Glutathione-stabilized Cu nanoclusters as fluorescent probes for sensing pH and vitamin B1

Fast synthesis of porous copper nanoclusters for fluorescence detection of iron ions in water samples

Copper nanoclusters (Cu NCs) have attracted great research interest in recent years owing to its unique physical, electrical and optical properties. Macromolecules have been widely used as templates to synthesize fluorescent Cu NCs. In this study, a simple method for synthesis of albumin chicken egg capped porous copper nanoclusters (p-Cu NCs) was developed for the first time. The obtained p-Cu NCs exhibited intense emission and excitation peaks at 280 nm and 340 nm, respectively. Besides, the p-Cu NCs fluorescence probe could be quenched by Fe³⁺ ions in aqueous solutions. Therefore, the p-Cu NCs can be excellently candidated as fluorescent probe for the detection of Fe³⁺ ions. Under optimized conditions, this fluorescent probe exhibited a wide linear response concentration range (0.2 to 100 μM) to Fe³⁺ with a detection limit of 0.0234 μM. In addition, the fluorescent probe has been successfully used for the detection of Fe³⁺ in natural water samples with satisfactory result.

Synthesis, optical properties and applications of light-emitting copper nanoclusters

Metal nanoclusters (NCs) containing a few to a few hundreds of atoms bridge the gap between nanoparticles and molecular compounds. The last decade evidenced impressive developments of noble metal NCs such as Au and Ag. Copper is an earth abundant, inexpensive metal from the same group of the periodic table, which is increasingly coming into focus for NC research. This review specifically addresses wet chemical synthesis methods, optical properties and some emerging applications of Cu NCs. As surface protecting templates/ligands play an important role in the stability and properties of Cu NCs, we classified the synthetic methods by the nature of the capping agents. The optical properties of Cu NCs are discussed from the point of view of the effects of the metal core, surface ligands and environment (solvents and aggregation) on the emission of the clusters. Applications of luminescent Cu NCs in biological imaging and light emitting devices are considered.

Inducible Sequential Oxidation Process in Water-Soluble Copper Nanoclusters for Direct Colorimetric Assay of Hydrogen Peroxide in a Wide Dynamic and Sampling Range

Direct and fast detection methods for H₂O₂ have great demand in materials science, biology, and medicine. Colorimetric assay of H₂O₂ has been regarded as one versatile approach that can avoid tedious operation and complicated setup. In this report, we provided a cost-effective and time-saving H₂O₂ colorimetric assay strategy based on a mercaptosuccinic acid (MSA)-stabilized Cu nanocluster (NC) probe without using any chromogenic reagent. Direct and fast colorimetric detection of H₂O₂ was realized based on the color change of MSA-capped Cu NCs in aqueous medium. It was found that the Cu NCs presented eligible resistance to natural oxidation either in concentrated solution or in the powder state. However, the dissolved oxygen in a highly diluted solution of the Cu NCs could trigger the aggregation of the Cu NCs and their further fusion into small Cu nanoparticles (NPs). When this diluted solution served as a probe solution for detecting H₂O₂, a sequential oxidation process occurred in the newly formed Cu NPs, including the cleavage of MSAs on the surface and conversion of Cu into Cu₂O, leading to the probe with capacity for H₂O₂ assay in a wide dynamic and sampling range. The sensitive solution color change was attributed to the growth of the Cu NPs (fading of plasmonic absorption) upon the addition of low levels of H₂O₂ and the transition of the valence states of Cu (color reactions) upon the addition of high levels of H₂O₂. A concentration range of H₂O₂ from 1 μM to 1 M could be detected by a small dose of the probe. Moreover, the Cu NCs powder subsequent to storage for 10 months could maintain a similar sensitivity for H₂O₂ assay, which provides possibilities for a wide range of practical applications in water samples.

Protein/peptide-templated biomimetic synthesis of inorganic nanoparticles for biomedical applications

Currently, protein/peptide-based biomimetic mineralization has been demonstrated to be an efficient and promising strategy for synthesis of inorganic/metal nanoparticles (NPs) for bioapplications.

Lanthanide coordination polymer probe for time-gated luminescence sensing of pH in undiluted human serum

Lanthanide coordination polymers (LCPs) have emerged as fascinating materials because of their specific structure and properties. In this work, utilizing hydrosoluble biomolecule of guanosine-5'-monophosphate (GMP) as bridging linker, lanthanide terbium ions (Tb³⁺) as metal nodes, and silver ions (Ag⁺) as sensitizers, we synthesized a pH responsive luminescent lanthanide CP probe of Tb/GMP/Ag. The probe possesses high luminescence due to the sensitization of Ag⁺; While in alkaline solutions, Ag⁺ in Tb/GMP/Ag immediately binds to OH^-, forming Ag₂O precipitation and resulting in a distinct fluorescence quenching of Tb/GMP/Ag. This probe displays high selectivity for OH^- and a broader pH detection range of 7.5-13.0. In addition, based on the high anti-interference ability in serum, we applied Tb/GMP/Ag to measure pH in undiluted human serum samples, yielding satisfactory results.

One-step green synthetic approach for the preparation of multicolor emitting copper nanoclusters and their applications in chemical species sensing and bioimaging

One-step green microwave synthetic approach was developed for the synthesis of copper nanoclusters (Cu NCs) and used as a fluorescent probe for the sensitive detection of thiram and paraquat in water and food samples. Unexpectedly, the prepared Cu NCs exhibited strong orange fluorescence and showed emission peak at 600 nm, respectively. Under optimized conditions, the quenching of Cu NCs emission peak at 600 nm was linearly proportional to thiram and paraquat concentrations in the ranges from 0.5 to 1000 µM, and from 0.2 to 1000 µM, with detection limits of 70 nM and 49 nM, respectively. In addition, bioimaging studies against Bacillus subtilis through confocal fluorescence microscopy indicated that Cu NCs showed strong blue and green fluorescence signals, good permeability and minimum toxicity against the various bacteria species, which demonstrates their potential feasibility for chemical species sensing and bioimaging applications.

One step synthesis of silane-capped copper clusters as a sensitive optical probe and efficient catalyst for reversible color switching

Luminescent silane-functionalized copper clusters are developed as a highly efficient catalyst to build up a recyclable and photoreversible color switching system based on the redox reactions of methylene blue.