The biofilm-mediated implant infections pose a huge threat to human health. It is urgent to explore strategies to reverse this situation. Herein, we design 3-amino-1,2,4-triazole-5-thiol (ATT)-modified gold nanoclusters (AGNCs) to realize biofilm-targeting and near-infrared (NIR)-II light-responsive antibiofilm therapy. The AGNCs can interact with the bacterial extracellular DNA through the formation of hydrogen bonds between the amine groups on the ATT and the hydroxyl groups on the DNA. The AGNCs show photothermal properties even at a low power density (0.5 W/cm2) for a short-time (5 min) irradiation, making them highly effective in eradicating the biofilm with a dispersion rate up to 90 %. In vivo infected catheter implantation model demonstrates an exceptional high ability of the AGNCs to eradicate approximately 90 % of the bacteria encased within the biofilms. Moreover, the AGNCs show no detectable toxicity or systemic effects in mice. Our study suggests the great potential of the AGNCs for long-term prevention and elimination of the biofilm-mediated infections.

Although nucleic acids have been widely used as templates for the synthesis of nanomaterials, the synthesis of RNA-templated gold nanoclusters (AuNCs) has not been explored. In this work, we developed a simple strategy for synthesis of RNA-templated fluorescent AuNCs. We first evaluated the adsorption of different nucleoside monophosphates (NMP) on gold atoms. Our density function theory simulation and isothermal titration calorimetry measurements demonstrated that adenosine monophosphate (AMP) is a superior gold binder than other NMPs or deoxyadenosine monophosphate. Afterwards, NMP-templated synthesis of AuNCs was conducted in various pH environments, and our results indicated that bright green light-emitting AMP-templated AuNCs can be obtained at pH ∼6.0. In order to study the synthesis mechanism of AuNCs, we investigated the effects of reducing agent type and addition time, and the negative charge carried by template nucleotides on the fluorescence of AuNCs. Finally, we extended the template AMP into RNA hairpin structure, the fluorescence intensity was the highest when the cyclic bases were poly 16 A. This study opens new routes to synthesize fluorescent AuNCs using RNA templates.

A dual-emission ratio-fluorescent sensing nanohybrid based on Radix Hedysari green-synthesized carbon quantum dots (CDs) and glutathione-functionalized gold nanoclusters (GSH-AuNCs) had been developed for the determination of cefodizime sodium (CDZM). The designed fluorescence nanohybrid had two significant fluorescence emission peaks at 458 nm and 569 nm when excited at 360 nm, which was attributed to the CDs and GSH-AuNCs. With the addition of CDZM, the fluorescence at 458 nm was slightly weakened while the fluorescence at 569 nm was enhanced obviously. Based on the relationship between the I569/I458 fluorescence intensity ratio and the concentration of CDZM, the designed nanohybrid exhibited a good linearity range of 1.0-1000.0 μM and the limit of detection (LOD) was 0.19 μM. The method was finally applied in the detection of CDZM in urine, showing the potential applications in complicated biological samples.

Plants exhibit rapid responses to biotic and abiotic stresses by releasing a range of volatile organic compounds (VOCs). Monitoring changes in these VOCs holds the potential for the early detection of plant diseases. This study proposes a method for identifying late blight in potatoes based on the detection of (E)-2-hexenal, one of the major VOC markers released during plant infection by Phytophthora infestans. By combining the Michael addition reaction with cysteine-mediated etching of aggregation-induced emission gold nanoclusters (Au NCs), we have developed a portable hydrogel kit for on-site detection of (E)-2-hexenal. The Michael addition reaction between (E)-2-hexenal and cysteine effectively alleviates the etching of cysteine-mediated Au NCs, leading to a distinct fluorescence color change in the Au NCs, enabling a detection limit of 0.61 ppm. Utilizing the superior loading and diffusion characteristics of the three-dimensional structure of agarose hydrogel, our sensor demonstrated exceptional performance in terms of sensitivity, selectivity, reaction time, and ease of use. Moreover, quantitative measurement of (E)-2-hexenal was made easier by using ImageJ software to transform fluorescent images from the hydrogel kit into digital data. Such method was effectively used for the early detection of potato late blight. This study presents a low-cost, portable fluorescent analytical tool, offering a new avenue for on-site detection of plant diseases.

Developing a simple, economical, sensitive, and selective method for label-free direct detection analytes is attractive, especially the strategies that could achieve signal amplification without complicated operations. Herein, a dual-fluorescence colorimetric nanoswitch sensing platform for label-free direct melamine (MEL) detection was established. We first explored the relationship between MEL-induced aggregation of gold nanoparticles (AuNPs) and size and determined the optimal size to be 37 nm. Using surfactant Triton X-100 to modify AuNPs and clarify possible interaction mechanisms to improve detection performance. The dynamic changes of surface plasmon resonance absorption peaks in the dispersed and aggregated states of AuNPs were skillfully utilized to match the emission of multicolor gold nanoclusters to trigger the multi-inner filter effect. Accompanied by the addition of MEL-induced AuNPs to change from dispersed to aggregated state, the fluorescence of green-emitting and red-emitting gradually turned on and turned off, respectively. The fluorescence turn-on mode detection limit was 10 times higher than the colorimetric method and as low as 5.5 ng/mL; the detection took only 10 min. The sensor detected MEL in spiked milk samples with a good recovery in the range of 81.2-111.0 % with a coefficient of variation less than 11.4 % and achieved a good correlation with commercial kits. The proposed sensor integrates numerous merits of label-free, multi-signal readout, self-calibration, simple operations, and economical, which provides a promising tool for convenient on-site detection of MEL.

The surfactant cetyltrimethylammonium bromide (CTAB) induces the aggregation of gold nanoclusters (GNCs), leading to the development of a proposed fluorometric technique for detecting thiocyanate (SCN-) ions based on an anti-aggregation mechanism. This approach is straightforward to execute, highly sensitive, and selective. A significant quenching effect occurs in fluorescence upon using the aggregation agent CTAB in GNCs synthesis, resulting in a transition from intense red fluorescence to dim red. The decrease in fluorescence intensity of GNCs in the presence of CTAB is caused by the mechanism of fluorescence quenching mediated by aggregation. As the levels of SCN- rise, the fluorescence of CTAB-GNCs increases; this may be detected using spectrofluorometry or by visually inspecting under UV irradiation. The recovery of red fluorescence of CTAB-GNCs in the presence of SCN- enables the precise and discerning identification of SCN- within the concentration range of 2.86-140 nM. The minimum detectable concentration of the SCN- ions was 1 nM. The selectivity of CTAB-GNCs towards SCN- ions was investigated compared to other ions, and it was demonstrated that CTAB-GNCs exhibit exceptional selectivity. Furthermore, we believe that CTAB-GNCs have novel possibilities as favorable sensor candidates for various industrial applications. Our detection technique was validated by analyzing SCN- ions in milk samples, which yielded promising results.

We report that constructed Au nanoclusters (NCs) can afford amazing white emission synergistically dictated by the Au(0)-dominated core-state fluorescence and Au(I)-governed surface-state phosphorescence, with record-high absolute quantum yields of 42.1% and 53.6% in the aqueous solution and powder state, respectively. Moreover, the dynamic color tuning is achieved in a wide warm-to-cold white-light range (with the correlated color temperature varied from 3426 to 24 973 K) by elaborately manipulating the ratio of Au(0) to Au(I) species and thus the electron transfer rate from staple motif to metal kernel. This study not only exemplifies the successful integration of multiple luminescent centers into metal NCs to accomplish efficient white-light emission but also inspires a feasible pathway toward customizing the optical properties of metal NCs by regulating electron transfer kinetics.

This paper revealed a new strategy for citric acid (CA) detection using aggregation-induced emission (AIE)-based fluorescent gold nanoclusters (AuNCs). AuNCs was synthesized using glutathione (GSH) as the template and reducing agent and used as the fluorescent probe to detect CA under aluminum ion (Al3+) mediation. The fluorescence intensity of AuNCs increased about 4 times with the addition of Al3+, but the enhanced fluorescence was quenched after the addition of CA. Based on this fluorescence phenomenon, an \"on-off\" fluorescence strategy was designed for the sensitive determination of CA and a linear detection range for CA was achieved within 0-80.0 μM. In addition, the developed probe exhibited high selectivity and accuracy for determination of CA. The mechanism of fluorescence enhancement and quenching of AuNCs was explored in detail. The established probe was used successfully for CA detection in beverages. The spiked recoveries from 97.50% to 103.67% were gratifying, which indicated the probe had potential prospects for detecting CA in food.

Gold nanoclusters are a smart platform for sensing potassium ions (K+). They have been synthesized using bovine serum albumin (BSA) and valinomycin (Val) to protect and cap the nanoclusters. The nanoclusters (Val-AuNCs) produced have a red emission at 616 nm under excitation with 470 nm. In the presence of K+, the valinomycin polar groups switch to the molecule\'s interior by complexing with K+, forming a bracelet structure, and being surrounded by the hydrophobic exterior conformation. This structure allows a proposed fluorometric method for detecting K+ by switching between the Val-AuNCs\' hydrophilicity and hydrophobicity, which induces the aggregation of gold nanoclusters. As a result, significant quenching is seen in fluorescence after adding K+. The quenching in fluorescence in the presence of K+ is attributed to the aggregation mechanism. This sensing technique provides a highly precise and selective sensing method for K+ in the range 0.78 to 8 µM with LOD equal to 233 nM. The selectivity of Val-AuNCs toward K+ ions was investigated compared to other ions. Furthermore, the Val-AuNCs have novel possibilities as favorable sensor candidates for various imaging applications. Our detection technique was validated by determining K+ ions in postmortem vitreous humor samples, which yielded promising results.

Gold nanoclusters (AuNCs) are a class of novel luminescent nanomaterials that exhibit unique properties of ultra-small size, featuring strong anti-photo-bleaching ability, substantial Stokes shift, good biocompatibility, and low toxicity. Various biomolecules have been developed as templates or ligands to protect AuNCs with enhanced stability and luminescent properties for biomedical applications. In this review, the synthesis of AuNCs based on biomolecules including amino acids, peptides, proteins and DNA are summarized. Owing to the advantages of biomolecule-protected AuNCs, they have been employed extensively for diverse applications. The biological applications, particularly in bioimaging, biosensing, disease therapy and biocatalysis have been described in detail herein. Finally, current challenges and future potential prospects of bio-templated AuNCs in biological research are briefly discussed.