Highly Reproducible Ag NPs/CNT-Intercalated GO Membranes for Enrichment and SERS Detection of Antibiotics

The increasing pollution of aquatic environments by antibiotics makes it necessary to develop efficient enrichment and sensitive detection methods for environmental antibiotics monitoring. In this work, silver nanoparticles and carbon nanotube-intercalated graphene oxide laminar membranes (Ag NPs/CNT-GO membranes) were successfully prepared for enrichment and surface-enhanced Raman scattering (SERS) detection of antibiotics. The prepared Ag NPs/CNT-GO membranes exhibited a high enrichment ability because of the π–π stacking and electrostatic interactions of GO toward antibiotic molecules, which enhanced the sensitivity of SERS measurements and enabled the antibiotics to be determined at sub-nM concentrations. In addition, the nanochannels created by the intercalation of CNTs into GO layers resulted in an 8-fold enhancement in the water permeance of Ag NPs/CNT-GO membranes compared to that of pure GO membranes. More importantly, the Ag NPs/CNT-GO membranes exhibited high reproducibility and long-term stability. The spot-to-spot variation in SERS intensity was less than 15%, and the SERS performance was maintained for at least 70 days. The Ag NPs/CNT-GO membranes were also used for SERS detection of antibiotics in real samples; the results showed that the characteristic peaks of antibiotics were obviously recognizable. Thus, the sensitive SERS detection of antibiotics based on Ag NPs/CNT-GO offers great potential for practical applications in environmental analysis

Partial-Redox-Promoted Mn Cycling of Mn(II)-Doped Heterogeneous Catalyst for Efficient H₂O₂‑Mediated Oxidation

The development of a heterogeneous catalyst with high catalytic activity and durability for H₂O₂-mediated oxidation is one of the most important industrial and environmental issues. In this study, a Mn­(II)-doped TiO₂ heterogeneous catalyst was developed for H₂O₂-mediated oxidation. The TiO₂ substrate-dependent partial-redox behavior of Mn was identified on the basis of our density functional theory simulations. This unique redox cycle was induced by a moderate electron transfer from Ti to Mn, which compensated for the electron loss of Mn and finally resulted in a high-efficiency cycling of Mn between its oxidized and reduced forms. In light of the theoretical results, a Mn­(II)-doped TiO₂ composite with well-defined morphology and large surface area (153.3 m² g^–1) was elaborately fabricated through incorporating Mn­(II) ions into a TiO₂ nanoflower, and further tested as the catalyst for oxidative degradation of organic pollutants in the presence of H₂O₂. Benefiting from the remarkable textural features and excellent Mn cycling property, this composite exhibited superior catalytic performance for organic pollutant degradation. Moreover, it could retain 98.40% of its initial activity even in the fifth cycle. Our study provides an effective strategy for designing heterogeneous catalytic systems for H₂O₂-mediated oxidations

The effects of genetic variation and environmental factors on rhynchophylline and isorhynchophylline in <i>Uncaria macrophylla</i> Wall. from different populations in China

<div><p><i>Uncaria macrophylla</i> Wall. is an important Chinese medicinal herb. Rhynchophylline (RIN) and isorhynchophylline (IRN) are its major active compounds. We investigated the influence of genetic differentiation and environmental factors on the RIN and IRN to find the main influencing factors of their contents and lay the foundation for the following cultivation and breeding. We used inter-simple sequence repeat (ISSR) markers to investigate the genetic diversity, and high-performance liquid chromatography (HPLC) to measure the contents of RIN and IRN in 200 samples of <i>U</i>. <i>macrophylla</i> obtained from nine natural populations, and then to analyze the correlation between genetic differentiation, environmental factors of sampling sites and the contents of RIN and IRN. We found that High intra-population (80.05%) and low inter-population (19.95%) genetic diversity existed in the samples of <i>U</i>. <i>macrophylla</i>. To some extent, genetic differentiation and the contents of RIN and IRN had correlation in individual populations (such as JH, MH, XM, and ML). The RIN and IRN contents were significant negatively correlated with the precipitation in May (R_IRN = -0.771, <i>p</i> = 0.015) and June (R_RIN = -0.814, <i>p</i> = 0.008; R_IRN = -0.921, <i>p</i> = 0.000), indicating that precipitation was the main affecting factor of their contents. Interestingly, the analysis results showed that the RIN content had a significant positive correlation (r = 0.585, <i>p</i> = 0.000) with the IRN content (they are isomers); the proportion of RIN had a significant negative correlation with the sum of the two (r = –0.390, <i>p</i><0.0001), while the proportion of IRN had a significant positive correlation (r = 0.390, <i>p</i><0.0001). It meant that, with the total quantity of the two compounds increased, the proportion of RIN decreased and the proportion of IRN increased, illustrating that their conversion exist some regularity. Moreover, the content ratio of RIN and IRN was significant positively correlated with the January precipitation (r = 0.716, <i>p</i> = 0.030), implying that January may be the key period for the mutual transformation of RIN and IRN.</p></div

The PCA distribution of different populations.

<p>The PCA distribution of different populations.</p

The sampling information for 9 populations.

<p>The sampling information for 9 populations.</p

Comparison between genetic dendrogram (A) and chemical dendrogram (B).

<p>Comparison between genetic dendrogram (A) and chemical dendrogram (B).</p

Results of correlation test based on chemical components content in 200 individuals.

<p>Results of correlation test based on chemical components content in 200 individuals.</p

The contents of chemical compounds in 9 populations.

<p>The contents of chemical compounds in 9 populations.</p

Distribution of the sampling location.

<p>Distribution of the sampling location.</p