Cloud point extraction (CPE) combined with single particle -inductively coupled plasma-mass spectrometry (SP-ICP-MS) to analyze and characterize nano-silver sulfide in water environment

Characterizing the Stoichiometry of Individual Metal Sulfide and Phosphate Colloids in Soils, Sediments, and Industrial Processes by Inductively Coupled Plasma Time-of-Flight Mass Spectrometry

Size and purity of metal phosphate and metal sulfide colloids can control the solubility, persistence, and bioavailability of metals in environmental systems. Despite their importance, methods for detecting and characterizing the diversity in the elemental composition of these colloids in complex matrices are missing. Here, we develop a single-particle inductively coupled plasma time-of-flight mass spectrometry (sp-icpTOF-MS) approach to characterize the elemental compositions of individual metal phosphate and sulfide colloids extracted from complex matrices. The stoichiometry was accurately determined for particles of known composition with an equivalent spherical diameter of ≥∼200 nm. Assisted by machine learning (ML), the new method could distinguish particles of the copper sulfides covellite (CuS), chalcocite (Cu2S), and chalcopyrite particles (CuFeS2) with 75% (for Cu2S) to 99% (for CuFeS2) accuracy. Application of the sp-icpTOF-MS method to particles recovered from natural samples revealed that iron sulfide (FeS) particles in lake sediment contained ∼4% copper and zinc impurities, whereas pure pyrite (FeS2) was identified in hydraulic fracturing wastewater and confirmed by selected area electron diffraction. Colloidal mercury in an offshore marine sediment was present as pure mercury sulfide (HgS), whereas geogenic HgS recovered from an industrial process contained ∼0.08 wt % silver per Hg, enabling source apportionment of these colloids using ML. X-ray absorption spectroscopy confirmed that Hg was predominantly present as metacinnabar (β-HgS) in the industrial process sample. The determination of impurities in individual colloids, such as zinc and copper in FeS, and silver in HgS may enable improved assessment of their origin, reactivity, and bioavailability potential.

Basic and advanced spectrometric methods for complete nanoparticles characterization in bio/eco systems: current status and future prospects

The use of engineered nanoparticles in the environment and human life has increased in the last 20 years. The risk assessment concerning application of nanomaterials in biological systems requires their thorough characterization. Understanding the correlations between physicochemical properties of nanoparticles concerning not only the size, particle size distribution, number concentration, degree of aggregation, or agglomeration but also solubility, stability, binding affinity, surface activity, chemical composition, and nanoparticle synthesis yield allows their reliable characterization. Thus, to find the structure-function/property relationship of nanoparticles, multifaceted characterization approach based on more than one analytical technique is required. On the other hand, the increasing demand for identification and characterization of nanomaterials has contributed to the continuous development of spectrometric techniques which enables for their qualitative and quantitative analysis in complex matrices giving reproducible and reliable results. This review is aimed at providing a discussion concerning four main aspects of nanoparticle characterization: nanoparticle synthesis yield, particle size and number concentration, elemental and isotopic composition of nanoparticles, and their surface properties. The conventional and non-conventional spectrometric techniques such as spectrophotometry UV-Vis, mass spectrometric techniques working in conventional and single-particle mode, or those based on optical emission detection systems are described with special emphasis paid on their advantages and drawbacks. The application and recent advances of these methods are also comprehensively reviewed and critically discussed.

Synthesis and Characterization of Boehmite Particles Obtained from Recycling: Water Disinfection Application

We report on the synthesis of boehmite aluminum oxide hydroxide particles with lamellar structure (γ-AlO(OH)) obtained from the recycling of metallic can seals, with the addition of silver nanoparticles (Ag-NPs) reduced by Aloe Vera extract. X-ray diffractometry (XRD) confirmed the γ-phase, and scanning electron microscopy (SEM) showed the presence of Ag-NPs on the boehmite particle surface, confirming the efficiency of the synthesis to obtain the composite material. The samples were used to treat lake water, according to the Standard Methods for the Examination of Water and Wastewater. The results indicated that the elimination of total coliforms and Escherichia coli occurred, with excellent efficiency for the Ag-boehmite sample. The tests show the possibility of reuse (5×) of the sample, as it maintained the efficiency of disinfection for E. coli. The preparation, use, and reuse of boehmite obtained from metallic waste is a case of a circular economy, focused on sustainability and green chemistry.

Fluorescent indicators for live-cell and in vitro detection of inorganic cadmium dynamics

Cadmium contamination is a severe threat to the environment and food safety. Thus, there is an urgent need to develop highly sensitive and selective cadmium detection tools. The engineered fluorescent indicator is a powerful tool for the rapid detection of inorganic cadmium in the environment. In this study, the development of yellow fluorescent indicators of cadmium chloride by inserting a fluorescent protein at different positions of the high cadmium-specific repressor and optimizing the flexible linker between the connection points is reported. These indicators provide a fast, sensitive, specific, high dynamic range, and real-time readout of cadmium ion dynamics in solution. The excitation and emission wavelength of this indicator used in this work are 420/485 and 528 nm, respectively. Fluorescent indicators N0C0/N1C1 showed a linear response to cadmium concentration within the range from 10/30 to 50/100 nM and with a detection limit of 10/33 nM under optimal condition. Escherichia coli cells containing the indicator were used to further study the response of cadmium ion concentration in living cells. E. coli N1C1 could respond to different concentrations of cadmium ions. This study provides a rapid and straightforward method for cadmium ion detection in vitro and the potential for biological imaging.