Interpretable Data-Driven Descriptors for Establishing the Structure-Activity Relationship of Metal-Organic Frameworks Toward Oxygen Evolution Reaction.

The development of readily accessible and interpretable descriptors is pivotal yet challenging in the rational design of metal-organic framework (MOF) catalysts. This study presents a straightforward and physically interpretable activity descriptor for the oxygen evolution reaction (OER), derived from a dataset of bimetallic Ni-based MOFs. Through an artificial-intelligence (AI) data-mining subgroup discovery (SGD) approach, a combination of the d-band center and number of missing electrons in eg states of Ni, as well as the first ionization energy and number of electrons in eg states of the substituents, is revealed as a gene of a superior OER catalyst. The found descriptor, obtained from the AI analysis of a dataset of MOFs containing 3-5d transition metals and 13 organic linkers, has been demonstrated to facilitate in-depth understanding of structure-activity relationship at the molecular orbital level. The descriptor is validated experimentally for 11 Ni-based MOFs. Combining SGD with physical insights and experimental verification, our work offers a highly efficient approach for screening MOF-based OER catalysts, simultaneously providing comprehensive understanding of the catalytic mechanism.

Toward Understanding the Formation Mechanism and OER Catalytic Mechanism of Hydroxides by In Situ and Operando Techniques.

Developing efficient and affordable electrocatalysts for the sluggish oxygen evolution reaction (OER) remains a significant barrier that needs to be overcome for the practical applications of hydrogen production via water electrolysis, transforming CO2 to value-added chemicals, and metal-air batteries. Recently, hydroxides have shown promise as electrocatalysts for OER. In situ or operando techniques are particularly indispensable for monitoring the key intermediates together with understanding the reaction process, which is extremely important for revealing the formation/OER catalytic mechanism of hydroxides and preparing cost-effective electrocatalysts for OER. However, there is a lack of comprehensive discussion on the current status and challenges of studying these mechanisms using in situ or operando techniques, which hinders our ability to identify and address the obstacles present in this field. This review offers an overview of in situ or operando techniques, outlining their capabilities, advantages, and disadvantages. Recent findings related to the formation mechanism and OER catalytic mechanism of hydroxides revealed by in situ or operando techniques are also discussed in detail. Additionally, some current challenges in this field are concluded and appropriate solution strategies are provided.

The Structure, Preparation, Characterization, and Intercalation Mechanism of Layered Hydroxides Intercalated with Guest Anions.

Since the intercalation of anions into layered hydroxides (LHs) has a great impact not only on their nucleation and growth but also on their structure, composition, and size, the intercalation chemistry of LHs has aroused the strong interest of researchers. However, the progress in the fundamental understanding of LHs intercalated with guest anions have not been paralleled by a concomitant development of the preparation and performance improvement of such materials. Considering the guidance of a timely in-depth review for scientists in this area, a systematic introduction about the development that is made on the above-mentioned issues is highly needed but yet missing so far. Herein, recent advances in understanding the chemical composition and structure of LHs intercalated with guest anions are systematically summarized. Meanwhile, typical and emerging bottom-up synthesis methods of LHs intercalated with anions are reviewed, and the potential impact of external reaction parameters on the intercalation of anions into LHs are discussed . Besides, different analytical characterization techniques employed in the examination of guest anion-intercalated LHs are deliberated upon. Finally, although progress is slow in exploring the intercalation mechanism, as many examples as possible are included in this review and inferred the possible intercalation mechanism.

Formation of Amorphous Iron-Calcium Phosphate with High Stability.

Amorphous iron-calcium phosphate (Fe-ACP) plays a vital role in the mechanical properties of teeth of some rodents, which are very hard, but its formation process and synthetic route remain unknown. Here, the synthesis and characterization of an iron-bearing amorphous calcium phosphate in the presence of ammonium iron citrate (AIC) are reported. The iron is distributed homogeneously on the nanometer scale in the resulting particles. The prepared Fe-ACP particles can be highly stable in aqueous media, including water, simulated body fluid, and acetate buffer solution (pH 4). In vitro study demonstrates that these particles have good biocompatibility and osteogenic properties. Subsequently, Spark Plasma Sintering (SPS) is utilized to consolidate the initial Fe-ACP powders. The results show that the hardness of the ceramics increases with the increase of iron content, but an excess of iron leads to a rapid decline in hardness. Calcium iron phosphate ceramics with a hardness of 4 GPa can be achieved, which is higher than that of human enamel. Furthermore, the ceramics composed of iron-calcium phosphates show enhanced acid resistance. This study provides a novel route to prepare Fe-ACP, and presents the potential role of Fe-ACP in biomineralization and as starting material to fabricate acid-resistant high-performance bioceramics.

A Bioinspired Gelatin-Amorphous Calcium Phosphate Coating on Titanium Implant for Bone Regeneration.

Biocompatible and bio-active coatings can enhance and accelerate osseointegration via chemical binding onto substrates. Amorphous calcium phosphate (ACP) has been shown as a precursor to achieve mineralization in vertebrates and invertebrates under the control of biological macromolecules. This work presents a simple bioinspired Gelatin-CaPO4 (Gel-CaP) composite coating on titanium surfaces to improve osseointegration. The covalently bound Gel-CaP composite is characterized as an ACP-Gel compound via SEM, FT-IR, XRD, and HR-TEM. The amorphous compound coating exhibits a nanometer range thickness and improved elastic modulus, good wettability, and nanometric roughness. The amount of grafted carboxyl groups and theoretical thickness of the coatings are also investigated. More importantly, MC3T3 cells, an osteoblast cell line, show excellent cell proliferation and adhesion on the Gel-CaP coating. The level of osteogenic genes is considerably upregulated on Ti with Gel-CaP coatings compared to uncoated Ti, demonstrating that Gel-CaP coatings possess a unique osteogenic ability. To conclude, this work offers a new perspective on functional, bioactive titanium coatings, and Gel-CaP composites can be a low-cost and promising candidate in bone regeneration.

Revealing the Formation Mechanism and Optimizing the Synthesis Conditions of Layered Double Hydroxides for the Oxygen Evolution Reaction.

Layered double hydroxides (LDHs), whose formation is strongly related to OH- concentration, have attracted significant interest in various fields. However, the effect of the real-time change of OH- concentration on LDHs' formation has not been fully explored due to the unsuitability of the existing synthesis methods for in situ characterization. Here, the deliberately designed combination of NH3 gas diffusion and in situ pH measurement provides a solution to the above problem. The obtained results revealed the formation mechanism and also guided us to synthesize a library of LDHs with the desired attributes in water at room temperature without using any additives. After evaluating their oxygen evolution reaction performance, we found that FeNi-LDH with a Fe/Ni ratio of 25/75 exhibits one of the best performances so far reported.

The Gut Microbiota in Liver Transplantation Recipients During the Perioperative Period.

Background: Chronic liver disease is a global problem, and an increasing number of patients receive a liver transplant yearly. The characteristics of intestinal microbial communities may be affected by changes in the pathophysiology of patients during the perioperative. Methods: We studied gut fecal microbial community signatures in 37 Chinese adults using 16S rRNA sequencing targeting V3-V4 hypervariable regions, with a total of 69 fecal samples. We analyzed the Alpha and Beta diversities of various groups. Then we compared the abundance of bacteria in groups at the phylum, family, and genus levels. Results: The healthy gut microbiota predominantly consisted of the phyla Firmicutes and Bacteroidestes, followed by Proteobacteria and Actinobacteria. Compared with healthy people, due to the dominant bacteria in patients with chronic liver disease losing their advantages in the gut, the antagonistic effect on the inferior bacteria was reduced. The inferior bacteria multiplied in large numbers during this process. Some of these significant changes were observed in bacterial species belonging to Enterococcus, Klebsiella, and Enterobacter, which increased in patients' intestines. There were low abundances of signature genes such as Bacteroides, Prevotella, and Ruminococcus. Blautia and Bifidobacterium (considered probiotics) almost disappeared after liver transplantation. Conclusion: There is an altered microbial composition in liver transplantation patients and a distinct signature of microbiota associated with the perioperative period.

Qualitative and quantitative detection of surgical pathogenic microorganisms Escherichia coli and Staphylococcus aureus based on ddPCR system.

Bacterial culture and drug susceptibility testing are used to identify pathogen infections. Nevertheless, the process requires several days from collection to the identification of bacterial species and drug-resistance patterns. The digital PCR system is a rapidly developing quantitative detection technology widely applied to molecular diagnosis, including copy number variations, single nucleotide variant analysis, cancer biomarker discovery, and pathogen identification. This study aimed to use a droplet digital PCR system to identify bacteria in blood samples and explore its ability to identify pathogen in bacteremia. Then, we designed primers and probes of SWG-9 and COA gene for E. coli and S. aureus to identify in blood samples with the ddPCR system. The system had demonstrated extremely high detection accuracy in blood samples, and the detection rate of E. coli was 13.1-21.4%, and that of S. aureus was 50-88.3%. Finally, blood samples containing both E. coli and S. aureus were tested to evaluate further the accuracy and applicability of this method, indicating the detection rates range from 18.1% to 97%. The ddPCR system is highly promising as a qualitatively and quantitatively screening method for rapidly detecting pathogen.

Nitrogen and Oxygen Co-Doping Assisted Synthesis of Highly Dispersed Pd Nanoparticles on Hollow Carbon Spheres as Efficient Electrocatalysts for Oxygen Reduction Reaction.

Electrochemical reduction of O2 (oxygen reduction reaction; ORR) provides an opportunity to achieve the commercial application of clean energy, but it remains challenging, so the rational design of inexpensive and efficient electrocatalysts is required. Palladium-based electrocatalysts have emerged as a class of the most promising candidates for the ORR, which could accelerate O2 adsorption, dissociation, and electron transfer. However, the metal Pd atoms tend to aggregate into nanoparticles, driven by the tendency of the metal surface free energy to decrease, which significantly reduces the atom utilization efficiency and the catalytic performance. Herein, a facile double solvent impregnation method is developed for the synthesis of highly dispersed Pd nanoparticles supported on hollow carbon spheres (Pd-HCS), which could act as efficient electrocatalysts for the ORR in basic solution. Systematic investigation reveals that the nitrogen-containing and oxygen-containing functional groups (especially -COOH groups) are essential for achieving the homogenous dispersion of Pd nanoparticles. Significantly, the optimized Pd-HCS electrocatalyst with homogeneously dispersed Pd nanoparticles and Pd-N sites delivers high electrocatalytic activity for the ORR and excellent stability, without significant decay in onset potential and half-potential and good resistance to methanol crossover. This work offers a new route for the rational design of efficient ORR electrocatalysts toward advanced materials and emerging applications.

Enhanced durability and activity of the perovskite electrocatalyst Pr0.5Ba0.5CoO3-δ by Ca doping for the oxygen evolution reaction at room temperature.

A promising Ca doping approach was reported to improve the durability and electrocatalytic OER activity of the perovskite Pr0.5Ba0.5CoO3-δ (PBC). Compared to the pristine PBC, the electrocatalytic activity of Ca-doped Pr0.5Ba0.3Ca0.2CoO3-δ perovskite was increased by ca. 90%. More importantly, its durability was significantly enhanced after doping with calcium.