Sta 409 pc thermal analyzer

pH values were measured by a Starter 3C digital pH meter, Ohaus, USA. Transmission electron microscopy (TEM), selected area electron diffraction (SAED), and elemental characterization were done on a JEOL 2010 microscope (Akishima-shi, Japan) with energy-dispersive X-ray spectrometer (EDS) at an accelerating voltage of 200 kV. X-ray powder diffraction (XRD) spectrum was taken on Rigaku Ultima III X-ray diffractometer (Shibuya-ku, Japan) operated at 40 kV voltage and 30 mA current with Cu Ka radiation. UV-visible (vis) spectra were recorded on a Varian Cary 50 UV/Vis spectrometer, Agilent Technologies, Inc., Santa Clara, CA, USA. Emission spectra were collected using a Varian Cary spectrometer. Thermogravimetric analysis (TGA) was done under nitrogen on a STA 409 PC thermal analyzer, Netzsch, Germany. The quantum yield (QY) of CdTe QDs was measured according to the methods described in [26 (link)] using rhodamine 6G as a reference standard (QY = 95%).

Hydrated potassium alum (99.9%), KAl(SO₄)₂·12H₂O (H-alum), was purchased from Samhyun Pharm (Incheon, Republic of Korea). Anhydrous potassium alum, KAl(SO₄)₂ (denoted as A-alum-1), was synthesized via the dehydration of H-alum at 400 °C for 4 h. For comparison, a commercial roasted potassium alum (denoted by A-alum-2) was purchased from Hyunjin Pharm (Seoul, Republic of Korea), which is typically produced by the heating of hydrated alum at 500 °C.
XRD measurements were performed using a Rigaku D/MAX2200PC with Cu Kα radiation (λ = 1.5418 Å). The data were recorded at room temperature in the 2θ range of 5–90° with a step size of 0.02° and a counting time of 4 s per step. Thermogravimetric analyses were performed using an STA 409 PC thermal analyzer (NETZSCH, Aacheen, Germany). Approximately 20 mg of sample was weighed in an alumina crucible, followed by heating from 25 °C to 500 °C under air condition at a heating rate of 10 °C/min. A Scanning Electron Microscope (SEM) was used to image the samples, employing JSM-6380 (JEOL, Akishima, Japan).