Novel competitive electrochemical impedance biosensor for the ultrasensitive detection of umami substances based on Pd/Cu-TCPP(Fe)

The development of biosensors capable of assessing umami intensity has elicited significant attention. However, the detection range of these biosensors is constrained by the sensing components and strategies used. In this study, we introduce a novel competitive, ultra-high-sensitivity impedance biosensor by utilizing composite nanomaterials and T1R1 as a composite signal probe. Pd/Cu-TCPP(Fe) had a substantial surface area, effectively enhancing the loading capacity of the T1R1 and thus augmenting the biosensor's recognition precision. Furthermore, the Pd/Cu-TCPP(Fe) elevated peroxidase-like activity catalyzed the formation of insoluble precipitates of 4-chloro-1-naphthol (4-CN), resulting in cascaded amplification of the impedance signal. The remarkable catalytic activity of the composite signal probe endowed the biosensor with exceptional analytical performance, featuring a limit of detection (LOD) of 0.86 pg/mL and a linear detection range spanning from 10 to 10,000 pg/mL. Successful application of the biosensor for umami detection in fish was demonstrated, signifying its substantial potential in food-flavor evaluation.

Alanine aminotransferase electrochemical sensor based on graphene@MXene composite nanomaterials

Graphene@MXene composite nanomaterials were utilized to construct an electrochemical sensor for alanine aminotransferase (ALT) detection. The combination of graphene nanosheets with MXene avoids the self-stacking of MXene and graphene, and broadens the charge transfer channel. In addition, the composite nanomaterial provides increased loading sites for pyruvate oxidase. The principle of ALT detection is a two-step enzymatic reaction. L-Alanine was initially transferred to pyruvate catalyzed by ALT. The formed pyruvate was then oxidized by pyruvate oxidase, generating H2O2. Through the detection of the generated H2O2, ALT activity was measured. The linear range of the sensor to ALT was from 5 to 400 U·L-1 with a detection limit of 0.16 U·L-1 (S/N = 3). For real sample analysis, the spiked recovery test results of ALT in serum samples were between 96.89 and 103.93% with RSD < 5%, confirming the reliability of the sensor testing results and potential clinical application of the sensor.

Application of perovskite oxides and their composites for degrading organic pollutants from wastewater using advanced oxidation processes: Review of the recent progress

In the recent years, perovskite oxides are gaining an increasing amount of attention owing to their unique traits such as tunable electronic structures, flexible composition, and eco-friendly properties. In contrast, their catalytic performance is not satisfactory, which hinders real wastewater remediation. To overcome this shortcoming, various strategies are developed to design new perovskite oxide-based materials to enhance their catalytic activities in advanced oxidation process (AOPs). This review article is to provide overview of basic principle and different methods of AOPs, while the strategies to design novel perovskite oxide-based composites for enhancing the catalytic activities in AOPs have been highlighted. Moreover, the recent progress of their synthesis and applications in wastewater remediation (pertaining to the period 2016-2022) was described, and the related mechanisms were thoroughly discussed. This review article helps scientists to have a clear outlook on the selection and design of new effective perovskite oxide-based materials for the application of AOPs. At the end of the review, perspective on the challenges and future research directions are discussed.

Design of composite nanosupports and applications thereof in enzyme immobilization: A review

Enzyme immobilization techniques have developed dramatically over the past several decades. Support materials are key in shaping the function of a specific immobilized enzyme. Although they have large specific surface areas and functional active sites, single-component nanomaterials and their surface chemical modification derivatives struggle to meet increasing demand. Thus, composite materials, compounds of two or more materials, have been developed and applied in efficient immobilization through advances in materials science. More methods have been developed and employed to design composite nanomaterials in recent years. These novel composite nanomaterials often show superior physical, chemical, and biological performance as supports in enzyme immobilization, among other applications. In this review, immobilization techniques and their supports are stated first and methods to design and fabricate composite nanomaterials as nanosupports are also shown in the following section. Applications of composite nanosupports in laccase immobilization are discussed as models in the later sections of the paper. This review is intended to help readers gain insight into the design principles of composite nanomaterials for immobilization supports.

Upconversion nanoparticles/carbon dots (UCNPs@CDs) composite for simultaneous detection and speciation of divalent and trivalent iron ions

In this study, the application of carbon dots (CDs) modified NaYF₄:Yb, Er nanoparticles (UCNPs@CDs) as the fluorescent nanoprobe for simultaneous detection of Fe²⁺ and Fe³⁺ was investigated. Fe³⁺ quantification (5-80 μmol L^-1) was achieved, as a result of Fe³⁺ induced fluorescence quenching of UCNPs@CDs at 434 nm (under the 336 nm excitation). The chelate (Fe²⁺-phen) formed by Fe²⁺ and 1,10-phenanthroline had a broad absorption centered at 510 nm, due to inner filter effect (IFE), Fe²⁺ quantification (4-120 μmol L^-1) was achieved as a result of (Fe²⁺-phen) induced fluorescence quenching of UCNPs@CDs at 545 nm (under the 980 nm excitation). The resultant UCNPs@CDs probe, with excellent anti-interference capability, favorable fluorescence stability, and convincing performance in real sample analysis, showed promising application in simultaneous detection of Fe²⁺ and Fe³⁺.