A discussion was held at the Institute of Laser for Postgraduate Studies, University of Baghdad, on the PhD thesis entitled “Green Synthesis of CdS:Cu using Laser Assisted for Controlled Particles” submitted by the student Ameen Waleed Jabbar, under the supervision of Prof. Dr. Nada Khudhair Abbas.
In this study, multifunctional sensors were synthesized using cadmium sulfide (CdS) nanoparticles with and without copper doping (CdS:Cu). These nanoparticles were prepared using two chemical methods: precipitation and pulsed laser deposition (PLD). Additionally, CdS and CdS:Cu nanoparticles were prepared using a green method utilizing starch to reduce the toxicity of the nanoparticles for use in medical applications.
The nanoparticles were prepared using cadmium acetate dihydrate (99% purity), thiourea (99% purity), sodium hydroxide to adjust the pH, and copper (99% purity). The structural, optical, and surface morphology properties, as well as the biological activity and gas sensitivity of the prepared samples, were studied.
The X-ray diffraction (XRD) results showed that all samples had a strong peak at a 2θ angle of approximately 26.58 degrees, which is associated with the (111) crystal plane. This confirms that the crystalline structure of the pure CdS and CdS:Cu samples is cubic and hexagonal in all prepared samples, and the particle size was also estimated.
The particle size measured was approximately 13.3 nm for undoped CdS, which decreased with the presence of copper until it reached 10.4 nm at a 5% copper concentration. For all samples, the average crystallite size increased with increasing laser power. The highest value of the average crystallite size (11.7 nm) was for CdS:5%Cu samples prepared by the green method using starch, while the smallest value (9.6 nm) was for CdS:1%Cu samples also prepared by the green method using starch.
The surface topology of the CdS and CdS:Cu nanoparticles was examined using field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). According to the AFM results, the particle shape was found to be spherical and polyhedral, with the largest average grain size (64.49 nm) for pure CdS samples prepared by the precipitation method, while the smallest average (34.97 nm) was for CdS:5%Cu nanoparticles.
The EDX analysis confirmed the presence of CdS:Cu composition in all samples, except for the pure samples which were free of copper. The UV-Vis analysis confirmed that the energy gap ranged between (2.42-2.27) eV for the samples prepared by the precipitation method, while it ranged between (3.2-3) eV for the samples prepared by the green method.
The gas sensitivity of the prepared CdS and CdS:Cu films was measured towards NO2 gas in an air environment at different operating temperatures (30, 100, and 200°C). The study confirmed that all films showed the highest sensitivity to NO2 gas at 200°C, and the sensor response reached (41.1) for CdS:5%Cu at a temperature of 30°C.
The nanoparticles in this study showed strong antibacterial and anticancer effects. Importantly, they were found to be safe for normal cells, causing less than 35% cytotoxicity. The materials were synthesized using an environmentally friendly process that utilized starch. The lowest cytotoxicity was recorded at 2.33% for pure CdS at a concentration of 12.5%, while the maximum cytotoxicity observed was 31% for CdS:5%Cu at a concentration of 100%.
The minimum inhibition ratio for cancer cells was 23.66% for pure CdS at a concentration of 12.5%, while the maximum ratio was 62.66% for CdS:5%Cu at a concentration of 100%. The antibacterial evaluation revealed that the CdS:Cu nanocomposite has significant antibacterial activity, with a minimum inhibition zone diameter of 22 mm for Staphylococcus aureus strain at a concentration of 50% for CdS:1%Cu, and a maximum inhibition zone diameter of 36.66 mm for Staphylococcus aureus strain at a concentration of 100% for CdS:5%Cu.
The minimum inhibition zone diameter for Escherichia coli strain was 12 mm at a concentration of 50% for CdS:3%Cu, while the maximum inhibition zone diameter was 18 mm for Escherichia coli strain at a concentration of 100% for CdS:5%Cu.
