Question

Inthis paper, the production of SnOX₂ nanoparticles through the chemical co-precipiation method is described using SnClX₂⋅2HX2_O as a precursor. According to their experimental section,SnOX₂ NPs were prepared by chemical co-precipitation method. 0.27M SnClX₂⋅2HX₂O was added to double destilled (DD) water and ethanol (2.2:1 v/v) in a 1000 mL beaker under continuous magnetic stirring for 60 min in order to obtain a homogeneous solution. 50 mL of HCl was added drop wise in order to reduce the precursor and the solution was kept on stirring for another 30 min to allow proper mixing resulting in a clear transparent solution. Later aqueousNHX3NHX3was added dropwise till the pH of the solution became 8.5 and a milky white solution was obtained. The solution was kept on continuous stirring for another 3 h. After this the stirring was stopped and the beaker was kept undisturbed overnight in order to facilitate the particles to settle down completely.The solution was then washed with DD water and ethanol multiple times so as to remove the residual chlorine content using 125 mm Whatman filter paper (Cat no. 1001 125). The resulting product was covered and left for drying overnight. The dried powder was then divided into three parts and annealed at 400 °C, 500 °C, and 600 °C named as Sn4, Sn5, and Sn6 respectively. However, the paper focuses mainly in the characterization of the syntetized nanoparticles, and it doesn't describe in further detail the chemical reactions of the process. What would the role of the added HCl be?

Answer 1

Hydrochloric acid (HCl) is used in the production of SnO2 nanoparticles to adjust the solution environment, maintain the tin in the desired oxidation state, and regulate the nucleation and growth of nanoparticles during the co-precipitation process.

Step-by-step explanation:

The role of hydrochloric acid (HCl) in the production of SnO2 nanoparticles via chemical co-precipitation primarily involves reducing the precursor and adjusting the pH of the solution. The addition of HCl serves to modify the solution environment that can lead to the reduction of metal ions.

While not explicitly stated in the question's text, it is likely that HCl helps to maintain the tin in a suitable oxidation state that is necessary for the subsequent formation of tin dioxide nanoparticles. Once aqueous ammonia is added, the pH increases, leading to the precipitation of SnO2.

During this process, HCl may also help to control the rate of precipitation by providing Cl- ions, which can influence the nucleation and growth of the nanoparticles by complexing with the tin ions or by changing the solubility of various species formed during the precipitation.