Development of high-performance point-of-care aqueous VEGF detection system and proof-of-concept validation in RVO patients.

OBJECTIVES: To develop a sensitive point-of-care testing (POCT) aqueous vascular endothelial growth factor (VEGF) detection system, and assess its role for predicting the response to anti-VEGF treatment in macular edema secondary to retinal vein occlusion (RVO-ME) patients. METHODS: An automatic point-of-care aqueous humor Magnetic Particle Chemiluminescence Enzyme Immuno-Assay (MPCLEIA) VEGF detection system was developed. The predictive values of aqueous cytokine levels, in combination with imaging parameters, on anatomical treatment response (ATR, the relative central macular thickness change [ΔCMT/bl-CMT]) were analyzed. RESULTS: The automatic MPCLEIA system was able to provide results in 45 min with only 20 µL sample. Among the 57 eyes with available pre- and post-treatment evaluation, ATR significantly correlated with levels of interleukin (IL)-6, IL-8, monocyte chemoattractant protein-1 (MCP-1) and VEGF measured by Luminex xMAP platform, and VEGF measured by MPCLEIA. Optimal cut-off values for these biomarkers were 13.26 ng/L, 23.57 ng/L, 1,110.12 ng/L, 105.52 ng/L, and 85.39 ng/L, respectively. Univariate analysis showed significant associations between ATR category (good response if ATR≤-25 % or poor response otherwise) and IL-6, IL-8, MCP-1, VEGF-xMAP, and VEGF-MPCLEIA (p<0.05). Multivariate logistic regression revealed that ATR category was significantly associated with aqueous VEGF-MPCLEIA (p=0.006) and baseline(bl)-CMT (p=0.008). Receiver operating characteristics analysis yielded an AUC of 0.959 for the regression model combining VEGF-MPCLEIA and bl-CMT, for predicting ATR category. CONCLUSIONS: Our novel MPCLEIA-based automatic VEGF detection system enables accurate POCT of aqueous VEGF, which shows promise in predicting the treatment response of RVO-ME to anti-VEGF agents when combined with bl-CMT.

Differences between young and elderly polypoidal choroidal vasculopathy patients with and without pachychoroid phenotypes.

PURPOSE: To investigate the distinct characteristics between young and elderly polypoidal choroidal vasculopathy (PCV) patients based on the pachy- or non-pachychoroid phenotypes. METHODS: PCV patients treated with intravitreal injections of Conbercept based on the 3 + PRN regimen from 27 centers of China PCV Research Alliance were included. Patients were categorized into the young and the elderly aged group based on the cut-off point determined using the Youden method according to the pachychoroid phenotypes. The characteristics of past medical history, lifestyle factors, fundus manifestations, and treatment response between the subgroups were analyzed. RESULTS: Three hundred eight eligible patients were included. Multivariate logistic regression showed a significant association between age and PCV subtype classification (OR = 0.921, P = 0.002). A cutoff age of 64.5 effectively distinguished between pachychoroid PCV and non-pachychoroid PCV (P < 0.001). Elderly PCV patients had a higher incidence of hypertension history (P = 0.044) but a lower incidence of diabetes history (P = 0.027). In terms of lifestyle, smoking history (P = 0.015) and staying up late (P = 0.004) were more significant in the young group of PCV patients. For clinical characteristics, the proportion of hemorrhagic PCV in the young group was significantly higher (P = 0.038), with a higher proportion of sharp-peaked PED (P = 0.049), thicker choroid (P < 0.001) but a lower portion of double-layer sign (P = 0.023) in OCT. Both groups showed significant anatomical changes compared to baseline in each follow-up period (P < 0.05), with the young group having a higher proportion of good anatomical response after the first injection (P = 0.009). CONCLUSION: PCV patients stratified by subtype exhibit distinct characteristics between the young and elderly groups.

DMSO synergized with sugars: optical clearing agent modulation of optical coherence tomography of skin tissues.

The stratum corneum of the outermost skin is an important barrier impeding transdermal permeation, and permeation enhancers can reduce the barrier resistance of the stratum corneum and enhance the permeation of drugs in tissues. The optical imaging depth, signal intensity, and scattering coefficient variation rules of skin tissues in time dimension are obtained by using optical coherence tomography (OCT). The effect of optical clearing agents (OCAs) on OCT imaging is obtained by quantitatively analyzing the changes in the optical properties of tissues. D-fructose, one of the monosaccharides, and sucrose, one of the disaccharides, were selected for the ex vivo optical clearing experiments on pig skin tissues utilizing the dimethyl sulfoxide (DMSO) carrier effect. We find that DMSO synergized with sugars applied to skin tissue has a more significant increase in the optical imaging depth and signal intensity, and a reduction in the scattering coefficient with an increasing concentration of DMSO. DMSO with a high concentration and D-fructose with saturated concentration (10:1; v/v) effectively reduce light attenuation in OCT imaging and improve the image quality. This operation will also shorten the application time to minimize skin damage from hyperosmotic agents.

Evaluation of the First-Dose Anti-VEGF Anatomical Response in Polypoidal Choroidal Vasculopathy Patients: Correlation with the Third-Dose Response and Risk Factor Analysis.

INTRODUCTION: The aims of the study were to investigate whether first-dose efficacy can predict third-dose anatomical response and analyze the risk factors for first-dose response of polypoidal choroidal vasculopathy (PCV) patients. METHODS: We retrospectively reviewed patients' medical records from 27 centers of China PCV Research Alliance. PCV patients treated with intravitreal injections of conbercept (IVC) based on the 3+ pro re nata regimen (three initial monthly injections, followed by injections as needed) with complete 3-month injection data were included. Response correlations, risk factor associations, changes in central macular thickness (CMT) or best-corrected visual acuity (BCVA), and number of injections in the first year of follow-up were evaluated separately in the pachy-PCV and non-pachy-PCV phenotypes. RESULTS: Overall, 165 eligible patients were included. There was a significant correlation between first-dose and third-dose anatomical response in pachy-PCV or non-pachy-PCV patients (rs = 0.611, p < 0.001; rs = 0.638, p < 0.001). Multivariate analysis revealed associations of good first-dose anatomical response in pachy-PCV patients with baseline CMT with a predicted area under the curve (AUC) of 0.847, while a good response in non-pachy-PCV patients was associated with baseline BCVA, baseline CMT, pigment epithelial detachment (PED) height, higher proportion of intraretinal fluid, and lower PED minimum diameter with a predicted AUC of 0.940. CMT in the good first-dose response group was significantly decreased from baseline at all first-year follow-up visits in both groups (p < 0.001), and mean BCVA was improved in the good versus poor first-dose anatomical response group (5.4 vs. 1.6 ETDRS letters in pachy-PCV, 10.6 vs. 7.4 letters in non-pachy-PCV) after the third injection. No significant difference was observed in the number of injections in the first year of follow-up between different response groups. CONCLUSION: In PCV patients receiving IVC, the first- and third-dose responses are significantly correlated, and different factors influence the first-dose response in different subtypes of PCV.

Construction and application of the conditionally essential gene knockdown library in Klebsiella pneumoniae to screen potential antimicrobial targets and virulence genes via Mobile-CRISPRi-seq.

Klebsiella pneumoniae is a ubiquitous human pathogen, and its clinical treatment faces two major challenges: multidrug resistance and the pathogenesis of hypervirulent K. pneumoniae. The discovery and study of conditionally essential (CE) genes that can function as potential antimicrobial targets has always been a research concern due to their restriction in the development of novel antibiotics. However, the lack of essential functional genomic data has hampered the study of the mechanisms of essential genes related to antimicrobial susceptibility. In this study, we developed a pooled CE genes mobile clustered regularly interspaced short palindromic repeat (CRISPR) interference screening method (Mobile-CRISPRi-seq) for K. pneumoniae to identify genes that play critical roles in antimicrobial fitness in vitro and host immunity in vivo. Targeting 870 predicted CE genes in K. pneumoniae, Mobile-CRISPRi-seq uncovered the depletion of tetrahydrofolate synthesis pathway genes folB and folP under trimethoprim pressure. Our screening also identified genes waaE and fldA related to polymyxin and ß-lactam susceptibility by applying a screening strategy based on Mobile-CRISPRi-seq and comparative genomics. Furthermore, using a mouse infection model and Mobile-CRISPRi-seq, multiple virulence genes were identified, and among these genes, pal, yciS, and ribB were demonstrated to contribute to the pathogenesis of K. pneumoniae. This study provides a simple, rapid, and effective platform for screening potential antimicrobial targets and virulence genes in K. pneumoniae, and this broadly applicable system can be expanded for high-throughput functional gene study in multiple pathogenic bacteria, especially in gram-negative bacteria. IMPORTANCE The discovery and investigation of conditionally essential (CE) genes that can function as potential antimicrobial targets has always been a research concern because of the restriction of antimicrobial targets in the development of novel antibiotics. In this study, we developed a pooled CE gene-wide mobile clustered regularly interspaced short palindromic repeat (CRISPR) interference sequencing (Mobile-CRISPRi-seq) strategy in Klebsiella pneumoniae to identify genes that play critical roles in the fitness of antimicrobials in vitro and host immunity in vivo. The data suggest a robust tool to screen for loss-of-function phenotypes in a pooled gene knockdown library in K. pneumoniae, and Mobile-CRISPRi-seq may be expanded to multiple bacteria for screening and identification of genes with crucial roles in the fitness of antimicrobials and hosts.

Broadly neutralizing antibodies recognizing different antigenic epitopes act synergistically against the influenza B virus.

The discovery of broadly neutralizing monoclonal antibodies against influenza viruses has raised hope for the successful development of new antiviral drugs. However, due to the speed and variety of mutations in influenza viruses, single-component antibodies that recognize specific epitopes are susceptible to viral escape and have limited efficacy when administration is delayed. Hence, it is necessary to develop alternative strategies with better antiviral activity. Influenza B virus infection can cause severe illness in children and the elderly. Commonly used anti-influenza drugs have low clinical efficacy against influenza B virus. In this study, we investigated the antiviral efficacy of combinations of representative monoclonal antibodies targeting different antigenic epitopes against the influenza B virus. We found that combinations of antibodies recognizing the hemagglutinin (HA) head and stem regions showed a stronger neutralizing activity than single antibodies and other antibody combinations in vitro. In addition, we found that pair-wise combinations of antibodies recognizing the HA head region, HA stem region, and neuraminidase enzyme-activated region showed superior antiviral activity than single antibodies in both mouse and ferret in vivo protection assays. Notably, these antibody combinations still displayed good antiviral efficacy when treatment was delayed. Mechanistic studies further revealed that combining antibodies recognizing different epitope regions resulted in extremely strong antibody-dependent cell-mediated cytotoxicity, which may partly explain their superior antiviral effects. Together, the findings of this study provide new avenues for the development of better antiviral drugs and vaccines against influenza viruses.

THERAPEUTIC EFFECT OF USING AUTOLOGOUS PLATELET CONCENTRATE IN VITRECTOMY FOR MACULAR HOLE: A Systematic Review and Meta-Analysis.

PURPOSE: To summarize the current evidence regarding the therapeutic effect of using autologous platelet concentrate (APC) in vitrectomy for macular hole (MH). METHODS: The PubMed, Web of Science, and Embase databases were searched according to the PROSPERO protocol (CRD42022366202). Controlled trials comparing whether APC was used in the vitrectomy of MH were included. The primary outcome was the closure rate of MH and postoperative best-corrected visual acuity, and the secondary outcome was the incidence of different types of complications. RESULTS: Seven studies that included 634 eyes were eligible. For the primary outcome, the usage of APC significantly improved the closure rate of MH in vitrectomy (odds ratio [OR] = 5.34, 95% confidence interval, 2.83-10.07, P < 0.001). Postoperative visual acuity did not significantly differ between the APC group and similar baseline controls (SMD = -0.07, 95% confidence interval, -0.35 to 0.22, P = 0.644). For the secondary outcome, using APC did not result in additional complications regarding postoperative retinal detachment or the recurrence of MH. CONCLUSION: The use of APC in vitrectomy was associated with a superior closure rate of the hole and no additional complications; therefore, it is effective and safe in MH surgery.

Thymol improves salinity tolerance of tobacco by increasing the sodium ion efflux and enhancing the content of nitric oxide and glutathione.

BACKGROUND AND OBJECTIVE: Salt stress is one of the most important abiotic stresses affecting the yield and quality of tobacco (Nicotiana tabacum). Thymol (a natural medicine) has been widely used in medical research because of its antibacterial and anti-inflammatory activities. However, the influence of thymol on the root growth of tobacco is not fully elucidated. In this study, the regulatory effects of different concentrations of thymol were investigated. METHODOLOGY: Here, histochemical staining and biochemical methods, non-invasive micro-test technology (NMT), and qPCR assay were performed to investigate the effect of thymol and mechanism of it improving salinity tolerance in tobacco seedlings. RESULTS: In this study, our results showed that thymol rescued root growth from salt stress by ameliorating ROS accumulation, lipid peroxidation, and cell death. Furthermore, thymol enhanced contents of NO and GSH to repress ROS accumulation, further protecting the stability of the cell membrane. And, thymol improved Na+ efflux and the expression of SOS1, HKT1, and NHX1, thus protecting the stability of Na+ and K+. CONCLUSION: Our study confirmed the protecting effect of thymol in tobacco under salt stress, and we also identified the mechanism of it, involving dynamic regulation of antioxidant system and the maintenance of Na+ homeostasis. It can be a new method to improve salinity tolerance in plants.

Humoral immune response to authentic circulating severe acute respiratory syndrome coronavirus 2 variants elicited by booster vaccination with distinct receptor-binding domain subunits in mice.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants could induce immune escape by mutations of the spike protein which are threatening to weaken vaccine efficacy. A booster vaccination is expected to increase the humoral immune response against SARS-CoV-2 variants in the population. We showed that immunization with two doses of wild type receptor-binding domain (RBD) protein, and booster vaccination with wild type or variant RBD protein all significantly increased binding and neutralizing antibody titers against wild type SARS-CoV-2 and its variants in mice. Only the booster immunization by Omicron (BA.1)RBD induced a strong antibody titer against the omicron virus strain and comparable antibody titers against all the other virus strains. These findings might shed the light on coronavirus disease 2019 booster immunogens.

THREE-DIMENSIONAL HEAD-UP DISPLAY VERSUS STANDARD OPERATING MICROSCOPE FOR VITRECTOMY SURGERY: A Systematic Review and Meta-analysis.

PURPOSE: To evaluate the effects of vitrectomy with three-dimensional head-up display (3D HUD) versus standard operating microscopy (SOM) for retinal diseases. METHODS: The PubMed, Cochrane Library, and Embase databases were comprehensively searched to identify studies that compared 3D HUD versus SOM in vitrectomy for retinal diseases (PROSPERO protocol CRD42021265827). The primary outcomes are duration of surgical time, postoperative best-corrected visual acuity, endoillumination levels, and intraoperative complications. The secondary outcomes are reattachment rate of rhegmatogenous retinal detachment, macular hole closure rate, and the like. RESULTS: Fifteen studies of 2,889 eyes were included. Compared with SOM, 3D HUD vitrectomy took a longer surgical time (weighted mean difference = 1.48; 95% confidence interval, 0.13-2.82), but it needed lower endoillumination levels (weighted mean difference = -16.04, 95% confidence interval, -18.33 to -13.75) than SOM. There were no significant differences in the postoperative best-corrected visual acuity, intraoperative complications, reattachment rate of rhegmatogenous retinal detachment, or closure rate of macular hole. CONCLUSION: Our results suggested that 3D HUD provides lower retinal illumine toxicities but with a longer surgical time. The surgical results and complications of vitrectomy were equally comparable for 3D HUD and SOM.

Observation, laser photocoagulation or anti-VEGF therapy in the management of retinal arterial macroaneurysms.

BACKGROUND: To explore the efficacy of observation, laser photocoagulation, and anti-VEGF in the management of retinal arterial macroaneurysm (RAM). METHODS: We retrospectively included patients diagnosed with RAM at the Peking Union Medical College Hospital (PUMCH) from 2003 to 2021, and comprehensively reviewed cases documented in the literature from multiple databases (PROSPERO protocol CRD42022310417). Patients were categorized into 3 groups: the observation group, anti-VEGF group, and laser photocoagulation group. LogMAR visual acuity (VA) and central retinal thickness (CMT) at the end of the follow-up were analyzed. RESULTS: A total of 14 patients from the PUMCH and 210 patients from the literature review were included. VA and CMT in patients who underwent observation, laser photocoagulation, and anti-VEGF therapies were significantly improved from baseline (p < 0.05), with changes in LogMAR VA improved by -0.34 ± 0.68, -0.17 ± 0.58, and -0.45 ± 0.62 and changes in CMT improved by -148.26 ± 138.99 µm, -185.61 ± 130.37 µm, and -287.45 ± 171.87 µm, respectively. Subgroup analysis revealed that anti-VEGF therapy was used in patients with worse VA than patients who underwent laser photocoagulation (p = 0.010), but achieved better improvement in VA than the laser photocoagulation group (p = 0.049). Patients treated with anti-VEGF also had thicker CMT than the observation group (p = 0.013), and experienced better changes in CMT than the observation, as well as laser photocoagulation groups (p = 0.005; p = 0.047). CONCLUSION: Observation, anti-VEGF, and laser photocoagulation are effective therapeutic methods for the management of RAM, and anti-VEGF therapy is intended to better improve patients with severe VA and CMT.

Progress of artificial intelligence in diabetic retinopathy screening.

Diabetic retinopathy (DR) is one of the leading causes of blindness worldwide, and the limited availability of qualified ophthalmologists restricts its early diagnosis. For the past few years, artificial intelligence technology has developed rapidly and has been applied in DR screening. The upcoming technology provides support on DR screening and improves the identification of DR lesions with a high sensitivity and specificity. This review aims to summarize the progress on automatic detection and classification models for the diagnosis of DR.

Deep learning-based detection and stage grading for optimising diagnosis of diabetic retinopathy.

AIMS: To establish an automated method for identifying referable diabetic retinopathy (DR), defined as moderate nonproliferative DR and above, using deep learning-based lesion detection and stage grading. MATERIALS AND METHODS: A set of 12,252 eligible fundus images of diabetic patients were manually annotated by 45 licenced ophthalmologists and were randomly split into training, validation, and internal test sets (ratio of 7:1:2). Another set of 565 eligible consecutive clinical fundus images was established as an external test set. For automated referable DR identification, four deep learning models were programmed based on whether two factors were included: DR-related lesions and DR stages. Sensitivity, specificity and the area under the receiver operating characteristic curve (AUC) were reported for referable DR identification, while precision and recall were reported for lesion detection. RESULTS: Adding lesion information to the five-stage grading model improved the AUC (0.943 vs. 0.938), sensitivity (90.6% vs. 90.5%) and specificity (80.7% vs. 78.5%) of the model for identifying referable DR in the internal test set. Adding stage information to the lesion-based model increased the AUC (0.943 vs. 0.936) and sensitivity (90.6% vs. 76.7%) of the model for identifying referable DR in the internal test set. Similar trends were also seen in the external test set. DR lesion types with high precision results were preretinal haemorrhage, hard exudate, vitreous haemorrhage, neovascularisation, cotton wool spots and fibrous proliferation. CONCLUSIONS: The herein described automated model employed DR lesions and stage information to identify referable DR and displayed better diagnostic value than models built without this information.

A flat-lying dimer as a key intermediate in NO reduction on Cu(100).

The reaction of nitric oxide (NO) on Cu(100) is studied by scanning tunneling microscopy, electron energy loss spectroscopy and density functional theory calculations. The NO molecules adsorb mainly as monomers at 64 K, and react and dissociate to yield oxygen atoms on the surface at ∼70 K. The temperature required for the dissociation is significantly low for Cu(100), compared to those for Cu(111) and Cu(110). The minimum energy pathway of the reaction is via (NO)2 formation, which converts into a flat-lying ONNO and then dissociates into N2O and O with a considerably low activation energy. We propose that the formation of (NO)2 and flat-lying ONNO is the key to the exceptionally high reactivity of NO on Cu(100).

FOVEA-SPARING VERSUS COMPLETE INTERNAL LIMITING MEMBRANE PEELING IN VITRECTOMY FOR VITREOMACULAR INTERFACE DISEASES: A Systematic Review and Meta-Analysis.

PURPOSE: To evaluate fovea-sparing internal limiting membrane (ILM) peeling in vitrectomy compared with traditional complete ILM peeling in vitreomacular interface diseases, including macular hole (MH), epiretinal membrane, macular foveoschisis, myopic traction maculopathy, and the like. METHODS: PubMed, EMBASE, Cochrane, CNKI Databases, and the ClinicalTrials.gov website (PROSPERO number CRD42020187401) were searched. Controlled trials comparing fovea-sparing with complete ILM peeling were included. Postoperative changes in best-corrected visual acuity, central retinal thickness in vitreomacular interface diseases, the incidence of MH closure in MH cases, full-thickness macular hole development in non-MH cases, and retinal reattachment in retinoschisis cases were extracted. RESULTS: Fourteen studies (487 eyes) were eligible. Compared with complete ILM peeling, the fovea-sparing technique revealed significant improvement in best-corrected visual acuity ( logarithm of the minimum angle of resolution; weighted mean difference = -0.70; 95% confidence interval, -1.11 to -0.30), and a reduced incidence of full-thickness macular hole was noted in non-MH cases (risk ratios = 0.25; 95% confidence interval, 0.08-0.76). However, no significant differences in mean change in central retinal thickness, incidence of MH closure in MH cases, and retinal reattachment in retinoschisis cases were noted. CONCLUSION: Based on current evidence, fovea-sparing ILM peeling significantly improve visual outcomes and decrease complications of full-thickness macular hole development in vitreomacular interface diseases.

Activation of quiescent polypoidal choroidal vasculopathy after membrane peeling vitrectomy for epiretinal membrane: a case report.

BACKGROUND: Regular membrane peeling vitrectomy for epiretinal membrane (ERM) patients seldom causes large pigment epithelial detachment (PED). We presented an unusual case of the activation of quiescent polypoidal choroidal vasculopathy (PCV) after membrane peeling vitrectomy for ERM, with an uneven therapeutic process. CASE PRESENTATION: A 75-year-old female patient complained of metamorphopsia in her left eye for 2 years. Her best-corrected visual acuity was 20/160 with a moderate nuclear cataract. An irregular ERM and slight PED were shown in optical coherence tomography (OCT). No obvious orange-red lesion was detected. The patient underwent vitrectomy + ERM peeling + cataract surgery. After the operation, large PED emerged, and indocyanine green angiography (ICGA) confirmed PCV. Four monthly injections of intravitreal ranibizumab were administered, but PED persisted. After focal laser therapy targeted to the polyps combined with ranibizumab treatment, PED was absorbed. CONCLUSIONS: Careful evaluation for PCV before membrane peeling vitrectomy for ERM is important, as indolent PCV may be activated postoperatively. Anti-VEGF therapy accompanied by laser photocoagulation may be more effective for PCV polyps located away from the fovea.

Evaluation of microvascular network with optical coherence tomography angiography (OCTA) in branch retinal vein occlusion (BRVO).

BACKGROUND: To evaluate changes of microvascular network of macular and peripapillary regions and to provide a quantitative measurement of foveal avascular zone (FAZ) in unilateral BRVO patients. METHODS: Forty-seven unilateral BRVO patients and forty-seven normal controls were enrolled. A 3*3 mm scan centered on fovea followed by a 4.5*4.5 mm scan centered on optic nerve head (ONH) were obtained in BRVO eyes, fellow eyes and control eyes of each individual using OCTA (Optovue Inc., Fremont, CA, USA). Vessel density (VD) in superficial (SVC) and deep vascular complex (DVC) of macula and radial peripapillary capillary (RPC) were automatically calculated. Parameters of FAZ region including size, perimeter, acircularity index (AI) and foveal vessel density 300 (FD-300) were measured. RESULTS: VDs of SCV and DVC were significantly lower, especially in affected regions, in BRVO eyes compared with fellow eyes (P < 0.05). BRVO affected eyes has larger FAZ size, FAZ perimeter, AI and lower FD-300 compared with fellow eyes (all P < 0.05). VD of SVC and FD-300 were lower in fellow eyes compared with normal control eyes (P < 0.05). The average vessel density in whole area and peripapillary area in BRVO eyes were significantly lower compared with fellow eyes (P < 0.05). VD of inside disc in fellow eyes was lower than normal eyes (P < 0.05). CONCLUSIONS: OCTA provided quantitative information of vascular changes in BRVO. FAZ in BRVO eyes showed significant morphological alterations and decreases of VD in surrounding area. Decreases of VD existed not only in SVC and DVC in macular region but also in RPCs in BRVO eyes. Unaffected eyes of unilateral BRVO showed vascular abnormalities in superficial retinal layer, peri-FAZ area and also peripapillary regions.

Syntheses, Structures, and Electrochemical Properties of Three New Acetate-Functionalized Zirconium-Substituted Germanotungstates: From Dimer to Tetramer.

Under hydrothermal conditions, three new acetate-functionalized zirconium-substituted polyoxometalates, H4Na2[Na6(H2O)22][Zr4(µ3-O)2(OH)2(OAc)2(α-GeW10O37)2]·32H2O (1), H8K3Na5[Zr6(µ3-O)3(OH)3(OAc)(H2O)(ß-GeW10O37)3]·20H2O (2), H6K4Na12[{Zr5(µ3-OH)4(OH)2}@{Zr2(OAc)2(α-GeW10O38)2}2]·22H2O (3), were synthesized and characterized. In 1, the sandwiched dimer [Zr4(µ3-O)2(OH)2(OAc)2(α-GeW10O37)2]12- was linked to a hexameric [Na6(H2O)22]6+ cluster to form a 1D chain. In 2, the trimer was constructed from three [ß2-GeW10O37]10- units and a new [Zr6O3(OH)3(OAc)(H2O)]14+ cluster. In 3, the tetramer was built by two novel sandwich-type dimers [Zr2(OAc)2(α2-GeW10O38)2]18- and one unique [Zr5(µ3-OH)4(OH)2]14+ core in an approximately orthogonal fashion, showing a staggered tetrahedral polyanion. Also, the electrochemistry and electrocatalytic properties of 3 were studied, exhibiting good catalytic activities toward the reduction of H2O2, BrO3-, and NO2-.

Enantiomeric Polyoxometalates Based on Malate Chirality-Inducing Tetra-ZrIV-Substituted Keggin Dimeric Clusters.

On the basis of the synergistic strategy of lacunary polyoxometalate structure-directing function and chiral ligand inducting role, two pairs of enantiomeric polyoxotungstates, (NH4)4(TMA)4[Zr4(µ3-O)2(l-/d-mal)2(B-α-HSiW10O37)2] (TMA = tetramethylammonium, mal = malate (C4H5O5); l-mal for 1a, d-mal for 1b) and (NH4)4(TMA)4[Zr4(µ3-O)2(l-/d-mal)2(B-α-PW10O37)2] (l-mal for 2a, d-mal for 2b), and a mesomeric polyoxotungstate, (NH4)3Na2K5[Zr4(µ3-O)2(l-mal)(d-mal)(B-α-SiW10O37)2] (3), were hydrothermally synthesized. 1a, 2a and 1b, 2b respectively exhibit 1-D 21 right- and left-hand helical chains formed by hydrogen-bonding interactions, and 3 forms a 3-D (3,10)-connected framework by Na+/K+ ions with {418.624.83}{43}2 topology. These homochiral compounds represent the first examples of enantiomerically pure ZrIV-substituted Keggin POMs. In this system, {Zr4(µ3-O)2(l-/d-mal)2} clusters transfer chirality from d- or l-mal to Keggin polyoxotungstate dimeric clusters, which was demonstrated by structural comparison between the homochiral architecture and mesomer as well as circular dichroism spectra of enantiomers. UV-vis diffuse reflectance spectra reveal that 1-3 are potential semiconductor materials. In addition, 1 and 2 exhibit second harmonic generation response with their response intensities of 0.8 times that of KDP.

Mechanistic insight into electroreduction of carbon dioxide on FeNx (x = 0-4) embedded graphene.

Searching for non-precious, active and stable catalysts for CO2 electrochemical reduction (CO2ER) has attracted extensive attention, while the high overpotential and low efficiency hinder their widespread commercial applications on a large scale. In this work, density functional theory (DFT) calculations were conducted on the CO2ER process over FeNx embedded graphene (i.e., FeNx-gra, x = 0-4). The results reveal that the Fe atom strongly interacts with the unsaturated N atoms of the substrate and acts as the active site. Due to the small limiting potential of -0.78 V and the activation barrier (1.56 eV), FeN3-gra exhibits the highest catalytic activity towards CO2 reduction. The products of CO2ER catalyzed by FeN3-gra are CH4 and CH3OH, in which CO* → HCO* is the potential-determining step. It is expected that FeN3-gra would be a promising catalyst for CO2ER.