多孔陶瓷膜用于碳量子点的分离与纯化

尺寸分布均一的碳量子点由于其良好的光学特性,在光电设备、离子检测、纳米传感器、生物成像和催化剂等领域具有广阔的应用前景。采用陶瓷膜"超滤-纳滤"双膜法,对微波合成的碳量子点进行分离和纯化。研究了pH对碳量子点料液荧光强度和粒径分布的影响。在pH=3时,碳量子点分散较好,荧光强度较高。陶瓷超滤膜可以有效截留碳量子点料液中的大颗粒杂质,渗透侧的碳量子点平均粒径约为2 nm,分散良好,无团聚现象。陶瓷纳滤膜对碳量子点具有良好的截留性能,在浓缩和水洗过程中可以进一步去除料液中的小分子杂质。经双膜法处理后,发射光谱由多峰分布变为单峰分布,且峰宽变窄,碳量子点的发光纯度得到了明显提高。     

煤基碳量子点的制备及其在离子检测中的应用

以长焰煤为碳源,使用空气氧化预处理与双氧水氧化结合的"分步法"成功制备出了煤基碳量子点(carbon quantum dot,CQD)。对碳量子点的表面形貌、化学组成和光学性质进行表征,并考察了碳量子点作为纳米荧光探针检测金属离子的性能。结果表明:煤基碳量子点平均粒径为13.1 nm,含氧量达30.56%,在波长为365 nm的紫外光照射下呈现出明亮的青蓝色荧光,其荧光强度在中性条件下最大,并可在较宽的pH范围内保持荧光稳定性;与Fe~(3+)能发生特异性荧光淬灭,在0μmol/L～9μmol/L Fe~(3+)浓度范围内,荧光猝灭程度与Fe~(3+)浓度呈良好的线性关系。     

碳量子点的光学性质及其应用研究进展

碳量子点是一种由碳原子组成的新型纳米结构,其粒径尺寸一般在10nm以下,具有很好的量子限域效应、荧光性能和光学性能等,有良好的应用前景。碳量子点在光催化反应中的作用主要体现在两个方面：作为电子接收器和用作太阳能电池光阳极的增敏剂。从荧光性能、光激发性、太阳能电池和光催化等方面总结了碳量子的荧光性质和光学性质,分析了碳量子点在光催化、太阳能电池和荧光转换等领域面临的挑战和问题。     

荧光碳点的绿色合成及发光影响因素

本实验以抗坏血酸为前驱体,一锅煮、绿色合成了荧光碳量子点,并考察了合成时间、合成温度对碳量子点发光效率的影响以及碳量子点对不同pH缓冲溶液和常见离子的耐受性。结果表明90℃时加热5 h时该碳量子点的荧光强度最强,不同的pH缓冲溶液对碳量子点的荧光猝灭作用较强,Pb2+、Cr~(3+)、Hg2+、NO2-离子对碳量子点的发光影响不大。     

基于量子点荧光强度变化检测陶瓷疲劳微裂纹

量子点具有荧光光谱窄、激发光谱宽、荧光强度高、稳定性好等优势,将量子点应用于微裂纹的监测有极大的优越性.本文利用量子点涂层的荧光性能进行了陶瓷裂纹的直接检测,并与实际裂纹比较发现仅有2％的差别;借助ANSYS有限元软件计算模拟了陶瓷在产生疲劳裂纹后的应力分布.对比发现,涂层荧光强度变化和应力变化都呈区域性分布,而且应力越大,荧光强度越强,说明该方法是一种简单有效的裂纹测试手段.     

以植物为碳源制备荧光碳量子点的研究

以植物为碳源,采用水热法制备稳定性好的水溶性碳量子点。通过荧光分光光度计对制备的碳量子点溶液的荧光性质进行了表征,研究了碳源用量、反应时间、反应温度、缓冲溶液pH值和激发波长对碳量子点溶液的荧光性质的影响,优化实验条件。实验结果表明,当碳源用量为2.0 g,反应温度为180℃,反应时间为9 h,缓冲溶液pH值为7.0,激发波长为370 nm时,制备的碳量子点溶液的荧光强度最强。本研究能为碳量子点的制备和应用提供一定的参考。     

一步法水相制备Cu–In–Zn–S量子点及其荧光性能

采用简单的一步法制备了水溶性Cu–In–Zn–S (CIZS)四元量子点,利用X射线衍射仪、透射电子显微镜和荧光光谱仪等测试手段研究了反应温度、阳离子浓度和前驱体溶液pH值对样品的物相组成、显微形貌以及荧光性能的影响规律。结果表明:随着反应温度的升高,量子点的结晶度逐渐提高,荧光强度显著增强,当反应温度为95℃时,荧光强度达到了最高值;随着阳离子浓度的逐渐增大,量子点的粒径逐渐减小,导致其发光峰位由634 nm蓝移至617 nm,当阳离子浓度为1.5 mmol/L时,量子点的荧光强度最高。此外,当溶液pH值=5.0时,配体对量子点的表面钝化效果最佳,荧光强度达到最高值。红外光谱表明,量子点表面存在多种功能基团,赋予了量子点优异的水溶性,因此在生物成像领域具有广阔的应用前景。     

基于荧光碳量子点对水中抗坏血酸的选择性检测

抗坏血酸,又称维生素C,广泛应用于医药,工业生产等领域,在生命进程中起着不可或缺的重要作用,对其快速准确分析具有重要意义。本工作利用尿素和柠檬酸钠通过水热法合成一种荧光碳量子点,能和抗坏血酸发生作用,荧光信号逐渐衰减,碳点在448 nm处的荧光强度随溶液中抗坏血酸含量的提高不断降低,在300～900μmol/L的范围内,荧光的强度变化与抗坏血酸浓度呈线性关系,通过干扰实验检测碳量子点的选择性,从而实现对抗坏血酸有效的荧光猝灭选择性检测。同时研究发现该碳量子点在较宽的pH值范围内荧光性质稳定,不易受环境酸碱度的影响。这一发现可以作为一个潜在的测试工具,用于在制药和食品行业中更选择性地检测抗坏血酸。     

生物质基碳量子点的制备及其光谱性质研究

以木屑为前驱物制备的活性炭为碳源,采用化学氧化法,用聚乙二醇2000进行表面钝化,制备出了水溶性的生物质基碳量子点。优化了CQDs的合成方法：0.3 g生物质基活性炭, 40 mL HAc-80 mL 30% H₂O₂ 混合氧化剂,反应温度为100 ℃,反应时间为12 h。采用微波和超声结合法进行钝化,修复了CQDs的表面缺陷,荧光强度和量子产率均得到了提高。采用透射电子显微镜、紫外-可见吸收光谱仪、荧光分光光度计和傅里叶红外分光光度计进行表征,所合成的碳量子点发光性能优异、粒径小、分散性好,且无团聚现象。进一步考察了光照、温度和体系pH值对碳量子点性能的影响,结果表明,光稳定性好,抗光漂白性优异,荧光强度具有pH值依赖性,且易于表面功能化。     

香豆素修饰的碳量子点光稳定剂的制备与性能

利用柠檬酸为碳源,通过水热反应制备碳量子点,再采用EDC/NHS酰胺反应催化体系,将7-氨基-4-甲基香豆素(AMC)修饰到碳量子点表面,合成出一种香豆素修饰的碳量子点光稳定剂 (AMC-CQDs),研究了其光学性能和在纸张表面的应用性能,并且运用1931-CIE色度坐标,初步探究了纸张返黄过程的色度变化规律。结果表明： 合成的AMC-CQDs粒径均匀(4.13nm),具有良好的水溶性和紫外吸收性能,基本实现紫外区的全覆盖吸收,且其最大荧光发射波长为431nm,荧光量子产率达到38.7%,适用于高得率浆纸张增白,对纸张的初始白度可以提高4.71 ISO%;色度坐标显示该碳量子点光稳定剂对于色度坐标位于y＝1.553x－0.184附近的纸张具有良好的光物理增白效果。     

检测环境水体中银离子含量的新型碳基光学传感器

以木质素磺酸钙为原料,通过常温下分子自组装和超声波辅助法制备木质素基碳量子点(CQDs),探究木质素磺酸钙和NaBH_(4)对CQDs荧光性能的影响并优化CQDs合成条件。研究结果显示:优化后的CQDs合成条件为木质素磺酸钙质量浓度60 g/L,还原剂NaBH_(4)质量浓度50 g/L。利用透射电子显微镜(TEM)、红外光谱(FT-IR)、X射线光电子能谱(XPS)、紫外-可见光谱(UV-vis)和荧光光谱(FL)对CQDs的结构形貌及光学特性进行分析,结果显示:CQDs粒径小((9.5±0.5)nm)且分布均匀、无团聚现象,光学性能优异且荧光量子产率达12.4%。此外,基于CQDs探究不同银离子浓度对其荧光强度的影响,结果表明:CQDs对Ag^(+)具有较好的荧光识别性和灵敏度,在0~250μmol/L范围内CQDs荧光淬灭强度比值与Ag^(+)浓度呈线性关系(R^(2)=0.998),检测限可达525 nmol/L。同时,CQDs荧光选择性优异且表现出较低的细胞毒性,有望在生物传感和环境检测领域展现出潜在应用价值。     

羧基化荧光碳量子点的合成及其在汞离子检测中的应用

通过一步法高压热处理柠檬酸粉末制备了羧基功能化的荧光碳量子点,荧光光谱表征显示所合成荧光碳量子点的最大激发波长为316 nm,最大发射波长为394 nm。Hg^2+对其具有较好的淬灭效果,在5~300μmol/L的浓度范围内,Hg^2+的浓度和体系荧光强度呈较好的线性关系,线性回归方程为F0=152.169 5-0.153 5c,相关系数R2=0.998。这种碳量子点的制备技术将为合成功能化荧光纳米材料提供有益的借鉴作用,并为开发新型传感检测技术提供理论支持。     

Polyamine-functionalized carbon quantum dots for chemical sensing

Polyamine-functionalized carbon quantum dots (CQDs) with high fluorescence quantum yield (42.5%) have been synthesized by the low temperature (<200 °C) carbonization of citric acid with branched polyethylenimine (BPEI) in one simple step. The obtained BPEI–CQDs are spherical graphite nanocrystals (average 6.2 nm in size) capped with abundant BPEI at their surfaces. It is the first report that CQDs are both amino-functionalized and highly fluorescent, which suggests their promising applications in chemical sensing.     

Preparation of functionalized water-soluble photoluminescent carbon quantum dots from petroleum coke

Here we report a new strategy for preparation of water-soluble photoluminescent carbon quantum dots (CQDs) from petroleum coke. Petroleum coke was oxidized first in mixed concentrated H₂SO₄ and HNO₃, and then functionalized by hydrothermal ammonia treatment. The as-made CQDs and nitrogen-doped CQDs (N-CQDs) were characterized by UV–Vis absorption spectroscope, fluorescence spectroscope, transmission electron microscope, atomic force microscope, Raman spectrometer, X-ray powder diffractometer, X-ray photoelectron spectroscope and Fourier transform infrared spectrometer. The results show that the quantum yield of CQDs increases greatly from 8.7 to 15.8%, and the fluorescent lifetime increases from 3.86 to 6.11 ns after the hydrothermal treatment in ammonia. Moreover, the fluorescent color of N-CQDs can be tuned through the amount of doped nitrogen. Both CQDs and N-CQDs are water-soluble, and have uniform particle distribution, strong luminescence, and highly fluorescent sensitivity to pH in a range of 2.0–12.0. The uniform size distribution and nitrogen-doping of N-CQDs help to lead to high yield of radiative recombination, resulting in improved fluorescence properties. This work offers a simple pathway to produce high quality and enhanced photoluminescent CQDs from petroleum coke.     

Green and continuous microflow synthesis of fluorescent carbon quantum dots for bio-imaging application

In this work, a simple, continuous and completely green method based on microflow technique is demonstrated for the synthesis of carbon quantum dots (CQDs) from diverse bio-based precursors. CQDs prepared from milk is illustrated as a case study to show the process feasibility. Crystalline fluorescent CQDs of 12.53% quantum yield and good stability are synthesized by the approach, even at 120°C. Systematic experiments further suggest their optical properties, bandgap energy, and fluorescence lifetime are closely related to the synthesis temperature. The maximum production rate of the CQDs was 51.1 mg/h at 180°C. Cytotoxicity and cellular imaging tests against 3T3 cells reveal the CQDs possess high biocompatibility, and can penetrate cell membranes and display bright fluorescence. The process versatility is investigated by expanding the precursor to watermelon juice, orange juice, and soy milk, indicating successful synthesis of small-sized CQDs of low cytotoxicity and strong photoluminescence by the technique.     

Comparative study of one-pot and facile methods to synthesize codoped CQDs with low band gap and photovoltaic properties

Three different one-pot methods of electrochemical, solvothermal, and pyrolysis were applied for the synthesis of nitrogen-doped carbon quantum dots (N-CQDs), N-F codoped carbon quantum dots (CQDs), and N-S codoped CQDs from monoethanolamine and citric acid precursors. Ammonium fluoride and/or thiourea were used as the precursors of the second dopant corporation. The effective synthesis parameters were studied on the basis of the factorial experimental design methodology to maximize absorption edge and reduce band gap in UV-visible spectroscopy. Among the best results, the synthesized N-F/CQDs prepared from ammonium fluoride and citric acid in monoethanolamine revealed the highest absorption edge of 650 nm, the band gap of 1.91 eV, and the particle size of 24 ± 7 nm using the pyrolysis method. The X-ray photoelectron spectroscopy (XPS) analysis indicated simultaneous doping of F and N atoms in the CQDs structure, and the photoluminescence (PL) analysis revealed excitation-dependent properties, which are effective for optical sensor and solar cell applications.     

混凝耦合多孔陶瓷膜净化河水简

Membrane filtration technology combined with coagulation is widely used to purify river water. In this study, micro filtration （MF） and ultrafiltration （UF） ceramic membranes were combined with coagulation to treat local river water located at Xinghua, Jiangsu province, China. The operation parameters, fouling mechanism and pilot-scale tests were investigated. The results show that the pore size of membrane has small effect on the pseudo-steady flux for dead-end filtration, and the increase of flux in MF process is more than that in UF process for cross-flow filtration with the same increase of cross-flow velocity. The membrane pore size has little influence on the water quality. The analysis on membrane fouling mechanism shows that the cake filtrationhas significant in fluence on the pseudo-steady flux and water quality for the membrane with pore size of 50, 200 and 500 nm. For the membrane with pore size of 200 nm and backwashing employed in our pilot study, a constant flux of 150 L-m^-2-h^-1 was reached during stable operation, with the removal efficiency of turbidity, total organic carbon （TOC） and UV254 higher than 99%, 45% and 48%, respectively. The study demonstrates that coagulation-porous ceramic membrane hybrid process is a reliable method for river water purification.     

Fluorescent CQD-Doped Styrene Acrylic Emulsion Coating Film with Enhanced Optical Properties

Styrene acrylic emulsions (SAEs) have emerged as a promising material for water-based coatings. However, they are still limited by their own defects in practical applications, poor weatherability, and degradation of performance at lower or higher temperatures. Here, we introduce a facile approach to producing fluorescent carbon quantum dots (CQDs) from wood processing residues and fabricating fluorescent CQD/SAE coating films via emulsion-casting. The addition of the fluorescent CQDs enhanced the optical performance of the CQD/SAE coating films. The fluorescent CQDs were prepared via a hydrothermal approach and were obtained after heating at 180 °C for 6 h at a reaction concentration of 50 mg/mL. The synthesized CQDs resulted in a high fluorescence, and the CQDs had an average size of 1.63 nm. Various concentrations of the fluorescent CQDs were doped into the SAE coating film, which improved its optical properties. We also characterized and discussed the products and then explored their optical properties. This study presents the potential of fluorescent CQD/SAE coating films for applications in anti-counterfeiting coatings, fluorescent adhesives, and papermaking.     

陶瓷纳滤膜制备与应用研究进展

陶瓷纳滤膜以其优良的热稳定性、化学稳定性和机械强度等特性,在涉及高温、酸碱、有机溶剂等苛刻环境的过程工业领域具有广阔的应用前景。因此,陶瓷纳滤膜材料的制备研究已引起众多科研工作者的关注。本文综述了陶瓷纳滤膜在制备及应用方面的研究进展,着重介绍了溶胶-凝胶法、化学气相沉积法、原子层沉积法及表面接枝等陶瓷纳滤膜制备方法。溶胶-凝胶法反应温度低、操作过程相对简单且精确可控,是目前国内外陶瓷纳滤膜制备的常用方法;化学气相沉积法及原子层沉积法则需借助气相化学反应在多孔基底表面进行材料沉积,从而修复缺陷,减小平均孔经;表面接枝技术可改变陶瓷膜表面亲疏水性,同时将陶瓷基膜孔径减小至纳滤范围。此外简单介绍了陶瓷纳滤膜的应用,并对未来陶瓷纳滤膜研究方向提出了建议,指出陶瓷纳滤膜微结构参数与分离性能之间的关系建立,以及探讨陶瓷纳滤膜在溶剂体系中的分离机理将成为今后一段时间内的研究热点。     

Ultrafiltration and nanofiltration membranes applied to the removal of the pharmaceuticals amoxicillin,naproxen, metoprolol and phenacetin from water

BACKGROUND: In the removal of pharmaceuticals present in aquatic systems by membrane processes, some important issues must be explored in order to obtain a better knowledge of the global process. Among these issues, a better understanding of the influences of the operating parameters on the membrane flux, an analysis of membrane resistances and fouling, and determination of the removal of specific substances, must be studied. RESULTS: Four selected pharmaceuticals (amoxicillin, naproxen, metoprolol and phenacetin) were subjected to ultrafiltration (UF) and nanofiltration (NF) processes for their removal from several water matrices. The determined permeate fluxes at the steady state were affected by the main operating conditions: molecular weight cut‐off (MWCO) of the membrane, transmembrane pressure TMP, cross‐flow velocity and temperature. The retention coefficients with the UF membranes followed the sequence naproxen > metoprolol > amoxicillin > phenacetin, and with the NF membranes, followed the trend: amoxicillin > naproxen > metoprolol > phenacetin, due to the role of other mechanisms such as size exclusion and electrostatic repulsion. In the case of the selected water matrices, the retention coefficient was referred to some quality parameters (total organic carbon, chemical oxygen demand and absorbance at 254 nm), leading to moderate (UF) or high (NF) removals of the organic matter content. CONCLUSIONS: The NF CK membrane achieved the highest retention of these pharmaceuticals (excepting phenacetin), and provided retentions for quality parameters around 80% in the four water systems tested. Copyright © 2011 Society of Chemical Industry