Molecular mechanism for the unusual enhancement of the second-step chemiluminescence production from the carcinogenic tetrabromohydroquinone and H2O2

We have found recently that two-step intrinsic hydroxyl radical (·OH)-dependent chemiluminescence (CL) could be produced by carcinogenic tetrahaloquinone and H2O2. However, the first-step CL was too fast to clearly detect the stepwise generation of ·OH and CL, and to distinguish the exact dividing point between the first-step and second-step CL. Here we found that, extremely clear two-step intrinsic CL could be produced by the relative slow reaction of tetrabromohydroquinone (TBHQ) with H2O2, which was directly dependent on the two-step ·OH generation. Interestingly, the second-step, but not the first-step CL production of TBHQ/H2O2 (CRET donor) was markedly enhanced by fluorescein (a typical xanthene dye, CRET acceptor) through a unique chemiluminescence resonance energy transfer (CRET) process. The novel CRET system of TBHQ/H2O2/fluorescein was successfully applied for the sensitive detection of TBHQ with the detection limit as low as 2.5 µmol/L. These findings will help to develop more sensitive and highly efficient CL or CRET systems and specific CL sensor to detect the carcinogenic haloquinones, which may have broad environmental applications.

Quercetin nanoparticles decorated on Arabic gum and polyvinyl alcohol composite as a film sensor for fluorescence detection of meropenem

Moving towards green chemistry to minimize the diverse effect of chemicals on human health and environment has become a great issue in chemistry. On the other hand, determination of pharmaceuticals is an important issue for both human health and environment. In this regard two natural and benign compounds such as quercetin a polyphenolic flavonoid and Arabic Gum (AG) a polysaccharide were used to construct a sensor for meropenem. Herein, a new method was established for the synthesis of AG and polyvinyl alcohol (PVA) composite decorated by quercetin nanoparticles (QUENPs) as a fluorimetric film sensor to measure meropenem. In order to embed QUENPs in the polymer composite substrate, first QUENPs were synthesized and then added to the prepared composite solution under optimal conditions. The characteristics of AG and PVA composite (AG-PVA) and AG-PVA composite decorated by QUENPs films (QUENPs-AG-PVA), before and after the addition of meropenem was studied by TEM, FT-IR and EDX-Mapping. The developed film sensor was placed in a holder made with 3D printer. The difference in the fluorescence intensity of the fabricated film before and after the addition of meropenem was taken as the signal for measuring meropenem. The effect of different parameters on the fabrication of film fluorimetric sensor such as the concentration of polymer solutions, the volume of QUENPs and the volume of glycerol were investigated. Factors affecting the measurement of meropenem such as pH, type of buffer, volume of meropenem solution added on the sensor and time were also investigated. Under the obtained optimum conditions, the calibration graph was linear in the concentration range of 50-800 ng mL-1 with a correlation coefficient (r) of 0.9976 and the detection limit was 42.6 ng mL-1. The relative standard deviation was 3.5% and 1.4%, for eight replicate determinations of 100 ng mL-1 and 400 ng mL-1 of meropenem, respectively. The proposed method was successfully utilized for determination of meropenem in blood serum, human urine and pharmaceutical samples.

Luminous Insights: Exploring Organic Fluorescent "Turn-On" Chemosensors for Metal-Ion (Cu+2, Al+3, Zn+2, Fe+3) Detection

There are several metal ions that are vital for the growth of the environmental field as well as for the biological field but only up to the maximum limit. If they are present in excess, it could be hazardous for the human health. With the growing technology, a series of various detection techniques are employed in order to recognize those metal ions, some of them include voltammetry, electrochemical methods, inductively couples, etc. However, these techniques are expensive, time consuming, requires large storage, advanced instrumentation, and a skilled person to operate. So, here comes the need of a sensor and it is defined as a miniature device which detects the substance of interest by giving response in the form of energy change. So, from past few decades, many sensors have been formulated for detecting metal ions with some basic characteristics like selectivity, specificity, sensitivity, high accuracy, lower detection limit, and response time. Detecting various metal ions by employing chemosensors involves different techniques such as fluorescence, phosphorescence, chemiluminescence, electrochemical, and colorimetry. The fluorescence technique has certain advantages over the other techniques. This review mainly focuses on the chemosensors that show a signal in the form of fluorescence to detect Al+3, Zn+2, Cu+2, and Fe+3 ions.

Nanomaterial-enhanced chemiluminescence reactions and their applications

Chemiluminescence (CL) analysis is a trace analytical method that possesses advantages including high sensitivity, wide linear range, easy operation, and simple instruments. With the development of nanotechnology, many nanomaterial (NM)-enhanced CL systems have been established in recent years and applied for the CL detection of metal ions, anions, small molecules, tumor markers, sequence-specific DNA, and RNA. This review summarizes the research progress of the nanomaterial-enhanced CL systems the past five years. These CL reactions include luminol, peroxyoxalate, lucigenin, ultraweak CL reactions, and so on. The CL mechanisms of the nanomaterial-enhanced CL systems are discussed in the first section. Nanomaterials take part in the CL reactions as the catalyst, CL emitter, energy acceptor, and reductant. Their applications are summarized in the second section. Finally, the challenges and opportunities are discussed.

A graphene quantum dot-assisted morin–KMnO4 chemiluminescence system for the precise recognition of cypermethrin

A novel and efficient chemiluminescence (CL) probe was developed for cypermethrin (CYPM) based on the sensitizing effect of graphene quantum dots (GQDs) on the morin–KMnO₄ CL reaction.