22 research outputs found
Interstitial sulfur photoluminescence in thermochemically synthesized CdS nanocrystals (NCs)
We have synthesized CdS NCs (NCs) by a thermochemical approach. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The structure and optical property of the NCs were characterized by means of XRD, TEM, UV-visible optical spectroscopy and photoluminescence (PL). XRD and TEM analyses demonstrated hexagonal phase CdS NCs with an average size of around 2 nm. Synthesized NCs exhibited a band gap of about 3.21 eV and showed a broad band emission from 400 to 750 nm centered at 503 nm. This broad band emission is related to surface states of CdS and our results showed that the emission peak can be attributed to the interstitial sulfur. The best attained photoluminescence quantum yield of the NCs was about 11%. At the same conditions the PL quantum yield of TGA capped NCs was about 20 times higher than that of TG capped NCs
Monolayers of spin-coated L1
Monolayers of FePt nanoparticles were synthesized on SiO2/Si substrates by
spin-coating method. The effects of spin-coating conditions on surface morphology of FePt
system was studied with FE-SEM. A high temperature annealing on the FePt monolayer films
resulted in phase transition from fcc into fct (L10 phase), while preventing
nanoparticles from sintering. Furthermore, L10 FePt nanoparticles with an
average size of 15 nm are coated on SiO2/Si surface. Uniform nanoparticle
monolayer was obtained by optimizing the experiment parameters such as spin time and
controlling hexane evaporation rate
Investigating the Effect of Hierarchical Carbon Micro/Nano Spheres on the Surface Wettability: Experimental and Theoretical Study
Carbon spheres with controllable structures (i.e., nano and microstructure)were prepared by using a hydrothermal method. By adjusting the concentration ofglucose solution at a both constant temperature and constant process time in a sealedautoclave, the total size of carbon spheres (CSs) was changed from nano to microscale.Then micronanobinary carbon spheres structure (MNCS) was successfully obtained bycoating colloidal solution of carbon nanospheres (CNSs, average diameter of 186 nm)and microspheres (CMSs, average diameter of 5 μm) on the FTO substrates. It wasrealized that by annealing of the carbon spheres under vacuum condition, theirfunctional groups were reduced, therefore, this effected on the wetting behavior ofcarbon spheres. The effect of hierarchical roughness as a beneficial factor on thesuperhydrophobicity of CSs was analyzed by the investigation of the contact angle(CA). The highest CA was measured for the mixture structures containing both themicro and nanoscale spheres. Based on the new research, CA of the surface withmicronanobinary structure is larger than the nanostructure and the nanostructure islarger than the microstructure and above all, theoretical calculations confirmed theexperimental measurements
Vertically Aligned MoS<sub>2</sub> Quantum Dots/Nanoflakes Heterostructure: Facile Deposition with Excellent Performance toward Hydrogen Evolution Reaction
A facile, low-cost, and straightforward
procedure was developed for vertical deposition of MoS<sub>2</sub> quantum dots (QDs)/nanoflakes (NFs) on fluorine-doped tin oxide
(FTO) substrate without any binder. Bulk MoS<sub>2</sub> powder was
exfoliated in a bath sonicator followed by tip sonicator inside a
water–ethanol (0.5/0.5 volume ratio) solution. The obtained
MoS<sub>2</sub> QDs/NFs are deposited on FTO substrate via a simple
electrophoretic technique which resulted in vertical deposition of
MoS<sub>2</sub> nanoflakes. Field emission scanning electron microscopy
(FESEM) and atomic force microscopy (AFM) confirmed the formation
of MoS<sub>2</sub> nanoflakes with thickness of ∼20 nm and
lateral dimension of ∼400 nm; transmission electron microscopy
(TEM) and AFM analysis revealed that many single- or two-layer MoS<sub>2</sub> quantum dots exist with lateral size of ∼5 nm on average
on the basal plains of MoS<sub>2</sub> nanoflakes. Electrochemical
measurements indicated that the vertical MoS<sub>2</sub> QDs/NFs/FTO
electrode has a Tafel slope of 74 mV/decade and charge transport resistance
(<i>R</i><sub>ct</sub>) of 16 Ω which is ∼1.9
and 2.7 times smaller than the Tafel slope and <i>R</i><sub>ct</sub> of the nonvertical MoS<sub>2</sub> NFs/FTO electrode, respectively.
This unique morphology exhibited excellent stability for the electrocatalytic
hydrogen evolution reaction (HER) after a repeating linear sweep voltammetry
(LSV) test for 1000 cycles