Selective and Sensitive Colorimetric Detection of Hg2+ at Wide pH Range Using Green Synthesized Silver Nanoparticles as Probe

N- and S-codoped carbon quantum dots for enhancing fluorescence sensing of trace Hg2

Carbon-quantum-dot-based fluorescence sensing of Hg2+ is a well-known cost-effective tactic with fast response and high sensitivity, while rationally constructing heteroatom-doped carbon quantum dots with improved fluorescence sensing performances through tuning the electronic and chemical structures of the reactive site still remains a challenging project for monitoring trace Hg2+ in aquatic ecosystems to avoid harm resulting from its high toxicity, nonbiodegradabilty and accumulative effects on human health. Herein, intriguing N,S-codoped carbon quantum dots were synthesized via a facile one-step hydrothermal procedure. As an admirable fluorescent probe with plentiful heteroatom-related functional groups, these N,S-codoped carbon quantum dots can exhibit an absolute fluorescence quantum yield as high as 11.6%, excellent solubility and stability over three months, remarkable sensitivity for Hg2+ detection with an attractive detection limit of 0.27 μg L-1 and admirable selectivity for Hg2+ against thirteen other metal ions. Density functional theory calculations reveal that electron-enriched meta-S of the unique graphitic N with homocyclic meta-thiophene sulfur structure can regulate this N site to have more electrons and preferable affinity towards Hg, hence achieving enhanced fluorescence quenching due to greater charge transfer from N to Hg after the coordination interaction. This strategy provides a promising avenue for precisely designing purpose-made quantum dots with the dedicated fluorescence sensing applications.

Rapid and efficient colorimetric sensing of clindamycin and Fe3+ using controllable phyto-synthesized silver/silver chloride nanoparticles by Syzygium cumini fruit extract

Abstract

The first evidence of a green, single-step, and additive-free process for the fabrication of silver/silver chloride nanoparticles (Ag/AgCl NPs) by fruit extract of Syzygium cumini (S. cumini) without the usage of any stabilizer and halide source was provided. The formation of nanoparticles was optimized to control the shape, size, and stability via various pHs of the reaction mixture, the quantity of fruit extract, temperature, concentrations of silver ion, and reaction time. The optimal conditions were determined: pH = 7.0, the quantity of the leaf extract = 3.0 mL, silver ion concentration = 1.0 mM, temperature = 60 °C, and incubation time = 40 min. As an application in colorimetric sensing, the ability of the prepared Ag/AgCl NPs to sense clindamycin and Fe3+ ion in an aqueous medium was investigated. The SPR band and color of the solution of Ag/AgCl NPs undergo dramatic changes in exposure to clindamycin with new SPR peaks appearing at 500 nm, accompanied by a color change from yellow to pink due to the aggregation of NPs. Under the optimized pH of 3.0, this sensor was shown a linear dynamic range from 10.0 to 100.0 µM with a LOD of 1.2 µM and good linear relationships (R2 = 0.99) for clindamycin. On the other hand, the quenching of the SPR peak at 412 nm was used to monitor the Fe3+ ions with wide linear ranges of 10.0–350.0 µM under the optimized pH (pH = 9) with a LOD of 5.6 µM. In addition, the proposed sensor displayed applicability in the real sample containing clindamycin (in capsules and injection ampoules) and Fe3+ ions (in water samples) detection.

Graphical Abstract

Colorimetric Detection of Ammonia Using Synthesized Silver Nanoparticles from Durian Fruit Shell

There has been increased interest in the production of nanoparticles (NP) through green chemistry. This article used durian fruit shell aqueous solution that acts as a reductive preparation of silver NPs. The silver nanoparticles have a size of approximately 25 nm. The NP size uniformity was determined by the SEM and TEM analysis. X-ray diffraction technique was used to characterize crystalline silver nanoparticles face-centered cubic structure. XPS spectrum showed distinct silver peaks on the nanoparticles’ surface. An optical method that was based on surface plasmon resonance (SPR) was used to perform the green Ag NPs aqueous ammonia sensing study. Optical measurement facilitated the ammonia sensing study of Ag NPs that had been prepared. The study also investigated the performance of the optical sensor, thus adding validity to the study. Also, the research sought to determine how the concentration of ammonia in ammonia sensing affects the Ag NPs that had been obtained. The study observed a linear relationship with R2 as the correlation factor which was equal to 0.9831. This was observed from the ammonia concentration plot versus absorption ratio that suggested that there was a linear increase in absorption ratio with increase in ammonia concentration. The study significance is that the room temperature optical ammonia sensor can be used in future for medical diagnosis in the detection of low levels of ammonia in biological fluid like sweat, cerebrospinal fluid, saliva, plasma, or biological samples. This enhances the application of the technique in human biomedical applications.

Colorimetric Detection of Mercury Ions in Water with Capped Silver Nanoprisms

The emission of mercury (II) from coal combustion and other industrial processes may have impacts on water resources, and the detection with sensitive but rapid testing methods is desirable for environmental screening. Towards this end, silver nanoprisms were chemically synthesized resulting in a blue reagent solution that transitioned towards red and yellow solutions when exposed to Hg²⁺ ions at concentrations from 0.5 to 100 µM. A galvanic reduction of Hg²⁺ onto the surfaces is apparently responsible for a change in nanoprism shape towards spherical nanoparticles, leading to the change in solution color. There were no interferences by other tested mono- and divalent metal cations in solution and pH had minimal influence in the range of 6.5 to 9.8. The silver nanoprism reagent provided a detection limit of approximately 1.5 µM (300 µg/L) for mercury (II), which compared reasonably well with other reported nanoparticle-based techniques. Further optimization may reduce this detection limit, but matrix effects in realistic water samples require further investigation and amelioration.

Low-temperature biosynthesis of silver nanoparticles using mango leaf extract: catalytic effect, antioxidant properties, anticancer activity and application for colorimetric sensing

Aqueous mango leaf extract was used as a reducing and capping agent for the biosynthesis of silver nanoparticles (AgNPs)viaa single-step, low cost and green process.

A novel electrochemical sensor based on a nickel-metal organic framework for efficient electrocatalytic oxidation and rapid detection of lactate

A novel Pt/Ni-MOF electrode was fabricated for the determination of lactate in cow-milk for the first time.