基于天冬氨酸与纤维素碳点材料的合成与性能研究

以羟乙基纤维素为碳源,L-天冬氨酸为氮源,通过一步水热合成法制备氮掺杂碳量子点(CDs)材料.利用红外光谱(FTIR)、X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)、荧光分光光谱仪(FS)和紫外-可见吸收光谱仪(UV-Vis)对产物进行表征分析,研究了不同氮掺杂含量和氧气对CDs的光致发光性能的影响.结果表明:制备得到的CDs材料表面富含O和N原子;掺杂N原子有效提高了CDs的荧光强度,且荧光强度随着激发波长的增大,呈现先增强后减弱的趋势;其中荧光量子产率最高达到27.5%;CDs材料在无氧环境下的荧光强度要比有氧环境下的大,表明氧气的存在对碳量子点材料表面荧光有猝灭作用.     

氮掺杂碳点作为荧光探针检测蛇床子素

本文以一水柠檬酸和尿素为原料,通过微波法合成氮掺杂碳点(N-CDs)。利用透射电子显微镜(TEM)、X-射线衍射法(XRD)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FT-IR)、紫外可见吸收光谱(UV-Vis)和荧光光谱对合成的N-CDs进行表征。N-CDs的荧光强度随着蛇床子素浓度的增加而逐渐被猝灭。在最佳实验条件下,N-CDs荧光探针对蛇床子素有较高的选择性和灵敏性。蛇床子素在5×10~(-6 )M～7.5×10~(-5 )M的浓度范围内与N-CDs的荧光强度呈良好的线性范围,检出限为3.8×10~(-9) M。基于此建立了一种以氮掺杂碳点(N-CDs)为荧光探针快速测定蛇床子素的方法。同时讨论了蛇床子素与N-CDs相互作用的机理,此方法已被应用于实际血样和尿样中微量蛇床子素的测定。     

用氮掺杂碳点为荧光探针检测对羟基苯甲醛

本文通过一步水热法,以菊花为原料,制备了氮掺杂碳点(N-CDs),并对N-CDs的粒径分布、元素组成、形貌结构及表面官能团进行了表征,考察了N-CDs的光谱性质。本实验基于PHBA有效猝灭N-CDs荧光的现象,以N-CDs为荧光探针,对PHBA进行了定量测定。结果显示该探针对PHBA的检测线性范围为10.0-150.0μM,检出限为63 nM。常见的离子、氨基酸和糖类对N-CDs检测PHBA基本无影响。同时,初步探讨了N-CDs与PHBA的反应机理主要为静态猝灭和内滤光效应。将该探针应用于健康人体血样和尿样中PHBA的微量测定。本实验为对羟基苯甲醛的检测提供了新的思路,也预示了该荧光探针在生物样品检测方面具有广阔的应用前景。     

微波辅助法合成硼、氮掺杂碳点用于检测抗坏血酸

以乙二胺为碳源和氮源,4-羟基苯硼酸为硼掺杂剂,采用微波辅助法一步合成了硼、氮掺杂碳点(B,N-CDs)。通过透射电子显微镜、紫外-可见吸收光谱、荧光光谱、X射线光电子能谱对其形貌、光学性质等进行表征。B,N-CDs的最大激发和发射波长分别为400和510 nm。以硫酸奎宁为参照,B,N-CDs的相对量子产率为9.94%。Fe³⁺的存在可使此CDs的荧光猝灭,而抗坏血酸(AA)可通过将Fe³⁺还原为Fe²⁺,使B,N-CDs的荧光恢复,基于此,建立了一种检测AA的荧光分析方法。本方法对AA具有良好的选择性,在1.0～80.0μmol/L浓度范围内,B,N-CDs的荧光恢复程度与AA的浓度呈良好的线性关系,检出限为0.49μmol/L(S/N=3)。将此方法应用于果汁中AA的测定,结果较好。     

一步水热法制备氮掺杂碳点用于Fe3+检测及细胞成像

以生物相容性优异的人体必需氨基酸分子色氨酸和苏氨酸为前驱体,通过一步水热法合成了水溶性良好的蓝色荧光氮掺杂碳点(N-CDs).采用高分辨率透射电镜、X射线衍射光谱、X射线光电子能谱、傅里叶红外吸收光谱、紫外可见吸收光谱、荧光光谱对其结构、组成和光学性质进行研究.结果表明所制备的N-CDs尺寸均一,平均粒径为4.1 nm...     

pH药物控释的氮掺杂碳点载运阿霉素用于光热与化疗的协同治疗

提出一种利用氮掺杂碳点(N-CDs)的光热性能与化疗药物阿霉素(Dox)相结合的联合治疗肿瘤模式。实验结果标明,所制备的N-CDs的分散液经光照后升温可达10℃,是性能优异的光热剂。同时,载运Dox后的N-CDs-Dox纳米复合物还具有pH触发的药物控释作用。因此,这种多功能的N-CDs-Dox纳米复合物能够实现光热和化疗的协同作用,有效杀伤肿瘤细胞。     

S-异丙甲草胺与小牛胸腺DNA的相互作用

应用紫外光谱、荧光光谱、DNA热变性法以及黏度法研究了S-异丙甲草胺与小牛胸腺DNA(ctDNA)的相互作用. 结果表明, S-异丙甲草胺使ctDNA在200 nm处的吸收峰发生明显改变, 表现出红移和减色效应, 而对260 nm处的吸收峰产生影响较小, 排除了嵌插作用的可能; ctDNA对S-异丙甲草胺内源性荧光表现出很强的猝灭作用, 且随温度的升高, 其猝灭程度有所下降, 表明S-异丙甲草胺是以形成加合物的方式与ctDNA结合的, 并求得了它们在不同温度下的结合常数; 将不同离子强度条件下S-异丙甲草胺与ctDNA作用以及不同S-异丙甲草胺浓度下ctDNA的热变性温度和黏度变化的研究结果与紫外光谱和荧光光谱相结合, 可以判断S-异丙甲草胺是以沟槽作用的方式与ctDNA结合的.     

氮掺杂碳点荧光增强型探针检测对硫磷

以石榴籽作为碳源,天冬氨酸和色氨酸作为钝化剂,结合水热法制备了氮掺杂碳点(N-CDs)。通过透射电镜、 X射线光电子能谱和红外光谱对N-CDs进行了表征。所制备的氮掺杂N-CDs具有良好的抗光漂白性,对常见金属离子具有优异的化学惰性。有机磷农药对硫磷能够和N-CDs发生强烈的相互作用,该相互作用显著增强了N-CDs的发光强度。以N-CDs作为荧光增强型探针测定对硫磷,方法的线性范围为0.01～1.1μmol/L,检出限低至3.7 nmol/L。同时探讨了对硫磷增强N-CDs发光强度的机理。所建立的方法用于环境水样中对硫磷的检测,结果的相对标准偏差小于3.2%,回收率在98.0%～102.7%之间。     

硅、氮共掺杂碳点荧光粉的制备及发光性能

采用N-苯基对苯二胺和3-氨基丙基三甲氧基硅烷为原料,通过光化学催化法合成了高荧光强度的硅、氮共掺杂碳点（Si/N-CDs）。通过透射电子显微镜（TEM）、X射线光电子能谱（XPS）、荧光光谱、X射线衍射（XRD）和红外光谱（FT-IR）等对Si/N-CDs进行了表征。制备的 Si/N-CDs形貌呈球形,平均直径约6.45 nm,在365 nm紫外光照射下发明亮的蓝绿色荧光,量子产率可达30.8%,连续30 d测试Si/N-CDs均保持高的荧光强度。用Si/N-CDs替代传统的红/绿/蓝三基色稀土荧光粉中的蓝/绿稀土荧光粉,并与红色荧光粉（Sr,Ca）AlSiN₃∶Eu²⁺复合制备白光二极管（White Light Emitting Diode, WLED）。在60 mA电流下运行WLED,可实现86.9的高显色指数和7.76 lm/W的发光效率,色坐标是（0.3773, 0.3734）,色温为4062 K,并且色点位于黑体普朗克轨迹上,表明制备的WLED可以产生高质量的照明效果。硅、氮共掺杂碳点具有简便的制备方法和优异的光学性质,并能够代替蓝/绿色稀土荧光粉与红光荧光粉复合制备高质量照明的WLED,扩展了碳点在发光器件中的应用。同时,Si/N-CDs兼具低毒性、稳定的光学性质和简单的合成工艺,使其在蓝色和绿色稀土荧光粉的替代中具有潜在的商业应用前景。     

制备MoS2修饰的秸秆碳点纳米酶及对人尿液中尿酸含量的检测

采用水热合成法制备了MoS2修饰的秸秆碳点纳米酶(Mo,S-CDs)用于人尿液中尿酸含量的检测,发挥了秸秆自身的结构优势,并实现了生物质废弃物的回收利用.对Mo,S-CDs的表征结果表明,Mo元素和S元素成功地修饰在秸秆碳点结构中,Mo,S-CDs为球形,表面有丰富的官能团,保障了其可较好地分散于水介质中,晶体层面为无...     

Fluorescence Intensity Enhancement of Green Carbon Dots: Synthesis,Characterization and Cell Imaging

The hydrothermal treatment of green carbon dots (CDs) is an appropriate fluorescent probe synthesis method. CDs are exploited as biological staining agents, especially for cellular detection and imaging. The nitrogen-doped green carbon dots (N-CDs) formation can improve the fluorescence intensity property in a one-step process. Here, we report two N-CDs from lemon and tomato extraction in the presence of hydroxylamine. Lemon and tomato N-CDs showed the blue fluorescence under ultraviolet radiation of about 360 nm. The characterization of CDs and N-CDs showed the presence of N-H and C–N bonds which enhanced the fluorescence efficiency. The mean size of lemon and tomato N-CDs were about 2 and 3 nm with an increased quantum yield (QY) of 5% and 3.38%, respectively. The CDs and N-CDs cytotoxicity assay exhibited high cell viability approximately 85% and 73%, respectively. N-CDs show superior fluorescent intensity in different solvents and significant stability under long-time UV irradiation, different PH and high ionic strength. Our results indicated that the use of N-CDs in cell imaging can lead to fluorescence intensity enhancement as well as proper biocompatibility. Therefore, the safe and high fluorescence intensity of green N-CDs can be utilized for fluorescent probes in biolabeling and bioimaging applications.     

Synthesis of carbon dots with a tunable photoluminescence and their applications for the detection of acetone and hydrogen peroxide

Carbon dots(CDs) with multi-color emissive properties and a high photoluminescent quantum yield(PLQY) have attracted great attention recently due to their potential applications in chemical,environmental,biological and photo-electronic fields.Solvent-dependent effect in photoluminescence provides a facial and effective approach to tune the emission of CDs.In this study,green emissive nitrogen-doped carbon dots(N-CDs) are synthesized from p-hydroquinone and ethylenediamine through a simple hydrothermal method.The as-prepared N-CDs possess a robust excitation-independent green luminescence and a high PLQY of up to 15.9%.Further spectroscopic characterization indicates that the high PLQY is achieved by the balance of nitrogen doping states and the surface passivation extent in CDs.The N-CDs also exhibit solvent-dependent multi-color emissive property and distinct PLQY in different solvents(the maximum can reach up to 25.3%).Furthermore,the as-prepared N-CDs are applied as fluorescence probes to detect acetone and H2O2 in water.This method has exhibited a low detection limit of acetone(less than 0.1 %) and a quick and linear response to the H_2O_2 with the concentration from 0 to 120 μmol/L.This work broadens the knowledge of applying CDs as probes in the bio and chemical sensing fields.     

Fluorine-defects induced solid-state red emission of carbon dots with an excellent thermosensitivity

Up to date, solid-state carbon dots (CDs) with bright red fluorescence have scarcely achieved due to aggregation-caused quenching (ACQ) effect and extremely low quantum yield in deep-red to near infrared region. Here, we report a novel fluorine-defects induced solid-state red fluorescence (λ_em = 676 nm, the absolute fluorescence quantum yields is 4.17%) in fluorine, nitrogen and sulfur co-doped CDs (F,N,S-CDs), which is the first report of such a long wavelength emission of solid-state CDs. As a control, CDs without fluorine-doping (N,S-CDs) show no fluorescence in solid-state, and the fluorescence quantum yield/emission wavelength of N,S-CDs in solution-state are also lower/shorter than that of F,N,S-CDs, which is mainly due to the F-induced defect traps on the surface/edge of F,N,S-CDs. Moreover, the solid-state F,N,S-CDs exhibit an interesting temperature-sensitive behavior in the range of 80–420 K, with the maximum fluorescence intensity at 120 K, unveiling its potential as the temperature-dependent fluorescent sensor and the solid-state light-emitting device adapted to multiple temperatures.     

Comparative study for N and S doped carbon dots: Synthesis,characterization and applications for Fe probe and cellular imaging

A facile and eco-friendly approach to prepare nitrogen(N)- and sulfur(S)-doped carbon dots (CDs) by one step microwave-assisted pyrolysis of the precursors with dl-malic acid as carbon source, ethanolamine and ethane-sulfonic acid as N and S dopants, respectively, was reported. Through the extensive investigation on morphology, chemical structures and optical properties of the carbon dots, it was found that the obtained CDs exhibited good luminescence stability, high resistance to photo bleaching and favorite solubility. Compared with undoped CDs, adding the N or S dopant could give rise to a slightly smaller particle size and a long fluorescence lifetime of CDs. Moreover, the optimal N-CDs was successfully employed as good multicolor cell imaging probes due to its fine dispersion in water, excitation-dependent emission, excellent biocompatibility and low toxicity. Besides, such N-CDs showed a wide detection range and excellent accuracy as fluorescent probe for Fe³⁺ ions. This probe enabled the selective detection of Fe³⁺ ions with a linear range of 6.0–200 μM and a limit of detection of 0.80 μM.     

Blood compatible heteratom-doped carbon dots for bio-imaging of human umbilical vein endothelial cells

Carbon dots have unique advantages in biological applications owing to their excellent optical prope rties.However,the biosafety evaluation of carbon dots has limitations owing to cytotoxicity in vitro,and the re is little pre-safety evaluation before in vivo and clinical applications.Whether the carbon dots are or not suitable for applications in vivo,evaluation analysis can be made based on hemolysis and changes in erythrocyte morphology.In this work,a green fluorescent N,S-doped carbon dots(N,S-CDs)were obtained by hydrothermal method,tobias acid,and m-phenylenediamine as precursors.N,S-CDs not only possessed excellent dispersibility,uniform particle size,high quantum yield(37.2%)and stable photoluminescence property but also retain their photostability and stro ng fluorescence intensity in the acid/alkaline solutions,different ionic strengths(NaCl)and under 365 nm UV illumination.Moreove r,the N,S-CDs displayed low cytotoxicity and high cellular uptake efficiency in human umbilical vein endothelial cells(HUVEC)and excellent blood compatibility to the erythrocyte.It is foreseeable that N,S-CDs could be further studied as a promising biological imaging agent in vivo.     

双功能碳点用于葡萄糖的比色/比率荧光测定

以生物质(合果芋叶片)、 十二水合硫酸铁铵和脲为原料, 采用水热法制备了铁、 氮共掺杂碳点(Fe,N-CDs), 采用透射电子显微镜和X射线光电子能谱对其形貌与元素组成进行了表征. 该Fe,N-CDs既具有类过氧化物酶活性, 也能在450 nm处产生强荧光发射. 以Fe,N-CDs和邻苯二胺(OPD)为探针, 建立了一种比色/比率荧光测定双氧水（H₂O₂）的双信号方法. 在H₂O₂存在下, Fe,N-CDs催化OPD氧化成黄色的2,3-二氨基吩嗪(DAP), DAP在420 nm处有1个特征吸收峰. 在360 nm波长光的激发下, DAP在550 nm处有强荧光发射; 由于荧光内滤效应, DAP又可猝灭Fe,N-CDs在450 nm处的荧光. 基于此, DAP在420 nm处的吸光度(A₄₂₀)及DAP与Fe,N-CDs的荧光强度比(I₅₅₀/I₄₅₀)均可用于H₂O₂的定量分析. 考虑到葡萄糖氧化酶能催化葡萄糖氧化生成H₂O₂, 进一步发展了一种比色/比率荧光双信号葡萄糖测定方法. 在pH=5.4, 温度40 ℃, 1.75 mmol/L OPD及反应时间25 min的条件下, 当葡萄糖浓度在1.0~100 μmol/L范围内时, A₄₂₀及I₅₅₀/I₄₅₀值与浓度呈良好的线性关系, 方法的检出限分别为0.8(比色)和0.6 μmol/L(比率荧光). 将该方法成功应用于人体血清中葡萄糖的测定.     

Multiplex binding modes of toluidine blue with calf thymus DNA and conformational transition of DNA revealed by spectroscopic studies

It is noteworthy to understand the details of interactions between antitumor drugs and DNA because the binding modes and affinities affect their antitumor activities. Here, The interaction of toluidine blue (TB), a potential antitumor drug for photodynamic therapy of tumor, with calf thymus DNA (ctDNA) was explored by UV–vis, fluorescence, circular dichroism (CD) spectroscopy, UV-melting method and surface-enhance Raman spectroscopy (SERS). The experimental results suggest that TB could bind to ctDNA via both electrostatic interaction and partial intercalation. The fluorescence quenching of TB by ctDNA was static and due to electron transfer from bases to the excited singlet state of TB. At low [TB]/[DNA] ratio, TB mainly partially intercalated into ctDNA resulting in the slight increase of base stacking degree; at high [TB]/[DNA] ratio, excessive TB externally stacked along the helix surface via coupling with partially intercalated ones, thereby inducing B-A transition of ctDNA. The conformational transition of DNA was confirmed by the obvious improvement of the thermal stability of ctDNA. The SERS spectra suggest that TB could partially intercalate into DNA basepairs with its ring C₁NC_1′ side buried.     

Insight into the Multistate Emissive N,P-doped Carbon Nano-Onions: Emerging Visible-Light Absorption for Photocatalysis

Carbon dots (CDs) have become one of the most emerging materials as an alternative solar light-induced photocatalyst in contrast to traditional metal-based systems. However, one of the major challenges is the lack of visible light absorption. Herein, we have fabricated unique N, P-co-doped CDs with a self-assembled onion-like layered structure by using a bottom-up facile synthesis technique from chitosan gel and phosphoric acid as molecular precursors. This typical layered structure of N, P-co-doped carbon nano onions (N, P-CNOs), with an average size of 25–50 nm, displays an enhanced visible light absorption. Detailed structural and elemental characterizations confirm the extensive aromatic domain with P-containing surface functionalities, while electrochemical study clarifies the lowering of band gaps as well as the creation of new electronic states in comparison to the pristine N-CDs. Furthermore, the intrinsic structural features are correlated with the underpinning photophysical processes by steady-state and time-resolved fluorescence spectroscopy. In addition, steady-state polarized emission and thermo-responsive PL properties have been carried out to unveil further the structure-property correlation of N, P-CNOs, and their comparative study with pristine N-CDs at the different excitation wavelengths. Finally, N, P-CNOs exhibit efficient visible-light-induced photocatalysis, and the detailed mechanistic study is carried out by trapping the photogenerated species in an aqueous medium. The prepared N, P-CNOs displayed an excellent visible-light photocatalytic performance over MB dye with a degradation efficiency of 75.8% within 120 min along with a degradation rate constant of ∼0.0109 min⁻¹. It is concluded that the easy to synthesize and low-cost N, P-CNOs with a unique morphology hold great potential for application in visible-light photocatalysis.     

Absorption,Fluorescence and Resonance Rayleigh Scattering Spectra of Interaction of Papain with Calf Thymus DNA

In weak acidic medium, interaction between papain and calf thymus DNA (ctDNA) resulted in absorption spectral change, fluorescence quenching of papain and remarkable enhancement of resonance Rayleigh scattering (RRS). The interaction types and binding modes were discussed by characteristics of RRS, absorption, fluorescence and circular dichroism spectra combining thermodynamic data. Four interaction types include electrostatic attraction, hydrophobic force, hydrogen bonding and aromatic stacking interaction. Papain interacted with the major groove of ctDNA. Aromatic stacking interaction is the main reason of change of absorption spectrum and fluorescence quenching of papain. Surface enhanced scattering effect, resonance energy transfer effect, increase of molecular volume and conformational change make contribution to RRS enhancement. The enhanced RRS intensity (ΔI) is directly proportional to the concentration of ctDNA or papain. The detection limit (3σ) is 5.2 ng·mL^?1 for ctDNA and 5.6 ng·mL^?1 for papain. This creates conditions for determination of papain and ctDNA.     

Facile synthesis of nitrogen-doped carbon dots for Fe sensing and cellular imaging

A fast and facile approach to synthesize highly nitrogen (N)-doped carbon dots (N-CDs) by microwave-assisted pyrolysis of chitosan, acetic acid and 1,2-ethylenediamine as the carbon source, condensation agent and N-dopant, respectively, is reported. The obtained N-CDs are fully characterized by elemental analysis, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction pattern, X-ray photoelectron spectroscopy, UV–vis absorption, and photoluminescence spectroscopy. Doping N heteroatoms benefits the generation of N-CDs with stronger fluorescence emission. As the emission of N-CDs is efficiently quenched by Fe³⁺, the as-prepared N-CDs are employed as a highly sensitive and selective probe for Fe³⁺ detection. The detection limit can reach as low as 10 ppb, and the linear range is 0.010–1.8 ppm Fe³⁺. The as-synthesized N-CDs have been successfully applied for cell imaging and detecting Fe³⁺ in biosystem.