Search

Carbon dots have promising prospects for analytical and monitoring purposes, but are greatly hindered by the aggregation-induced luminescence quenching owing to the π-π interaction or the non-radiation-excited radical complex formation. Herein hydrothermally prepared orange-yellow fluorescent carbon dots (O-CDs) show an aggregation-induced fluorescence enhancement (AIFE) with Cu 2+ owing to the complexation of Cu(II) and the O-CDs. Cu 2+ was then sensitively and selectively detected in the linear range from 0.02 to 30 μM with the detection limit of 14 nM, making the detection of Cu 2+ in fresh water and E. coli lysate successful, showing that the as-prepared O-CDs could be well applied to the environmental monitoring of heavy metals.

An OFF-ON detection method for Cu 2+ was developed at the AgAu bimetallic nanoparticle decorated nitrogen-doped graphene (AgAu-NG) nanocomposite modified electrode. The measurement was based on the copper-catalyzed oxidation of cysteamine (Cys) to regulate the oxidation peak current of Ag. In the absence of Cu 2+ , Cys can bind to the surface of AgAu-NG via the Ag-S or Au-S bond, thus leading to an obvious decrease of the oxidation peak current of Ag. However, in the presence of Cu 2+ , Cu 2+ can greatly catalyze the oxidation of Cys by dissolved O 2 to form cystamine, which would fall off the surface of AgAu-NG nanocomposites, leading to the partial recovery of the oxidation peak current of Ag. With the increase in the concentration of Cu 2+ , the oxidation peak current of Ag in the presence of Cys increases accordingly. So, the concentration of Cu 2+ can be measured. By using the optimum conditions, this method can detect Cu 2+ concentrations down to 0.3 nM (S/N = 3) with a linear response range of 1 nM-1 mM. Furthermore, this method was applied to determine Cu 2+ concentrations in river water samples and showed excellent analytical performance.

Highly sensitive colorimetric detection of silver(i) ions (Ag+) at the single-particle level was developed based on the color of a gold nanoparticle (AuNP) assembly captured by dark-field microscopy (DFM) imaging. Formation of C-Ag+-C bonding between cytosines was utilized to induce interparticle coupling of AuNPs modified with single-strand DNA, resulting in a color change as the signal transduction to quantify Ag+ under DFM imaging. This method allowed visual quantitation of Ag+ in the range of 0.05 nM-250.00 nM and a detection limit of 28.8 pM was achieved. Furthermore, we demonstrated its applicability for the colorimetric detection of Ag+ in a small quantity of real samples, showing the good potential of this developed method for environmental monitoring and drug quality control.

A simple protocol for in situ growth of Cu 2-x Se nanoparticles on graphene oxide hybrids (Cu 2-x Se/rGO) acting as an efficient nanozyme is developed and thus a sensitive visual detection method of cancer cells is proposed. The Cu 2-x Se/rGO heterogeneous nanomaterials have been proven to exhibit high peroxidase-like activity to catalyze the reaction of the peroxidase substrate in the presence of hydrogen peroxide. Herein, we used Cu 2-x Se/rGO as a signal transducer to develop a colorimetric assay for the direct detection of cancer cells and a total of 63 cancer cells (MCF-7) can be distinguished by naked-eye observation. The results showed that the Cu 2-x Se/rGO hybrids could be the promising nanozyme mimetics for potential applications in bioanalytical fields.

Besides its widely known role as an endogenous antioxidant in scavenging free radicals, glutathione (GSH) can also play the role of prooxidant and promote CuO-induced formation of hydroxyl radicals to light up a fluorescent signal through Cu(i)-O2 chemistry without requiring additional H2O2. This approach is independent of the mechanisms of enzyme mimics, such as the well-known oxidase and peroxidase mimetics, providing a new method to simply and effectively analyze intracellular GSH.

The detection of nitroaromatic explosives is of great importance owing to their strong explosive power and harmfulness in terms of the environment, homeland security and public safety. Herein, rare earth-doped carbon dots with multifunctional features were firstly prepared by simply keeping the mixture of terbium(iii) nitrate pentahydrate and citric acid at 190 °C for 30 min. The as-prepared terbium doped carbon dots (Tb-CDs), through a rapid and simple direct carbonization route, have a size of about 3 nm, and exhibit excitation wavelength dependent emission of blue fluorescence, are stable, and can be applied for the selective and colorimetric detection of 2,4,6-trinitrophenol (TNP) in the range of 500 nM-100 μM with a limit of detection of 200 nM based on the inner filtering effect (IFE) of the excitation and emission bands of Tb-CDs by TNP and the electron transfer (ET) from Tb-CDs to TNP, giving a precise and highly reproducible result for detecting complex water samples.

Full understanding and easy construction of specific biosensing principles is necessary for disease diagnostics and therapeutics in the hope of creating new types of biosensors. Herein, we developed a new conceptual nanobiosensing platform by coupling nanometal surface energy transfer (NSET) and photo-induced electron transfer (PET) with polydopamine-embedded Cu(2-x)Se nanoparticles (Cu(2-x)SeNPs@pDA) and DNA-conjugated fluorescent organic dyes. The new prepared Cu(2-x)SeNPs@pDA has intense and broad localized surface plasmon resonance (LSPR) absorption over UV to near infrared (NIR) wavelengths, with different affinities toward ssDNA versus dsDNA. It also exhibits a high multiplexed fluorescence quenching ability, and thus can act as an acceptor in the energy transfer and electron transfer interactions between Cu(2-x)SeNPs@pDA and fluorescent organic dyes. As a proof of concept, a new biosensing platform has been successfully developed to target biomacromolecules such as DNA and proteins, in which the NSET and PET interactions between Cu(2-x)SeNPs@pDA and three different DNA-conjugated fluorescent dyes have been identified using steady-state and time-resolved fluorescence. A simple mathematical model was further applied to simulate the respective contributions of the coexisting NSET and PET to the total quenching observed for each DNA-conjugated dye in this sensing system. This study highlights the importance of understanding the mechanistic details of NSET and PET coupling processes, and the disclosed coupling mechanism of NSET and PET (NSET©PET) in the systems of Cu(2-x)SeNPs@pDA with wide wavelength range dyes provides new opportunities for sensitive biosensing applications.