The Preparation Of Fluorescent Carbon Nanomaterials And Its Application On Sensors

The unique properties of carbonic nanmaterials,such as nanodiamonds,fullerenes,carbon nanotubes,graphene sheets and fluorescent carbon nanoparticles or carbon dots(CDs),have inspired extensive studies on them due to their great potential for a wide variety of technical applications.CDs offer many advantages over other fluorescence materials such as high good photostability,tunable emission wavelengths.CDs are promising optical labels,which have been widely used for chemosensing and biosensing.In recent years,CDs have become one of the most exciting fields.In this dissertation,we prepared different colored fluorescent carbon dots using various methods,and with heavy metal ions as the analytical target,make full use of the nature of the surface functional groups of CDs to constructed optical sensors based on CDs.The sensing methods were constructed for on-site,rapid,sensitive,and visual detection of heavy metals by the naked eye.On other hand,high-energy laser is a very simple and powerful tool to produce the white-light silica nanoparticles;it is potential in the display and lighting applications in the future.The main parts of the results are summarized briefly as follows:1.Classical pH test papers are widely employed to measure the acid-base degree of media in a qualitative or semi-quantitative way.However,the extension of the portable and inexpensive methods to a wide range of analytes so as to liberate us from the disbursements of instrumental assays remains unsuccessful.A novel kind of dual-colored carbon dots(CDs)ratiometric-fluorescent test paper for the semi-quantitative assay of copper ions(Cu2+)by a dosage-sensitive color evolution.The creation of the test paper is based on the two interesting findings:on the one hand,the residual p-phenylenediamine(p-PDA)at the surface of as-synthesized red-emissive CDs efficiently binds Cu2+ ions to produce a strong visible absorption that overlaps with the emission of blue CDs(b-CDs),on the other hand,Cu2+ ions render small b-CDs adsorbed onto the surface of larger-sized r-CDs through its dual-coordinating interactions with the surface ligands of both r-CDs and b-CDs.The two mechanisms lead to a specific spectral energy transfer to quench the fluorescence of b-CDs with a sensitive detection limit of 8.82 nM Cu2+,while the red fluorescence of r-CDs keeps unaffected as a stable internal standard.Ratiometric-fluorescent test papers have been prepared using a mixture of b-CDs and r-CDs(7:1)as ink by jetprinting on a piece of paper.With the addition of Cu2+ ions,the blue test paper produces a consecutive wide-colored evolution from blue to orange red with a dosage-discerning ability as low as 25 nM.2.A ratiometric fluorescent probe was prepared to selectively detection of mercury ions(Hg2+),and the probe was mixed the blue-emission silicon nanocrystal(Si CNs)and red-emission carbon dots(r-CDs).The Si CNs serve as the reporter signal and the r-CDs as the internal reference.Upon the addition of Hg2+,the blue fluorescence of the Si CNs was quenched while the red fluorescence r-CDs keep constant,resulting in the consecutive fluorescence color changes from blue to orange red.The probe demonstrates high selectivity and sensitively of visualization detection of Hg2+ with detection limit of 7.63 nM.Moreover,we printed the ratiometric fluorescence probe onto a piece of filter paper to prepare a test paper,which exhibits an on-site,sensitive,rapid and cost-effective method for the visualization determination of Hg2+ by the naked eye.3.White-light-emitting materials for the applications in display and lighting have widely been prepared by the rare earth with high photoluminescent efficiency and stability,but the short resource,high cost,and serious environmental concerns are the insurmountable barriers of rare-earth-based materials.The instant high temperature and pressure induced by strong laser simultaneously caused the reduction of partial silica and the pyrolysis of carbon chains in the interior of silica nanoparticles,in which the rapid crystallizations of the silicon and carbon vapor led to the formations of silicon dots and diamond-like carbon dots in the silica matrix.Significantly,the resultant silica nanoparticles containing different sized silicon and diamond dots exhibited a wide fluorescence spectrum to display bright white light under UV excitation.Moreover,the light emission diode(LED)device prepared by using the ablated silica nanoparticles as light source gave off the warm white light with Commission Internationale de l'Eclairage(CIE)coordinates(0.34,0.32).The strategy reported here opens a new window to the exploration of white-light-emitting materials through the very simple,inexpensive,and environment-friendly pathway.