Enhanced photocatalytic hydrogen production from Co-MOF/CN by nitrogen and sulfur co-doped coal-based carbon quantum dots

A novel composite photocatalyst for photocatalytic decomposition of water for hydrogen evolution was successfully synthesized by in-situ growth of nitrogen and sulfur co-doped coal-based carbon quantum dots(NSCQDs)nanoparticles on the surface of sheet cobalt-based metal-organic framework(Co-MOF)and graphitic carbon nitride(g-C_(3)N_(4),CN).The structure and properties of the obtained catalysts were systematically analyzed.NSCQDs effectively broaden the absorption of Co-MOF and CN in the visible region.The new composite photocatalyst has high hydrogen production activity and the hydrogen production rate reaches 6254μmol/(g·h)at pH=9.At the same time,NSCQDs synergy Co-MOF/CN composites have good stability.After four cycles of hydrogen production,the performance remains relatively stable.The tran sient photocurrent response and Nyquist plot experimental results further demonstrate the improvement of carrier separation efficiency in composite catalysts.The semiconductor type(n-type semico nductor)of the single-phase catalyst was determined by the Mott-Schottky test,and the band structure was analyzed.The conductive and valence bands of CN are-0.99 and 1.72 eV,respectively,and the conduction and valence bands of Co-MOF are-1.85 and 1.33 eV,respectively.Th e mechanism of the photocatalytic reaction can be inferred,that is,Z-type heterojunction is formed between CN an d Co-MOF,and NSCQDs was used as cocatalyst.

Biocompatible carbon nitride quantum dots nanozymes with high nitrogen vacancies enhance peroxidase-like activity for broadspectrum antibacterial

Nanozyme antibacterial agents with high enzyme-like catalytic activity and strong bacteria-binding ability have provided an alternative method to efficiently disinfect drug-resistance microorganism.Herein,the carbon nitride quantum dots(CNQDs)nanozymes with high nitrogen vacancies(NVs)were mass-productively prepared by a simple ultrasonic-crushing method assisted by propylene glycol.It was found that the NVs of CNQDs were stemmed from the selective breaking of surface N-(C)_(2)sites,accounting for 6.2%.Experiments and density functional theory(DFT)simulations have demonstrated that the presence of NVs can alter the local electron distribution and extend theπ-electron delocalization to enhance the peroxidase-like activity.Biocompatible CNQDs could enter inside microorganisms by diffusion and elevate the bacteria-binding ability,which enhanced the accurate and rapid attack of·OH to the microorganisms.The sterilization rate of CNQDs against Gram-negative bacteria(E.coli),Gram-positive bacteria(S.aureus,B.subtilis),fungi(R.solani)reaches more than 99%.Thus,this work showed great potential for engineered nanozymes for broad-spectrum antibacterial in biomedicine and environmental protection.

Designed synthesis of chlorine and nitrogen co-doped Ti_(3)C_(2)MXene quantum dots and their outstanding hydroxyl radical scavenging properties

As a novel zero-dimensional(0D)material,metal carbides and/or carbonitrides(MXenes)quantum dots(MQDs)show unique photoluminescence properties and excellent biocompatibility.However,due to the limited synthesis methods and research to date,many new features have yet to be uncovered.Here,to explore their new properties and expand biological applications,chlorine and nitrogen co-doped Ti_(3)C_(2)MXene quantum dots(Cl,N-Ti_(3)C_(2)MQDs)were designed and synthesized,and their hydroxyl radical scavenging properties were investigated for the first time,revealing outstanding performance.Cl,N-Ti_(3)C_(2)MQDs was directly stripped from bulk Ti_(3)Al C_(2)by electrochemical etching,while N and Cl are successfully introduced to carbon skeleton and Ti boundaries in the etching process by electrochemical reactions between selected electrolytes and Ti_(3)C_(2)skeleton,respectively.The obtained Cl,N-Ti_(3)C_(2)MQDs exhibit large surface-to-volume ratio due to small particle size(ca.3.45 nm)and excellent higher scavenging activity(93.3%)and lower usage(12.5μg/m L)towards hydroxyl radicals than the previous reported graphene-based nanoparticles.The underlying mechanism of scavenging activity was also studied based on the reduction experiment with potassium permanganate(KMnO_(4)).The reducing ability of the intrinsic Ti_(3)C_(2)structure and electron donation of double dopants are the main contributors to the outstanding scavenging activity.

Construction of dual Z-scheme Bi2WO6/g-C_(3)N_(4)/black phosphorus quantum dots composites for effective bisphenol A degradation

In this work,a novel dual Z-scheme Bi_(2)WO_(6)/g-C_(3)N_(4)/black phosphorus quantum dots(Bi_(2)WO_(6)/g-C_(3)N_(4)/BPQDs)composites were fabricated and utilized towards photocatalytic degradation of bisphenol A(BPA)under visible-light irradiation.Optimizing the content of g-C_(3)N_(4) and BPQDs in Bi_(2)WO_(6)/g-C_(3)N_(4)/BPQDs composites to a suitable mass ratio can enhance the visible-light harvesting capacity and increase the charge separation efficiency and the transfer rate of excited-state electrons and holes,resulting in much higher photocatalytic activity for BPA degradation(95.6%,at 20 mg/L in 120 min)than that of Bi2WO6(63.7%),g-C_(3)N_(4)(25.0%),BPQDs(8.5%),and Bi_(2)WO_(6)/g-C_(3)N_(4)(79.6%),respectively.Radical trapping experiments indicated that photogenerated holes(h+)and superoxide radicals(•O_(2)−)played crucial roles in photocatalytic BPA degradation.Further,the possible degradation pathway and photocatalytic mechanism was proposed by analyzing the BPA intermediates.Thiswork also demonstrated that the Bi2WO6/g-C_(3)N_(4)/BPQDs as effective photocatalystswas stable and have promising potential to remove environmental contaminants from real water samples.

掺氮碳量子点用于柳氮磺吡啶的快速检测

以微波法一步合成制备出荧光性能强、荧光量子产率为89.38%的掺氮碳量子点(N-CDs),并通过荧光猝灭法建立了快速准确测定柳氮磺吡啶(SSZ)的新方法。通过透射电子显微镜、傅里叶红外光谱对碳量子点进行表征,结果显示N-CDs的平均粒径为2.91 nm,主要由C、O、N元素组成,大量羰基、羟基和羧基存在于N-CDs表面。在最佳条件下,柳氮磺吡啶浓度在0.1~2μmol/L和3~200μmol/L范围内线性良好,检出限为0.2μmol/L。将所建方法用于柳氮磺吡啶肠溶片中柳氮磺吡啶含量的测定,回收率为97.3%~102%。

Boosting lithium storage performance of Si nanoparticles via thin carbon and nitrogen/phosphorus co-doped two-dimensional carbon sheet dual encapsulation

Silicon(Si)is a promising anode candidate for next-generation lithium-ion batteries(LIBs),but it suffers from poor electronic conductivity and dramatic volume variation during cycling,which poses a critical challenge for stable battery operation.To mitigate these issues simultaneously,we propose a"double carbon synergistic encapsulation"strategy,namely thin carbon shell and nitrogen/phosphorus co-doped two-dimensional(2D)carbon sheet dual encapsulate Si nanoparticles(denoted as 2D NPC/C@Si).This double carbon structure can serve as a conductive medium and buffer matrix to accommodate the volume expansion of Si nanoparticles and enable fast electron/ion transport,which promotes the formation of a stable solid electrolyte interphase film during cycling.Through structural advantages,the resulting 2 D NPC/C@Si electrode demonstrates a high reversible capacity of592 mAh·g^(-1) at 0.2 A·g^(-1) with 90.5%excellent capacity retention after 100 cycles,outstanding rate capability(148 mAh·g^(-1) at 8 A·g^(-1)),and superior long-term cycling stability(326 mAh·g^(-1) at 1 A·g^(-1) for 500 cycles,86%capacity retention).Our findings elucidate the development of high-performance Si@C composite anodes for advanced LTBs.

Wide emission shifts and high quantum yields of solvatochromic carbon dots with rich pyrrolic nitrogen

Carbon dots(CDs)with solvatochromic emission colors in different solvents have attracted much attention as a new class of luminescent nanomaterial owing to their facile synthesis and low production cost.In this work,we prepared two kinds of CDs with solvatochromic emissions:green emission CDs(G-CDs)and multicolor emission CDs(M-CDs).G-CDs synthesized from o-phenylenediamine exhibited weak photoluminescence emission(quantum yield 2.8%-6.1%)and 39 nm solvatochromic shifts(492-531 nm).In contrast,M-CDs prepared from o-phenylenediamine and 4-aminophenol showed 87 nm solvatochromic shift range(505-592 nm)and much higher photoluminescence quantum yield(18.4%-32.5%).The two CDs exhibited different emission,absorption,and photoluminescence lifetime.The origin of solvatochromic shifts and the formation mechanism of CDs were demonstrated by analyzing the structures and compositions of two CDs.High percentages of pyrrolic nitrogen and amino nitrogen make wider solvatochromic shifts and higher quantum yields.The results were well supported by density functional theory calculations.This effective strategy to expand solvatochromic shift range and improve quantum yields could open a new window to prepare satisfied solvatochromic carbon dots.

烷基化碳量子点表面活性剂的制备及性能

目的通过对水热法制备的氮掺杂碳量子点进行烷基化改性,对碳量子点在油气开发领域中的应用潜力进行研究。方法在水热条件下,以柠檬酸作为碳源、二乙烯三胺为氮源合成了碳量子点(CQDs)和氮掺杂碳量子点(N-CQDs);通过烷基化反应对制备出的N-CQDs进行表面改性,得到一种两亲性表面活性物质R-(N-CQDs)。结果CQDs和N-CQDs的粒径分布均匀,具有碳量子点的典型粒径特征;CQDS和N-CQDs的荧光量子产率在各自最大激发波长下分别为10%和47%,氮掺杂极大地提高了碳量子点的荧光性能;与常用表面活性剂SDBS相比,R-(N-CQDs)具有更好的降低表面张力能力、稳泡性能和乳化性能。结论烷基化改性后的碳量子点具有良好的降低表面张力的能力,优异的乳化性能和稳泡性能,在油气开发领域中有一定的应用潜力。

基于量子化学计算优化的氮掺杂碳量子点缓蚀剂制备及其缓蚀性能

[目的]氮掺杂碳量子点(N-CQDs)作为一种绿色高效的新型缓蚀剂,在腐蚀控制领域具有巨大的应用潜力。但由于其结构无法精确调控,很难对制备N-CQDs的众多前驱体进行筛选。[方法]依据密度泛函理论(DFT),通过Fukui指数计算各前驱体分子的优先反应活性位点,确定前驱体分子间一步脱水缩合反应产物的分子结构,并进行全局参量和局部参量的计算,分析了采用柠檬酸分别与乙二胺、尿素和氨基胍盐酸盐作为前驱体所合成的3种N-CQDs的缓蚀性能,再通过称重法对水热法合成的3种N-CQDs的缓蚀性能进行验证,优选出缓蚀性能最佳的缓蚀剂。采用紫外可见吸收光谱、荧光光谱和高分辨率场发射透射电镜表征优选缓蚀剂的荧光性能和表面形貌,并以电化学方法和表面分析方法研究此缓蚀剂对Q235碳钢在0.5 mol/L硫酸溶液中的缓蚀机理。[结果]以柠檬酸和氨基胍盐酸盐为前驱体制备的N-CQDs-3缓蚀性能最佳,且试验结果和理论计算结果一致。N-CQDs-3在紫外激发光下显示蓝绿光,平均粒径为(2.5±0.8)nm。该缓蚀剂是一种混合型缓蚀剂,主要通过物理和化学吸附同时抑制金属在酸溶液中腐蚀反应的发生,其对Q235碳钢在0.5 mol/L硫酸溶液中的缓蚀效率最高可达95.3%。[结论]通过量子化学计算方法对制备N-CQDs所用的前驱体进行筛选,提前预测其缓蚀性能,可提高试验效率。

氮掺杂碳量子点荧光法检测猪肉中的四环素

四环素(TC)作为一种广谱抗生素,用于预防和治疗细菌性疾病,以及作为饲料添加剂促进动物生长。本文旨在建立一种菠萝皮来源的氮掺杂碳量子点(N-CQDs)荧光猝灭法快速检测TC。以菠萝皮和二乙烯三胺为原料,通过水热法制备高量子产率的蓝色荧光N-CQDs。通过透射电子显微镜、傅里叶红外光谱、X射线光电子能谱对N-CQDs进行结构表征。结果表明,N-CQDs的平均粒径为3.53 nm,主要由C、N、O 3种元素组成,表面具有含氧和含氮基团。主要猝灭机理为静态猝灭和内滤效应。在最优试验条件下,该方法在0.3~40μg/mL范围线性良好,检出限为89.26μg/L。该检测方法被用于猪肉中四环素的检测,回收率在98.40%~106.02%之间,相对标准偏差1.29%~3.88%。

量子点碳修饰生物阴极提高BC-MFC系统脱氮及产电性能

为提高生物阴极微生物燃料电池系统脱氮及产电性能,提出采用量子点碳对生物阴极微生物燃料电池系统(BC-MFC)的生物阴极(BC)进行修饰,以增加阴极附着面积提高微生物附着量。以脱氮作为首要目标,产电作为次要目标,设计了4组不同类型生物阴极的BC-MFC系统进行实验。结果表明,利用量子点碳对生物阴极进行修饰,能提高系统的脱氮能力,氨氮和总氮去除率最高可达到80%和77%,相比于对照组均提升约10%;系统微生物群落形成更快,启动时间缩短,且系统内阻最高下降24.19Ω,平均下降约23Ω,功率密度最高提升9.42 mW·m^(-3),平均提升6.76 mW·m^(-3);增加了系统的不稳定因素,采用微生物提前挂膜培养和在阴极区域栽种湿地植物的方法可提高系统稳定性。

氮掺杂碳量子点的制备及在细胞温度传感中的应用

该研究以生物质西红柿为碳源和氮源,通过微波法制备了氮自掺杂碳量子点(N-CQDs)。通过场发射透射电子显微镜(TEM)、X射线光电子能谱仪(XPS)和荧光光度计等对其形貌、结构、稳定性、光电性能、温敏性及细胞毒性进行考察,并用于活细胞温度传感研究。实验结果表明,所制备的N-CQDs稳定性强,光电性能优异,对温度具有较强的敏感性。在25~65℃范围内,N-CQDs的荧光强度随着温度的升高而降低,两者呈良好的线性关系。N-CQDs能穿透4T1细胞的细胞膜,显示出低毒性和生物相容性,在4T1细胞中具有良好的温度传感性能。该N-CQDs在活细胞荧光温度传感领域具有较大的应用潜能,有望作为温敏型纳米荧光探针在细胞研究等生物医学领域得到广泛应用。

双氮源共掺杂木素碳量子点/有机溶剂水份探针的构建及性能

以木素为碳源,以盐酸为解聚剂,以邻苯二胺和尿素为氮掺杂剂,通过一锅水热法获得了碳量子点。该碳量子点的荧光量子产率为2.05%,其水溶液在紫外区具有明显的吸收,并表现出较强的溶剂依赖性。将其用于检测实验室常用的三种有机溶剂(乙醇、N,N-二甲基甲酰胺和四氢呋喃)时,随着有机溶剂中水份含量的增加,发射光谱出现红移,且其荧光强度下降。在所构建的双氮源共掺杂木素碳量子点/有机溶剂水份荧光探针中,碳量子点的荧光强度与有机溶剂的水份含量存在良好的线性关系,对乙醇、N,N-二甲基甲酰胺和四氢呋喃中水份的检出下限分别为0.079%、0.075%和0.080%,并实现了可视化的水份检测。该研究结果可为有机溶剂中微量水份的检测提供理论和实验参考。

氮掺杂碳量子点与牛血清白蛋白相互作用的研究

采用光谱法研究了掺氮碳量子点(N-CQDs)与牛血清白蛋白(BSA)的相互作用机理。光谱分析表明,N-CQDs能有效猝灭BSA的内源性荧光,属于静态猝灭机制。N-CQDs的加入导致色氨酸残基微环境的疏水性降低,继而引起BSA的构象产生变化。N-CQDs与BSA可能是以1∶1的比例相互结合形成了稳定的复合物。结合热力学参数进行分析,N-CQDs与BSA相互结合的作用力主要为静电吸引力,反应为自发进行。同步荧光光谱也表明,N-CQDs与BSA的结合改变了BSA的构象。此研究数据可为进一步了解N-CQDs纳米颗粒在生物体内的应用提供参考。

掺氮碳量子点与牛血清白蛋白相互作用机制研究

当碳纳米材料进入生物体的血液中时,与血浆中的血清白蛋白相互作用可能会导致蛋白质的构象改变,从而影响其生物活性。利用荧光光谱、紫外吸收光谱、三维荧光光谱法研究掺氮碳量子点(N-CQDs)与牛血清白蛋白(BSA)的相互作用机制。结果表明,N-CQDs能够有效猝灭BSA内部荧光,符合静态猝灭机制。N-CQDs与BSA能够自发性结合,其结合作用力主要是静电吸引力。N-CQDs的加入导致色氨酸和酪氨酸残基微环境发生变化,继而改变了BSA的分子构象。该研究可为N-CQDs在体内的进一步应用提供参考依据。

掺氮荧光碳量子点的制备及性能研究

以柠檬酸为碳源、对氨基苯甲酸为氮源,通过一步水热法制备了氮掺杂荧光碳量子点(N-CQDs),采用透射电子显微镜、傅里叶变换红外光谱仪、稳态瞬态荧光磷光光谱仪对其形貌、结构和光谱进行表征,研究了反应温度、反应时间、酸碱度对N-CQDs荧光性能的影响。结果表明:N-CQDs呈球形,具有良好的分散性;N-CQDs的荧光强度较碳量子点增强约17倍,N-CQDs最佳激发波长为404nm,最佳发射波长为480nm,说明氮的掺杂有助于碳量子点荧光强度的增强;反应温度为180℃、反应时间为6h,酸碱度为中性时,N-CQDs荧光强度最强。

LaFeO_(3)/CQDs-g-C_(3)N_(x)催化剂的光催化性能研究

本实验制备了一种Z型含氮缺陷的石墨相氮化碳(LaFeO_(3)/CQDs-g-C_(3)N_(x))复合光催化剂。利用X射线衍射(XRD)、紫外-可见光漫反射(UV-Vis DRS)、光致发光光谱(PL)、扫描电镜(SEM)、透射电镜(TEM)以及X射线光电子能谱(XPS)等手段对催化剂进行了表征。结果表明,氮缺陷和CQDs的引入能增强光生载流子的迁移效率。LaFeO_(3)/CQDs-g-C_(3)N_(x)复合材料对罗丹明B(RhB)的光催化降解率是纯g-C_(3)N_(4)的3.98倍,并具有良好的光催化稳定性。同时对抗生素和其他有机污染物也表现出良好的降解能力。

氮硼共掺杂碳量子点的制备及其对六价铬的检测

目的建立一种基于荧光碳量子点的快速检测方法,定量检测饮用水和食品中的六价铬[hexavalent chromium,Cr(Ⅵ)]。方法以无水柠檬酸和3-氨基苯硼酸分别作为碳、氮和硼源,通过一步水热法合成氮硼共掺杂碳量子点(nitrogen-boron-doped carbon quantum dots,N,B-CQDs),基于荧光内滤效应对Cr(Ⅵ)进行检测。结果在优化后的最佳检测条件下,N,B-CQDs对Cr(Ⅵ)在0.01~10.00 mg/L内呈现良好的线性关系,检出限低至3.81μg/L,表现出选择性好、灵敏度高等特点。将此方法应用于饮用水、白醋和虾皮中Cr(Ⅵ)含量的测定,加标回收率在85.8%~112.3%之间,相对标准偏差低于5%。结论本研究制备的N,B-CQDs在Cr(Ⅵ)检测方面具有检出限低、灵敏度高、选择性好等优点,可以为Cr(Ⅵ)快速检测提供一定的理论和技术参考。

高量子产率的氮掺杂碳量子点荧光猝灭检测Hg^(2+)

以三羟甲基氨基甲烷和柠檬酸为前驱体,通过一步水热法合成了粒径约为3 nm的氮掺杂碳量子点(NCQDs)。该N-CQDs发明亮的蓝光,最佳激发和发射波长分别为370 nm和429 nm,荧光量子产率(QY)73.31%,并且Hg^(2+)能高选择、高灵敏地猝灭N-CQDs的荧光,猝灭率85%,在室温pH=5的环境下,检出限低至2.28μmol·L^(-1),线性范围为0.1~0.4 mmol·L^(-1),R2=0.9965。将该N-CQDs用于检测实际水样中的Hg^(2+),加标回收率在94.4%~107.6%之间。

红外成像研究PLLA/N-CQDs复合薄膜的结晶性能

将水热法制得的氮掺杂碳量子点(N-CQDs)加入聚乳酸(PLLA)基质中,以溶剂浇铸法制备了PLLA/N-CQDs复合薄膜,并通过红外成像分析了N-CQDs的加入对PLLA结晶性能的影响。结果显示,加入N-CQDs可以显著提高PLLA的结晶性能。