Brain-inspired modular echo state network for EEG-based emotion recognition.

Previous studies have successfully applied a lightweight recurrent neural network (RNN) called Echo State Network (ESN) for EEG-based emotion recognition. These studies use intrinsic plasticity (IP) and synaptic plasticity (SP) to tune the hidden reservoir layer of ESN, yet they require extra training procedures and are often computationally complex. Recent neuroscientific research reveals that the brain is modular, consisting of internally dense and externally sparse subnetworks. Furthermore, it has been proved that this modular topology facilitates information processing efficiency in both biological and artificial neural networks (ANNs). Motivated by these findings, we propose Modular Echo State Network (M-ESN), where the hidden layer of ESN is directly initialized to a more efficient modular structure. In this paper, we first describe our novel implementation method, which enables us to find the optimal module numbers, local and global connectivity. Then, the M-ESN is benchmarked on the DEAP dataset. Lastly, we explain why network modularity improves model performance. We demonstrate that modular organization leads to a more diverse distribution of node degrees, which increases network heterogeneity and subsequently improves classification accuracy. On the emotion arousal, valence, and stress/calm classification tasks, our M-ESN outperforms regular ESN by 5.44, 5.90, and 5.42%, respectively, while this difference when comparing with adaptation rules tuned ESNs are 0.77, 5.49, and 0.95%. Notably, our results are obtained using M-ESN with a much smaller reservoir size and simpler training process.

Significant enhancement of proton conductivity in solid acid at the monolayer limit.

Proton transport in nanofluidic channels is not only fundamentally important but also essential for energy applications. Although various strategies have been developed to improve the concentration of active protons in the nanochannels, it remains challenging to achieve a proton conductivity higher than that of Nafion, the benchmark for proton conductors. Here, taking H3Sb3P2O14 and HSbP2O8 as examples, we show that the interactions between protons and the layer frameworks in layered solid acid HnMnZ2O3n+5 are substantially reduced at the monolayer limit, which significantly increases the number of active protons and consequently improves the proton conductivities by ∼8 ‒ 66 times depending on the humidity. The membranes assembled by monolayer H3Sb3P2O14 and HSbP2O8 nanosheets exhibit in-plane proton conductivities of ~ 1.02 and 1.18 S cm-1 at 100% relative humidity and 90 °C, respectively, which are over 5 times higher than the conductivity of Nafion. This work provides a general strategy for facilitating proton transport, which will have broad implications in advancing both nanofluidic research and device applications from energy storage and conversion to neuromorphic computing.

Marine Alkaloid Lepadins E and H Induce Ferroptosis for Cancer Chemotherapy.

Induction of ferroptosis emerges as an effective method for cancer treatment. With massive efforts to elucidate the ferroptosis mechanism, the development of new ferroptosis inducers proceeds rather slowly, with only a few small molecules identified. Herein, we report our discovery of marine alkaloid lepadins E and H as a new class of ferroptosis inducers. Our in vitro studies show that lepadins E and H exhibit significant cytotoxicity, promote p53 expression, increase ROS production and lipid peroxides, reduce SLC7A11 and GPX4 levels, and upregulate ACSL4 expression, all of which consistently support induction of ferroptosis through the classical p53-SLC7A11-GPX4 pathway. Our animal model study of lepadin H confirms its in vivo antitumor efficacy with negligible toxicity to normal organs. This work elucidates the mode of action of lepadins (E and H) and verifies their in vivo efficacy as a new class of ferroptosis inducers for anticancer therapy with translational potential.

A Robust Brain Tumor Detector Using BiLSTM and Mayfly Optimization and Multi-Level Thresholding.

A brain tumor refers to an abnormal growth of cells in the brain that can be either benign or malignant. Oncologists typically use various methods such as blood or visual tests to detect brain tumors, but these approaches can be time-consuming, require additional human effort, and may not be effective in detecting small tumors. This work proposes an effective approach to brain tumor detection that combines segmentation and feature fusion. Segmentation is performed using the mayfly optimization algorithm with multilevel Kapur's threshold technique to locate brain tumors in MRI scans. Key features are achieved from tumors employing Histogram of Oriented Gradients (HOG) and ResNet-V2, and a bidirectional long short-term memory (BiLSTM) network is used to classify tumors into three categories: pituitary, glioma, and meningioma. The suggested methodology is trained and tested on two datasets, Figshare and Harvard, achieving high accuracy, precision, recall, F1 score, and area under the curve (AUC). The results of a comparative analysis with existing DL and ML methods demonstrate that the proposed approach offers superior outcomes. This approach has the potential to improve brain tumor detection, particularly for small tumors, but further validation and testing are needed before clinical use.

Gene expression variability across cells and species shapes the relationship between renal resident macrophages and infiltrated macrophages.

BACKGROUND: Two main subclasses of macrophages are found in almost all solid tissues: embryo-derived resident tissue macrophages and bone marrow-derived infiltrated macrophages. These macrophage subtypes show transcriptional and functional divergence, and the programs that have shaped the evolution of renal macrophages and related signaling pathways remain poorly understood. To clarify these processes, we performed data analysis based on single-cell transcriptional profiling of renal tissue-resident and infiltrated macrophages in human, mouse and rat. RESULTS: In this study, we (i) characterized the transcriptional divergence among species and (ii) illustrated variability in expression among cells of each subtype and (iii) compared the gene regulation network and (iv) ligand-receptor pairs in human and mouse. Using single-cell transcriptomics, we mapped the promoter architecture during homeostasis. CONCLUSIONS: Transcriptionally divergent genes, such as the differentially TF-encoding genes expressed in resident and infiltrated macrophages across the three species, vary among cells and include distinct promoter structures. The gene regulatory network in infiltrated macrophages shows comparatively better species-wide consistency than resident macrophages. The conserved transcriptional gene regulatory network in infiltrated macrophages among species is uniquely enriched in pathways related to kinases, and TFs associated with largely conserved regulons among species are uniquely enriched in kinase-related pathways.

Bistable Optoelectronic Properties Originated from the Scissoring Motion of the TEMPO Skeleton in Supramolecular Radical Ferroelectrics.

Bistable materials with multiphysical channels, such as optical, electrical, and magnetic properties, have been paid dramatic attention due to their alternativity of the signal status in electronic devices. Herein, three stable supramolecular radicals ([(NH3-TEMPO)(18-crown-6)][XF6] (1, X = P; 2, X = As; 3, X = Sb)) were synthesized and characterized. The former two molecules present ferroelectric phase transitions around 381.7 and 382.7 K, respectively, with bistability in dielectric property and second-harmonic generation (SHG) effect, which are first found in supramolecular radicals. Their ferroelectric transition and bistable properties are generated from a net polar crystal structure owing to the static ordered packing of NH3-TEMPO radical cations in the low-temperature phase (LTP) to a nonpolar structure owing to a distinctive symmetric scissoring motion of NH3-TEMPO radical cations between two 18-crown-6 molecules in the high-temperature phase (HTP). Both of them exhibit paramagnetic properties in HTP and LTP states since no intermolecular spin-spin interaction occurs due to the long distances among the radicals in their crystals. These results make us possible to design bistable optoelectronic radical materials with bistability in magnetic property in the future.

Corrigendum: Bibliometric and visual analysis of neutrophil extracellular traps from 2004 to 2022.

[This corrects the article DOI: 10.3389/fimmu.2022.1025861.].

Bibliometric and visual analysis of neutrophil extracellular traps from 2004 to 2022.

Background: Neutrophil extracellular traps (NETs) are specialized structures formed by neutrophils that were initially found to be important in killing pathogenic bacteria during infection. With the development of related research, the relationship between NETs and diseases such as sepsis, cancer, and systemic lupus erythematosus has received close attention. However, there is a lack of reports that comprehensively and objectively present the current status of NETs-related studies. Therefore, this study aims to visually analyze the current status and trends of NETs-related research by means of bibliometrics and knowledge mapping. Methods: NETs-related articles and reviews were retrieved using the Web of Science core collection subject search, and bibliometric analysis was performed in Excel 365, CiteSpace, VOSviewer, and Bibliometrix (R-Tool of R-Studio). Results: A total of 4866 publications from 2004 to 2022 were included in the bibliometric analysis. The number of publications shows an increasing trend from year to year. Collaborative network analysis shows that the United States and Germany are the most influential countries in this field, with the highest number of publications and citations. The journal with the most publications is Frontiers in Immunology. Brinkmann Volker is an authoritative author in this field, and his publication "Neutrophil extracellular traps kill bacteria" is the most frequently cited. The literature and keyword analysis shows that the relationship between NETs and diseases (hematological diseases, sepsis, cancer, etc.) and cell death (apoptosis, necroptosis, pyroptosis, etc.) is a popular research topic. Currently, NETs and SARS-CoV-2-related studies are at the forefront of the field. Conclusion: This study is the first to visualize the research in NETs-related fields using bibliometric methods, revealing the trends and frontiers of NETs research. This study will provide valuable references for scholars to find research focus questions and partners.

Supercycled R-symmetry sequences for robust heteronuclear polarization transfer in solid-state NMR.

Herein, we introduce supercycle of R-symmetry sequences (SR-sequences) and incomplete supercycle schemes of R-symmetry sequences (iSR-I- and iSR-II-sequences) to improve the robustness of PRESTO for heteronuclear polarization transfer in MAS NMR. The constructions of SR- and iSR-I/II- sequences are based on the different phase-inverted supercycles of R-symmetry sequences, and such supercycles can suppress the influence of CSA, resonance offset and RF mismatch when incorporated into the PRESTO method. Moreover, the SR- and iSR-II-sequences are more efficient in suppressing the interference of homonuclear dipolar coupling. The improved robustness of SR-, iSR-I- and iSR-II-PRESTO over the original R-PRESTO has been verified by numerical simulations and NMR experiments on NH4H2PO4 and gamma-alumina at fast MAS conditions. It is also important to note that the SR- and iSR-II-PRESTO can greatly lengthen the transverse relaxation times and lead to much higher polarization transfer efficiency compared to R-PRESTO, thanks to their superior tolerance to RF inhomogeneity and homonuclear dipolar coupling.

Electrochemical oxidative rearrangement of tetrahydro-ß-carbolines in a zero-gap flow cell.

Oxidative rearrangement of tetrahydro-ß-carbolines (THßCs) is one of the most efficient methods for the synthesis of biologically active spirooxindoles, including natural products and drug molecules. Here, we report the first electrochemical approach to achieve this important organic transformation in a flow cell. The key to the high efficiency was the use of a multifunctional LiBr electrolyte, where the bromide (Br-) ion acts as a mediator and catalyst and lithium ion (Li+) acts as a likely hydrophilic spectator, which might considerably reduce diffusion of THßCs into the double layer and thus prevent possible nonselective electrode oxidation of indoles. Additionally, we build a zero-gap flow cell to speed up mass transport and minimize concentration polarization, simultaneously achieving a high faradaic efficiency (FE) of 96% and an outstanding productivity of 0.144 mmol (h-1 cm-2). This electrochemical method is demonstrated with twenty substrates, offering a general, green path towards bioactive spirooxindoles without using hazardous oxidants.

Direct Detection of Reactive Gallium-Hydride Species on the Ga2O3 Surface via Solid-State NMR Spectroscopy.

Surface metal hydrides (M-H) are ubiquitous in heterogeneous catalytic reactions, while the detailed characterizations are frequently hindered by their high reactivity/low concentration, and the complicated surface structures of the host solids, especially in terms of practical solid catalysts. Herein, combining instant quenching capture and advanced solid-state NMR methodology, we report the first direct and unambiguous NMR evidence on the highly reactive surface gallium hydrides (Ga-H) over a practical Ga2O3 catalyst during direct H2 activation. The spectroscopic effects of 69Ga and 71Ga isotopes on the 1H NMR signal are clearly differentiated and clarified, allowing a concrete discrimination of the Ga-H signal from the hydroxyl crowd. Accompanied with quantitative and two-dimensional NMR spectroscopical methods, as well as density functional theory calculations, information on the site specification, structural configuration, and formation mechanism of the Ga-H species has been revealed, along with the H2 dissociation mechanism. More importantly, the successful spectroscopic identification and isolation of the surface Ga-H allow us to clearly reveal the critical but ubiquitous intermediate role of this species in catalytic reactions, such as propane dehydrogenation and CO2 hydrogenation reactions. The analytic approach presented in this work can be extended to other M-H analysis, and the insights will benefit the design of more efficient Ga-based catalysts.

[Outcome indicators in randomized controlled trials on traditional Chinese medicine intervention of sepsis-induced myocardial injury in recent five years].

This study aims to analyze the outcome indicators of randomized controlled trial(RCT) on traditional Chinese medicine(TCM) intervention of sepsis-induced myocardial injury(SIMI) in recent five years, which is expected to lay a basis for the construction of core outcome set(COS) for this disease treated by TCM. To be specific, RCT on the treatment of SIMI with TCM was retrieved from 4 Chinese databases, 3 English databases, and 2 clinical trial protocol registries. The quality of the included studies was evaluated with Cochrane risk-of-bias(ROB) tool, and the outcome indicators were analyzed. Finally, 42 RCTs were included, of which 2 were clinical trial registration schemes. The study found that 42 RCTs had a high risk of bias, and reported a total of 86 indicators in "clinical effective rate, disease severity, TCM syndrome score, inflammation, myocardium, cardiac structure and hemodynamics, electrocardiogram, immunology, metabolism and liver and kidney function, and safety". Outcome indicators on myocardium had the highest emergence frequency, followed by indicators on the cardiac structure and hemodynamics. A total of 8 RCTs reported TCM syndrome scores. Further analysis suggested the following problems in the selection of outcome indicators in the RCTs on TCM intervention of SIMI: no classification of primary and secondary indicators, disregard of endpoint indicators, irrational selection of alternative indicators, neglection of TCM characteristics, no assessment of patients' immune status, and no emphasis on economic indicators and safety indicators. Therefore, according to the recommendations of the core outcome measures in effectiveness trials(COMET) working group, a COS for TCM intervention of TCM for SIMI should be developed, so as to facilitate clinical researchers to select appropriate outcome indicators, the combination of conclusions of similar clinical studies, and the promotion of TCM interventions.

Achmatowicz Rearrangement-Inspired Development of Green Chemistry, Organic Methodology, and Total Synthesis of Natural Products.

The six-membered heterocycles containing oxygen and nitrogen (tetrahydropyrans, pyrans, piperidines) are among the most common heterocyclic structures ubiquitously present in bioactive molecules such as carbohydrates, small-molecule drugs, and natural products. Chemical synthesis of fully functionalized pyrans and piperidines is a research theme of practical importance and scientific significance and, thus, has attracted continuous interest from synthetic chemists. Among the numerous synthetic approaches, Achmatowicz rearrangement (AchR) represents a general and unique strategy that uses biomass-derived furfuryl alcohols as the renewable starting material to obtain fully functionalized six-membered oxygen/nitrogen heterocycles, which provides golden opportunities for organic chemists to address various synthetic challenges.This Account summarizes our 10 years of work on exploiting AchR to address some challenges in organic synthesis ranging from green chemistry and organic methodology to the total synthesis of natural products. We enabled the sustainable and safe use of AchR in a small (academia) or large (industrial) scale by developing two generations of green approaches for AchR (oxone-halide and Fenton-halide), which largely eliminate the use of the most popular, but more toxic and expansive, NBS and m-CPBA. This triggered our intensive interest in developing new green chemistry for important organic reactions, in particular, halogenation/oxidation reactions involving reactive halogenating species with the aim of eliminating the use of commonly used toxic halogen agents such as elemental bromine, chlorine gas, and various N-haloamide reagents (NBS, NCS, and NIS). We successfully employed oxone-halide and Fenton-halide as green alternatives to several mechanistically related organic reactions including arene/alkene halogenation, oxidation or oxidative rearrangement of indoles, oxidation of alcohols/thioacetals, and oxidative halogenation of aldoximes for the in situ generation of nitrile oxide. These green reactions are expected to have a solid impact on the future of organic synthesis in academia and industries.We expanded the synthetic utility of AchR by exploring several new transformations of AchR products and developed a cascade reductive ring expansion, reductive deoxygenation/Heck-Matsuda arylation, palladium-catalyzed C-arylation, and regiodivergent [3 + 2] cycloaddition with 1,3-dicarbonyls. These methodologies offer a new avenue to fully functionalized six-membered heterocycles.The synthetic utility of AchR was demonstrated in our total synthesis of 28 natural products with a pyran/piperidine moiety. The AchR-based strategy endows the total synthesis with scalability, sustainability, and flexibility. The green and scalable approaches developed in our lab for AchR allow us to easily obtain decagrams of synthetically valuable pyrans and/or piperidines with low risk and low cost from biomass-derived furfuryl alcohol/aldehyde.

Nature of Five-Coordinated Al in γ-Al2O3 Revealed by Ultra-High-Field Solid-State NMR.

Five-coordinated Als (Al(V)) on the surface of aluminas play important roles when they are used as catalysts or catalyst supports. However, the comprehensive characterization and understanding of the intrinsic structural properties of the Al(V) remain a challenge, due to the very small amount in commonly used aluminas. Herein, the surface structures of γ-Al2O3 and Al(V)-rich Al2O3 nanosheets (Al2O3-NS) have been investigated and compared in detail by multinuclear high-field solid-state NMR. Thanks to the high resolution and sensitivity of ultra-high-field (up to 35.2 T) NMR, the arrangements of surface Als were clearly demonstrated, which are substantially different from the bulk phase in γ-Al2O3 due to the structure reconstruction. It reveals for the first time that most of the commonly observed Al(V)s tend to exist as aggregated states on the surface of γ-Al2O3, like those in amorphous Al2O3-NS liable to structure reconstruction. Our new insights into surface Al(V) species may help in understanding the structure-function relationship of alumina.

Towards more efficient ophthalmic disease classification and lesion location via convolution transformer.

OBJECTIVE: A retina optical coherence tomography (OCT) image differs from a traditional image due to its significant speckle noise, irregularity, and inconspicuous features. A conventional deep learning architecture cannot effectively improve the classification accuracy, sensitivity, and specificity of OCT images, and noisy images are not conducive to further diagnosis.  This paper proposes a novel lesion-localization convolution transformer (LLCT) method, which combines both convolution and self-attention to classify ophthalmic diseases more accurately and localize the lesions in retina OCT images. METHODS: A novel architecture design is accomplished through applying customized feature maps generated by convolutional neutral network (CNN) as the input sequence of self-attention network. This design takes advantages of CNN's extracting image features and transformer's consideration of global context and dynamic attention. Part of the model is backward propagated to calculate the gradient as a weight parameter, which is multiplied and summed with the global features generated by the forward propagation process to locate the lesion. RESULTS: Extensive experiments show that our proposed design achieves improvement of about 7.6% in overall accuracy, 10.9% in overall sensitivity, and 9.2% in overall specificity compared with previous methods. And the lesions can be localized without the labeling data of lesion location in OCT images. CONCLUSION: The results prove that our method significantly improves the performance and reduces the computation complexity in artificial intelligence assisted analysis of ophthalmic disease through OCT images. SIGNIFICANCE: Our method has a significance boost in ophthalmic disease classification and location via convolution transformer. This is applicable to assist ophthalmologists greatly.1.

Chronic disease management practices and factors associated with health-related quality-of-life for persons with chronic myeloid leukemia receiving tyrosine kinase inhibitor therapy.

BACKGROUND: The main objective of this study was to explore health-related quality of life (HRQoL) profiles, chronic disease management practices and key factors associated with HRQoL in 540 patients with chronic myeloid leukemia in chronic phase (CML-CP) administered tyrosine kinase inhibitors (TKIs). METHODS: Adult CML-CP patients treated with TKIs in Henan Cancer Hospital from March 2015 to October 2019 were assessed via questionnaires, including demographic characteristics, TKI medications, participation in CML disease management, and HRQoL, in a cross-sectional investigation. Respondents were anonymous. Functional Assessment of Cancer Therapy-Leukemia (FACT-Leu) was used to measure HRQoL. A multivariate linear regression model with stepwise entry was used to investigate variables independently associated with HRQoL domain and total scores. RESULTS: Totally, 540 respondents were included; 302 (55.93%) were male. Mean participant age was 42.90±13.00 years; 169 (31.3%), 178 (32.9%) and 193 (35.7%) individuals had a low, moderate or high disease management level, respectively. Except for insignificant event-free survival information, participants with higher disease management levels also had significantly higher rates of completing re-examination, drug withdrawal, cytogenetic response (CcyR) and/or major molecular response (MMR) (all P<0.01). Moreover, higher disease management level was accompanied by eight significantly higher HRQoL domains (all P<0.01). In multivariate linear regression analysis, variables significantly associated with a higher HRQoL included: (I) high disease management level (B=3.68, P=0.046); (II) transportation convenience (B=6.67, P<0.001); (III) family annual income >10,000 CNY (B=5.97, P<0.001); (IV) completed re-examination (B=4.58, P=0.036); (V) MMR (B=3.75, P=0.021) and CcyR (B=5.15, P=0.035). Female sex (B=-3.53, P=0.010), single status or divorce (B=-1.89 and -2.94, P=0.005 and 0.011), and low education level (B=-1.44, P=0.019) were significantly associated with lower HRQoL. CONCLUSIONS: Higher disease management level was significantly associated with higher elevated treatment efficacy and HRQoL in Chinese individuals with CML-CP administered TKIs. These data indicate the importance of chronic disease management on people's HRQoL and clinical outcome.

A risk-prediction score for colorectal lesions on 12,628 participants at high risk of colorectal cancer.

BACKGROUND: The uptake of colonoscopy is low in individuals at risk of colorectal cancer (CRC). We constructed a risk-prediction score (RPS) in a large community-based sample at high risk of CRC to enable more accurate risk stratification and to motivate and increase the uptake rate of colonoscopy. METHODS: A total of 12,628 participants classified as high-risk according to positivity of immunochemical fecal occult blood tests or High-Risk Factor Questionnaire underwent colonoscopy. Logistic regression was used to derive a RPS and analysed the associations of the RPS with colorectal lesions, giving odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Of the participants, men (OR = 1.73, 95% CI = 1.58-1.90), older age (≥65 years; 1.41, 1.31-1.53), higher body mass index (≥28 kg/m2; 1.22, 1.07-1.39), ever smoking (1.47, 1.31-1.65), and weekly alcohol use (1.28, 1.09-1.52) were associated with a higher risk of colorectal lesions. We assigned 1 point to each of the above five risk factors and derived a RPS ranging from 0 to 5, with a higher score indicating a higher risk. Compared with a RPS of 0, a RPS of 1, 2, 3, and 4-5 showed a higher risk of colorectal lesions, with the OR (95% CI) being 1.50 (1.37-1.63), 2.34 (2.12-2.59), 3.58 (3.13-4.10), and 3.91 (3.00-5.10), respectively. The area under the receiver-operating characteristic curve of RPS in predicting colorectal lesions was 0.62. CONCLUSIONS: Participants with an increase in the RPS of ≥1 point had a significantly higher risk of colorectal lesions, suggesting the urgency for measuring colonoscopy in this very high-risk group. High-risk strategies incorporating RPS may be employed to achieve a higher colonoscopy-uptake rate.

Solid-State NMR Dipolar and Chemical Shift Anisotropy Recoupling Techniques for Structural and Dynamical Studies in Biological Systems.

With the development of NMR methodology and technology during the past decades, solid-state NMR (ssNMR) has become a particularly important tool for investigating structure and dynamics at atomic scale in biological systems, where the recoupling techniques play pivotal roles in modern high-resolution MAS NMR. In this review, following a brief introduction on the basic theory of recoupling in ssNMR, we highlight the recent advances in dipolar and chemical shift anisotropy recoupling methods, as well as their applications in structural determination and dynamical characterization at multiple time scales (i.e., fast-, intermediate-, and slow-motion). The performances of these prevalent recoupling techniques are compared and discussed in multiple aspects, together with the representative applications in biomolecules. Given the recent emerging advances in NMR technology, new challenges for recoupling methodology development and potential opportunities for biological systems are also discussed.

Unraveling the Surface Hydroxyl Network on In2O3 Nanoparticles with High-Field Ultrafast Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy.

Hydroxyl groups are among the major active surface sites over metal oxides. However, their spectroscopic characterizations have been challenging due to limited resolutions, especially on hydroxyl-rich surfaces where strong hydroxyl networks are present. Here, using nanostructured In2O3 as an example, we show significantly enhanced discrimination of the surface hydroxyl groups, owing to the high-resolution 1H NMR spectra performed at a high magnetic field (18.8 T) and a fast magic angle spinning (MAS) of up to 60 kHz. A total of nine kinds of hydroxyl groups were distinguished and their assignments (µ1, µ2, and µ3) were further identified with the assistance of 17O NMR. The spatial distribution of these hydroxyl groups was further explored via two-dimensional (2D) 1H-1H homonuclear correlation experiments with which the complex surface hydroxyl network was unraveled at the atomic level. Moreover, the quantitative analysis of these hydroxyl groups with such high resolution enables further investigations into the physicochemical property and catalytic performance characterizations (in CO2 reduction) of these hydroxyl groups. This work provides insightful understanding on the surface structure/property of the In2O3 nanoparticles and, importantly, may prompt general applications of high-field ultrafast MAS NMR techniques in the study of hydroxyl-rich surfaces on other metal oxide materials.

89Y chemical shift anisotropy: a sensitive structural probe of layered yttrium hydroxides revealed by solid-state NMR spectroscopy and DFT calculations.

Anion-exchangeable Y2(OH)5X·nH2O (LYH-X, X = monovalent anions, n ≈ 1.5) materials are an ideal platform for incorporating the unique properties of layered metal hydroxides and rare-earth (RE) ions, and thus have exhibited promising prospects for various applications. To further improve the performance of LYH-X and related functional materials, their structure-property relationships must be explored. However, due to the intrinsic felxibility, extracting the local structural details of these materials is particularly challenging. In this work, we utilized a combined approach of 89Y solid-state NMR (ssNMR) spectroscopy and density functional theory (DFT) calculations to reveal the response of 89Y chemical shift anisotropy (CSA) in LYH-X to the structural changes including a small displacement of cationic yttrium hydroxide layers and intercalated anions. Such subtle structural changes are often associated with dehydration/rehydration, anion-exchange, exfoliation, and the self-assembly process of LYH-X and related functional materials, which are exceedingly difficult to detect using other techniques. The principal components of 89Y CSA show a larger variation range than isotropic chemical shifts, making CSA a more sensitive probe. In addition, it is found that the response of 89Y CSA to structural changes is distinct for Y sites with different local coordination environments, opening great opportunities to analyze each Y site within these materials. All these observations suggest that the strategy involving both experimental (89Y ssNMR) and theoretical (DFT) approaches can be utilized to extract previously unavailable ultrafine structural information of LYH-X and related materials, and provide fruitful insights into their thorough structure-property relationships.