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Plasmonic nanomaterial-enhanced fluorescence and Raman sensors: Multifunctional platforms and applications
No full textPlasmonic nanomaterials could improve various optical performance including fluorescence emission, Raman scattering, infrared absorption, etc. Among them, plasmon-enhanced fluorescence (PEF) can realize highsensitivity sensing and super -resolution imaging quickly, but with inferior multiplexed detection capability. Surface -enhanced Raman scattering (SERS) can offer fingerprint -like spectra for multiplexing, but its imaging speed and resolution are limited. The PEF-SERS integrated sensors could congregate their individual strengths while overcoming inherent weaknesses. Specifically, they can use fluorescence signals to rapidly screen out "suspicious" locations within numerous samples or a broad area, and then conduct multi -peak SERS measurements there to gather more detailed information. Besides, cross -verification of PEF and SERS results is possible to realize self -correction. Hence, many existing issues could be addressed including sensitivity, accuracy, speed, and multiplexing. Attracted by these superior advantages, we review here the interaction between plasmonic nanomaterials and fluorescence/Raman probes to explain enhancement mechanisms, the construction strategies for plasmonic substrates with better PEF-SERS performance, different modes for transforming analyte's information into measurable optical signals, as well as the main application in substance research, disease diagnosis, cell imaging, drug delivery. We believe, a deeper understanding of the state -of -arts of multifunctional plasmonic platforms could provide a generic guideline for their future development and practical application
The metal- and covalent-organic frameworks-based molecularly imprinted polymer composites for sample pretreatment
No full textExploiting sorbents with predictable structure, specific recognition, and broad applications is a vivid strategy in analytical approaches. Molecularly imprinted polymers (MIPs)-based sample preparation techniques show promise in meeting the requirements of an ideal sample preparation method. However, concerns persist regarding the throughput and real-world applications of traditional MIPs-based sample preparation due to inherent defects. Integrating MIPs with functional materials not only presents viable solutions to these challenges but also expands composite practical applications. In this review, we examine the advancements in synthesis strategies and applications of MOFs- and COFs-based MIPs composites in various sample pretreatment techniques. The less-considered aspects of recognition characteristics of MIPs are surveyed. The attributes of MOFs and COFs as sorbents are discussed. Recent progress in the design and preparation of MOFs- and COFs-based MIPs composites is summarized, by highlighting their practical applications. Future perspectives and challenges to facilitate the development of corresponding analytical methods are outlined
黄渤海聚球藻对有机碳的转化过程及输出效应
No full text聚球藻是一类普遍存在于全球海洋中的微微型浮游生物，贡献约全球海洋净初级产量的16.7%。目前，已对海洋中由聚球藻介导的海洋碳汇过程有了一定的认识，明确了聚球藻对包括生物泵和微生物碳泵在内途径的参与。然而，即将实施的负碳实践要求我们进一步加强对由聚球藻介导的海洋储碳过程及蓝碳产生机制的研究，夯实聚球藻对海洋碳汇贡献的原理论证，并深入研究环境变化对近海生态系统中聚球藻碳输出效应的影响。为了阐明在以黄渤海为代表的中国边缘海中，聚球藻对有机碳的转化及输出等碳循环过程的参与及其在环境变化下的碳氮耦合机制，本论文结合扩增子、宏基因组和宏转录组测序等多组学分子生态学研究手段以及机器学习等前沿模型构建算法，对黄渤海聚球藻开展了原位采样调查和实验室模拟培养研究，主要研究结论如下：
（1）成功构建了中国边缘海中包括颗粒有机碳（Particulate organic carbon，POC）和三种荧光溶解性有机碳（Fluorescent dissolved organic carbon，FDOC）组分C1、C2、C3在内的有机碳异质性对各种生物和非生物因素响应的人工神经网络（Artificial neural networks，ANNs）模型，并揭示了聚球藻对有机碳异质性的关键影响作用。所构建ANNs的皮尔逊相关系数（Pearson correlation coefficient，PCC）值最高可达0.87，模型性能优良可以实现对预测变量的拟合。对预测变量相对重要性的分析发现，聚球藻的丰度在本研究所构建的ANNs中是重要的生物预测变量，这可能预示其对边缘海生物泵和微生物碳泵途径的重要参与。
（2）通过调查黄河口沿海水域中以聚集（Aggregating，AG）为生活方式的聚球藻，揭示了具有充足压载矿物的水域中，微微型浮游植物对POC输出的潜在贡献，并深入探讨了不同生活方式聚球藻的分布、谱系特征以及与异养细菌的相互作用。结果表明，黄河河口近海海水中的聚球藻能形成大于3 μm的聚集体，占比14.7%至85.4%。相关性分析揭示了AG聚球藻与POC含量之间的显著关联。随机森林回归分析及基于单个细胞碳含量的估算，则进一步证明其在该海域对POC形式的碳输出具有较大潜在贡献。对rpoC1基因的高通量测序表明，AG和游离状态（Free-living，FL）聚球藻谱系的比例存在差异，特别是S5.1分支I在AG样本中的相对丰度显著高于FL样本（p < 0.05）。构建的聚球藻和异养细菌共现网络显示，聚集体具有“小世界”特性和更高的稳定性。通过功能预测和线性拟合分析发现，这可能是因为聚球藻和共存细菌之间存在更密切的基于碳-氮元素互换的相互作用。
（3）通过光照和黑暗两个阶段的连续培养揭示了来自渤海不同海域的富集聚球藻及其共生细菌之间的相互作用关系，探讨了聚球藻-细菌共培养体系中以聚球藻衍生有机碳为基础的碳流特征。研究结果表明，聚球藻宏基因组组装基因组（Metagenome-assembled genomes，MAGs）中存在prc、prlC、guaA、sppA、dacB和pepN等基因，在黑暗中有异养营养的潜力。当光合作用无法满足其能量需求时，可以将有机营养进行转化，在获得能量的同时生成较为稳定的有机碳。不同类型的聚球藻在异养代谢及合成包括色氨酸、生育酚和异戊二烯类化合物等抗逆物质的能力上存在差异，这些差异决定了其在黑暗中的生存能力。相关能力较强的聚球藻能在黑暗中可以通过异养代谢获得能量并将有机营养物质转化为较为稳定的有机碳；而能力较弱的则无法维持其在黑暗中的生存，从而被逐渐分解，分解后的有机营养物被其他异养细菌转化为较为稳定的有机碳。对主要细菌MAGs功能注释的结果显示，不同的聚球藻类群的共存菌群功能也存在差异，主要体现在异化硝酸还原途径、硫代硫酸盐水解、有机碳利用、和包括磷酸盐、L-氨基酸及磷酸盐等物质的转运途径中，因此与聚球藻之间产生了不同的相互作用，并在二者的协同作用下对有机碳的转化产生影响。
（4）通过渤海海域聚球藻原位调查，并结合生理、基因组和转录组分析进行了室内氮模拟实验，研究了聚球藻在氮源浓度和类型变化下的驱动模式、分子适应和与碳循环相关的生态效应。原位调查的结果表明，聚球藻群落的多样性和谱系结构受到无机氮的强烈影响。尤其是硝态氮在促进聚球藻群落的多样性增加方面发挥了显著作用（p < 0.01）。在谱系组成上，受硝酸盐等环境因子的驱动，亚簇S5.1的II、VIII和IX分支，以及亚簇S5.2和亚簇S5.3在硝酸盐和亚硝酸盐浓度较高的中央和海湾区域相对丰度较高，而聚球藻S5.1的I、III、WPC1和VI则在与黄海北部水体交换良好的海峡地区有较高比例。对富集聚球藻的梯度氮模拟实验进一步证明了无机氮变化对聚球藻谱系的多样性和生态位分化的关键驱动作用。模拟实验的结果发现，在目前原位所能达到的无机氮浓度范围内（0.1~10 μmol L–1），增加无机氮的浓度将会提高聚球藻的多样性和碳固定能力。然而，进一步增加无机氮浓度至100 μmol L–1将会减少多样性并抑制固碳相关过程。基于生理、基因组和宏转录组的分析进一步揭示了氮对聚球藻群落的影响与氮代谢和富氮色素蛋白合成中相关基因的差异表达有关，而这最终影响了聚球藻的光合作用和碳固定过程。
综上所述，本研究揭示了聚球藻在近海碳氮生物地球化学循环中的重要作用，探究了环境条件改变对近海生态系统中由聚球藻介导的元素循环的影响效应，研究结果有助于理解微微型浮游生物在碳转化和输出过程中的驱动机制并可作为负碳实践的理论基础
Biohydrogen Production from Methane-Derived Biomass of Methanotroph and Microalgae by <i>Clostridium</i>
No full textMethane, a potent greenhouse gas, represents both a challenge and an opportunity in the quest for sustainable energy. This work investigates the biotechnology for converting methane into clean, renewable hydrogen. The co-culture of Chlorella sacchrarophila FACHB 4 and Methylomonas sp. HYX-M1 was demonstrated to completely convert 1 mmol of methane to biomass within 96 h. After acid digestion of such biomass, up to 45.05 mu mol of glucose, 4.07 mu mol of xylose, and 26.5 mu mol of lactic acid were obtained. Both Clostridium pasteurianum DSM525 and Clostridium sp. BZ-1 can utilize those sugars to produce hydrogen without any additional organic carbon sources. The higher light intensity in methane oxidation co-culture systems resulted in higher hydrogen production, with the BZ-1 strain producing up to 14.00 mu mol of hydrogen, 8.19 mu mol of lactate, and 6.09 mu mol of butyrate from the co-culture biomass obtained at 12,000 lux. The results demonstrate that the co-culture biomass of microalgae and methanotroph has the potential to serve as a feedstock for dark fermentative hydrogen production. Our study highlights the complexities inherent in achieving efficient and complete methane-to-hydrogen conversion, positioning this biological approach as a pivotal yet demanding area of research for combating climate change and propelling the global energy transition
Does invasive submerged macrophyte diversity affect dissimilatory nitrate reduction processes in sediments with varying microplastics?
No full textNitrogen removal is essential for restoring eutrophic lakes. Microorganisms and aquatic plants in lakes are both crucial for removing excess nitrogen. However, microplastic (MP) pollution and the invasion of exotic aquatic plants have become increasingly serious in lake ecosystems due to human activity and plant -dominant traits. This field mesocosm study explored how the diversity of invasive submerged macrophytes affects denitrification (DNF), anammox (ANA), and dissimilatory nitrate reduction to ammonium (DNRA) in lake sediments with varying MPs. Results showed that invasive macrophytes suppressed DNF rates, but DNRA and ANA were less sensitive than DNF to the diversity of invasive species. Sediment MPs increased the biomass of invasive species more than native species, but did not affect microbial processes. The effects of MPs on nitrate dissimilatory reduction were process -specific. MPs increased DNF rates and the competitive advantage of DNF over DNRA by changing the sediment environment. The decoupling of DNF and ANA was also observed, with increased DNF rates and decreased ANA rates. The study findings suggested new insights into how the invasion of exotic submerged macrophytes affects the sediment nitrogen cycle complex environments
Enhancing the sensitivity of polymeric membrane polycation-sensitive electrodes by surface modification of a polydopamine nanolayer
No full textIn this work, a potentiometric polyion sensing strategy based on the surface layer-enhanced transmembrane ion transfer is demonstrated. A polydopamine (PDA) nanolayer with negative charges is modified onto the surface of the polycation-sensitive electrode membrane and used to increase the ion fluxes from the sample phase to the membrane phase. Such modification can significantly improve the detection sensitivity of potentiometric polyion sensors through electrostatic interactions between the cationic targets and anionic PDA groups, which can effectively promote the accumulation of the targets in the boundary layer of the organic membrane phase. By using a thin membrane protamine-sensitive electrode as a model, the detection sensitivity of the PDA-coated electrode (55 mV/mu g & sdot;mL-1) is nearly five times higher than that of the unmodified electrode (12 mV/ mu g & sdot;mL-1). Moreover, the proposed surface PDA-modified polyion sensor can also be utilized as a general tool for sensitive detection of other polycationic targets and polyanionic species (e.g., the new cancer biomarker cell-free DNA). The proposed potentiometric sensing platform based on surface enhancement of ion transfer offers great potential for sensitive detection of various polyionic targets
Treatment of landfill leachate nanofiltration concentrate by a three-dimensional electrochemical technology with waste aluminum scraps as particle electrodes: Efficacy, mechanisms, and enhancement effect of subsequent electrocoagulation
No full textLandfill leachate nanofiltration concentrate is a kind of wastewater containing high concentrations of color and refractory organics. Herein, we proposed a novel three-dimensional electrochemical technology (3DET) with waste aluminum scraps as particle electrodes for its treatment. The planar and particle electrodes were first optimized. Ti/RuO2 and graphite were used as anodes in the two-dimensional electrochemical technology (2DET). In the light of contaminant removal (color, UV254, COD, and TOC), chlorine reduction, and energy consumption, graphite was selected as planar anodes and cathodes. Moreover, 3DET with Al particle electrodes (Al 3DET) outperformed that with conventional granular activated carbon electrodes, 2DET, and Al particles. At 120 min, the removal efficiencies of color, UV254, COD, and TOC using Al 3DET were 98.94 %, 84.72 %, 51.93 %, and 67.46 %, respectively. UV-vis and EEM spectroscopy, and GC-MS analyses indicate that macromolecular organic matter such as humic-like substances could be effectively degraded and simultaneously removed. Reactive species identification tests including free radical quenching and EPR spectra were conducted. The results indicate that in addition to anodic direct oxidation, indirect oxidation by oxidative species (H2O2, (OH)-O-center dot, and RCS) and flocculation by Al species also played a vital role in contaminant removal. Continuous-flow experiments show that Fe EC as a post -treatment step of Al 3DET could effectively provide a neutralization effect for the 3DET effluent and enhance the removal efficiency of contaminants. The total operating cost of combined process was 1.307 USD/m(3). This study shows that the Al 3DET-Fe EC process is a promising technology for the treatment of nanofiltration concentrate
In situ biomass burning enhanced the contribution of biogenic sources to sulfate aerosol in subtropical cities
No full textSulfurous gases released by biogenic sources play a key role in the global sulfur cycle. However, the contribution of biogenic sources to sulfate aerosol in the urban atmosphere has received little attention. Emission sources and formation process of sulfate in Guangzhou, a subtropical mega-city in China, were clarified using multiple methods, including isotope tracers and chemical markers. The delta 18O of sulfate suggested that secondary sulfate was the dominant component (84 %) of sulfate aerosol, which mainly formed by transition metal ion (TMI) catalyzed oxidation (31 %) and OH radical oxidation (30 %). The factors driving secondary sulfate formation were revealed using a tree boosting model, which suggested that NH3, temperature, and oxidants were the most important factors. The delta 34S of sulfate indicated that biogenic sources accounted for annual average of 26.0 % of the sulfate, which increased to 30.4 % in winter monsoon period. Rice straw burning enhanced sulfate formation by promoting the release of reduced sulfur from soil, which is rapidly converted into sulfate under a subtropical urban atmosphere with high concentration of NH3 and oxidants. This study revealed the important influence of rice straw burning on biogenic sulfur emission during the rice harvest, thereby providing insight into the sulfur cycle and regional air pollution
Molecular signatures and formation mechanisms of water-soluble chromophores in particulate matter from Karachi in Pakistan
No full textExcitation -emission matrix (EEM) fluorescence spectroscopy is a widely -used method for characterizing the chemical components of brown carbon (BrC). However, the molecular basics and formation mechanisms of chromophores, which are decomposed by parallel factor (PARAFAC) analysis, are not yet fully understood. In this study, we characterized the water-soluble organic carbon (WSOC) in aerosols collected from Karachi, Pakistan, using EEM spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We identified three PARAFAC components, including two humic-like components (C1 and C2) and one phenolic -like species (C3). We determined the molecular families associated with each component by performing Spearman correlation analysis between FT-ICR MS peaks and PARAFAC component intensities. We found that the C1 and C2 components were associated with nitrogen -enriched compounds, where C2 with the longest emission wavelength exhibited a higher level of aromaticity, N content, and oxygenation than C1. The C3 associated formulas have fewer nitrogen -containing species, a lower unsaturation degree, and a lower oxidation state. An oxidation pathway was identified as an important process in the formation of C1 and C2 components at the molecular level, particularly for the assigned CHON compounds associated with the gas -phase oxidation process, despite their diverse precursor types. Numerous C2 formulas were found in the "potential BrC" region and overlapped with the BrC-associated formulas. It can be inferred that the compounds that fluoresce C2 contributed considerably to the light absorption of BrC. These findings are essential for future studies utilizing the EEM-PARAFAC method to explore the sources, processes, and compositions of atmospheric BrC
A honeycomb-like micro-needle sensor with gold nanoparticles embedded for the determination of hexavalent chromium in seawater
No full textAs one of the most toxic heavy metals, hexavalent chromium (Cr(VI)) is a typical environmental pollutant that directly affects human health. In this work, a novel micro-needle sensor with honeycomb-like structure and embedded gold nanoparticles was proposed for the stable and sensitive determination of Cr(VI). The honeycomblike structure provided larger specific surface area to support more gold nanoparticles which exhibited excellent catalytic activity towards the electrochemical reduction of Cr(VI) to Cr(III). In addition, gold nanoparticles were embedded into the holes of the honeycomb-like structure, which can effectively prevent them from falling off from the electrode surface due to the protection of the holes. Combining the honeycomb-like structure of microneedle electrode with the excellent catalytic activity of gold nanoparticles, the fabricated sensor exhibited outstanding stability and sensitivity for the cathodic stripping determination of Cr(VI). A linear range of Cr(VI) from 0.5 to 300 mu mol/L was obtained, with the detection limit of 0.15 mu mol/L. The recovery of the sensor for the determination of hexavalent chromium in seawater samples was also investigated. Moreover, the sensor might be further adapted for the determination of other heavy metals with different nanoparticles embedded