Controllable Crystallization of Two-Dimensional Bi Nanocrystals with Morphology-Boosted CO2 Electroreduction in Wide pH Environments.

Two-dimensional low-melting-point (LMP) metal nanocrystals are attracting increasing attention with broad and irreplaceable applications due to their unique surface and topological structures. However, the chemical synthesis, especially the fine control over the nucleation (reduction) and growth (crystallization), of such LMP metal nanocrystals remains elusive as limited by the challenges of low standard redox potential, low melting point, poor crystalline symmetry, etc. Here, a controllable reduction-melting-crystallization (RMC) protocol to synthesize free-standing and surfactant-free bismuth nanocrystals with tunable dimensions, morphologies, and surface structures is presented. Especially, ultrathin bismuth nanosheets with flat or jagged surfaces/edges can be prepared with high selectivity. The jagged bismuth nanosheets, with abundant surface steps and defects, exhibit boosted electrocatalytic CO2 reduction performances in acidic, neutral, and alkaline aqueous solutions, achieving the maximum selectivity of near unity at the current density of 210 mA cm-2 for formate evolution under ambient conditions. This work creates the RMC pathway for the synthesis of free-standing two-dimensional LMP metal nanomaterials and may find broader applicability in more interdisciplinary applications.

Ultrathin Dendritic Pd-Ag Nanoplates for Efficient and Durable Electrocatalytic Reduction of CO2 to Formate.

CO2 reduction reactions (CO2 RR) powered by renewable electricity can directly convert CO2 to hydrocarbons and fix the sustainable but intermittent energy (e. g., sunlight, wind, etc.) in stable and portable chemical fuels. Advanced catalysts boosting CO2 RR with high activity, selectivity, and durability at low overpotentials are of great importance but still elusive. Here, we report that the ultrathin Pd-Ag dendritic nanoplates (PdAg DNPs) exhibited boosted activity, selectivity, and stability for producing formate from CO2 at a very low overpotential in aqueous solutions under ambient conditions. As a result, the PdAg DNPs exhibited a Faradaic efficiency (FE) for formate of 91% and a cathodic energy efficiency (EE) of ∼90% at the potential of -0.2 V versus reversible hydrogen electrode (vs. RHE), showing significantly enhanced durability as compared with pure Pd catalysts. Our strategy represents a rational catalyst design by engineering the surface geometrical and electronic structures of metal nanocrystals and may find more applicability in future electrocatalysis.

Controlled Synthesis of Intermetallic Au2 Bi Nanocrystals and Au2 Bi/Bi Hetero-Nanocrystals with Promoted Electrocatalytic CO2 Reduction Properties.

The electrocatalytic properties of metal nanoparticles (NPs) strongly depend on their compositions and structures. Rational design of alloys and/or heterostructures provides additional approaches to modifying their surface geometric and electronic structures for optimized electrocatalytic performance. Here, a solution synthesis of freestanding intermetallic Au2 Bi NPs, the heterostructures of Au2 Bi/Bi hetero-NPs, and their promoted electrocatalytic CO2 reduction reaction (CO2 RR) performances were reported. It was revealed that the formation and in-situ conversion of heterogeneous seeds (e. g., Au) were of vital importance for the formation of intermetallic Au2 Bi and Au2 Bi/Bi hetero-NPs. It was also found that the Au components would act as the structure promoter moderating the binding strength for key intermediates on Bi surfaces. The alloying of Bi with Au and the formation of heterogeneous Au2 Bi/Bi interfaces would create more surface active sites with modulated electronic structures and stronger adsorption strengths for key intermediates, promoting the CO2 -to-HCOOH conversion with high activity and selectivity. This work presents a novel route for preparing intermetallic nanomaterials with modulated surface geometric/electric structures and promoting their electrocatalytic activities with alloying effects and interfacial effects. Such strategy may find wide application in catalyst design and synthesis for more electrocatalytic reactions.

Promoting the Electrocatalytic Reduction of CO2 on Ultrathin Porous Bismuth Nanosheets with Tunable Surface-Active Sites and Local pH Environments.

Electrochemical CO2 reduction reaction (CO2RR) yielding value-added chemicals provides a sustainable approach for renewable energy storage and conversion. Bismuth-based catalysts prove to be promising candidates for converting CO2 and water into formate but still suffer from poor selectivity and activity and/or sluggish kinetics. Here, we report that ultrathin porous Bi nanosheets (Bi-PNS) can be prepared through a controlled solvothermal protocol. Compared with smooth Bi nanoparticles (Bi-NPs), the ultrathin, rough, and porous Bi-PNS provide more active sites with higher intrinsic reactivities for CO2RR. Moreover, such high activity further increases the local pH in the vicinity of the catalyst surfaces during electrolysis and thus suppresses the competing hydrogen evolution reaction. As a result, the Bi-PNS exhibit significantly boosted CO2RR properties, showing a Faradaic efficiency of 95% with an effective current density of 45 mA cm-2 for formate evolution at the potential of -1.0 V versus reversible hydrogen electrode.

Modulating the electrocatalytic CO2 reduction performances of bismuth nanoparticles with carbon substrates with controlled degrees of oxidation.

The catalytic performances of metal nanoparticles can be widely tuned and promoted by the metal-support interactions. Here, we report that the morphologies and electrocatalytic CO2 reduction reaction (CO2RR) properties of bismuth nanoparticles (BiNPs) can be rationally modulated by their interactions with carbon black (CB) supports by controlling the degree of surface oxidation. Appropriately oxidized CB supports can provide sufficient oxygen-containing groups for anchoring BiNPs with tunable sizes and surface areas, desirable key intermediate adsorption abilities, appropriate surface wettability, and adequate electron transfer abilities. As a result, the optimized Bi/CB catalysts exhibited a promoted CO2RR performance with a Faradaic efficiency of 94% and a current density of 16.7 mA cm-2 for HCOO- at -0.9 V versus a reversible hydrogen electrode. Our results demonstrate the significance of regulating the interactions between supports and metal nanoparticles for both synthesis of the catalyst and electrolysis applications, which may find broader applicability in more electrocatalyst designs.

Metal-organic framework membranes with single-atomic centers for photocatalytic CO2 and O2 reduction.

The demand for sustainable energy has motivated the development of artificial photosynthesis. Yet the catalyst and reaction interface designs for directly fixing permanent gases (e.g. CO2, O2, N2) into liquid fuels are still challenged by slow mass transfer and sluggish catalytic kinetics at the gas-liquid-solid boundary. Here, we report that gas-permeable metal-organic framework (MOF) membranes can modify the electronic structures and catalytic properties of metal single-atoms (SAs) to promote the diffusion, activation, and reduction of gas molecules (e.g. CO2, O2) and produce liquid fuels under visible light and mild conditions. With Ir SAs as active centers, the defect-engineered MOF (e.g. activated NH2-UiO-66) particles can reduce CO2 to HCOOH with an apparent quantum efficiency (AQE) of 2.51% at 420 nm on the gas-liquid-solid reaction interface. With promoted gas diffusion at the porous gas-solid interfaces, the gas-permeable SA/MOF membranes can directly convert humid CO2 gas into HCOOH with a near-unity selectivity and a significantly increased AQE of 15.76% at 420 nm. A similar strategy can be applied to the photocatalytic O2-to-H2O2 conversions, suggesting the wide applicability of our catalyst and reaction interface designs.

Morphology-dependent electrocatalytic nitrogen reduction on Ag triangular nanoplates.

Electrocatalytic nitrogen reduction reactions (ENRR) can produce ammonia from nitrogen and water under ambient conditions. Here, we report the morphology-dependent electro-catalytic nitrogen reduction on Ag triangular nanoplates. Boosted by potassium cations, Ag triangular nanoplates with sharp edges exhibit a high faradaic efficiency of 25% with an ammonia yield of 58.5 mg gAg-1 h-1 at a low overpotential of -0.25 V vs. RHE. In comparison, rounded Ag nanoparticles mainly enclosed by {111} and {100} surfaces show a much smaller faradaic efficiency of 16% and ammonia yield of 38 mg gAg-1 h-1 at a larger overpotential (-0.35 V vs. RHE).

Nitric oxide blocks the development of the human parasite Schistosoma japonicum.

Human schistosomiasis, caused by Schistosoma species, is a major public health problem affecting more than 700 million people in 78 countries, with over 40 mammalian host reservoir species complicating the transmission ecosystem. The primary cause of morbidity is considered to be granulomas induced by fertilized eggs of schistosomes in the liver and intestines. Some host species, like rats (Rattus norvegicus), are naturally intolerant to Schistosoma japonicum infection, and do not produce granulomas or pose a threat to transmission, while others, like mice and hamsters, are highly susceptible. The reasons behind these differences are still a mystery. Using inducible nitric oxide synthase knockout (iNOS-/-) Sprague-Dawley rats, we found that inherent high expression levels of iNOS in wild-type (WT) rats play an important role in blocking growth, reproductive organ formation, and egg development in S. japonicum, resulting in production of nonfertilized eggs. Granuloma formation, induced by fertilized eggs in the liver, was considerably exacerbated in the iNOS-/- rats compared with the WT rats. This inhibition by nitric oxide acts by affecting mitochondrial respiration and energy production in the parasite. Our work not only elucidates the innate mechanism that blocks the development and production of fertilized eggs in S. japonicum but also offers insights into a better understanding of host-parasite interactions and drug development strategies against schistosomiasis.

Soluble antigens from the neurotropic pathogen Angiostrongylus cantonensis directly induce thymus atrophy in a mouse model.

The nematode Angiostrongylus cantonensis (A.C.) is a neurotropic pathogen; stage-III larva invade the human (non-permissive host) central nervous system (CNS) to cause eosinophilic meningitis or meningoencephalitis accompanied by immunosuppression. In an A.C.-infectedmouse (another non-permissive host) model, CNS damage-associated T cell immune deficiency and severe inflammation were proposed to result from activation of the hypothalamic-pituitary-adrenal (HPA) axis. However, glucocorticoids are anti-inflammatory agents. Additionally, while defects in thymic stromal/epithelial cells (TECs) are the major reason for thymic atrophy, TECs do not express the glucocorticoid receptor. Therefore, activation of the HPA axis cannot fully explain the thymic atrophy and inflammation. Using an A.C.-infected mouse model, we found that A.C.-infected mice developed severe thymic atrophy with dramatic impairments in thymocytes and TECs, particularly cortical TECs, which harbor CD4+CD8+ double-positive thymocytes. The impairments resulted from soluble antigens (sAgs) from A.C. in the thymuses of infected mice, as intrathymic injection of these sAgs into live mice and the addition of these sAgs to thymic cell culture resulted in thymic atrophy and cellular apoptosis, respectively. Therefore, in addition to an indirect effect on thymocytes through the HPA axis, our study reveals a novel mechanism by which A.C. infection in non-permissive hosts directly induces defects in both thymocytes and TECs via soluble antigens.

[Congenital stenosis of external auditory canal with cholesteatoma and skin fistulae or sinuses].

OBJECTIVE: To investigate the clinical features, differential diagnosis and management of congenital stenosis of external auditory canal (CSEAC) with cholesteatoma. METHODS: The clinical information for 10 cases of CSEAC with cholesteatoma was retrospectively reviewed. RESULTS: The patients' ages ranged from 4.75 to 22 years (average 12 years). The diameter of the external auditory canal (EAC) was < 2 mm. All 10 ears had a history of postural fistulae or sinuses. Bone erosion of EAC was distinctly shown in high-resolution computed tomography (HRCT) of all cases, as well as soft tissue masses, which led to enlargement of the bony canals. All patients underwent canaloplasty; eight ears received hearing reconstructions at the same time. Cholesteatoma in EACs was confirmed during the operations, accompanied by compression and destruction of the post-superior and/or inferior bony wall. Postoperative pathologic examinations proved the diagnosis of cholesteatoma, and excluded any tissue of bronchial cleft cyst or fistula. After a follow-up 1 to 3 years, no recurrent cholesteatoma was found in any of the 10 cases. All reconstructed EACs were clean and smooth. The hearing levels in the eight ears that received hearing reconstructions improved 20 - 35 dBHL. CONCLUSIONS: In CSEAC with cholesteatoma, the bony wall of EAC is most commonly involved. This involvement will lead to bone erosion of the EAC and may subsequently lead to the formation of postural or cervical sinuses. HRCT of temporal bone can show characteristic signs of soft tissue mass in EAC, with adjacent bone erosion.

[Long-term results and an analysis of surgically related factors in myringoplasty with sandwich method].

OBJECTIVE: To evaluate the effect of the prognostic factors on long-term surgical outcome in myringoplasty. METHODS: Retrospective cohort 205 patients (223 ears) with sandwich temporal fascia myringoplasty were analyzed using the multiple logistic regression analysis. The charts of inpatients had undergone myringoplasty before at least 2 years between January 1999 and November 2003 at Beijing Tongren Hospital. Postoperative follow-up rate was 78.2%. Their ages ranged from 12 to 65 years (mean = 34. 3 years). Their durations of disease ranged from 1 month to 25 years (mean = 16.07 months). The effect of prognostic factors on myringoplasty were investigated by variables noted from patients' files such as age, sex, causes of disease, duration of disease, period of dry ear of disease, operation types, places of tympanic membrane perforation, size of tympanic membrane perforation, status of middle ear and status of eardrum. RESULTS: There were 11 ears with re-perforation of eardrum at the last follow-up. Successful closure of the tympanic membrane perforation was obtained in 95.1% of the ears (212 ears) with 2 to 5 years follow-up. There were 26 ears with other complications at the last follow-up. Operations were successful in 186 patients. The overall take rate of the myringoplasty was 83.4%. Multiple logistic regression analysis (ward) was subsequently carried out on these prognostic factors on overall take rate of the myringoplasty and yielded the following classification. Relative importance of the predictive variables was as follows: size of tympanic membrane perforation (OR = 1.900), duration of disease (OR = 1.003) and period of dry ear of disease (OR = 0.908). Hearing outcomes: the average air-bone gap improvement was 7.0 dB and the average air conduction improvement was 6.8 dB for all 175 myringoplasty procedures. CONCLUSIONS: A long term follow-up was important. Late atelectatic pocket was a late complication and a cause of failure. A relatively smaller tympanic membrane perforation, a relatively shorter duration of disease and a relatively longer period of dry ear of disease were found to be significant prognostic factors positively influencing the success rate of myringoplasty.

[Vestibulotomy about the displaced facial nerve].

OBJECTIVE: To investigate the feasibility of vestibulotomy above the displaced facial nerve. METHODS: From January 2000 to January 2002, eight patients with severe congenital conductive hearing loss underwent the vestibulotomy above displaced facial nerve and reconstruction of the ossicular chain with a total ossicular replacement prosthesis, which all for the congenital middle ear deformity and the facial nerve overhang and concealed the oval window niche or lied inferior to the oval window. In four of eight cases, the facial nerve was transposed in order to access the oval window niche. RESULTS: Hearing of this patients improved 15 dB in 2 ears, 16-25 dB in 3 ears and 26 dB or more in 3 ears. In no case was there a postoperative facial paresis. With 4 months to 28 months follow-up, the postoperative hearing gain was stable. CONCLUSIONS: Vestibulotomy above displacement of the facial nerve allows a final chance of achieving serviceable hearing through surgery. The lack of facial nerve injury and the potential for hearing restoration make this procedure feasible in otherwise marginal or poor surgical candidates.