broad-specificity DNA aptamers, a novel ratiometric detection strategy was proposed for the sensitive detection of organophosphorus pesticides by capillary electrophoresis with laser-induced fluorescence (CE-LIF). The as-prepared QDs were first conjugated with the amino-modified oligonucleotide (AMO) by amidation reaction, which is partial complementary to the DNA aptamer of organophosphorus pesticides. Then QD-labeled AMO (QD-AMO) was incubated with the DNA aptamer to form QD-AMO-aptamer duplex. When the target organophosphorus pesticides were added, they could specifically bind the DNA aptamer, leading to the cleavage of QD-AMO-aptamer duplex, accompany with the release of QD-AMO. As a result, the ratio of peak height between QD-AMO and QD-AMO-aptamer duplex changed in the detection process of CE-LIF. This strategy was subsequently applied for the detection of phorate, profenofos, isocarbophos, and omethoate with the detection limits of 0.20, 0.10, 0.17, and 0.23μM, respectively. This is the first report about using QDs as the signal indicators for organophosphorus pesticides detection based on broad-specificity DNA aptamers by CE-LIF, thus contributing to extend the scope of application of QDs in different fields. The proposed method has great potential to be a universal strategy for rapid detection of aptamer-specific small molecule targets by simply changing the types of aptamer sequences.

Highly sensitive visual detection of copper ions based on the shape-dependent LSPR spectroscopy of gold nanorods

We have developed a novel approach to the rapid visual detection of Cu(2+) in natural samples based on the copper-mediated leaching of gold nanorods (GNRs). In the presence of hexadecyltrimethylammonium bromide, which can reduce the redox potential of Au(I)/Au, the GNRs are catalytically etched by Cu(2+) preferentially along the longitudinal direction. And as a result, the localized surface plasmon resonance extinction peak shifts to short wavelength, accompanied by a color change from blue to red. The leaching mechanism has been carefully discussed in a series of control experiments. Under optimal conditions, this sensor exhibits good sensitivity (LOD = 0.5 nM). Most importantly, the approach is highlighted by its high selectivity for and tolerance of interference, which enables the sensor to detect Cu(2+) directly in a complex matrix, especially in seawater. Moreover, such a nanoparticle-based sensor is also successfully applied to test paper for the visual detection of Cu(2+).