Elemental Mass Size Distribution for Characterization, Quantification and Identification of Trace Nanoparticles in Serum and Environmental Waters

Accurate characterization, quantification, and identification of nanoparticles (NPs) are essential to fully understand the environmental processes and effects of NPs. Herein, the elemental mass size distribution (EMSD), which measures particle size, mass, and composition, is proposed for the direct size characterization, mass quantification, and composition identification of trace NPs in complex matrixes. A one-step method for the rapid measurement of EMSDs in 8 min was developed through the online coupling of size-exclusion chromatography (SEC) with inductively coupled plasma mass spectrometry (ICP-MS). The use of a mobile phase with a relatively high ionic strength (a mixture of 2% FL-70 and 2 mM Na₂S₂O₃) ensured the complete elution of different-sized NPs from the column and, therefore, a size-independent response. After application of a correction for instrumental broadening by a method developed in this study, the size distribution of NPs by EMSD determination agreed closely with that obtained from transmission electron microscopy (TEM) analysis. Compared with TEM, EMSD allows a more rapid determination with a higher mass sensitivity (1 pg for gold and silver NPs) and comparable size discrimination (0.27 nm). The proposed EMSD-based method was capable of identifying trace Ag₂S NPs and core–shell nanocomposite Au@Ag, as well as quantitatively tracking the dissolution and size transformation of silver nanoparticles in serum and environmental waters

Highly Efficient Removal of Silver-Containing Nanoparticles in Waters by Aged Iron Oxide Magnetic Particles

Methods for the removal of silver nanoparticles (AgNPs) and their transformation products, silver-containing nanoparticles (AgCNPs), are important, because of their potential risks to the general population and the environment. In this study, aged iron oxide magnetic particles (IOMPs) were synthesized by a simple solvothermal reaction and used for the removal of AgCNPs. The prepared IOMPs exhibit a high adsorption capacity toward AgCNPs in aqueous medium. Kinetic studies indicated that the adsorption of AgCNPs is a pseudo-second-order process. The experimental data for the adsorption of AgCNPs follow the Langmuir isotherm model, and their maximum adsorption capacities were 19.9–62.8 mg/g at pH 6.2 and 298 K. The sorption mean free energy calculated by the Dubinin–Radushkevich isotherm was 4.09–5.17 kJ/mol, indicating the occurrence of physisorption, which was mainly due to the electrostatic interactions. The IOMP adsorbents maintained high removal efficiencies after four cycles of adsorption–desorption, suggesting good reusability of the developed IOMPs. Moreover, good removal efficiencies (63.3%–99.9%) and recoveries (67.1%–99.9%) were obtained from the real samples spiked with AgCNPs at levels of 10 μg/L, showing that the aged IOMPs could be used as efficient and low-cost adsorbents for the removal and recovery of AgCNPs from real waters

Highly Dynamic PVP-Coated Silver Nanoparticles in Aquatic Environments: Chemical and Morphology Change Induced by Oxidation of Ag⁰ and Reduction of Ag⁺

The fast growing and abundant use of silver nanoparticles (AgNPs) in commercial products alerts us to be cautious of their unknown health and environmental risks. Because of the inherent redox instability of silver, AgNPs are highly dynamic in the aquatic system, and the cycle of chemical oxidation of AgNPs to release Ag⁺ and reconstitution to form AgNPs is expected to occur in aquatic environments. This study investigated how inevitable environmentally relevant factors like sunlight, dissolved organic matter (DOM), pH, Ca²⁺/Mg²⁺, Cl^–, and S^2– individually or in combination affect the chemical transformation of AgNPs. It was demonstrated that simulated sunlight induced the aggregation of AgNPs, causing particle fusion or self-assembly to form larger structures and aggregates. Meanwhile, AgNPs were significantly stabilized by DOM, indicating that AgNPs may exist as single particles and be suspended in natural water for a long time or delivered far distances. Dissolution (ion release) kinetics of AgNPs in sunlit DOM-rich water showed that dissolved Ag concentration increased gradually first and then suddenly decreased with external light irradiation, along with the regeneration of new tiny AgNPs. pH variation and addition of Ca²⁺ and Mg²⁺ within environmental levels did not affect the tendency, showing that this phenomenon was general in real aquatic systems. Given that a great number of studies have proven the toxicity of dissolved Ag (commonly regarded as the source of AgNP toxicity) to many aquatic organisms, our finding that the effect of DOM and sunlight on AgNP dissolution can regulate AgNP toxicity under these conditions is important. The fact that the release of Ag⁺ and regeneration of AgNPs could both happen in sunlit DOM-rich water implies that previous results of toxicity studies gained by focusing on the original nature of AgNPs should be reconsidered and highlights the necessity to monitor the fate and toxicity of AgNPs under more environmentally relevant conditions

New Surface-Enhanced Raman Sensing Chip Designed for On-Site Detection of Active Ricin in Complex Matrices Based on Specific Depurination

Quick and accurate on-site detection of active ricin has very important realistic significance in view of national security and defense. In this paper, optimized single-stranded oligodeoxynucleotides named poly­(21dA), which function as a depurination substrate of active ricin, were screened and chemically attached on gold nanoparticles (AuNPs, ∼100 nm) via the Au–S bond [poly­(21dA)–AuNPs]. Subsequently, poly­(21dA)–AuNPs were assembled on a dihydrogen lipoic-acid-modified Si wafer (SH–Si), thus forming the specific surface-enhanced Raman spectroscopy (SERS) chip [poly­(21dA)–AuNPs@SH–Si] for depurination of active ricin. Under optimized conditions, active ricin could specifically hydrolyze multiple adenines from poly­(21dA) on the chip. This depurination-induced composition change could be conveniently monitored by measuring the distinct attenuation of the SERS signature corresponding to adenine. To improve sensitivity of this method, a silver nanoshell was deposited on post-reacted poly­(21dA)–AuNPs, which lowered the limit of detection to 8.9 ng mL^–1. The utility of this well-controlled SERS chip was successfully demonstrated in food and biological matrices spiked with different concentrations of active ricin, thus showing to be very promising assay for reliable and rapid on-site detection of active ricin

Time-Resolved Fluoroimmunoassay as an Advantageous Analytical Method for Assessing the Total Concentration and Environmental Risk of Fluoroquinolones in Surface Waters

Due to the widespread occurrence in the environment and potential risk toward organisms of fluoroquinolones (FQs), it is of importance to develop high efficient methods for assessing their occurrence and environmental risk. A monoclonal antibody (Mab) with broad cross-reactivity to FQs was produced by immunizing BALB/c mice with a synthesized immunogen prepared by conjugating ciprofloxacin with bovine serum albumin. This developed Mab (C2F3C2) showed broad and high cross-reactivity (40.3–116%) to 12 out of the 13 studied FQs. Using this Mab and norfloxacin conjugated with carrier protein ovalbumin as coating antigen, a time-resolved fluoroimmunoassay (TRFIA) method was developed for determining the total concentration of at least 12 FQs in environmental waters. The respective detection limit (LOD) and IC₅₀ calculated from the standard curve were 0.053 μg/L and 1.83 μg/L for enrofloxacin (ENR). The LODs of the other FQs, estimated based on the corresponding cross-reactivity and the LOD of ENR, were in the range of 0.051–0.10 μg/L. The developed TRFIA method showed good tolerance to various interfering substances present in environmental matrix at relevant levels, such as humic acids (0–10 mg/L DOC), water hardness (0–2% Ca²⁺ and Mg²⁺, w/v), and heavy metals (0–1 mg/L). The spiked recoveries estimated by spiking 0.5, 1, and 2 μg/L of five representative FQs into various water samples including paddy water, tap water, pond water, and river water were in the range of 63–120%. The measured total FQ concentration by TRFIA agreed well with that of liquid chromatography–tandem mass spectrometry and was applied to directly evaluate the occurrence and environmental risk of FQs in the surface water of a case area. TRFIA showed high efficiency and great potential in environmental risk assessment as it measures directly the total concentration of a class of pollutants

Au@Pd Bimetallic Nanocatalyst for Carbon–Halogen Bond Cleavage: An Old Story with New Insight into How the Activity of Pd is Influenced by Au

AuPd bimetallic nanocatalysts exhibit superior catalytic performance in the cleavage of carbon–halogen bonds (C–X) in the hazardous halogenated pollutants. A better understanding of how Au atoms promote the reactivity of Pd sites rather than vaguely interpreting as bimetallic effect and determining which type of Pd sites are necessary for these reactions are crucial factors for the design of atomically precise nanocatalysts that make full use of both the Pd and Au atoms. Herein, we systematically manipulated the coordination number of Pd–Pd, d-orbital occupation state, and the Au–Pd interface of the Pd reactive centers and studied the structure–activity relationship of Au–Pd in the catalyzed cleavage of C–X bonds. It is revealed that Au enhanced the activity of Pd atoms primarily by increasing the occupation state of Pd d-orbitals. Meanwhile, among the Pd sites formed on the Au surface, five to seven contiguous Pd atoms, three or four adjacent Pd atoms, and isolated Pd atoms were found to be the most active in the cleavage of C–Cl, C–Br, and C–I bonds, respectively. Besides, neighboring Au atoms directly contribute to the weakening of the C–Br/C–I bond. This work provides new insight into the rational design of bimetallic metal catalysts with specific catalytic properties