The Effect of Ultraviolet Radiation on the Chemical Bath Deposition of Bis(thiourea) Cadmium Chloride Crystals and the Subsequent CdS Obtention

This method can help answer key questions on the crystal world-field. Such as interaction of UV light and the world of bis-thiourea cadmium chloride crystals. The main advantage of this technique is that it’s possible to modify the morphology of bis-thiourea cadmium chloride crystals.

Demonstrating the procedure will be MCM Luis Eduardo Trujillo-Villanueva. A grad student of our laboratory. First, pour 500 milliliters of deionized water into a one liter beaker, with constant agitation.

Then add 3 milliliters of 36.5%hydrochloric acid. Making sure that the ph of this solution is as close as possible to three. Next, pour 50 milliliters of the pre-cursor solution into two 100 milliliter beakers labeled A and B.Add 2.29 grams of cadmium chloride and 1.33 grams of thiourea in each beaker.

Following this, place beaker A on a stirring hot plate and heat to 334 kelvin;with moderate stirring speed for two hours. Place beaker B on a stirring hot plate and heat to 334 kelvin, with moderate stirring. Turn on the UV light source and allow the reaction to proceed for two hours.

Place a glass funnel with filter paper on two 100 milliliter volumetric flasks. Immediately filter each solution from beakers A and B, into separate flasks. Filter the solutions quickly, because the cooling initiates the crystal growth.

Now allow both solutions to cool to room temperature. Place a glass funnel with filter paper on two new 100 milliliter volumetric flasks. Filter the solutions with the crystals into separate flasks.

Transfer the crystals from the filter paper to separate watch glasses. Place the crystals into two separate crucibles labeled A and B.Preheat an electric laboratory furnace and stabilize its temperature at 773 kelvin or higher. Once the furnace temperature is stabilized, place the crucibles containing the crystals inside the furnace.

After one hour, turn off the furnace and allow it to cool to room temperature. Then remove the crucibles containing the crystals from the furnace. The UV-vis diffusions reflectance absorption spectra in both pre-cursor solutions, show the bis-thiourea cadmium chloride complex, which is evidenced by a broad absorption band from 250 to 500 nanometers.

The cadmium chloride and thiourea absorption bands are also observed in the spectra of the complex. The Raman spectra of the crystals display peaks corresponding to the cadmium chlorine nitrogen carbon sulfur and carbon sulfur bonds. Although the same bonds are observed for both experiments, such intensities are lower without UV assistance.

Which indicates a smaller number of bonds. The XRD pattern shows preferential growth in the zero two zero and zero zero one planes with UV light;which corresponds to sulfur and cadmium atoms, within the complex, respectively. The SEM images show that acicular crystals, four to six times larger, are formed with UV light.

TGA analysis of the crystals exhibits a similar behavior for both the UV and non-UV assisted experiments. DRX of the calcium complex shows no differences in the cadmium sulfide, obtained by chemical bath deposition versus photo-chemical bath deposition. A slightly more prominent average particle size for photo-chemical bath deposition is observed.

Demonstrating that UV light promotes sulfur incorporation into the cadmium. The UV light promotes chemical balance between cadmium and sulfur-ions, which causes preferential growth in the crystallized total of the bis-thiourea cadmium chloride crystals. The cadmium sulfide obtained after calcination showed no evident difference.