Boosting exciton dissociation and charge transfer in CsPbBr3 QDs via ferrocene derivative ligation for CO2 photoreduction.

Photo-catalytic CO2 reduction with perovskite quantum dots (QDs) shows potential for solar energy storage, but it encounters challenges due to the intricate multi-electron photoreduction processes and thermodynamic and kinetic obstacles associated with them. This study aimed to improve photo-catalytic performance by addressing surface barriers and utilizing multiple-exciton generation in perovskite QDs. A facile surface engineering method was employed, involving the grafting of ferrocene carboxylic acid (FCA) onto CsPbBr3 (CPB) QDs, to overcome limitations arising from restricted multiple-exciton dissociation and inefficient charge transfer dynamics. Kelvin Probe Force Microscopy and XPS spectral confirmed successfully creating an FCA-modulated microelectric field through the Cs active site, thus facilitating electron transfer, disrupting surface barrier energy, and promoting multi-exciton dissociations. Transient absorption spectroscopy showed enhanced charge transfer and reduced energy barriers, resulting in an impressive CO2-to-CO conversion rate of 132.8 µmol g-1 h-1 with 96.5% selectivity. The CPB-FCA catalyst exhibited four-cycle reusability and 72 h of long-term stability, marking a significant nine-fold improvement compared to pristine CPB (14.4 µmol g-1 h-1). These results provide insights into the influential role of FCA in regulating intramolecular charge transfer, enhancing multi-exciton dissociation, and improving CO2 photoreduction on CPB QDs. Furthermore, these findings offer valuable knowledge for controlling quantum-confined exciton dissociation to enhance CO2 photocatalysis.

Ligand-mediated exciton dissociation and interparticle energy transfer on CsPbBr3 perovskite quantum dots for efficient CO2-to-CO photoreduction.

Perovskite quantum dots (PQDs) hold immense potential as photocatalysts for CO2 reduction due to their remarkable quantum properties, which facilitates the generation of multiple excitons, providing the necessary high-energy electrons for CO2 photoreduction. However, harnessing multi-excitons in PQDs for superior photocatalysis remains challenging, as achieving the concurrent dissociation of excitons and interparticle energy transfer proves elusive. This study introduces a ligand density-controlled strategy to enhance both exciton dissociation and interparticle energy transfer in CsPbBr3 PQDs. Optimized CsPbBr3 PQDs with the regulated ligand density exhibit efficient photocatalytic conversion of CO2 to CO, achieving a 2.26-fold improvement over unoptimized counterparts while maintaining chemical integrity. Multiple analytical techniques, including Kelvin probe force microscopy, temperature-dependent photoluminescence, femtosecond transient absorption spectroscopy, and density functional theory calculations, collectively affirm that the proper ligand termination promotes the charge separation and the interparticle transfer through ligand-mediated interfacial electron coupling and electronic interactions. This work reveals ligand density-dependent variations in the gas-solid photocatalytic CO2 reduction performance of CsPbBr3 PQDs, underscoring the importance of ligand engineering for enhancing quantum dot photocatalysis.

Halogen-Site Regulation in Cs3Bi2X9 Quantum Dots for Efficient and Selective Oxidation of Benzyl Alcohol Driven by Solar Light.

Sluggish charge kinetics and low selectivity limit the solar-driven selective organic transformations under mild conditions. Herein, an efficient strategy of halogen-site regulation, based on the precise control of charge transfer and molecule activation by rational design of Cs3Bi2X9 quantum dots photocatalysts, is proposed to achieve both high selectivity and yield of benzyl-alcohol oxidation. In situ PL spectroscopy study reveals that the Bi─Br bonds formed in the form of Br-associated coordination can enhance the separation and transfer of photoexcited carriers during the practical reaction. As the active center, the exclusive Bi─Br covalence can benefit the benzyl-alcohol activation for producing carbon-centered radicals. As a result, the Cs3Bi2Br9 with this atomic coordination achieves a conversion ratio of 97.9% for benzyl alcohol and selectivity of 99.6% for aldehydes, which are 56.9- and 1.54-fold higher than that of Cs3Bi2Cl9. Combined with quasi-in situ EPR, in situ ATR-FTIR spectra, and DFT calculation, the conversion of C6H5-CH2OH to C6H5-CH2* at Br-related coordination is revealed to be a determining step, which can be accelerated via halogen-site regulation for enhancing selectivity and photocatalytic efficiency. The mechanistic insights of this research elucidate how halogen-site regulation in favor of charge transfer and molecule activation toward efficient and selective oxidation of benzyl alcohol.

Dual-quantum-dots heterostructure with confined active interface for promoted photocatalytic NO abatement.

Constructing heterostructure is an effective way to fabricate advanced photocatalysts. However, the catalytic performance of typical common multi-dimensional bulk heterostructure still suffers from the limited active interface and inefficient carrier migration. Herein, we successfully synthesize the SnO2/Cs3Bi2I9 dual-quantum-dots nanoheterostructure (labeled as SCX, X = 1, 2, 3) for efficiently and stably photocatalytic NO removal under visible light irradiation. The NO removal rate of SC2 is almost 8 and 17 times higher than that of the single SnO2 and Cs3Bi2I9, respectively. Moreover, the SC2 photocatalyst shows only 3 % attenuation after five consecutive cycles, demonstrating good photocatalytic stability. Systematic experimental characterization and theoretical density functional theory calculations revealed that the high activity and stability of SCX originated from the efficient charge transfer at the confined interface between SnO2 and Cs3Bi2I9 quantum dots. This work provides a new perspective for constructing innovative dual-quantum-dots nanoheterostructure and assesses their potential in photocatalytic environmental applications.

Promotion mechanism of -OH group intercalation for NOx purification on BiOI photocatalyst.

Bismuth oxyiodide (BiOI) is a traditional layered oxide photocatalyst that performs in a wide visible-light absorption band, owing to its appropriate band structure. Nevertheless, its photocatalytic efficiency is immensely inhibited due to the serious recombination of photogenerated charge carriers. Herein, this great challenge is addressed via a new strategy of intralayer modification by -OH groups in BiOI, which leads to enhancement of the reactants' activation capacity to promote photocatalytic activity and generate more active species. Furthermore, analysis via a combination of experimental and theoretical methods revealed that the -OH group-functionalized samples reduce the energy barriers for conversion of the main intermediate (NO2), which is easily transformed to NO2-, thus accelerating the oxidation of NO to the final product (NO3-). This study gives insight into NO oxidation, improving the photocatalytic efficiency, and mastering the photocatalysis reaction mechanism to curb air pollution.

[Immunosuppressive therapy for 54 children patients with acquired severe aplastic anemia].

OBJECTIVE: Aplastic anemia is characterized by bone marrow failure and marked reduction of white blood cells, red blood cells and platelets in peripheral blood. Clinical studies have shown that immunosuppressive therapy greatly prolonged the long-term survival of some patients with aplastic anemia. But in severe aplastic anemia (SAA) patients whose ANC was < 0.5 x 10(9)/L, platelets were < 20 x 10(9)/L, very low bone marrow proliferation and high death rate were observed. The present study aimed to evaluate the efficacy of immunosuppressive treatments with cyclosporine A (CSA) alone or CSA combined with antithymocyte globin (ATG) in children with acquired SAA. METHODS: Fifty-four cases with SAA were treated with immunosuppressive agents mentioned above in our department from Jan. 1997 to June 2003, 31 of the cases had treated with CSA combined with ATG. There were 18 cases with SAA type I and 13 cases with SAA type II in CSA combined with ATG group, and 13 cases had very severe aplastic anemia. The other 23 cases were treated with CSA alone (CSA group), 10 of these cases had SAA-I and 13 had SAA-II, and 5 cases had very severe aplastic anemia. The responsive rate, relapse, adverse reactions and event free survival (EFS) were compared between CSA combined with ATG group and CSA group. RESULTS: The proportions of patients with different types of the disease and severity were comparable between the two groups. The responsive time of the CSA combined with ATG group and CSA group was 2.5 months and 3.5 months, respectively (P < 0.05), the responsive rate in two groups was 81% (25/31) and 52% (12/23), respectively (chi(2) = 4.962, P < 0.05). In 37 cases who were responsive to therapy, the relapse rate was 8% (2/25) and 50% (6/12) respectively (chi(C)(2) = 6.143, P < 0.05). There were no significant differences in adverse reactions to the immunosuppressive agents. All cases were followed-up for more than 1 year, and the event-free survival over one year in these two groups was 81% (25/31) and 52% (12/23), respectively. Forty-seven cases were followed-up for more than two years, and the event-free survival was 74% (20/27) and 50% (10/20), respectively (P < 0.01). Twelve cases were followed-up for over 5 years. There were no secondary tumor, myelodysplastic syndrome and other colony diseases. CONCLUSION: The immunosuppressive therapies for acquired severe aplastic anemia in childhood were effective. The effect of CSA combined with ATG was better than that of CSA alone, and the relapse rate was lower with the combined treatment. However, the long-term effect needs longer follow-up studies to evaluate.

[Diagnostic values of serum levels of HA, PC III, C IV and LN to the liver fibrosis in children with beta-thalassemia major].

OBJECTIVE: The presence of liver fibrosis in patients with beta-thalassemia major has been demonstrated to be an important negative prognostic factor. Identification of liver fibrosis in early stage would be of great value. Hyaluronic acid (HA), type III pre-collagen (PC III), collagen IV (C IV) and laminin (LN) as serum markers were widely used in the diagnosis of liver fibrosis in patients with chronic viral infections or alcoholic liver diseases. However, their values in thalassemic liver fibrosis have not been studied. This work was to determine the serum HA, PC III, C IV and LN levels in children with beta-thalassemia major and evaluate the diagnostic utility. METHOD: Serum HA, PC III, C IV and LN in 49 hospitalized children with beta-thalassemia major (aged 1 - 15 years with the media age of 6.27 years) and 41 healthy children served as controls (aged 1 - 13 years with media age of 6.40 years) were detected by radioimmunoassay (RIA). Forty-five of 49 cases were performed percutaneous liver biopsies, and the histopathological fibrosis was compared with the four serum markers. The correlation and discriminate analysis were used. RESULTS: All the serum levels of HA, PC III, C IV and LN in beta-thalassemia were significantly higher than those in controls (P < 0.01). In 36 of 45 cases, the histopathology showed liver fibrosis including stage I and stage II by biopsies with a positive rate of 80%. The serum levels of four markers increased successively with the aggravation of liver fibrosis from stage 0 to stage II, and significant correlation was observed between the level of HA or PC III and the stage of fibrosis (HA, r = 0.379, P = 0.017; PC III, r = 0.455, P = 0.04). While there was no difference between the level of C IV or LN and fibrosis (C IV, r = 0.312, P = 0.053; LN, r = 0.310, P = 0.055). Using discriminate analysis, the discriminate function of co-detection of the four markers for the diagnosis of fibrosis was 0.002 HA + 0.003 PC III + 0.002 C IV + 0.006 LN-1.859, which had a sensitivity of 93.88%, specificity of 68.29%, predictive value of positive test and negative test of 77.97% and 90.32%, respectively. Moreover, there was a significant correlation between the serum level of HA or PC III and the liver iron concentration (HA, r = 0.318, P = 0.035; PC III, r = 0.305, P = 0.044). CONCLUSION: The results suggest that, in beta-thalassemia major with chronic liver disease, HA and PC III showed more practical value in diagnosing liver fibrosis than the levels of C IV and LN. The combination of the four serum markers could improve the accuracy and reliability of the diagnosis. A validation study is necessary before introducing into the prediction function during the clinical practice.