Visual Chronometric Assay for Chromium(III) Ions Based on the Cu2O Nanocube-Mediated Clock Reaction

Advances in the application of logic gates in nanozymes

Nanozymes are a class of nanomaterials with biocatalytic function and enzyme-like activity, whose advantages include high stability, low cost, and mass production. They can catalyze the substrates of natural enzymes based on specific nanostructures and serve as substitutes for natural enzymes. Their applied research involves a wide range of fields such as biomedicine, environmental governance, agriculture, and food. Molecular logic gates are a new cross-disciplinary discipline, which can simulate the function of silicon circuits on a molecular scale, perform single or multiple input logic operations, and generate logic outputs. A molecular logic gate is a binary operation that converts an input signal into an output signal according to the rules of Boolean logic, generating two signals, a high level, and a low level. The high and low levels represent the "true" and "false" values of the logic gates, and their outputs correspond to "l" and "0" of the molecular logic gates, respectively. The combination of nanozymes and logic gates is a novel and attractive research direction, and the cross-application of the two brings new opportunities and ideas for various fields, such as the construction of efficient biocomputers, intelligent drug delivery systems, and the precise diagnosis of diseases. This review describes the application of logic gates based on nanozymes, which is expected to provide a certain theoretical foundation for researchers' subsequent studies.

An instrument-free visual quantitative detection method based on clock reaction: the detection of thrombin as an example

Instrument-free visual quantitative detection in chemical and biochemical analysis is of great significance in practical applications especially in point-of-care testing and in places where resources are limited. In this paper, we report the development of a time-based instrument-free visual quantitative detection method by employing a clock reaction, a type of chemical reaction displaying characteristic clocking behavior. The feasibility of the method was illustrated by the quantitative detection of thrombin in buffer solution using the lapse of time as the readout signal. The linear range of detection was from 1.3 to 43 nM (r² = 0.990, n = 3) with a LOD of 0.9 nM, which is lower than the physiological concentrations of thrombin in the resting and activated blood, which range from low nanomolar to low micromolar, respectively. This method was also validated by detecting thrombin in the serum and a good recovery of nearly 100 ± 8.0% was obtained. To the best of our knowledge, this work is the first report that uses the characteristic time of a clock reaction as the readout signal in instrument-free colorimetry for quantitative bioanalysis.

Well-Designed Au Nanorod-Doped Cu2O Core-Shell Nanocube-Embedded Reduced Graphene Oxide Composite for Efficient Removal of a Water Pollutant Dye

To ensure environmental safety, the removal of organic pollutants has gained increasing attention globally. We have synthesized uniform Au nanorod (NR)-doped Cu₂O core-shell nanocubes (CSNCs) via a seed-mediated route embedded on the surface of rGO sheets. The Au NRs@Cu₂O/rGO nanocomposite was characterized using various techniques such as transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FT-IR) and Raman spectroscopies. The scanning TEM-energy-dispersive spectroscopy (STEM-EDS) elemental mapping of the AuNRs@Cu₂O/rGO nanocomposite indicates that the Au NR (40 nm) is fully covered with the Cu₂O particles (∼145 nm) as a shell. N₂ gas sorption analysis shows that the specific surface area of the composite is 205.5 m²/g with a mesoporous character. Moreover, incorporation of Au NRs@Cu₂O CSNCs increases the nanogaps around the nanoparticles and suppresses the stacking/bundling of rGO, which significantly influences the pore size and increase the surface area. A batch adsorption experiment was carried out under various parameters, such as the effect of pH, contact time, temperature, initial dye concentration, and adsorbent dosage, for the removal of methylene blue (MB) in aqueous solution. The high surface area and mesoporosity can cause the adsorption capacity to reach equilibrium within 20 min with a 99.8% removal efficiency. Both kinetic and isotherm data were obtained and fitted very well with the pseudo-second-order kinetic and Langmuir isotherm model. The Langmuir isotherm revealed an excellent dye sorption capacity of 243.9 mg/g at 298 K. Moreover, after five adsorption cycles, the dye removal efficiency decreased from 99 to 86%. This novel route paves a new path for heterogeneous adsorbent synthesis, which is useful for catalysis and electrochemical applications.

Chemical clocks, oscillations, and other temporal effects in analytical chemistry: oddity or viable approach?

Most analytical methods are based on "analogue" inputs from sensors of light, electric potentials, or currents. The signals obtained by such sensors are processed using certain calibration functions to determine concentrations of the target analytes. The signal readouts are normally done after an optimised and fixed time period, during which an assay mixture is incubated. This minireview covers another-and somewhat unusual-analytical strategy, which relies on the measurement of time interval between the occurrences of two distinguishable states in the assay reaction. These states manifest themselves via abrupt changes in the properties of the assay mixture (e.g. change of colour, appearance or disappearance of luminescence, change in pH, variations in optical activity or mechanical properties). In some cases, a correlation between the time of appearance/disappearance of a given property and the analyte concentration can be also observed. An example of an assay based on time measurement is an oscillating reaction, in which the period of oscillations is linked to the concentration of the target analyte. A number of chemo-chronometric assays, relying on the existing (bio)transformations or artificially designed reactions, were disclosed in the past few years. They are very attractive from the fundamental point of view but-so far-only few of them have be validated and used to address real-world problems. Then, can chemo-chronometric assays become a practical tool for chemical analysis? Is there a need for further development of such assays? We are aiming to answer these questions.

Synthesis of highly fluorescent Cu/Au bimetallic nanoclusters and their application in a temperature sensor and fluorescent probe for chromium(iii) ions

Bimetallic nanoclusters (BNCs) have attracted great attention due to their cooperative electronic, optical, and catalytic properties. Here, a novel one-step synthetic method is presented to prepare highly fluorescent bimetallic copper–gold nanoclusters (Cu/Au BNCs) in ambient conditions by using glutathione (GSH) as both the reducing agent and the protective layer preventing the aggregation of the as-formed NCs. The resultant Cu/Au BNCs are uniformly dispersed, with an average diameter of 1.5 nm, and it exhibits emission at 450 nm with excitation at 380 nm. Interestingly, the fluorescence signal of the Cu/Au BNCs is reversibly responsive to the environmental temperature, and it shows good sensitivity in the range of 20–70 °C (F = −23.96T + 3149.2 (R = 0.94)). Furthermore, it was found that the fluorescence of Cu/Au BNCs was quenched selectively by Cr³⁺, and a detection method was further developed with detection linear range from 50 nM to 1 mM (F = −174.85[Cr³⁺] + 1686.69 (R = 0.98)) and high sensitivity (LOD = 10 nM, S/N = 3).

The Cu/Au BNCs have been successfully synthesized as a temperature sensor and it successful detection Cr³⁺.