Silver Nanoclusters as Label Free Non-enzymatic Fast Glucose Assay with the Fluorescent Enhancement Signal

A simple and low-cost green preparation method was used for BSA capped silver nanoclusters (BSA-Ag NCs) as turn on fluorescent probe for glucose. Non-enzymatic fast glucose detection assay with a widest concentration range was proposed which requires neither nanoclusters (NCs) modification nor complicated enzyme immobilization. The DLS analysis, HRTEM patterns, fluorescence and UV-visible measurement well supported the synthesis product. The advantages of the fabricated glucose sensor based on fluorescence increasing of probe compared to other established optical techniques was inspected and summarized as well. The glucose sensor exhibited a high sensitivity, fast response time (in seconds), satisfactory selectivity, well stability (at least two months), low detection limit (31 µmol L- 1) and a wide concentration response (three orders of magnitudes) to glucose between 0.1 and 92 mmol L- 1 as calibration plot. A theoretical model of the sensing mechanism based on the binding interaction of glucose to BSA-Ag NCs is proposed and data fitting demonstrated a good agreement between the experimental and theoretically calculated fluorescence data. The facile preparation and excellent sensing performance of BSA-Ag NCs in the real samples (plasma and juice) make sure that synthesized probe material is a promising candidate for advanced enzyme-free glucose sensing approach.

Monitoring of organophosphorus pesticide residues in plant and vegetable tissues by a novel silver nanocluster probe

More and more attention has been paid to the problem of pesticide residues, especially in plants and vegetables, due to their close relationship with human health and food safety. Compared to conventional detecting techniques, the fluorescence sensing method has achieved good results for pesticides detection. However, most of the reported fluorescent probes needed two or more steps to achieve the detection of pesticide residues, which greatly limited their application for in vivo imaging and in situ analysis of agricultural residues in plants and vegetables. In this paper, an Ag nanoclusters (AgNCs) based fluorescent probe is developed for one-step detection of pesticide residues. The novel nanoprobe displayed impressive advantages, such as a selective response to glyphosate pesticide, rapid response within 1 min and an ultralow detection limit of 21 nM. The sensing mechanism is attributed to the unique coordination interaction between AgNCs and glyphosate, which not only increased the size of AgNCs to form big Ag particles, but also caused the fluorescence quenching of AgNCs system. Due to its favorable properties, the probe has been successfully applied to imaging the organophosphorus pesticide of glyphosate in the leave tissues of Arabidopsis thaliana and the root tip cells of lettuce for the first time.

Demystifying Lysosomal α-l-Fucosidase in Liver Cancer-Bearing Mice by Specific Two-Photon Fluorescence Imaging

Liver cancer is one of the most frequently diagnosed cancers and has high mortality. However, the early treatment and prognosis can greatly prolong the survival time of patients, which depends on its early detection. α-l-Fucosidase (AFU), as a vital lysosomal hydrolase, is considered to be an ideal biomarker for early stage liver cancer. So, in vivo monitoring of AFU is essential for the early and accurate diagnosis of liver cancer. Hence, we designed the first two-photon turn-on fluorescent reporter, termed HcyCl-F, which localized to lysosomes for fast imaging of AFU. The 2-chloro-4-phenyl-α-l-fucoside bond of HcyCl-F could be effectively hydrolyzed by AFU and released the hydroxyl on the benzene ring, eventually obtaining a strong conjugated compound (HcyCl-OH) with shiny fluorescence. We demonstrated that HcyCl-F was able to rapidly and accurately respond to AFU. Using a two-photon fluorescence microscope, we successfully visualized the fluctuation of AFU in lysosomes. More importantly, a fascinatingly strong fluorescence signal was observed in the tumor tissue of liver cancer-bearing mice. Of note, we confirmed that HcyCl-F could clearly detect liver tumors in stage I. Altogether, our work provides a simple and convenient method for deciphering the critical pathological function of AFU in depth and facilitates the nondestructive and effective diagnosis of liver cancer in the early stage.

Computational Approaches to the Electronic Properties of Noble Metal Nanoclusters Protected by Organic Ligands

Organometallic nanoparticles composed by metal cores with sizes under two nanometers covered with organic capping ligands exhibit intermediate properties between those of atoms and molecules on one side, and those of larger metal nanoparticles on the other. In fact, these particles do not show a peculiar metallic behavior, characterized by plasmon resonances, but instead they have nonvanishing band-gaps, more along molecular optical properties. As a consequence, they are suitable to be described and investigated by computational approaches such as those used in quantum chemistry, for instance those based on the time-dependent density functional theory (TD-DFT). Here, I present a short review of the research performed from 2014 onward at the University of Modena and Reggio Emilia (Italy) on the TD-DFT interpretation of the electronic spectra of different organic-protected gold and/or silver nanoclusters.

Stability, electronic structure, and optical properties of protected gold-doped silver Ag29−xAux (x = 0–5) nanoclusters

The stability and optical properties of Au-doped [Ag_29−xAu_x(BDT)₁₂(TPP)₄]³⁻ nanoclusters are importantly determined by the formation of Au–TPP bonds.

Fluorescent metal quantum clusters: an updated overview of the synthesis, properties, and biological applications

A brief history of metal quantum clusters, their synthesis methods, physical properties, and an updated overview of their applications is provided.

One-pot synthesis of active copper-containing carbon dots with laccase-like activities

Herein, an effective strategy for designing a new type of nanozyme, blue fluorescent laccase mimics, is reported. Active copper-containing carbon dots (Cu-CDs) were synthesized through a simple, nontoxic and one-pot hydrothermal method, which showed favorable photoluminescence properties and good photostability under high-salt conditions or in a broad pH range (3.0-13.5). The Cu-CDs possessed intrinsic laccase-like activities and could catalyze the oxidation of the laccase substrate p-phenylenediamine (PPD) to produce a typical color change from colorless to brown. Poly(methacrylic acid sodium salt) (PMAA) not only was used as the carbon source and reducing agent, but also provided carboxyl groups to assist flocculation between Cu-CDs and polyacrylamide, which facilitated the removal of PPD. Importantly, the intrinsic fluorescence of the as-prepared Cu-CDs could indicate the presence of hydroquinone, one of the substrates of laccases, based on laccase mimics and fluorescence quenching.

The relationship between DNA sequences and oligonucleotide-templated silver nanoclusters and their fluorescence properties

A novel approach was developed to study the relationship between DNA sequences and DNA-templated silver nanoclusters (DNA-Ag NCs) in detail by using an ordinary DNA strand as an example. Three kinds of Ag NCs are formed by using the DNA strand as a scaffold. By dividing the DNA template into several parts according to their different affinities to Ag(+) , it was found that the fluorescence properties of DNA-Ag NCs are related to not only the sequences but also to the position of different parts in the template, which provides a more efficient approach to obtain DNA-Ag NCs with required photoluminescence properties and may ultimately contribute to the targeted synthesis of DNA-Ag NCs.

Sensitive and selective detection of Hg2+ and Cu2+ ions by fluorescent Ag nanoclusters synthesized via a hydrothermal method

An easily prepared fluorescent Ag nanoclusters (Ag NCs) probe for the sensitive and selective detection of Hg(2+) and Cu(2+) ions was developed here. The Ag NCs were synthesized by using polymethacrylic acid sodium salt as a template via a convenient hydrothermal process. The as-prepared fluorescent Ag NCs were monodispersed, uniform and less than 2 nm in diameter, and can be quenched in the presence of mercury (Hg(2+)) or copper (Cu(2+)) ions. Excellent linear relationships existed between the quenching degree of the Ag NCs and the concentrations of Hg(2+) or Cu(2+) ions in the range of 10 nM to 20 μM or 10 nM to 30 μM, respectively. By using ethylenediaminetetraacetate (EDTA) as the masking agent of Cu(2+), Hg(2+) was exclusively detected in coexistence with Cu(2+) with high sensitivity (LOD = 10 nM), which also provided a reusable detection method for Cu(2+). Furthermore, the different quenching phenomena caused by the two metals ions such as changes in visible colour, shifts of UV absorbance peaks and changes in size of Ag NCs make it easy to distinguish between them. Therefore the easily synthesized fluorescent Ag NCs may have great potential as Hg(2+) and Cu(2+) ions sensors.