RESUMEN
Synthesis of catalysts with high catalytic degradation activity for formaldehyde (HCHO) at room temperature is highly desirable for indoor air quality control. Herein, a novel K-Mn3O4@CeO2 catalyst with excellent catalytic oxidation activity toward HCHO at near room temperature was reported. In particular, the K addition in K-Mn3O4@CeO2 considerably enhanced the oxidation activity, and importantly, 99.3 % conversion of 10 mL of a 40 mg/L HCHO solution at 30 °C for 14 h was achieved, with simultaneous strong cycling stability. Moreover, the addition of K species considerably influenced the chemical valence state of Mn from +4 (ε-MnO2) to +8/3 (Mn3O4) on the surface of CeO2, which obviously changed the tunnel structure and the number of oxygen vacancies. One part of K species is uniformly dispersed on K-Mn3O4@CeO2, and the other part exists in the tunnel structure of Mn3O4@CeO2, which is mainly used to balance the negative charge of the tunnel and prevent collapse of the structure, providing enough active sites for the catalytic oxidation of HCHO. We observed a phase transition from tunneled KMnO2 to Mn3O4 to tunneled MnO2 with the decreasing K+ content, in which K-Mn3O4@CeO2 exhibited higher HCHO oxidation activity. In addition, K-Mn3O4@CeO2 exhibited lower oxygen vacancy formation and HCHO adsorption energies in aqueous solution based on density functional theory calculations. This is because the K species provide more active oxygen species and richer oxygen vacancies on the surface of K-Mn3O4@CeO2, promote the mobility of lattice oxygen and the room-temperature reduction properties of oxygen species, and enhance the ability of the catalyst to replenish the consumed oxygen species. Finally, a possible HCHO catalytic oxidation pathway on the surface of K-Mn3O4@CeO2 catalyst is proposed.
RESUMEN
BACKGROUND: Cryptococcal meningitis (CM) has a high morbidity and mortality due to the low detection of Cryptococcus in cerebrospinal fluid (CSF) during the early stage of the disease with traditional methods. CASE PRESENTATION: In addition to the traditional methods of India ink staining and cryptococcal antigen (CrAg), we used nanopore sequencing and next-generation sequencing (NGS) to detect pathogenic DNA in CSF samples of three patients with CM. The CSF samples of all three patients were positive by India ink staining and CrAg. NGS also detected Cryptococcus in all three CSF samples. Nanopore sequencing detected Cryptococcus in two CSF samples. CONCLUSION: Nanopore sequencing may be useful in assisting with the clinical diagnosis of CM. Further research is needed to determine the sensitivity and specificity of nanopore sequencing of CSF.