Single Gold Nanoparticle-Based Colorimetric Detection of Picomolar Mercury Ion with Dark-Field Microscopy

Mercury severely damages the environment and human health, particularly when it accumulates in the food chain. Methods for the colorimetric detection of Hg²⁺ have increasingly been developed over the past decade because of the progress in nanotechnology. However, the limits of detection (LODs) of these methods are mostly either comparable to or higher than the allowable maximum level (10 nM) in drinking water set by the US Environmental Protection Agency. In this study, we report a single Au nanoparticle (AuNP)-based colorimetric assay for Hg²⁺ detection in solution. AuNPs modified with oligonucleotides were fixed on the slide. The fixed AuNPs bound to free AuNPs in the solution in the presence of Hg²⁺ because of oligonucleotide hybridization. This process was accompanied by a color change from green to yellow as observed under an optical microscope. The ratio of changed color spots corresponded with Hg²⁺ concentration. The LOD was determined as 1.4 pM, which may help guard against mercury accumulation. The proposed approach was applied to environmental samples with recoveries of 98.3 ± 7.7% and 110.0 ± 8.8% for Yuquan River and industrial wastewater, respectively

Low Serum Levels of Vitamins A, D, and E Are Associated with Recurrent Respiratory Tract Infections in Children Living in Northern China: A Case Control Study

<div><p>Background</p><p>This study aimed to investigate the association of serum concentrations of vitamin A, D, and E with recurrent respiratory tract infections (RRTIs).</p><p>Methods</p><p>A total of 1200 children aged at 0.5–14 years were selected via a face-to-face survey in Harbin, China. Among the participants, 600 children with RRTIs comprised the symptomatic group (RRTI group), whereas 600 healthy children were used as controls (control group). Blood samples were collected to measure serum levels of vitamins A and E by HPLC; the serum level of 25-hydroxycholecalciferol (25(OH)D), was measured by HPLC-MS/MS.</p><p>Results</p><p>Serum levels of vitamins A and E, as well as 25(OH)D, were significantly lower in the RRTI group than the control group. The conditional logistic regression model and the receiver-operating characteristic curve showed that the insufficiency or deficiency of vitamins A, D, and E was positively correlated with RRTI occurrence (<i>p</i> < 0.05).</p><p>Conclusions</p><p>Low serum concentrations of vitamins A, D, and E were associated with RRTIs in children from northern China.</p></div

Diagnostic Criteria of RRTIs.

<p>Diagnostic Criteria of RRTIs.</p

Vitamin A, D, and E concentrations.

<p>Vitamin A, D, and E concentrations.</p

Sensing Active Heparin by Counting Aggregated Quantum Dots at Single-Particle Level

Developing highly sensitive and highly selective assays for monitoring heparin levels in blood is required during and after surgery. In previous studies, electrostatic interactions are exploited to recognize heparin and changes in light signal intensity are used to sense heparin. In the present study, we developed a quantum dot (QD) aggregation-based detection strategy to quantify heparin. When cationic micelles and fluorescence QDs modified with anti-thrombin III (AT III) are added into heparin sample solution, the AT III-QDs, which specifically bind with heparin, aggregate around the micelles. The aggregated QDs are recorded by spectral imaging fluorescence microscopy and differentiated from single QDs based on the asynchronous process of blue shift and photobleaching. The ratio of aggregated QD spots to all counted QD spots is linearly related to the amount of heparin in the range of 4.65 × 10 ^–4 U/mL to 0.023 U/mL. The limit of detection is 9.3 × 10 ^–5 U/mL (∼0.1 nM), and the recovery of the spiked heparin at 0.00465 U/mL (∼5 nM) in 0.1% human plasma is acceptable

BMI-for-age, with WBC and HGB levels.

<p>BMI-for-age, with WBC and HGB levels.</p

Associated factors screened in logistic regression model.

<p>Associated factors screened in logistic regression model.</p

Porous Ti/Zr Microspheres for Efficient Transfer Hydrogenation of Biobased Ethyl Levulinate to γ‑Valerolactone

γ-Valerolactone (GVL) is one of the versatile platform molecules and biofuel additives derived from the lignocellulosic biomass. Herein, the efficient synthesis of GVL from biobased ethyl levulinate (EL) using alcohol as both H-donor and solvent without an external hydrogen source has been achieved over porous Ti/Zr microspheres. The catalysts (Ti_<i>x</i>Zr_<i>y</i>) with different Ti/Zr molar ratios were synthesized using hexadecylamine (HDA) as a structure-directing agent via a sol–gel process combined with solvothermal treatment and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermal gravimetric analysis, NH₃/CO₂-TPD, N₂ adsorption–desorption, and pyridine-IR. A high GVL yield of 90.1% at 100% EL conversion was obtained at 180 °C for 6 h over Ti₂Zr₈ in 2-propanol. The microspheric and porous structure, enhanced surface areas, and acid/base contents by the proper introduction of Ti species into Zr oxide were demonstrated to be responsible for the pronounced performance. The microspheric Ti₂Zr₈ porous catalyst could be reused at least six times with no decrease in catalytic activity

Highly Recyclable Fluoride for Enhanced Cascade Hydrosilylation–Cyclization of Levulinates to γ‑Valerolactone at Low Temperatures

A facile and benign catalytic route has been developed to quantitatively yield γ-valerolactone (GVL; ca. 97%) from biomass-based levulinates at room temperature to 80 °C by using easily available polymethylhydrosiloxane (PMHS) and KF as the liquid H-donor and recyclable catalyst, respectively. No extra step was required to liberate GVL from the in situ-formed siloxane, and this catalytic system exhibited a lower activation energy (40.9 kJ/mol) compared to previously reported ones. The deuterium-labeled study further demonstrated the reaction proceeding through cascade hydrosilylation and cyclization with fluoride successively acting as the nucleophile and base. In addition, the PMHS-derived resin was extremely favorable to restrain the leaching of fluoride and maintain its constant activity for at least six cycles

Highly Recyclable Fluoride for Enhanced Cascade Hydrosilylation–Cyclization of Levulinates to γ‑Valerolactone at Low Temperatures

A facile and benign catalytic route has been developed to quantitatively yield γ-valerolactone (GVL; ca. 97%) from biomass-based levulinates at room temperature to 80 °C by using easily available polymethylhydrosiloxane (PMHS) and KF as the liquid H-donor and recyclable catalyst, respectively. No extra step was required to liberate GVL from the in situ-formed siloxane, and this catalytic system exhibited a lower activation energy (40.9 kJ/mol) compared to previously reported ones. The deuterium-labeled study further demonstrated the reaction proceeding through cascade hydrosilylation and cyclization with fluoride successively acting as the nucleophile and base. In addition, the PMHS-derived resin was extremely favorable to restrain the leaching of fluoride and maintain its constant activity for at least six cycles