Integration detection of mercury(ii) and GSH with a fluorescent “on-off-on” switch sensor based on nitrogen, sulfur co-doped carbon dots

NS-CDs are employed as a sensitive sensor for the integration detection of Hg2+ and GSH. Hg2+ effectively quenching the fluorescence by static quenching. GSH is able to recover the fluorescence owing to the stronger binding between Hg2+ and GSH.

A study of the binding between radicicol and four proteins by means of spectroscopy and molecular docking

The interactions between radicicol and four proteins (catalase, trypsin, pepsin, and human serum protein) are investigated by spectroscopic techniques and molecular docking. A static quenching process is confirmed. The binding constant value between radicicol and human serum protein is the largest among the four proteins. Results reveal changes in the micro-environment of the protein by the addition of radicicol. It is found that radicicol shows an inhibitory effect on the activity of proteins (catalase, trypsin, and pepsin). Molecular docking results are consistent with the thermodynamic experimental results. This work provides clues to the elucidation of the mechanisms of the interactions between radicicol and proteins.

A Ground-State Complex Between Methyl Viologen and the Fluorescent Whitening Agent 4, 4’–bis (2-sulfostyryl)-biphenyl disodium salt: A Fluorescence Spectroscopy Study

This study explores the quenching of the dianionic fluorescent whitening agent, NFW, by various substances, including methyl viologen (MV), in water and in the presence of Beta-cyclodextrin (β-CD). Results of a fluorescence spectroscopic examination of the β-CD-NFW system are presented. It was found that NFW forms a 1:1 inclusion complex with β-CD with an association constant of 2540 ± 380 M^-1. The included NFW fluorescent state is protected by the β-CD cavity from a range of water-based quenchers (neutral, anionic and cationic). Quenching proceeds near the diffusion-controlled limit in water for the quenchers tested with the exception of the dicationic MV. MV is an extremely efficient quencher of NFW fluorescence with a nominal K_SV ~ 5.0x10³ M^-1 in water alone, corresponding to a nominal k_q of ~ 4x10¹² M^-1s^-1, which exceeds the diffusion-controlled limit in this solvent. The quenching efficiency of MV is strongly suppressed in the presence of 10 mM β-CD (K_SV = 105 ± 12 M^-1) and in the presence of NaCl (K_SV = 106 ± 9 M^-1 at 0.5 M salt). In the absence of CD or salt, there is a strong contribution from static quenching in the MV system; the presence of these additives suppresses the static quenching. Various results suggest the static quenching is due to formation of a ground-state complex between the dianion NFW and the dication MV.

Static quenching upon adduct formation: a treatment without shortcuts and approximations

Treatment of luminescence quenching upon adduct formation is often overlooked, leading to macroscopic errors. Here we provide a complete guide to its treatment, for correct mechanism assessment and to obtain reliable association constants.

Sensitive and selective determination of tetracycline in milk based on sulfur quantum dot probes

A SQD-based fluorescent probe was applied to detect TC based on the inner filter effect (IFE) and static quenching effect (SQE) without any extra surface modification for the first time.