Controllable synthesis of transition metal nitride materials and performance tuning in photocatalysis and piezoelectric catalysis

Energy crisis has become imminent owing to the increasing energy demand in recent years. Renewable and sustainable alternative energy resources, such as hydrogen have attracted significant attentions. In order to produce hydrogen energy efficiently, artificial photocatalysis is an attractive way forward. Use of piezoelectric materials for solar energy conversion is being researched in this context. However, such materials that are semiconductor-based are not practically viable applications. Simultaneously, as a kind of most efficient catalyst, the noble metal is difficult to apply in large-scale. Transition metal nitrides (TMNs) have become a family of alternatives of noble metal catalysts due to their unique properties. However, the present synthesis methodologies of TMNs are complex with severe conditions. Maintenance of morphology of TMNs also remains a challenge, since morphological changes do influence their activity. This thesis has provided a new strategy for production of TMNs with stable nano-morphology. These have been used for photocatalytic and piezoelectric H2 evolution, while discussing the structure-activity relationship. The details are listed below: (1) A novel hard template/rapid-nitridation synthesis of ordered mesoporous metal nitrides is reported, which is based on a nanocasting-thermal nitridation process. This method uses 2D ordered hexagonal mesoporous SBA-15 as the hard template. A series of TMNs with ordered and regular mesoporous structures have been successfully synthesized from the corresponding mesoporous oxides. A comparative experiment shows that when a long-time heating process is employed, the ordered mesopores are hard to maintain anymore due to the collapse and coalescence of the porous structure. This proves the necessity of rapid-nitridation for keeping nanostructures of materials. (2) Prussian blue (PB) precursors are first oxidized and then subjected to rapid-nitridation to obtain pure porous Fe2N nanocubes while maintaining the pattern and structure of the parent MOF precursor. The samples are sensitized using Eosin-Y (EY) in photocatalytic HER. The performance of cube-like Fe2N is duly rationalized using DFT-based calculations and its metallic nature is also duly elaborated. The optimal Fe2N/EY system exhibits excellent photocatalytic hydrogen evolution performance. (3) MOF-derived Fe2N with different types of doped elements (Co, Cr, W and V) are successfully synthesized. Rapid-nitridation has been applied as a synthesized method, which is efficient for retaining the morphology of catalyst. The regular nanocubic pattern of samples has been maintained. The doped Fe2N have been utilized for piezoelectric catalytic H2 evolution and the Co-doped Fe2N has achieved the highest activity (122.8 μmol g-1h-1). After tuning the doping ratio, the Co and V doped Fe2N have greatly improved their H2 evolution performance. Compared with the control experiments, the sample with nanocubic morphology has a higher H2 evolution rate than that of the nanoparticle sample. These doped Fe2N catalysts also have the ability to degrade different types of dye, while improving their H2 production efficiency. Besides, the DFT calculation has elucidated the activity improvement of doped nitrides. In summary, this thesis has introduced a method for synthesizing several types of ordered porous TMN materials. They have exhibited considerable activity and properties in the application of H2 evolution by photocatalysis and piezoelectric catalysis. The relationship between the performance and the morphology as well as nanostructure has been demonstrated

Controllable synthesis of transition metal nitride materials and performance tuning in photocatalysis and piezoelectric catalysis

Energy crisis has become imminent owing to the increasing energy demand in recent years. Renewable and sustainable alternative energy resources, such as hydrogen have attracted significant attentions. In order to produce hydrogen energy efficiently, artificial photocatalysis is an attractive way forward. Use of piezoelectric materials for solar energy conversion is being researched in this context. However, such materials that are semiconductor-based are not practically viable applications. Simultaneously, as a kind of most efficient catalyst, the noble metal is difficult to apply in large-scale. Transition metal nitrides (TMNs) have become a family of alternatives of noble metal catalysts due to their unique properties. However, the present synthesis methodologies of TMNs are complex with severe conditions. Maintenance of morphology of TMNs also remains a challenge, since morphological changes do influence their activity. This thesis has provided a new strategy for production of TMNs with stable nano-morphology. These have been used for photocatalytic and piezoelectric H2 evolution, while discussing the structure-activity relationship. The details are listed below: (1) A novel hard template/rapid-nitridation synthesis of ordered mesoporous metal nitrides is reported, which is based on a nanocasting-thermal nitridation process. This method uses 2D ordered hexagonal mesoporous SBA-15 as the hard template. A series of TMNs with ordered and regular mesoporous structures have been successfully synthesized from the corresponding mesoporous oxides. A comparative experiment shows that when a long-time heating process is employed, the ordered mesopores are hard to maintain anymore due to the collapse and coalescence of the porous structure. This proves the necessity of rapid-nitridation for keeping nanostructures of materials. (2) Prussian blue (PB) precursors are first oxidized and then subjected to rapid-nitridation to obtain pure porous Fe2N nanocubes while maintaining the pattern and structure of the parent MOF precursor. The samples are sensitized using Eosin-Y (EY) in photocatalytic HER. The performance of cube-like Fe2N is duly rationalized using DFT-based calculations and its metallic nature is also duly elaborated. The optimal Fe2N/EY system exhibits excellent photocatalytic hydrogen evolution performance. (3) MOF-derived Fe2N with different types of doped elements (Co, Cr, W and V) are successfully synthesized. Rapid-nitridation has been applied as a synthesized method, which is efficient for retaining the morphology of catalyst. The regular nanocubic pattern of samples has been maintained. The doped Fe2N have been utilized for piezoelectric catalytic H2 evolution and the Co-doped Fe2N has achieved the highest activity (122.8 μmol g-1h-1). After tuning the doping ratio, the Co and V doped Fe2N have greatly improved their H2 evolution performance. Compared with the control experiments, the sample with nanocubic morphology has a higher H2 evolution rate than that of the nanoparticle sample. These doped Fe2N catalysts also have the ability to degrade different types of dye, while improving their H2 production efficiency. Besides, the DFT calculation has elucidated the activity improvement of doped nitrides. In summary, this thesis has introduced a method for synthesizing several types of ordered porous TMN materials. They have exhibited considerable activity and properties in the application of H2 evolution by photocatalysis and piezoelectric catalysis. The relationship between the performance and the morphology as well as nanostructure has been demonstrated

Unsupervised Explanation Generation via Correct Instantiations

While large pre-trained language models (PLM) have shown their great skills at solving discriminative tasks, a significant gap remains when compared with humans for explanation-related tasks. Among them, explaining the reason why a statement is wrong (e.g., against commonsense) is incredibly challenging. The major difficulty is finding the conflict point, where the statement contradicts our real world. This paper proposes Neon, a two-phrase, unsupervised explanation generation framework. Neon first generates corrected instantiations of the statement (phase I), then uses them to prompt large PLMs to find the conflict point and complete the explanation (phase II). We conduct extensive experiments on two standard explanation benchmarks, i.e., ComVE and e-SNLI. According to both automatic and human evaluations, Neon outperforms baselines, even for those with human-annotated instantiations. In addition to explaining a negative prediction, we further demonstrate that Neon remains effective when generalizing to different scenarios.Comment: Accepted to AAAI-2

Plasmonic Nanoparticles with Quantitatively Controlled Bioconjugation for Photoacoustic Imaging of Live Cancer Cells

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135410/1/advs216_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135410/2/advs216-sup-0001-S1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135410/3/advs216.pd

Interface engineering of mesoporous triphasic cobalt-copper phosphides as active electrocatalysts for overall water splitting

Efficient electrocatalysts for water splitting are essential for viable generation of highly purified hydrogen. Hence there is a need to develop robust catalysts to eliminate barriers associated with sluggish kinetics associated with both anodic oxygen and cathodic hydrogen evolution reactions. Herein, we report a two-step nanocasting-solid phase phosphorization approach to generate ordered mesoporous triphasic phosphides CoP@Cu2P-Cu3P. We show that it is a highly efficient bifunctional electrocatalyst useful for overall water splitting. The mesoporous triphasic CoP@Cu2P-Cu3P only requires a low overpotential of 255 mV and 188 mV to achieve 10 mA cm(-2) for oxygen and hydrogen evolution reactions, respectively. The combination of mesoporous pores (similar to 5.6 nm) with very thin walls (similar to 3.7 nm) and conductive networks in triphasic CoP@Cu2P-Cu3P enable rapid rate of electron transfer and mass transfer. In addition, when CoP@Cu2P-Cu3P is used to fabricate symmetric electrodes, the high surface area mesoporous structure and synergetic effects between phases together contribute to a low cell voltage of 1.54 V to drive a current density 10 mA cm(-2). This performance is superior to noble-metal-based Pt/C-IrO2/C. This work provides a new approach for the facile design and application of multiphase phosphides as highly active bifunctional and stable electrocatalysts for water-alkali electrolyzers

Clinical Features and Visual Acuity Outcomes in Culture-Positive Endogenous Fungal Endophthalmitis in Southern China

Purpose. To report the causative organisms, management strategies, and visual outcomes of culture-proven endogenous fungal endophthalmitis in a case series from southern China. Methods. We reviewed the microbiological and medical records of patients with culture-positive endogenous fungal endophthalmitis visiting the Zhongshan Ophthalmic Center, Guangzhou, China, between January 1, 2006, and March 31, 2016. Results. The inclusion criteria were met in 32 eyes of 29 patients. Molds were a common causative organism in 15 patients (51.7%), while yeasts appeared in 14 patients (48.3%). Initial visual acuity (VA) at the level of finger counting or better was significantly related to a good visual outcome (P=0.002). Molds as a causative agent were significantly associated with worse visual outcome than yeasts (P=0.020). Conclusion. Molds were a common cause of culture-proven fungal endophthalmitis. Endogenous fungal endophthalmitis is generally associated with poor VA outcomes, especially if caused by molds and if the patient’s initial VA is too low to permit finger counting

Measurements of the pp → ZZ production cross section and the Z → 4ℓ branching fraction, and constraints on anomalous triple gauge couplings at √s = 13 TeV

Four-lepton production in proton-proton collisions, pp -> (Z/gamma*)(Z/gamma*) -> 4l, where l = e or mu, is studied at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb(-1). The ZZ production cross section, sigma(pp -> ZZ) = 17.2 +/- 0.5 (stat) +/- 0.7 (syst) +/- 0.4 (theo) +/- 0.4 (lumi) pb, measured using events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60 4l) = 4.83(-0.22)(+0.23) (stat)(-0.29)(+0.32) (syst) +/- 0.08 (theo) +/- 0.12(lumi) x 10(-6) for events with a four-lepton invariant mass in the range 80 4GeV for all opposite-sign, same-flavor lepton pairs. The results agree with standard model predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ. couplings at 95% confidence level: -0.0012 < f(4)(Z) < 0.0010, -0.0010 < f(5)(Z) < 0.0013, -0.0012 < f(4)(gamma) < 0.0013, -0.0012 < f(5)(gamma) < 0.0013

Inhibition of Notch1 Signaling Alleviates Endotoxin-Induced Inflammation Through Modulating Retinal Microglia Polarization

Microglial cells are resident immune cells and play an important role in various cerebral and retinal inflammatory diseases. Notch1 signaling is involved in the microglia polarization and the control of cerebral inflammatory reactions. However, its role in endotoxin-induced uveitis (EIU) remains unknown. This study aimed to investigate the role of Notch1 signaling on retinal microglia polarization and inflammation in the cultured retinal microglial cells and EIU rat model. We found that Notch1 signaling blockade with N-[N-(3, 5-difluorophenacetyl)-1-alany1-S-phenyglycine t-butyl ester (DAPT) shifted retinal microglia phenotype from pro-inflammatory M1 phenotype (COX2+ and iNOS+) to anti-inflammatory M2 phenotype (Arg-1+) and reduced the release of pro-inflammatory cytokines both in vivo and in vitro. Moreover, DAPT treatment contributed to prevent retinal ganglion cells from apoptosis, reduce the intraocular infiltrating cells, and attenuate the impairment of retinal function. Taken together, these results suggest that inhibition of Notch1 signaling could alleviate the inflammatory response in EIU rat mainly through regulating the polarization of retinal microglia. Therefore, Notch1 signaling might be a promising therapeutic target in the treatment of ocular inflammatory diseases