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.

Synthesis of highly stable fluorescent poly(methacrylic acid-co-itaconic)-protected silver nanoclusters and sensitive detection of Cu2

Stable fluorescent silver nanoclusters (AgNCs) were synthesized through one-step UV photoreduction using the multiple carboxyl copolymer poly(methacrylic acid-co-itaconic acid) P(MAA-co-IA) as a novel template. The fluorescence lifetime and the quantum yield of the obtained AgNCs were 1.84 ns and 8.9% in an aqueous solution, respectively. Owing to the multiple carboxyls of the protective P(MAA-co-IA) template, the obtained AgNCs have excellent advantages such as good dispersity, and high stability, which make them suitable for highly sensitive and selective detection of Cu²⁺ by fluorescence quenching. A good linear relationship exists between the degree of fluorescence quenching for silver nanoclusters and Cu²⁺ concentration ranging from 0 to 10 μM. The limit of detection (LOD) is 6.36 nM. The result implies that the as-synthesized AgNCs show great potential in the analysis field.

Chitosan-stabilized silver nanoclusters with luminescent, photothermal and antibacterial properties

The aim of this paper is to achieve in situ photochemical synthesis of silver nanoclusters (AgNCs) stabilized by the multiple-amine groups of chitosan (Ch@AgNCs) with luminescent and photothermal properties. Ch@AgNCs were obtained by applying a fast and simple methodology previously described by our group. Direct functionalization of AgNCs with chitosan template provided new nanohybrids directly in water solution, both in the presence or absence of oxygen. The formation of hybrid AgNCs could be monitored by the rapid increase of the absorption and emission maximum band with light irradiation time. New Ch@AgNCs not only present photoluminescent properties but also photothermal properties when irradiated with near infrared light (NIR), transducing efficiently NIR into heat and increasing the temperature of the medium up to 23 °C. The chitosan polymeric shell associated to AgNCs works as a protective support stabilizing the metal cores, facilitating the storage of nanohybrids and preserving luminescent, photothermal and bactericide properties.

Europium-functionalized luminescent titania nanotube arrays: Utilizing interactions with glucose, cholesterol and triglycerides for rapid detection application

In this work, titania nanotube arrays (TiO₂-NTs) were prepared by anodization, and the Eu(III) complexes (Eu (TTA)₃ phen with 2-thenoyltrifluoroacetone (TTA) and 1, 10-phenanthroline (phen)) were successfully coated onto the walls of the nanotubes. When a solution of glucose, cholesterol or triglycerides was dropped onto Eu(III) complex-modified TiO₂-NTs, the fluorescence intensity of this material changes (glucose enhances fluorescence, cholesterol and triglycerides quench fluorescence). These phenomena are explained via an energy transfer process. The sensitivity of the fluorescence intensity to glucose, cholesterol or triglycerides concentration enables design of a multifunctional solid sheet-like detector. Under optimized experimental conditions, the change in fluorescence intensity ratio (ΔF/F₀) is linear with the concentration of glucose, cholesterol or triglycerides. To test the utility of the detector, glucose in orange juice, cholesterol in milk powder, and triglycerides in coconut oil were measured using this method and the results were in good agreement analytical data provided by a food testing company. The new method proposed here is simple, sensitive, reliable and suitable for practical applications.

Dual-emitting zein-protected gold nanoclusters for ratiometric fluorescence detection of Hg2+/Ag+ ions in both aqueous solution and self-assembled protein film

An abundant plant-sourced protein, zein, is used to prepare fluorescent Au nanoclusters as a promising alternative to animal/microorganism proteins.