ABSTRACT
This manuscript details a comprehensive investigation into the synthesis, structural characterization, thermal stability, and optical properties of nickel-containing hybrid perovskites, namely CH3NH3NiCl3, CsNiCl3, and CH3NH3NiBrCl2. The focal point of this study is to unravel the intricate crystal structures, thermal behaviors, and optical characteristics of these materials, thereby elucidating their potential application in energy conversion and storage technologies. X-ray powder diffraction measurements confirm that CH3NH3NiCl3 adopts a crystal structure within the Cmcm space group, while CsNiCl3 is organized in the P63/mmc space group, as reported previously. Such structural diversity underscores the complex nature of these perovskites and their potential for tailored applications. Thermal analysis further reveals the stability of CH3NH3NiCl3 and CH3NH3NiBrCl2, which begin to decompose at 260 °C and 295 °C, respectively. The optical absorption properties of these perovskites studied by UV-VIS-NIR spectroscopy revealed the bands characteristic of Ni2+ ions in an octahedral environment. Notably, these absorption bands exhibit subtle shifts upon bromide substitution, suggesting that optical properties can be finely tuned through halide modification. Such tunability is paramount for the design and development of materials with specific optical requirements. By offering a detailed examination of these properties, the study lays the groundwork for future advancements in material science, particularly in the development of innovative materials for sustainable energy technologies.
ABSTRACT
We report the synthesis, characterization, and photoelectric and electrochemical properties of (CH3NH3)2Zn1-xCoxBr4 (x = 0.0, 0.3, 0.5, 0.7, and 1.0) samples. X-ray powder and single-crystal diffraction confirm the formation of solid solution across the entire range. Additionally, as the cobalt concentration increases, the crystallinity of the samples decreases, as indicated by the powder diffraction patterns. All samples remain stable up to 560 K, beyond which they decompose into CH3NH3Br and the respective bromide. The semiconductor behavior of the compounds is confirmed through optical absorption measurements, and band gap values are determined by using the Tauc method from diffuse reflectance spectra. Raman spectroscopy reveals a slight redshift in all vibration modes with increasing cobalt content. Finally, photovoltaic measurements on solar cells constructed with (MA)2CoBr4 perovskite exhibit modest performance, and electrochemical measurements indicate that the compound with the composition (MA)2Zn0.3Co0.7Br4 exhibits the highest current for electrochemical water reduction during oxygen evolution.
ABSTRACT
BACKGROUND: Hepatitis B virus (HBV) infection is prevalent in Asian immigrants in the USA. California's Inland Empire region has a population of approximately four million, including an estimated 19,000 first generation Koreans. Our aim was to screen these adult individuals to establish HBV serological diagnoses, educate, and establish linkage to care. METHODS: A community-based program was conducted in Korean churches from 11/2009 to 2/2010. Subjects were asked to complete a HBV background related questionnaire, provided with HBV education, and tested for serum HBsAg, HBsAb and HBcAb. HBsAg positive subjects were tested for HBV quantitative DNA, HBeAg and HBeAb, counseled and directed to healthcare providers. Subjects unexposed to HBV were invited to attend a HBV vaccination clinic. RESULTS: A total of 973 first generation Koreans were screened, aged 52.3y (18-93y), M/F: 384/589. Most (75%) had a higher than high school education and were from Seoul (62.2%). By questionnaire, 24.7% stated they had been vaccinated against HBV. The serological diagnoses were: HBV infected (3.0%), immune due to natural infection (35.7%), susceptible (20.1%), immune due to vaccination (40.3%), and other (0.9%). Men had a higher infection prevalence (4.9% vs. 1.7%, p = 0.004) and a lower vaccination rate (34.6% vs. 44.0%, p = 0.004) compared to women. Self-reports of immunization status were incorrect for 35.1% of subjects. CONCLUSIONS: This large screening study in first generation Koreans in Southern California demonstrates: 1) a lower than expected HBV prevalence (3%), 2) a continued need for vaccination, and 3) a need for screening despite a reported history of vaccination.
