Investigation On Photostability Of Nitrogen-doped Carbon Dots And Electrocatalysis Of Platinum-loaded Hollow Carbon Spheres

Carbon nanomaterials contain Fullerene,carbon nanotubes,carbon spheres,carbon dots and graphene quantum dots.Owing to the intrinsic optical,electronic and magnetic properties,carbon nanomaterials have attracted enormous attention of the researchers in the fields of biochemical analysis,bio-medication,catalysis,resources and enviroments.In this paper,carbon dots and hollow carbon spheres were selected.Based on the synthesis of nitrogen-doped carbon dots?N-CDs?,the photostability of N-CDs in various conditions have been investigated.Nitrogen-doped hollow carbon sphere?NHCS?and platinum-loaded NHCS?Pt-NHCS?were synthesized with Si O₂spheres as template,the catalysis of Pt-NHCS on electro-oxidation of ethylene glycol was studied.The details of the progress are as followed:1. N-CDs with proeminent solubility,monodispersity and fluorescent properties were synthesized via a facile hydrothermal method with MABA.Transmission electron microscope?TEM?,X-ray photoelectronic spectroscopy?XPS?,Fourier transform infrared spectroscopy?FT-IR?,ultraviolet visible?UV-vis?absorption spectroscopy and fluorescence spectroscopy were applied to characterize the N-CDs.The obtained N-CDs had an average size of around 1.6 nm,and emitted a strong blue fluorescence under UV excitation.The quantum yield?QY?of the N-CDs was 6.5%.Based on this,the influence of different irradiation time,p H value,dopping-atom on the photostability of the N-CDs has been studied thoroughly.The result showed that the N-CDs exhibited a fluorescence red-shift among all different p H conditions with increase intensity at first and then decrease as the irradiation time prolonged.Further investigation with high-resolution TEM?HR-TEM?and FT-IR explained that the red-shift could be attributed to the N-CDs aggregation and oxidation of surface functional groups.The result provided a guideline to the application of CDs in biochemical analysis and bioimaging.2. A novel NHCS has been obtained through a Si O₂ template synthetic method.Furthermore,microwave-assisted synthesis was followed to decorate platinum nanoparticles onto the NHCS to obtain Pt-NHCS.The as-prepared NHCS and Pt-NHCS were characterized with TEM,HR-TEM,XPS,XRD,X-ray energy dispersive spectroscopy with elemental mapping?EDS-Mapping?and selected area electron diffraction?SAED?et al.The results showed that the average size of the NHCS was about 290 nm,with an average wall thickness of around 34 nm.The XPS characterized the NHCS contained 48.76%of carbon,1.52%of nitrogen and 49.72%of oxygen.After platinum decoration,the loading rate of the platinum was determined with inductively coupled plasma-mass spectroscopy?ICP-MS?to be 19.35 wt%.The obtained Pt-NHCS possessed a rough surface with Pt nanoparticles on them.The Pt-NHCS was attached on a glassy carbon electrode?GCE?followed with cyclic voltammetry?CV?and chronoampermetry tests.The electrochemical active surface area?ECSA?of the Pt-NHCS was determined to be 32.86 m²/g and Pt-NHCS showed satisfactory catalysis on the elethylene glycol oxidation reaction?EGOR?.The result provided certain reference value towards carbon hollow sphere and platinum-based catalysts application in proton exchange membrane fuel cells.