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1.
Life Sci ; : 122778, 2024 Jun 13.
Article En | MEDLINE | ID: mdl-38879157

Even though the genus Mycobacterium is a diverse group consisting of a majority of environmental bacteria known as non-tuberculous mycobacteria (NTM), it also contains some of the deadliest pathogens (Mycobacterium tuberculosis) in history associated with chronic disease called tuberculosis (TB). Formation of biofilm is one of the unique strategies employed by mycobacteria to enhance their ability to survive in hostile conditions. Biofilm formation by Mycobacterium species is an emerging area of research with significant implications for understanding its pathogenesis and treatment of related infections, specifically TB. This review provides an overview of the biofilm-forming abilities of different species of Mycobacterium and the genetic factors influencing biofilm formation with a detailed focus on M. tuberculosis. Biofilm-mediated resistance is a significant challenge as it can limit antibiotic penetration and promote the survival of dormant mycobacterial cells. Key genetic factors promoting biofilm formation have been explored such as the mmpL genes involved in lipid transport and cell wall integrity as well as the groEL gene essential for mature biofilm formation. Additionally, biofilm-mediated antibiotic resistance and pathogenesis highlighting the specific niches, sites of infection along with the possible mechanisms of biofilm dissemination have been discussed. Furthermore, drug targets within mycobacterial biofilm and their role as potential biomarkers in the development of rapid diagnostic tools have been highlighted. The review summarises the current understanding of the complex nature of Mycobacterium biofilm and its clinical implications, paving the way for advancements in the field of disease diagnosis, management and treatment against its multi-drug resistant species.

2.
Pediatr Qual Saf ; 9(3): e729, 2024.
Article En | MEDLINE | ID: mdl-38751892

Background: Unplanned Extubation (UE) remains an important patient safety issue in the Neonatal Intensive Care Unit. Our SMART AIM was to decrease the rate of UE by 10% from the baseline from January to December 2022 by emphasizing collaboration among healthcare professionals and through the use of shared decision-making. Methods: We established an interdisciplinary Quality Improvement team composed of nurses, respiratory therapists, and physicians (MDs). The definition of UE was standardized. UE was audited using an apparent cause analysis form to discern associated causes and pinpoint areas for improvement. Interventions were implemented in a step-by-step fashion and reviewed monthly using the model for improvement. A shared decision-making approach fostered collaborative problem-solving. Results: Our baseline UE rate was 2.3 per 100 ventilator days. Retaping, general bedside care, and position change accounted for over 50% of the UE events in 2022. The rate of UE was reduced by 48% by the end of December 2022. We achieved special-cause variation by the end of March 2023. Conclusions: The sole education of medical and nursing providers about various approaches to decreasing unnecessary retaping was ineffective in reducing UE rates. Shared decision-making incorporating inputs from nurses, respiratory therapists, and MDs led to a substantial reduction in the UE rate and underscores the potential of systematic evaluation of risk factors combined with collaborative best practices.

3.
Heliyon ; 10(10): e31116, 2024 May 30.
Article En | MEDLINE | ID: mdl-38799742

The emergence of multidrug-resistant mycobacterial strains is a significant crisis that has led to higher treatment failure rates and more toxic and expensive medications for tuberculosis (TB). The urgent need to develop novel therapeutics has galvanized research interest towards developing alternative antimicrobials such as silver nanoparticles (AgNPs). The current study focused on the anti-mycobacterial activity of green-synthesized AgNPs and its polyethylene glycol encapsulated derivative (PEG-AgNPs) with improved stability using the leaves extract of Clerodendrum serratum. Different characterization methods were used to analyze them. DLS analysis revealed a lower polydispersity index of PEG-AgNPs, suggesting a more uniform size distribution than that of AgNPs. The HR-TEM results revealed that the AgNPs and PEG-AgNPs have predominantly spherical shapes in the size range of 9-35 nm and 15-60 nm, respectively, while positive values of Zeta potential indicate their stability. FTIR-ATR analysis confirmed the presence of functional groups responsible for reducing and capping the bio-reduced AgNPs, whereas the XRD data established its crystalline nature. Impressively, the PEG-AgNPs exhibited maximum inhibitory activity against different Tubercular and Non-Tuberculous Mycobacterium species i.e., Mycobacterium smegmatis, Mycobacterium fortuitum and Mycobacterium marinum, relative to those of AgNPs and Linezolid. The flow cytometry assay showed that the anti-mycobacterial action was mediated by an increase in cell wall permeability. Notably, the results of AFM confirm their ability to inhibit mycobacterial biofilm significantly. We demonstrated the nontoxic nature of these AgNPs, explicated by the absence of hemolytic activity against human RBCs. Overall, the results suggest that PEG-AgNPs could offer a novel therapeutic approach with potential anti-mycobacterial activity and can overcome the limitations of existing TB therapies.

4.
J Mol Recognit ; : e3087, 2024 Apr 30.
Article En | MEDLINE | ID: mdl-38686731

Epitope imprinting has shown better prospects to synthesize synthetic receptors for proteins. Here, dual epitope imprinted polymer electrode (DEIP) matrix was fabricated on gold surface of electrochemical quartz crystal microbalance (EQCM) for recognition of target epitope sequence in blood samples of patients suffering from brain fever. Epitope sequences from outer membrane protein Por B of Neisseria meningitidis (MC58) bacteria predicted through immunoinformatic tools were chosen for imprinting. Self-assembled monolayers (SAM) of cysteine appended epitope sequences on gold nanoparticles were subjected to polymerization prior to electrodeposition on gold coated EQCM electrode. The polymeric matrix was woven around the cysteine appended epitope SAMs through multiple monomers (3-sulfo propyl methacrylate potassium salt (3-SPMAP), benzyl methacrylate (BMA)) and crosslinker (N, N'-methylene-bis-acrylamide). On extraction of the peptide sequences, imprinted cavities were able to selectively and specifically bind targeted epitope sequences in laboratory samples as well as 'real' samples of patients. Selectivity of sensor was examined through mismatched peptide sequences and certain plasma proteins also. The sensor was able to show specific binding towards the blood samples of infected patients, even in the presence of 'matrix' and other plasma proteins such as albumin and globulin. Even other peptide sequences, similar to epitope sequences only with one or two amino acid mismatches were also unable to show any binding. The analytical performance of DEIP-EQCM sensor was tested through selectivity, specificity, matrix effect, detection limit (0.68-1.01 nM), quantification limit (2.05-3.05 nM) and reproducibility (RSD ~ 5%). Hence, a diagnostic tool for bacterium causing meningitis is successfully fabricated in a facile manner which will broaden the clinical access and make efficient population screening feasible.

5.
Biol Futur ; 75(2): 251-257, 2024 Jun.
Article En | MEDLINE | ID: mdl-38578587

Arbuscular mycorrhizal fungi (AMF) have been known to enhance plant growth and nutrient uptake. In this study, we investigated the effects of Funneliformis mosseae, Rhizophagus intraradices, and their co-inoculation on the growth and biochemical composition of tomato (Solanum lycopersicum L.) plants. The findings demonstrated that the inoculation of AMF significantly enhanced shoot and root length, shoot and root dry weight, number of fruits per plant, as well as concentrations of anthocyanin, phenolic compounds, and antioxidants in tomato plants. Both individual and co-inoculation of AMF also significantly increased nitrogen, phosphorus, and potassium concentrations in tomato plants. Our findings suggest that AMF can be used as a potential biofertilizer to enhance the growth and biochemical composition of tomato plants.


Mycorrhizae , Solanum lycopersicum , Solanum lycopersicum/microbiology , Solanum lycopersicum/metabolism , Solanum lycopersicum/growth & development , Mycorrhizae/physiology
7.
Indian J Community Med ; 48(4): 556-561, 2023.
Article En | MEDLINE | ID: mdl-37662118

Background: Anemia is the most common nutritional disease in pregnancy with significant adverse maternofetal outcome. The objective of the present study is to study the impact of COVID-19 pandemic on the pregnancy outcomes of women with severe anemia. Methodology: A retrospective observational study was conducted in the Department of Obstetrics and Gynaecology at LHMC and SSK Hospital, Delhi. The study included all antenatal women admitted at a gestational age of >26 weeks (third trimester) with severe anemia and hemoglobin level of 7 g/dL. In our study, a total of 4031 women were included as cases during study period (July to December 2022) and 6659 women as controls from pre-COVID-19 period (July to December 2019). Results: In present study, a total of 4031 women delivered during study period as compared to 6659 in control period. In the present study, the prevalence of anemia was observed to be 74.7% in the study group and 51.6% in the control group (P < 0.001). Mean hemoglobin level was significantly lower in study group as compared to the control groups P<0.05. Microcytic hypochromic anemia was the most common morphological type of anemia in both groups. Serum ferritin, serum iron, serum B12, and folic acid levels among cases were significantly (P < 0.05) lower as compared to controls. Odds of fetal growth restriction were 1.4 times higher among study group as compared to control groups. The odds of newborn complications such as low birth weight were 2.49 (95% CI: 1.04-5.91) and need for nursery or NICU admission were 4.84 times (95% CI: 0.48-48.24) higher in cases as compared to controls. Low birth rate was higher in cases and was found to be statistically significant. Conclusion: COVID-19 pandemic had indirect impact on adverse maternal and fetal outcome in women with severe anemia.

8.
Gynecol Oncol ; 177: 38-45, 2023 Oct.
Article En | MEDLINE | ID: mdl-37634258

OBJECTIVES: Clear cell carcinoma is a high-risk subtype of endometrial cancer. Some patients have a mixture of clear cell carcinoma with other histologic types (endometrioid or serous) or cannot be neatly assigned to one of these types. Protocol GOG-8032 within GOG-210 was designed to determine whether these tumors differ from pure clear cell carcinoma in stage at diagnosis, initial pattern of spread, or patient survival. METHODS: The term "mixed" was applied to tumors with multiple identifiable components, and "indeterminate" was applied to tumors with features intermediate between different histologic types. Three hundred eleven women with pure, mixed, or indeterminate clear cell carcinoma were identified in a larger cohort of patients undergoing hysterectomy for endometrial cancer in GOG-210. Histologic slides were centrally reviewed by expert pathologists. Baseline and follow-up data were analyzed. RESULTS: One hundred thirty-six patients had pure clear cell carcinoma and 175 had a mixed or indeterminate clear cell pattern. Baseline clinicopathologic characteristics were similar except for a small difference in age at presentation. Univariate survival analysis confirmed the significance of typical endometrial cancer prognostic factors. Patients in the mixed categories had disease-free and overall survival similar to pure clear cell carcinoma, but the indeterminate clear cell/endometrioid group had longer survival. CONCLUSION: In clear cell endometrial cancer, the presence of a definite admixed endometrioid or serous component did not correlate with a significant difference in prognosis. Patients whose tumors had indeterminate clear cell features had better prognosis. Some of these tumors may be endometrioid tumors mimicking clear cell carcinoma.


Adenocarcinoma, Clear Cell , Carcinoma, Endometrioid , Endometrial Neoplasms , Female , Humans , Carcinoma, Endometrioid/pathology , Neoplasm Staging , Endometrial Neoplasms/pathology , Prognosis , Adenocarcinoma, Clear Cell/pathology , Uterus/pathology
9.
HLA ; 102(5): 634-635, 2023 Nov.
Article En | MEDLINE | ID: mdl-37649248

Novel HLA-C*06:02:01:94 and -C*15:02:01:58 alleles were detected during the routine HLA typing process.

10.
HLA ; 102(5): 625-626, 2023 Nov.
Article En | MEDLINE | ID: mdl-37551036

The novel HLA-B*15:665 and HLA-C*12:02:02:23 alleles were detected during the routine HLA typing process.

11.
Am J Perinatol ; 2023 Sep 08.
Article En | MEDLINE | ID: mdl-37549883

OBJECTIVE: Coronavirus disease 2019 (COVID-19) generally causes milder illness in the pediatric population. However, infants represent a higher-risk population with evolving symptomatology and severity. There is a paucity of large population-based data on the impact of COVID-19 on hospitalized infants. STUDY DESIGN: In this large cohort study, the National Inpatient Sample database was queried for all infant hospital admissions between January and December 2020 in the United States, with and without a diagnosis of COVID-19 based on ICD-10-CM U07. The mortality and morbidity of infants with and without COVID-19 were evaluated. Parent-reported race and outcomes were also analyzed. RESULTS: A weighted total of 3,754,236 infants who were hospitalized were identified, of which 4,265 patients (0.11%) had a concomitant diagnosis of COVID-19. Infants with COVID-19 had similar mortality and extracorporeal membrane oxygenation utilization. Infants with concomitant COVID-19 had a higher rate of respiratory failure, congestive heart failure, acute kidney injury, and coagulopathy. Compared with Caucasian infants and Asian infants, Hispanic and African American infants were more likely to have COVID-19 hospital admissions than hospitalizations without COVID-19 diagnosis. Patients with lower median household income represented the majority of the COVID-19 hospitalization. The infants with COVID-19 were more likely to have Medicaid or Medicare insurance and less likely to have private insurance. CONCLUSION: In this large cohort of hospitalized infants with COVID-19, the infection was associated with complications, including respiratory failure and endotracheal intubations but not associated with a higher risk for mortality. Infants from racial minorities and lower socioeconomic strata carry the highest burden of COVID-19 infection. KEY POINTS: · Infants with COVID-19 represent a higher-risk group with evolving symptomatology and severity.. · Infants with COVID-19 had similar mortality rates and extracorporeal membrane oxygenation utilization as those without COVID-19.. · Racial minorities and lower socioeconomic strata carry the highest burden of COVID-19 infection..

12.
Int Immunopharmacol ; 122: 110585, 2023 Sep.
Article En | MEDLINE | ID: mdl-37421777

Ulcerative colitis (UC) is an idiopathic, chronic disorder of the intestines characterized by excessive inflammation and oxidative stress. Loganic acid (LA) is an iridoid glycoside reported to have antioxidant and anti-inflammatory properties. However, the beneficial effects of LA on UC are unexplored yet. Thus, this study aims to explore the potential protective effects of LA and its possible mechanisms. In-vitro models were employed using LPS-stimulated RAW 264.7 macrophage cells, and Caco-2 cells, whereas an in-vivo model of ulcerative colitis was employed using 2.5% DSS in BALB/c mice. Results indicated that LA significantly suppressed the intracellular ROS levels and inhibited the phosphorylation of NF-κB in both RAW 264.7 and Caco-2 cells, contrarily LA activated the Nrf2 pathway in RAW 264.7 cells. In DSS-induced colitis mice, LA significantly alleviated the inflammation and colonic damage by decreasing the pro-inflammatory cytokines (IL-1ß, IL-6, TNF-α, and IFN-γ), oxidative stress markers (MDA, and NO), and also expression levels of various inflammatory proteins (TLR4 and NF-кB) which was evidenced by immunoblotting. On the contrary, the release of GSH, SOD, HO-1, and Nrf2 were profoundly increased upon LA treatment.Subsequently, molecular docking studies showed that LA interacts with active site regions of target proteins (TLR4, NF-κB, SIRT1, and Nrf2) through hydrogen bonding and salt bridge interaction. The current findings demonstrated that LA could exhibit a protective effect in DSS-induced ulcerative colitis through its anti-inflammatory and anti-oxidant effects via inactivating the TLR4/NF-κB signaling pathway and activating the SIRT1/Nrf2 pathways.


Colitis, Ulcerative , Humans , Mice , Animals , Colitis, Ulcerative/chemically induced , Colitis, Ulcerative/drug therapy , NF-kappa B/metabolism , Antioxidants/pharmacology , Antioxidants/therapeutic use , NF-E2-Related Factor 2/metabolism , Toll-Like Receptor 4/metabolism , Sirtuin 1 , Molecular Docking Simulation , Caco-2 Cells , Inflammation/drug therapy , Anti-Inflammatory Agents/adverse effects , Dextran Sulfate
13.
Front Immunol ; 14: 1112059, 2023.
Article En | MEDLINE | ID: mdl-37228595

Acute Myeloid Leukemia (AML) is a complex disease with rapid progression and poor/unsatisfactory outcomes. In the past few years, the focus has been on developing newer therapies for AML; however, relapse remains a significant problem. Natural Killer cells have strong anti-tumor potential against AML. This NK-mediated cytotoxicity is often restricted by cellular defects caused by disease-associated mechanisms, which can lead to disease progression. A stark feature of AML is the low/no expression of the cognate HLA ligands for the activating KIR receptors, due to which these tumor cells evade NK-mediated lysis. Recently, different Natural Killer cell therapies have been implicated in treating AML, such as the adoptive NK cell transfer, Chimeric antigen receptor-modified NK (CAR-NK) cell therapy, antibodies, cytokine, and drug treatment. However, the data available is scarce, and the outcomes vary between different transplant settings and different types of leukemia. Moreover, remission achieved by some of these therapies is only for a short time. In this mini-review, we will discuss the role of NK cell defects in AML progression, particularly the expression of different cell surface markers, the available NK cell therapies, and the results from various preclinical and clinical trials.


Leukemia, Myeloid, Acute , Humans , Leukemia, Myeloid, Acute/pathology , Killer Cells, Natural , Immunotherapy, Adoptive/methods , Receptors, KIR/metabolism , Cytokines/metabolism
14.
World J Microbiol Biotechnol ; 39(8): 210, 2023 May 29.
Article En | MEDLINE | ID: mdl-37246185

The emergence of drug-resistant microbial pathogens is a matter of global concern and become more serious if they linked with healthcare-associated infections (HAIs). As per World Health Organization statistics, multidrug-resistant (MDR) bacterial pathogens account for between 7 and 12% of the worldwide burden of HAIs. The need for an effective and environmentally sustainable response to this situation is urgent. The primary goal of this study was to create copper nanoparticles that are biocompatible and non-toxic by using an extract of Euphorbia des moul, and then to test these nanoparticles' bactericidal efficacy against MDR strains of Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, and Acinetobacter baumannii. UV-Vis spectroscopy, dynamic light scattering, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy techniques were used to characterize the biogenic G-CuNPs. It was found that G-CuNPs were spherical in shape, with an average diameter of ~ 40 nm and a charge density of - 21.52 mV. The G-CuNPs fully eradicated the MDR strains at a dosage of 2 mg/ml with 3 h of incubation time. Mechanistic analysis showed that the G-CuNPs efficiently disrupted the cell membrane and damaged the DNA and by generating more reactive oxygen species. Moreover, cytotoxic examination revealed that G-CuNPs displayed < 5% toxicity at 2 mg/ml concentration on human RBCs, PBMCs, and A549 cell lines, suggesting that they are biocompatible. This nano-bioagent is an eco-friendly, non-cytotoxic, non-hemolytic organometallic copper nanoparticles (G-CuNPs) with a high therapeutic index for possible use in the prevention of biomedical device-borne infections by preparing an antibacterial layer on indwelling medical devices. However, its potential clinical use has to be further studied through in vivo testing with an animal model.


Anti-Infective Agents , Euphorbia , Metal Nanoparticles , Nanoparticles , Animals , Humans , Copper/chemistry , Nanoparticles/chemistry , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/chemistry , Escherichia coli , Metal Nanoparticles/chemistry , Spectroscopy, Fourier Transform Infrared , Microbial Sensitivity Tests
15.
Bioorg Chem ; 134: 106434, 2023 05.
Article En | MEDLINE | ID: mdl-36863075

The short peptides, containing the amino acid sequence asparagine-glycine-arginine (NGR) and arginine-glycine-aspartic acid (RGD), possess the strong binding ability to N (APN/CD13) aminopeptidase receptor and integrin proteins involved in antitumor properties are overexpressed. A novel short N-terminal modified hexapeptides P1 and P2 was designed and synthesized using the Fmoc-chemistry solid phase peptide synthesis protocol. Notably, the cytotoxicity of the MTT assay demonstrated the viability of normal and cancer cells up to lower peptide concentrations. Interestingly, both peptides show good anticancer activities against the four cancer cells and normal cells namely, Hep-2, HepG2, MCF-7, A375, and Vero and compared with standard drugs, doxorubicin and paclitaxel. Additionally, in silico studies were applied to predict the binding sites and binding orientation of the peptides for potential anticancer targets. Steady-state fluorescence measurements showed that peptide P1 exhibits preferential interactions with POPC/POPG anionic bilayers rather than the zwitterionic POPC lipid bilayers and peptide P2, did not show any preferential interaction with lipids bilayers. But impressively, peptide P2 shows anticancer activity due to the NGR/RGD motif. Circular dichroism studies demonstrated that the peptide's secondary structure changes only minimally upon binding to the anionic lipid bilayers.


Aminopeptidases , Lipid Bilayers , Lipid Bilayers/chemistry , Integrins , Peptides , Oligopeptides/pharmacology , Oligopeptides/chemistry
16.
Qual Manag Health Care ; 32(3): 170-176, 2023.
Article En | MEDLINE | ID: mdl-36940365

BACKGROUND AND OBJECTIVES: Close monitoring of patients in the first 2 hours after cesarean delivery (CD) is crucial. Delays in shifting of the post-CD patients led to a chaotic environment in the postoperative ward, suboptimal monitoring, and inadequate nursing care. Our aim was to increase the percentage of post-CD patients shifted from transfer trolley to bed within 10 minutes of arrival in the postoperative ward from a baseline of 64% to 100%, and to maintain that rate for more than 3 weeks. METHODS: A quality improvement team including physicians, nurses, and workers was constituted. Problem analysis revealed lack of communication among the caregivers as the main cause of delay. The percentage of post-CD patients shifted from trolley to bed within 10 minutes of being wheeled into the postoperative ward out of the total number of post-CD patients transferred from the operation theater to the postoperative ward was taken as the outcome indicator for the project. Multiple Plan-Do-Study-Act cycles based on the Point of Care Quality Improvement methodology were undertaken to achieve the target. Main interventions were: 1) written information of patient being transferred to operation theater for CD sent to the postoperative ward; 2) stationing of a duty doctor in the postoperative ward; and 3) keeping a buffer of 1 vacant bed in the postoperative ward. The data were plotted weekly as a dynamic time series chart and signals of change were observed. RESULTS: Eighty-three percent (172 out of 206) of women were shifted in time by 3 weeks. After Plan-Do-Study-Act 4, the percentages kept improving leading to a median shift from 85.6% to 100% after 10 weeks post-initiation of the project. Sustainment was confirmed by continuing observations for 6 more weeks to ensure that the changed protocol was assimilated in the system. We found that all women were shifted within 10 minutes of their arrival in postoperative ward from trolley to bed. CONCLUSION: Providing high-quality care to patients must be a priority for all health care providers. High-quality care is timely, efficient, evidence based, and patient-centric. Delays in transfer of postoperative patients to the monitoring area can be detrimental. The point of Care Quality Improvement methodology is useful and effective in solving complex problems by understanding and fixing the various contributory factors one by one. Reorganization of processes and available manpower without any extra investment in terms of infrastructure and resources is pivotal for long term success of a quality improvement project.


Hospitals , Quality Improvement , Humans , Female , Quality of Health Care , Patients
19.
Indian J Hematol Blood Transfus ; 39(1): 50-56, 2023 Jan.
Article En | MEDLINE | ID: mdl-36699439

Relationship between various combinations of KIR ligands and HLA alleles have been studied in several diseases. The aim of this retrospective study was to estimate the frequency of HLA alleles and KIR ligands among acute myeloid leukemia patients and healthy controls in order to examine the possible association of HLA alleles and KIR ligands with AML. A total of 439 acute myeloid leukemia patients and 1317 unrelated, healthy ethnic Indian controls were included in the study. HLA typing was performed using PCR-SSP. KIR ligands were assigned by using the KIR ligand Calculator. The frequency of HLA alleles and KIR ligands in patients was then compared with the controls. As compared to controls, frequencies of HLA-A*03 and HLA-B*35 were increased in AML patients, whereas, that of HLA-C*03 was decreased. Frequencies of HLA-A*03 and HLA-C*15 were increased in male patients, however, no significant difference was observed in female patients as compared to controls. In the pediatric group, the frequencies of HLA-A*01 was decreased and that of HLA-A*03 and HLA-B*18 were increased, whereas, frequencies of HLA-B*13 was decreased and that of HLA-B*27 was increased in the adult patients. In the haplotype analysis, the frequency of HLA-A*24/B*35/DRB1*15 was increased in overall patients. In adult group, the frequency of HLA-A*01/B*44/DRB1*07 was increased in patients than in controls. No significant association was observed between KIR ligands and susceptibility/ protection to AML. Our results indicate that certain HLA alleles and haplotypes have presumptive positive or negative role in conferring protection/susceptibility to AML. Supplementary Information: The online version contains supplementary material available at 10.1007/s12288-022-01550-0.

20.
Inorg Chem ; 62(18): 6882-6892, 2023 May 08.
Article En | MEDLINE | ID: mdl-36715366

At low guest atom concentrations, Si clathrates can be viewed as semiconductors, with the guest atoms acting as dopants, potentially creating alternatives to diamond Si with exciting optoelectronic and spin properties. Studying Si clathrates with different guest atoms would not only provide insights into the electronic structure of the Si clathrates but also give insights into the unique properties that each guest can bring to the Si clathrate structure. However, the synthesis of Si clathrates with guests other than Na is challenging. In this study, we have developed an alternative approach, using thermal diffusion into type II Si clathrate with an extremely low Na concentration, to create Si clathrate with Li guests. Using time-of-flight secondary-ion mass spectroscopy, X-ray diffraction, and Raman scattering, thermal diffusion of Li into the nearly empty Si clathrate framework is detected and characterized as a function of the diffusion temperature and time. Interestingly, the Si clathrate exhibits reduced structural stability in the presence of Li, converting to polycrystalline or disordered phases for anneals at temperatures where the starting Na guest Si clathrate is quite stable. The Li atoms inserted into the Si clathrate lattice contribute free carriers, which can be detected in Raman scattering through their effect on the strength of Si-Si bonds in the framework. These carriers can also be observed in electron paramagnetic resonance (EPR). EPR shows, however, that Li guests are not simple analogues of Na guests. In particular, our results suggest that Li atoms, with their smaller size, tend to doubly occupy cages, forming "molecular-like" pairs with other Li or Na atoms. Results of this work provide a deeper insight into Li guest atoms in Si clathrate. These findings are also relevant to understanding how Li moves through and interacts with Si clathrate anodes in Li-ion batteries. Additionally, techniques presented in this work demonstrate a new method for filling the Si clathrate cages, enabling studies of a broad range of other guests in Si clathrates.

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