Label-Free Highly Sensitive Detection of Proteins in Aqueous Solutions Using Surface-Enhanced Raman Scattering

We detected concentration-dependent surface-enhanced Raman scattering (SERS) spectra of several label-free proteins (lysozyme, ribonuclease B, avidin, catalase, and hemoglobin) for the first time in aqueous solutions. Acidified sulfate was used as an aggregation agent to induce high electromagnetic enhancement in SERS. Strong SERS spectra of simple and conjugated protein samples could easily be accessed after the pretreatment with the aggregation agent. The detection limits of the proposed method for lysozyme and catalase were as low as 5 μg/mL and 50 ng/mL, respectively. This detection protocol for label-free proteins has combined simplicity, sensitivity, and reproducibility and allows routine qualitative and relatively quantitative detections. Thus, it has great potential in practical high-throughput protein detections

Accelerated Sulfur Oxidation by Ozone on Surfaces of Single Optically Trapped Aerosol Particles

The sulfur oxidation in mixed sodium thiosulfate/sucrose/aqueous microdroplets by gaseous ozone is studied in this work via aerosol optical tweezers coupled with Raman spectroscopy, which can simultaneously determine various physicochemical properties and the heterogeneous reaction kinetics of single optically trapped microdroplets, allowing for elucidating their complicated interplay. According to the kinetics measurement results at different relative humidities, ozone concentrations, and stoichiometries of inorganic and organic solutes, this work finds that a high aerosol ionic strength can accelerate the ozone oxidation of thiosulfate at air–water interfaces, while a high aerosol viscosity prolongs the reaction time scales due to diffusion-limited kinetics. The kinetic multilayer model of aerosol surface and bulk chemistry (KM-SUB) is utilized to investigate the observed heterogeneous kinetics results and to retrieve the surface reaction rate coefficients. The KM-SUB model fit results indicate that the observed kinetics of sulfur oxidation in binary sodium thiosulfate aqueous microdroplets with high ionic strengths is dominated by interfacial reactions, and the fitted surface reaction rate coefficients increase 1 order of magnitude when the droplet ionic strength increases around 40 M. This work further utilizes the kinetics measurements of ozone dependence to discuss the coupling among properties of ozone gas-interface-bulk partitioning and surface reaction rate in the kinetics model. Finally, this work also exploits the surface reaction of thiosulfate with ozone to retrieve the aerosol viscosity of microdroplets containing ternary aqueous sodium thiosulfate and sucrose mixtures, demonstrating the feasibility of pinning down aerosol viscosities via reaction kinetics

Cranberry Beans Derived Carbon Dots as a Potential Fluorescence Sensor for Selective Detection of Fe³⁺ Ions in Aqueous Solution

Recently, synthesis, characterization, and application of carbon dots have received much attention. Natural products are the effectual carbon precursors to synthesize carbon dots with fascinating chemical and physical properties. In this study, the fluorescent sensor of carbon dots derived from cranberry beans without any functionalization and modification was developed. The carbon dots were prepared with a cheap, facile, and green carbon precursor through a hydrothermal treatment method. The synthetic process was toxic chemical-free, convenient, and environmentally friendly. To find the optimized synthetic conditions, the temperature, heating time duration, and carbon precursor weight were evaluated. The prepared carbon dots were characterized by UV light, transmission electron microscopy, Raman, Fourier transform infrared, UV–vis, and fluorescence spectroscopy. The resulting carbon dots exhibit stable fluorescence with a quantum yield of approximately 10.85%. The carbon dots emitted the broad fluorescence emission range between 410 and 540 nm by changing the excitation wavelength and were used for the detection of Fe3+ ions at the excitation of 380 nm. It is found that Fe3+ ions induced the fluorescence intensity quenching of the carbon dots stronger than other heavy metals and the Fe3+ ion detection can be achieved within 3 min. Spectroscopic data showed that the obtained carbon dots can detect Fe3+ ions within the wide concentration range of 30–600 μM with 9.55 μM detection limit

Rhenium-Based Molecular Trap as an Evanescent Wave Infrared Chemical Sensing Medium for the Selective Determination of Amines in Air

An evanescent wave infrared chemical sensor was developed to selectively detect volatile amines with heterocyclic or phenyl ring. To achieve this goal, a rhenium-based metallacycle with a “molecular-trap” structure was designed and synthesized as host molecules to selectively trap amines with heterocyclic or phenyl ring through Re–amine and π–π interactions. To explore the trapping properties of the material, a synthesized Re-based molecular trap was treated on an IR sensing element, and wide varieties of volatile organic compounds (VOCs) were examined to establish the selectivity for detection of amines. Based on the observed IR intensities, the Re-based molecular trap favors interaction with amines as evidenced by the variation of absorption bands of the Re molecular trap. With extra π–π interaction force, molecules, such as pyridine and benzylamine, could be detected. After optimization of the parameters for IR sensing, a rapid response in the detection of pyridine was observed, and the linear ranges were generally up to 10 mg/L with a detection limit around 5.7 μg/L. In the presence of other VOCs, the recoveries in detection of pyridine were all close to 100%

Single-Step Preparation of Silver-Doped Magnetic Hybrid Nanoparticles for the Catalytic Reduction of Nitroarenes

This study adopts a simple but facile process for preparing silver-doped magnetic nanoparticles by the spontaneous oxidation–reduction/coprecipitation method. The preparation can be achieved in one pot with a single step, and the prepared silver-doped magnetic nanoparticles were utilized as nanocatalysts for the reduction of <i>o</i>-nitroaniline. Utilizing the magnetic characteristics of the prepared nanoparticles, the catalytic reactions can be carried out under quasi-homogeneous condition and the nanocatalysts can be easily collected after the conversion is achieved. It can be revealed from the results that the morphologies and the composition of the prepared silver-doped magnetic nanoparticles can be adjusted by changing the conditions during the production, which affects the efficacy of the catalysis. In addition, the catalysis efficiency is also controlled by the pH, temperature, and the amounts of nanocatalysts used during the catalytic reaction. Finally, the silver-doped magnetic nanocatalysts prepared in this study own the advantages of easy preparation, room-temperature catalysis, high conversion ability, and recyclability, which make them more applicable in real utilities