Halogen-bonding-promoted Photo-induced C–X Borylation of Aryl Halide using Phenol Derivatives

This study investigates the photo-induced C–X borylation reaction of aryl halides by forming a halogen-bonding complex. The method employs 2-naphthol as a halogen-bonding acceptor and proceeds under mild conditions without a photoredox catalyst under 420 nm blue light irradiation. The method is highly chemoselective, broadly functional group tolerant, and provides concise access to corresponding boronate esters. Mechanistic studies reveal that forming the halogen-bonding complex between aryl halide and naphthol acts as an electron donor-acceptor complex to furnish aryl radicals through photo-induced electron transfer.

An efficient 2-aminothiazolesalicylaldehyde Fluorescent Chemosensor for Fe2+ ion Detection and Potential Inhibitor of NUDT5 Signaling Hormone for Breast Cancer Cell and Molecular Keypad Lock Application

A novel thiazole phenol conjugate 2-aminothiazolesalicylaldehyde (receptor1) was designed and synthesized for the first time through a single step process via schiff base condensation reaction. The formation of receptor1 was confirmed by FTIR, 13C NMR and 1H NMR. The receptor1 complexing with various metal ions studied through fluorescence spectroscopy showed its selectivity towards Fe2+ ion following a reverse photo induced electron transfer (PET) process compared to all other potentially competing ions. Furthermore, the receptor1 showed excellent reversibility property on adding EDTA solution. The binding affinity between receptor1-Fe2+ ion was found to be Ka = 2.22x102 M-1 and the sensing affinity of receptor1 towards Fe2+ ion at nanolevel concentration was 33.7x10-9 M which is lower than the detection limit of existing Schiff base. The receptor1 was used to detect Fe2+ ion in different water samples. Using molecular docking the chelating function of ligand (receptor1) was assessed as a potential inhibitor of NUDT5, a silence hormone signaling for breast cancer. The excellent reversibility property is used to construct INHIBIT molecular logic gate.

Carbon Dots: Synthesis, Properties and Applications

Carbon dots (CDs) are known as the rising star of carbon-based nanomaterials and, by virtue of their unique structure and fascinating properties, they have attracted considerable interest in different fields such as biological sensing, drug delivery, photodynamic therapy, photocatalysis, and solar cells in recent years. Particularly, the outstanding electronic and optical properties of the CDs have attracted increasing attention in biomedical and photocatalytic applications owing to their low toxicity, biocompatibility, excellent photostability, tunable fluorescence, outstanding efficient up-converted photoluminescence behavior, and photo-induced electron transfer ability. This article reviews recent progress on the synthesis routes and optical properties of CDs as well as biomedical and photocatalytic applications. Furthermore, we discuss an outlook on future and potential development of the CDs based biosensor, biological dye, biological vehicle, and photocatalysts in this booming research field.

Direct evidence for metallic mercury causing photo-induced darkening of red cinnabar tempera paints

Photo-induced darkening of red cinnabar (HgS) has attracted the interest of many researchers as it drastically impacts the visual perception of artworks. Darkening has commonly been related to metallic mercury (Hg0) formation in the presence of chlorides. Based on the study of UV-aged cinnabar pigment and tempera paint we propose an alternative pathway for the blackening reaction of cinnabar, considering its semiconductor properties and pigment-binder interactions. We demonstrate that darkening is caused by the oxidation of cinnabar to mercury sulfates and subsequent reduction to Hg0 via photo-induced electron transfer without the involvement of chlorides, and provide direct evidence for the presence of Hg0 on UV-aged tempera paint. Photooxidation also affects the organic binder, causing a competing depletion of photo-generated holes and consequently limiting but not impeding mercury sulfate formation and subsequent reduction to Hg0. In addition, organics provide active sites for Hg0 sorption, which is ultimately responsible for the darkening of cinnabar-based paint.

A Novel Calix[4]Crown-Based 1,3,4-Oxadiazole as a Fluorescent Chemosensor for Copper(II) Ion Detection

The synthesis and characterization of a novel florescent chemosensor 1 with two different types of cationic binding sites have been reported in this work, which is a calix[4]crown derivative in 1,3-alternate conformation bearing two 2-phenyl-5-(4-dimethylaminopyenyl)-1,3,4-oxadiazole units. The recognition behaviors of 1 in dichloromethane/acetonitrile solution to alkali metal ions (Na+ and K+), alkaline earth metal ions (Mg2+ and Ca2+), and transition metal ions (Co2+, Ni2+, Zn2+, Cd2+, Cu2+, Mn2+, and Ag+) have been investigated by UV-Vis and fluorescence spectra. The fluorescence of 1 might be quenched selectively by Cu2+ due to the photo-induced electron transfer mechanism, and the quenched emission from 1 could be partly revived by the addition of Ca2+ or Mg2+; thus, the receptor 1 might be worked as an on–off switchable fluorescent chemosensor triggered by metal ion exchange.

Donor-Acceptor Pyridinium Salts for Photo-Induced Electron Transfer Driven Modification of Tryptophan in Peptides, Proteins, and Proteomes using Visible Light

Tryptophan (Trp) plays a variety of critical functional roles in protein biochemistry however, owing to its low natural frequency and poor nucleophilicity, the design of effective methods for both single protein bioconjugation at Trp as well as for in situ chemoproteomic profiling re-mains a challenge. Here, we report a method for covalent Trp modification that is suitable for both scenarios by invoking photo-induced electron transfer (PET) as a means of driving efficient reactivity. We have engineered biaryl N-carbamoyl pyridinium salts that possess a donor-acceptor relationship enabling optical triggering with visible light whilst simultaneously attenuating the probe’s photo-oxidation potential in order to prevent photodegradation. This probe was assayed against a small bank of eight peptides and proteins, where it was found that micromolar concentrations of probe and short irradiation times (10-60 min) with violet light enabled efficient reactivity towards surface exposed Trp residues. The carbamate transferring group can be used to transfer useful functional groups to proteins including affinity tags and click handles. DFT calculations and other mechanistic analyses reveal correlations between excited state lifetimes, relative fluorescent quantum yields, and chemical reactivity. Biotinylated and azide-functionalized pyridinium salts were used for Trp profiling in HEK293T lysates and in situ in HEK293T cells using 450 nm LED irradiation. Peptide level enrichment from live cell labelling experiments identified 290 Trp modifications, with an 82% selectivity for Trp modification over other π-amino acids; demonstrating the ability of this method to identify and quantify reactive Trp residues from live cells.

Molecularly Imprinted Silica-Coated CdTe Quantum Dots for Fluorometric Determination of Trace Chloramphenicol

A dual recognition system with a fluorescence quenching of quantum dots (QDs) and specific recognition of molecularly imprinted polymer (MIP) for the detection of chloramphenicol (CAP) was constructed. MIP@SiO2@QDs was prepared by reverse microemulsion method with 3-aminopropyltriethoxysilane (APTS), tetraethyl orthosilicate (TEOS) and QDs being used as the functional monomer, cross-linker and signal sources, respectively. MIP can specifically recognize CAP, and the fluorescence of QDs can be quenched by CAP due to the photo-induced electron transfer reaction between CAP and QDs. Thus, a method for the trace detection of CAP based on MIP@SiO2@QDs fluorescence quenching was established. The fluorescence quenching efficiency of MIP@SiO2@QDs displayed a desirable linear response to the concentration of CAP in the range of 1.00~4.00 × 102 μmol × L−1, and the limit of detection was 0.35 μmol × L−1 (3σ, n = 9). Importantly, MIP@SiO2@QDs presented good detection selectivity owing to specific recognition for CAP, and was successfully applied to quantify CAP in lake water with the recovery ranging 102.0~104.0%, suggesting this method has the promising potential for the on-site detection of CAP in environmental waters.

Preparation and characterization of novel Yellow-Green fluorescent polymerizable dye and its copolymer with application of highly selective sensor for cations iron

Purpose In this work, A new 4–(2-aminoethylene) amino-N-(2-hydroxyethyl)-1,8-naphthalimide with intense green fluorescent was synthesized. This low molecular weight compound was immobilized by forming a covalent-bond with an acrylonitrile polymer containing carboxylic acid groups. The new prepared dye and self-coloured polymer were characterized by analytical techniques. Design/methodology/approach The synthesized compounds were characterized by TLC, DSC, FTIR, 1HNMR, 13CNMR, GPC, UV–visible and Fluorometery. The photophysical characteristics of the dye and polymer containing naphthalimide moiety in the side chain, were measured both in the absence and in the presence of Ag+, Cd+2, Co+2, Cr+3, Cu+2, Fe+3, Hg+2, Ni+2, Pb+2 and Zn+2 cations. Findings The results showed that the characterization of the synthesized dye and its polymer verified their structural correctness. It is shown that dye and polymer are photo-induced electron transfer (PET) fluorescent sensors which exhibit fluorescence quenching in the presence of metal ions. Among the various metal ions, both dye and polymer are more sensitive to Fe+3 cations. Originality/value This study is original. A 4–(2-aminoethylene) amino-N-(2-hydroxyethyl)-1,8-naphthalimide and its self-coloured polymer were synthesized for the first time, successfully.

Estimating the Prevalence of Asymptomatic Malaria Parasite Carriage in Southern Ghana: Utility of Molecular and Serological Diagnostic Tools

Background. Asymptomatic malaria infections can serve as potential reservoirs for malaria transmission. These infections range from microscopic to submicroscopic densities, making an accurate estimation of asymptomatic parasite carriage highly dependent on the sensitivity of the tool used for the diagnosis. This study sought to evaluate the sensitivities of a variety of molecular and serological diagnostic tool at determining the prevalence of asymptomatic Plasmodium falciparum parasite infections in two communities of varying malaria parasite prevalence.Methods. Whole blood from 194 afebrile participants aged between 6- and 70-years old living in a high (Obom) and a low (Asutsuare) malaria transmission setting of Ghana was used in this study. Thick and thin blood smears, an HRP2-based malaria rapid diagnostic test (RDT) and filter paper dried blood spots (DBS) were prepared from each blood sample. Genomic DNA was extracted from the remaining blood and used in Plasmodium specific photo-induced electron transfer polymerase chain reaction (PET-PCR) and Nested PCR, whilst the HRP2 antigen content of the DBS was estimated using a bead immunoassay. Comparison of prevalence as determined by each method was performed.Results. Parasite prevalence in the high transmission site of Obom was estimated at 71.4%, 61.9%, 60%, 37.8% and 19.1% by Nested PCR, the HRP2 bead assay, PET-PCR, HRP2-RDT and microscopy respectively. Parasite prevalence in the low transmission site of Asutsuare was estimated at 50.1%, 11.2%, 5.6%, 0% and 2.2% by Nested PCR, the HRP2 bead assay, PET-PCR, RDT and microscopy respectively.Conclusions: Nested PCR exhibited the highest sensitivity by identifying the highest prevalence of asymptomatic P. falciparum in both the high and low parasite prevalence setting. However, parasite prevalence estimated by the HRP2 bead assay and PET-PCR had the highest level of inter-rater agreement relative to all the other tools tested and have the advantage of requiring fewer processing steps and producing quantitative results relative Nested PCR. These advantages make PET-PCR and the HRP2 bead assay very useful tools for estimating malaria parasite prevalence in community surveys in these settings.