Two types of photoluminescent carbon dots(CDs)-embedded polyelectrolyte(PE) microcapsules were successfully prepared via the layer-by-layer(LbL) assembly approach on sacrificial templates.For the first type,the PE microcapsules with CDs embedded in the cavity were produced from assembly of five pairs of poly(sodium 4-styrensulfonate)(PSS) and poly(allylamine hydrochloride)(PAH) on CDs-pre-loaded meso-porous silica.For the second type,the PE microcapsules with CDs embedded in the wall were made of CDs and PAH,which were derived from SiO_2 particles as templates.Microscope images confirmed the introduction of CDs into the two CDs-embedded microcapsules.These two microcapsules also retained the optical properties of free CDs.Photoluminescence spectra revealed that the two types of microcapsules had excitation-dependent photoluminescence behavior.When the excitation wavelength changed from280 to 340 nm,photoluminescence emission peak of the PE microcapsules with CDs embedded in the cavity shifts from 369 to 377 nm,while for microcapsules with CDs embedded in the wall,emission peak shifts from 367 to 390 nm.Due to low toxicity,good hydrophilicity and photoluminescence properties of CDs,these two kinds of photo-luminescent microcapsules have competitive potential for application in carriers for imaging,drug delivery and biosensors.
A hybrid system of carbon nanotubes(CNTs)coated with poly(amidoamine)(PAMAM)dendrimerencapsulated platinum nanoparticles(Pt-DENs)and glucose oxidase(GOx)was prepared through the layer-by-layer(LbL)self-assembly approach and then used as anode in enzyme-based biofuel cells(BFCs). The assembly process was monitored by-potential measurement,and the as-resulted Pt-DENs/CNTs nanocomposites were characterized by transmission electron microscopy(TEM).The performance of electrodes modified by Pt-DENs/CNTs was also investigated by electrochemical impedance spectroscopy (EIS)and cyclic voltammetry(CV).We found that the Pt-DENs/CNTs could enhance the electron transfer between the redox centers in enzyme and the electrode surfaces.Furthermore,by employing the Pt-DENs/CNTs modified electrodes as anode,the enzyme-based BFCs operated in a solution containing glucose generated an open-circuit voltage of approximately 640.0 mV and a maximum current density of about 90.0 A/cm2,suggesting that Pt-DENs/CNTs may serve as an alternative anode to previously used noble metals in BFC applications.
Jianmei ZhangYihua ZhuCheng ChenXiaoling YangChunzhong Li
Hollow Al2O3 nanospheres with well-defined structure and shape were successfully prepared via flame spray pyrolysis (FSP) in the presence of a surfactant as droplet stabilizer. The morphology and structure of the nanospheres were systematically characterized by transmission electron microscopy, scanning electron microscopy, and N 2 sorption. A solution of hydrated aluminum nitrate, polyethylene glycol (PEG) and absolute ethanol was sprayed into a flame to transform droplets into particles after evaporation and surface nucleation, forming hollow Al2O3 nanospheres from aluminum nitrate decomposition. The surfactant was found effective in producing smaller droplets because of decreased surface tension and viscosity, while the combination of oxygen atoms on PEG chains and aluminum ions in solution reduced interfacial turbulence, leading to increased stability of the droplets.
