Sharif Digital Repository

Free Content Selective synthesis of conjugated enynes from α-arylalkynols using LiCl-Acidic Al2O3 under solvent-free conditions  

7H-benzimidazo[2,1-a]benz[de]isoquinolin-7-one compounds were prepared in a selective manner by reaction between o-phenylenediamines and appropriate 1,8-naphthalenedicarboxylic anhydrides using acidic alumina under microwave irradiation  

CdS nanoparticles were grown using CdSO4 and Na 2S2O3 as the precursors and thioglycerol (TG) as the capping agent. TG was shown to exhibit a catalytic role in the reaction and also acted as a capping agent. It was demonstrated that size growth is linearly related to the temperature of the reaction, i.e.the sizes can be controllably adjusted by temperature. The crystalline phase of the nanocrystals was also dependent on the temperature of growth: higher temperature favours the cubic phase. The pH also plays an important role in nanoparticle growth, as lower pH leads to a higher release rate of sulfur species. At pH as high as 10, the growth rate remains slow even at boiling temperature. This... 

γ-Alumina is used to catalyze the Cannizzaro reaction in the absence of any base under microwave irradiation in high yields. In the case of terephthalaldehyde the reaction is carried out with high selectivity  

Highly sensitive nickel sensor based on repeatable fluorescence quenching-emerging mechanism was developed. Highly luminescent thioglycolic acid capped CdTe nanocrystals in aqueous solution were applied as the fluorescence probe. These nanocrystals represented a considerable photoluminescence quantum yield as high as 61%. The florescence was quenched by addition of Ni ions to the CdTe nanocrystals solution. Then it was recovered by injection of the proper amount of dimethylglyoxime as the releasing reagent. The relative fluorescence intensity (F0/F) was linearly proportional to the concentration of nickel ions in the range of 0.01–10 μM, with detection limit as low as 7 nM. Described method... 

In this paper, the stable and reproducible tellurium doped ZnO nanowires (Te-ZnO NWs) photodetector with intensive responsively is presented. The Te-ZnO NWs were fabricated by physical vapor deposition (PVD) growth mechanism. Field emission scanning electron microscope (FESEM) images showed that the fabricated nanowires were 50 nm in diameter and several microns in length. The high resolution transmission electron microscopy indicated that the synthesized nanowires were crystalline and their phase characterization was validated by the X-ray diffraction (XRD). The photoluminescence (PL) studies of these nanowires showed a strong photoluminescence (PL) emission peak in the green region. It was... 

The highly sensitive impedimetric biosensor in label free approach for hepatitis B virus DNA (HPV DNA) detection based on tellurium doped ZnO nanowires was fabricated. The NWs were grown by hybrid thin film oxidation in the physical vapor deposition (PVD) mechanism. The morphology characterization of the synthesized NWs was performed by field emission scanning electron microscopy (FESEM) and the images demonstrated that the diameter and the length of the materialized NWs were around 50 nm and several micrometers, respectively. The high-resolution transmission electron microscopy (HRTEM) image indicated that the fabricated NWs were crystalline and their phase characterization was validated by... 

In this work we report a fast two-step microwave activated synthesis of the ZnS:Mn nanocrystals. Zn(NO3)2 and Na2S 2O3 were used as the precursors and Mn(NO 3)2 was employed as the source of the impurity. The aqueous synthesis was based on the heat sensitivity of Na2S 2O3, which releases some S species on heating. Consequently, the reaction was well activated under microwave irradiation resulting in formation of ZnS:Mn nanocrystals. Thioglycerol (TG) was also used as the capping agent and the catalyst of the reaction. The synthesis process was done in two steps, i.e. 1 min irradiation without TG and then injection of TG and continuation of irradiation. ZnS:Mn nanocrystals were quickly formed... 

CdS nanoparticles were synthesized by a thermochemical method by using Na2S2O3 and CdSO4 as the precursors and thioglycerol as the capping agent. We have investigated the effect of different temperatures on the size and crystalline phase of the CdS nanoparticles. The results of the optical spectroscopy and XRD analyses clarified that increasing the synthesis temperature increased the final nanoparticles size and also changed the crystalline phase of the particles from hexagonal to cubic phase. The size of the synthesized particles was less than 4nm. TEOS was also used in cooperation with thioglycerol for better surface passivation. The results of the PL analysis showed that using this... 

We have synthesized CdS NCs (NCs) by a thermochemical approach. CdSO 4 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... 

In this work we have synthesized CdS nanocrystals with thermochemical method. 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 nanocrystals were characterized by means of XRD, TEM, UV-visible optical spectroscopy and photoluminescence (PL). X-ray diffraction (XRD) and TEM analyses demonstrated hexagonal phase CdS nanocrystals with an average size around 2 nm. Synthesized nanocrystals exhibited band gap of about 3.2 eV and showed a broad band emission from 400-750 nm centered at 504 nm with a (0.27, 0.39) CIE coordinate. This emission can be attributed to recombination of an electron in... 

We report a novel method of growing red luminescent (635 nm) Mn-doped CdS (CdS:Mn) nanoparticles capped by an inorganic shell of Mn(OH)2. CdSO4, Na2S2O3 and Mn(NO3)2 were used as the precursors, and thioglycerol (C3H8O2S) was employed as the capping agent and also the catalyst of the reaction. Using these materials resulted in very slow rate of the reaction and particles growth. The self-assembled one-pot process was performed at pH of 8 and Mn:Cd ratio of 10, and took about 10 days for completion. CdS:Mn nanoparticles are slowly formed in the first day of the process; however, the luminescence is weak. After 7 days, the solution turns white turbid through the formation of additional... 

In this work, we propose a combined photochemical-chemical method that enables us to grow CdS nanoparticles with ångström precision. CdS nanoparticles were formed through a photo-induced reaction between CdSO 4 and Na2S2O3. Thioglycerol (C 3H8O2S) was used as the capping agent. Fine tuning of the size was subsequently carried out by controlling the pH of the solution. Optical absorption spectroscopy was mainly used to monitor the process of particle formation, and to measure the bandgap and size. X-ray diffraction spectra confirmed the optical sizes and demonstrated crystalline nanoparticles. In the presence of the capping agent there was a dark growth that was completely dependent on the pH... 

The optical and electrical properties of semiconductor nanoparticles are strongly dependent on their size. A flexible control of the size of the nanoparticles is of interest for tuning their properties for different applications. Here we use a coupled method to control the size of CdS nanoparticles. The method involves the photochemical growth of CdS nanoparticles together with the use of a capping agent as an inhibiting factor. CdS nanoparticles were formed through a photoinduced reaction of CdSO4 and Na2S2O3 in an aqueous solution. Mercaptoethanol (C2H6OS) was used as the capping agent, and we investigated the effect of illumination time, illumination intensity and the concentration of... 

A novel superabsorbent hydrogel composite based on gelatin has been prepared by graft copolymerisation of acrylic acid and acrylamide in the presence of kaolin powder, using methylene-bisacrylamide (MBA) as a crosslinking agent and ammonium persulfate as an initiator. The synthetic variables affecting the water absorbency of the resulting superabsorbent composite were studied and the composite structure was confirmed using FT-IR spectroscopy. A new absorption band at 1728 cm-1 in the composite spectrum confirmed the presence of a kaolin-organic polymer linkage. The effect of kaolin content and MBA concentration showed that increasing these parameters decreased the water absorbency of the... 

Arylalkynols were converted into both conjugated enynes and arylacetylenic compounds using p-TsCl/Al2O3 and KOH/Al2O3 respectively in classical heating or microwave irradiation methods in good yields  

TiO 2 nanorods, TiO 2 nanorod/TiO 2 nanoparticle and TiO 2 nanorod/ZnO nanoparticle composite structures were integrated as photoanodes in backside illuminated dye-sensitized solar cells (DSSCs). Incorporation of TiO 2 nanoparticles into the bare nanorods increased the dye loading and improved the short-circuit current density (J sc) from 2.22 mA/cm 2 to 3.57 mA/cm 2. ZnO nanoparticles electrochemically grown into the TiO 2 nanorod layer could increase the surface area. Nevertheless, this considerably reduced the J sc to 0.57 mA/cm 2 and consequently cell efficiency. Electrochemical impedance spectroscopy (EIS) results showed that ZnO incorporated samples have better effective diffusion... 

We have synthesized CdS nanocrystals (NCs) by a microwave activated method. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The aqueous synthesis was based on the heat sensitivity of Na2S 2O3. In this method, microwave irradiation creates the activation energy for dissociation of Na2S2O3 and leads to the CdS NCs formation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses demonstrated hexagonal phase CdS NCs with an average size around 3 nm for sample prepared at 5 min irradiation time. A band gap range of 3.38-2.89 eV was possible only by increasing the microwave irradiation time, corresponding to a... 

CdS nanocrystals were thermochemically (thermally activated) synthesized thorough the reaction between CdSO4 and Na2S 2O3 in an aqueous solution. Thioglycolic Acid (TGA) was used as the capping agent and catalyst of the reaction. The method was based on heat activated dissociation of Na2S2O3 and controllable release of S and free electrons in the solution. CdS NCs were formed by heating the sample solution at 96 C for 1 h. The results of optical spectroscopy and transmission electron microscopy demonstrated round shape NCs with sizes about 3.0 nm. The nanocrystals were also luminescent and represented a broad emission with a peak located at 515 nm and FWHM of 160 nm. Several samples were... 

CdS nanocrystals were prepared through a thermally activated (thermochemical) method. The synthesis was performed in two different oxygen-saturated and Ar purged atmospheres. Na2S2O3 was used as a heat-sensitive source of S in the experiments. Thioglycerol was also applied as the capping agent to restrain the growth. The growth was activated by heating and controlled by solution pH. The results demonstrated a considerably higher luminescence intensity for the synthesis in oxygen-saturated atmosphere. This could show the role of luminescent oxygen trap states created inside the CdS nanocrystals. The improved luminescence was observed for the synthesis at different solution pHs. Nevertheless,...