The kinetics of photo-colloidal systems

Imperial Users onl

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 MoS₂ 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 MoS₂ quantum dots (QDs)/nanoflakes (NFs) on fluorine-doped tin oxide (FTO) substrate without any binder. Bulk MoS₂ powder was exfoliated in a bath sonicator followed by tip sonicator inside a water–ethanol (0.5/0.5 volume ratio) solution. The obtained MoS₂ QDs/NFs are deposited on FTO substrate via a simple electrophoretic technique which resulted in vertical deposition of MoS₂ nanoflakes. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) confirmed the formation of MoS₂ 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 MoS₂ quantum dots exist with lateral size of ∼5 nm on average on the basal plains of MoS₂ nanoflakes. Electrochemical measurements indicated that the vertical MoS₂ QDs/NFs/FTO electrode has a Tafel slope of 74 mV/decade and charge transport resistance (<i>R</i>_ct) of 16 Ω which is ∼1.9 and 2.7 times smaller than the Tafel slope and <i>R</i>_ct of the nonvertical MoS₂ 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