Fluorescence Detection for H_2PO_4^- based on Carbon Dots/Fe^(3＋) Composite

A novel fluorescent probe for H_2PO_4^- was designed and fabricated based on the carbon dots/Fe^（3＋） composite. The carbon dots were synthesized by an established one-pot hydrothermal method and characterized by transmission electron microscope, X-ray diffractometer, UV-Vis absorption spectrometer and fluorescence spectrophotometer. The carbon dots/Fe^（3＋） composite was obtained by aqueous mixing of carbon dots and FeCl_3, and its fluorescence property was characterized by fluorescence spectrophotometer. The fluorescence of carbon dots was quenched by aqueous Fe^（3＋） cations, resulting in the low fluorescence intensity of the carbon dots/Fe^（3＋） composite. On the other hand, H_2PO_4^- reduced the concentration of Fe^（3＋） by chemical reaction and enhanced the fluorescence of the carbon dots/Fe^（3＋） composite. The Stern-Volmer equation was introduced to describe the relation between the relative fluorescence intensity of the carbon dots/Fe^（3＋） composite and the concentration of H_2PO_4^-, and a fine linearity（R2=0.997） was found in the range of H_2PO_4^- concentration of 0.4-12 m M.

Study of Photocatalytic Activity of a Nanostructured Composite of ZnS and Carbon Dots

Environmental pollution jeopardizes our existence. For this purpose, research is moving more and more towards the search for economic means and green chemistry to curb this phenomenon. In this context, the photocatalytic activity of zinc sulfide nanoparticles (ZnS NPs) and nanostructured composite ZnS/carbon dots (ZnS/CDs) was evaluated after their synthesis. The results of X-ray diffraction (XRD) analysis indicate that the crystal structure of ZnS/CDs is identical to that of the cubic phase structure of ZnS, revealing that the cubic phase structure of ZnS was not altered in the presence of CDs. Indeed, there is no additional peak in the crystal structure of ZnS/CDs, revealing that the crystalline structure of ZnS is not responsible for the difference in photocatalytic activity between ZnS/CDs and ZnS NPs. Moreover, analysis performed by transmission electron microscopy (TEM) shows aggregation of the synthesized ZnS and ZnS/CDs nanoparticles with an average size estimated around 10 nm and 12 nm, respectively. In addition, the reflectance study in the visible range shows a reduction in the sunlight reflection intensity using ZnS/CDs compared to the capability of ZnS NPs. Photocatalytic degradation tests reveal that ZnS/CDs have the best methylene blue (MB) degradation rate. Indeed, under the optimal conditions, the photocatalytic activity can reach 100% efficiency within 100 min and 240 min of sunlight exposure for the degradation of 7.5 mg/L MB using ZnS/CDs and ZnS, respectively. This improvement in photocatalytic activity of ZnS/CDs may be due to the presence of CDs which can permit to undergo a reduction of reflection properties of ZnS NPs in the visible range. These results show that CDs can play a key role in enhancing the photocatalytic activity of ZnS, and suggest that ZnS/CDs could be used as eco-friendly composite materials for the degradation of organic pollutants of similar structures in the aquatic environment under solar irradiation.

A new fluorescence probing strategy for the detection of parathion-methyl based on N-doped carbon dots and methyl parathion hydrolase

A new facile fluorescence probing strategy, which was based on N-doped carbon dots（NCDs） and methyl parathion hydrolase（MPH）, was developed for the determination of parathion-methyl（PM）. The fluorescence intensity of NCDs-MPH system was proportional to PM concentration in the range of 2.38–73.78 mmol/L, with a detection limit of 0.338 mmol/L. Moreover, the present simple and facile method could be used to determine methyl parathion in environmental and agricultural samples successfully.Furthermore, the detection mechanism of this system is inner filter effect and molecular interactions between NCDs and p-nitrophenol, which is the hydrolysis product of PM catalyzed by methyl parathion hydrolase.

Fluorescence Retention of Organosilane-polymerized Carbon Dots Inverse Opals in CuCl Suspension

A novel and fluorescence retention inverse opal has been achieved from organosilane-polymerized carbon dots（SiCDs）, which is prepared via infiltrating SiCD solution into the interstice of photonic crystal（PC） template, low temperature treatment, heating polymerization and removing the colloidal template. The as-prepared SiCD inverse opals demonstrate close-cell structure, which is completely different from conventional open-cell structure. Then the fluorescence signal of as-prepared sample keeps almost unchanged in CuCl suspension while the fluorescence of SiCD solution can be quenched by CuCl suspension through an effective electron transfer process. This phenomenon can be attributed to the combined effect of high hydrostatic pressure in the pore structure, stable crosslinking network and fluorescence enhancement by PC structure. The SiCD inverse opals have advantages of unique close-cell structure, easy preparation and good repeatability that give an important insight into the design and manufacture of novel and advanced optical devices.

One-step straightfoward solid synthesis of high yield white fluorescent carbon dots for white light emitting diodes

Herein,we directly prepared white fluorescent CDs(W-CDs) using 1,6-dihydroxynaphthalene(1,6-DHN)and L-asparagine(L-Asn) as carbon sources through a simple solvent-free method.As-prepared W-CDs can be obtained in high yield(95%).A relative pure white LEDs(WLEDs) were fabricated with Commission Internationale de Eclairage(CIE) coordinates of(0.32,0.31).As-prepared W-CDs will have promising future for a wide range of optoelectronic devices.