N-doped graphene quantum dot-decorated N-TiO2/P-doped porous hollow g-C_(3)N_(4) nanotube composite photocatalysts for antibiotic photodegradation and H2 production

Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO_(2)/P-doped porous hollow g-C_(3)N_(4) nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1% G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of0.1% G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO_(2), PCN, and N-TiO_(2)/PCN(TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO_(2) and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO_(2), PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1% G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1% G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.

Plasma density enhancement in radio-frequency hollow electrode discharge

The plasma density enhancement outside hollow electrodes in capacitively coupled radio-frequency(RF) discharges is investigated by a two-dimensional(2D) particle-in-cell/Monte-Carlo collision(PIC/MCC) model. Results show that plasma exists inside the cavity when the sheath inside the hollow electrode hole is fully collapsed, which is an essential condition for the plasma density enhancement outside hollow electrodes. In addition, the existence of the electron density peak at the orifice is generated via the hollow cathode effect(HCE), which plays an important role in the density enhancement. It is also found that the radial width of bulk plasma at the orifice affects the magnitude of the density enhancement, and narrow radial plasma bulk width at the orifice is not beneficial to obtain high-density plasma outside hollow electrodes.Higher electron density at the orifice, combined with larger radial plasma bulk width at the orifice,causes higher electron density outside hollow electrodes. The results also imply that the HCE strength inside the cavity cannot be determined by the magnitude of the electron density outside hollow electrodes.

Hollow cathode effect in radio frequency hollow electrode discharge in argon

Radio frequency capacitively coupled plasma source(RF-CCP)with a hollow electrode can increase the electron density through the hollow cathode effect(HCE),which offers a method to modify the spatial profiles of the plasma density.In this work,the variations of the HCE in one RF period are investigated by using a two-dimensional particle-in-cell/Monte-Carlo collision(PIC/MCC)model.The results show that the sheath electric field,the sheath potential drop,the sheath thickness,the radial plasma bulk width,the electron energy distribution function(EEDF),and the average electron energy in the cavity vary in one RF period.During the hollow electrode sheath's expansion phase,the secondary electron heating and sheath oscillation heating in the cavity are gradually enhanced,and the frequency of the electron pendular motion in the cavity gradually increases,hence the HCE is gradually enhanced.However,during the hollow electrode sheath's collapse phase,the secondary electron heating is gradually attenuated.In addition,when interacting with the gradually collapsed hollow electrode sheaths,high-energy plasma bulk electrons in the cavity will lose some energy.Furthermore,the frequency of the electron pendular motion in the cavity gradually decreases.Therefore,during the hollow electrode sheath's collapse phase,the HCE is gradually attenuated.

Atomically Dispersed Ruthenium Catalysts with Open Hollow Structure for Lithium-Oxygen Batteries

Lithium–oxygen battery with ultrahigh theoretical energy density is considered a highly competitive next-generation energy storage device,but its practical application is severely hindered by issues such as difficult decomposition of discharge products at present.Here,we have developed N-doped carbon anchored atomically dispersed Ru sites cathode catalyst with open hollow structure(h-RuNC)for Lithium–oxygen battery.On one hand,the abundance of atomically dispersed Ru sites can effectively catalyze the formation and decomposition of discharge products,thereby greatly enhancing the redox kinetics.On the other hand,the open hollow structure not only enhances the mass activity of atomically dispersed Ru sites but also improves the diffusion efficiency of catalytic molecules.Therefore,the excellent activity from atomically dispersed Ru sites and the enhanced diffusion from open hollow structure respectively improve the redox kinetics and cycling stability,ultimately achieving a high-performance lithium–oxygen battery.

Controllable fabrication of FeCoS_(4) nanoparticles/S-doped bowl-shaped hollow carbon as efficient lithium storage anode

To address the low conductivity and easy agglomeration of transition metal sulfide nanoparticles,FeCoS_(4) nanoparticles embedded in S-doped hollow carbon(FeCoS_(4)@S-HC)composites were successfully fabricated through a combination of hydrothermal processes and sulfidation treatment.The unique bowlshaped FeCoS_(4)/S-HC composites exhibit excellent structural stability with a high specific surface area of 303.7 m^(2)·g^(-1) and a pore volume of 0.93 cm^(3)·g^(-1).When applied as anode material for lithium-ion batteries,the FeCoS_(4)@S-HC anode exhibits efficient lithium storage with high reversible specific capacity(970.2 mA·h·g^(-1) at 100 mA·g^(-1))and enhanced cycling stability(574 mA·h·g^(-1) at 0.2 A·g^(-1) after 350 cycles,a capacity retention of 84%).The excellent lithium storage is attributed to the fact that the bimetallic FeCoS_(4) nanoparticles with abundant active sites can accelerate the electrochemical reaction kinetics,and the bowl-shaped S-HC structure can provide a stable mechanical structure to suppress volume expansion.

Hollow ZIF-67-derived Co@N-doped carbon nanotubes boosting the hydrogenation of phenolic compounds to alcohols

The selective hydrogenation of highly toxic phenolic compounds to generate alcohols with thermal stability,environmental friendliness,and non-toxicity is of great importance.Herein,a series of Co-based catalysts,named Co@NCNTs,were designed and constructed by direct pyrolysis of hollow ZIF-67(HZIF-67)under H_(2)/Ar atmosphere.The evolution of the catalyst surface from the shell layer assembled by ZIF-67-derived particles to the in situ-grown hollow nitrogen-doped carbon nanotubes(NCNTs)with certain length and density is achieved by adjusting the pyrolysis atmosphere and temperature.Due to the synergistic effects of in situ-formed hollow NCNTs,well-dispersed Co nanoparticles,and intact carbon matrix,the as-prepared Co@NCNTs-0.10-450 catalyst exhibits superior catalytic performance in the hydrogenation of phenolic compounds to alcohols.The turnover frequency value of Co@NCNTs-0.10-450is 3.52 h^(-1),5.9 times higher than that of Co@NCNTs-0.40-450 and 4.5 times higher than that of Co@NCNTs-0.10-550,exceeding most previously reported non-noble metal catalysts.Our findings provide new insights into the development of non-precious metal,efficient,and cost-effective metal-organic framework-derived catalysts for the hydrogenation of phenolic compounds to alcohols.

Functional Outcomes of Adult Tibia Shaft Fractures Treated with Solid Intramedullary Nails versus Hollow Nails: A Systematic Review

Introduction: The management of fractures of the tibia shaft is an important aspect of orthopaedic care, and the selection of the surgical method for fixation can substantially impact patient outcomes. The current review aims to compare the outcomes of adult tibia fractures treated with solid nails to those treated with hollow nails. Methods: A search on Scopus, PubMed, and Cochrane Library, using three keywords (Outcome, Tibia shaft fractures, Nail) was conducted in April 2023. Results were compiled and two independent reviewers screened and selected eligible articles After removing duplicates, titles and abstracts were read to exclude ineligible studies. Full-text articles of the remaining papers were read to select eligible studies which were further critically appraised to ascertain their methodological quality. The data extracted from the selected papers were synthesized using a combination of pooling of results, tests of statistical difference (t-test and chi-square) and narrative synthesis methods. Results: A total of 2295 articles were obtained from the databases and citation searching. A total of 9 papers were identified as eligible and included in the review. Findings revealed that there is no statistical difference in the outcomes of tibia fractures treated with either solid or hollow nail groups such as duration of surgery (p = 0.541), rate of delayed and non-union (p = 0.342), and rate of surgical site infections (p = 0.395). Conclusion: Intramedullary nailing of tibia shaft fractures with either solid or hollow nails have similar functional outcomes.

Core-shell mesoporous carbon hollow spheres as Se hosts for advanced Al-Se batteries

Incorporating a selenium(Se)positive electrode into aluminum(Al)-ion batteries is an effective strategy for improving the overall battery performance.However,the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products.In this work,we aim to harness the advantages of Se while reducing its limitations by preparing a core-shell mesoporous carbon hollow sphere with a titanium nitride(C@TiN)host to load 63.9wt%Se as the positive electrode material for Al-Se batteries.Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN,the obtained core-shell mesoporous carbon hollow spheres coated with Se(Se@C@TiN)display superior utilization of the active material and remarkable cycling stability.As a result,Al-Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g^(-1)at a current density of 1000 mA·g^(-1)while maintaining a discharge specific capacity of 86.0 mAh·g^(-1)over 200 cycles.This improved cycling performance is ascribed to the high electrical conductivity of the core-shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.

Imidazole linker‐induced covalent triazine framework-ZIF hybrids for confined hollow carbon super‐heterostructures toward a long‐life supercapacitor

Carbon super-heterostructures with high nitrogen contents from the covalent hybrid precursors of covalent triazine frameworks(CTFs)and zeolitic imidazolic frameworks(ZIFs)are scarcely explored because of CTF's ordered structure and toxic superacid that dissolves or destabilizes the metal nodes.To solve this problem,herein,we report a straightforward two-step pathway for the covalent hybridization of disordered CTF(d–CTF)–ZIF composites via preincorporation of an imidazole(IM)linker into ordered CTFs,followed by the imidazole-site-specific covalent growth of ZIFs.Direct carbonization of these synthesized d–CTF−IM−ZIF hybrids results in unique hollow carbon super-heterostructures with ultrahigh nitrogen content(>18.6%),high specific surface area(1663m^(2)g^(−1)),and beneficial trace metal(Co/Zn NPs)contents for promoting the redox pseudocapacitance.As proof of concept,the obtained carbon super-heterostructure(Co–Zn–NC_(SNH)–800)is used as a positive electrode in an asymmetric supercapacitor,demonstrating a remarkable energy density of 61Wh kg^(−1)and extraordinary cyclic stability of 97%retention after 30,000 cycles at the cell level.Our presynthetic modifications of CTF and their covalent hybridization with ZIF crystals pave the way toward new design strategies for synthesizing functional porous carbon materials for promising energy applications.

Fabrication of ZIF-8 membranes on dual-layer ZnO-PES/PES organic hollow fibers by in-situ crystallization

Compared to inorganic supports, polymeric supports can offer additional benefits, e.g., easier processing and cheaper. However, the organic surface has weak adhesion to the zeolitic imidazolate frameworks(ZIFs) membrane layer, which usually requires complex surface modification or seeding. Herein, we demonstrate that a dual-layer asymmetric polymer support prepared by a simple spinning process is a good candidate for the preparation of ZIF-8 membrane. The inner layer of the support is an organic hollow fiber(PES) with finger-like pores, and the outer layer is a ZnO-PES composite layer with finger-like pores also. The ZnO-PES composite layer is expected to contain uniform ZnO crystals in the polymer matrix, i.e., the ZnO particles in the skin layer of the support are not easy to fall off. Under the induction of ZnO particles in the outer layers, continuous ZIF-8 membranes can be prepared by single in-situ crystallization, showing good adhesion to the supports. The obtained ZIF-8 membranes show a H_(2) permeance of 8.7 × 10^(-8)mol·m^(-2)·s^(-1)·Pa^(-1) with a H_(2)/N_(2) ideal separation selectivity of 18.0. The design and preparation of this dual-layer polymer support is expected to promote the large-scale application of MOF membranes on polymer supports.

Pea-like MoS_(2)@NiS_(1.03)-carbon heterostructured hollow nanofibers for high-performance sodium storage

The rational synergy of chemical composition and spatial nanostructures of electrode materials play important roles in high-performance energy storage devices.Here,we designed pea-like MoS_(2)@NiS_(1.03)-carbon hollow nanofibers using a simple electrospinning and thermal treatment method.The hierarchical hollow nanofiber is composed of a nitrogen-doped carbon-coated NiS_(1.03) tube wall,in which pea-like uniformly discrete MoS_(2) nanoparticles are enclosed.As a sodium-ion battery electrode material,the MoS_(2)@NiS_(1.03)-carbon hollow nanofibers have abundant diphasic heterointerfaces,a conductive network,and appropriate volume variation-buffering spaces,which can facilitate ion diffusion kinetics,shorten the diffusion path of electrons/ion,and buffer volume expansion during Na^(+)insertion/extraction.It shows outstanding rate capacity and long-cycle performance in a sodium-ion battery.This heterogeneous hollow nanoarchitectures designing enlightens an efficacious strategy to boost the capacity and long-life stability of sodium storage performance of electrode materials.

Design of ZnSe-CoSe heterostructure decorated in hollow N-doped carbon nanocage with generous adsorption and catalysis sites for the reversibly fast kinetics of polysulfide conversion

Although lithium-sulfur batteries(Li SBs)are regarded as one of the most promising candidates for the next-generation energy storage system,the actual industrial application is hindered by the sluggish solid–liquid phase conversion kinetics,severe shuttle effect,and low sulfur loadings.Herein,a zeolitic imidazolate framework(ZIF)derived heterogeneous ZnSe-CoSe nanoparticles encapsulated in hollow N-doped carbon nanocage(ZnSe-CoSe-HNC)was designed by etching with tannic acid as a multifunctional electrocatalyst to boost the polysulfide conversion kinetics in LiSBs.The hollow structure in ZIF ensures large inner voids for sulfur and buffering volume expansions.Abundant exposed ZnSe-CoSe heterogeneous interfaces serve as bifunctional adsorption-catalytic centers to accelerate the conversion kinetics and alleviate the shuttle effect.Together with the highly conductive framework,the ZnSe-CoSeHNC/S cathode exhibits a high initial reversible capacity of 1305.3 m A h g-1at 0.2 C,high-rate capability,and reliable cycling stability under high sulfur loading and lean electrolyte(maintaining at 745 m A h g-1after 200 cycles with a high sulfur loading of 6.4 mg cm-2and a low electrolyte/sulfur ratio of 6μL mg^(-1)).Theoretical calculations have demonstrated the heterostructures of ZnSe-CoSe offer higher binding energy to lithium polysulfides than that of ZnSe or CoSe,facilitating the electron transfer to lithium polysulfides.This work provides a novel heterostructure with superior catalytic ability and hollow conductive architecture,paving the way for the practical application of functional sulfur electrodes.

Rationally designed hollow carbon nanospheres decorated with S,P co-doped NiSe_(2) nanoparticles for high-performance potassium-ion and lithium-ion batteries

Hollow nanostructures with external shells and inner voids have been proved to greatly shorten the transport distance of ions/electrons and buffer volume change,especially for the large-sized potassium-ions in secondary batteries.In this work,hollow carbon(HC) nanospheres embedded with S,P co-doped NiSe_(2)nanoparticles are fabricated by "drop and dry" and "dissolving and precipitation" processes to form Ni(OH)2nanocrystals followed by annealing with S and P dopants to form nanoparticles.The resultant S,P-NiSe_(2)/HC composite exhibits excellent cyclic performance with 131.6 mA h g^(-1)at1000 mA g^(-1)after 3000 cycles for K^(+)storage and a capacity of 417.1 mA h g^(-1)at 1000 mA g^(-1)after1000 cycles for Li^(+)storage.K-ion full cells are assembled and deliver superior cycling stability with a ca pacity of 72.5 mA h g^(-1)at 200 mA g^(-1)after 500 cycles.The hollow carbon shell with excellent electrical conductivity effectively promotes the transporta tion and tolerates large volume variation for both K^(+)and Li^(+).Density functional theory calculations confirm that the S and P co-doping NiSe_(2) enables stronger adsorption of K^(+)ions and higher electrical conductivity that contributes to the improved electrochemical performance.

Engineering hollow core-shell hetero-structure box to induce interfacial charge modulation for promoting bidirectional sulfur conversion in lithium-sulfur batteries

Severe polysulfide shuttling and sluggish sulfur redox kinetics significantly decrease sulfur utilization and cycling stability in lithium-sulfur batteries(LSBs).Herein,we develop a hollow CoO/CoP-Box core-shell heterostructure as a model and multifunctional catalyst modified on separators to induce interfacial charge modulation and expose more active sites for promoting the adsorption and catalytic conversion ability of sulfur species.Theoretical and experimental findings verify that the in-situ formed core-shell hetero-interface induces the formation of P-Co-O binding and charge redistribution to activate surface O active sites for binding lithium polysulfides(LiPSs)via strong Li-O bonding,thus strongly adsorbing with Li PSs.Meanwhile,the strong Li-O bonding weakens the competing Li-S bonding in LiPSs or Li2S adsorbed on CoO/CoP-Box surface,plus the hollow heterostructure provides abundant active sites and fast electron/Li+transfer,so reducing Li2S nucleation/dissolution activation energy.As expected,LSBs with CoO/CoP-Box modified separator and traditional sulfur/carbon black cathode display a large initial capacity of 1240 mA h g^(-1)and a long cycling stability with 300 cycles(~60.1%capacity retention)at 0.5C.Impressively,the thick sulfur cathode(sulfur loading:5.2 mg cm^(-2))displays a high initial areal capacity of 6.9 mA h cm^(-2).This work verifies a deep mechanism understanding and an effective strategy to induce interfacial charge modulation and enhance active sites for designing efficient dual-directional Li-S catalysts via engineering hollow core-shell hetero-structure.

Hollow ZSM-5 encapsulated with single Ga-atoms for the catalytic fast pyrolysis of biomass waste

The development of efficient metal-zeolite bifunctional catalysts for catalytic fast pyrolysis(CFP) of biomass waste is highly desirable for bioenergy and renewable biofuel production.However,conventional metal-loaded zeolites often suffer from metal sintering during pyrolysis and are thus inactivated.In this study,single-site Ga-functionalized hollow ZSM-5(GaO_x@HS-Z5) was synthesized via an impregnationdissolution-recrystallization strategy without H_(2) reduction.The Ga atom was coordinated to four oxygen atoms in HS-Z5 frameworks.Benefitting from the highly dispersed single-Ga atoms and hollow zeolite framework,3GaO_x@HS-Z5 performed the best in producing hydrocarbon-rich bio-oil compared to impregnated 3GaO_x/HS-Z5 and H_(2)-reduced 3Ga@HS-Z5 in the maize straw CFP.In particular,3GaO_x@HS-Z5 delivered the highest bio-oil yield(23.6 wt%) and hydrocarbon selectivity(49.4 area%).3GaO_x@HS-Z5 also retained its structural integrity and catalytic activity after five pyrolysis-regeneration cycles,demonstrating its advantage in practical biomass CFP.The elimination of H_(2) reduction during the synthesis of catalyst provides an additional advantage for simplifying the CFP process and reducing operating costs.The retained Ga micro-environment and anti-sintering properties were unique for 3GaO_x@HS-Z5,as severe metal sintering occurred during pyrolysis for other metals(e.g.,NiO_x,ZnO_x,FeO_x,and CoO_x) that encapsulated HS-Z5.

Smart heat isolator with hollow multishelled structures

Safe, green and efficient industrial production has always been the pursuit of the chemical industry. Since thermal energy is the driving force for most of chemical reactions, an ideal reaction tank would have the capacity to automatically regulate heat conduction rate. In detail, this reaction tank should endow an ability that resists the heat loss when the reaction temperature is lower than the target, while accelerating the heat dissipation when the system is overheated. In this case, this smart reactor can not only minimize energy consumption but also reduce safety risks.Hollow structures are known to reduce heat conductivity. Particularly, the hollow structure with multishells can provide more interfaces and thus further inhibit heat transmission, which would be more favorable for heat isolation. Step forward, by coupling HoMSs with temperature-sensitive polymer, a smart heat isolation material has been fabricated in this work. It performs as a good heat isolator at a relatively lower temperature. A heat insulation effect of 6.5℃ can be achieved for the TSPU/3S–TiO_(2)HoMSs with a thickness of 1 mm under the temperature field of 50℃.The thermal conductivity of composite material would be raised under overheating conditions. Furthermore, this composite displays an unusual two-stage phase transformation during heating. Benefiting from the unique multishelled structure, energy is found to be gradually guided into the hollow structure and stored inside. This localized heat accumulation enables the composite to be a potential coating material for intelligent thermal-regulator and site-defined micro-reactor.

Synthesis and Characterization of Hollow Strontium Carbonate Pompons by Composite Soft Template Method

The hollow strontium carbonate pompons was synthesized for the first time by a controlled reaction precipitation method with sodium dodecyl benzene sulfonate(SDBS)and polyvinyl pyrrolidone(PVP)work together as template.The sampled particles were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),nitrogen adsorption-desorption measurement,X-ray diffraction(XRD),Energy dispersive X-Ray spectroscopy(EDX),Fourier transform infrared spectroscopy(FTIR),Thermogravimetric analysis and differential scanning calorimetry(TGA-DSC),etc.It is shown that the assynthesized hollow strontium carbonate pompons with the size of about 2μm consist of flake-like particles under the optimal reaction conditions.The formation mechanism of hollow strontium carbonate pompons was preliminarily explored.

Hollow sphere of heterojunction(NiCu)S/NC as advanced anode for sodium-ion battery

Metal sulfide is considered as a potential anode for sodium-ion batteries(SIBs),due to the high theoretical capacity,strong thermodynamic stability and low-cost.However,their cycle capacity and rate performance are limited by the excessive expansion rate and low intrinsic conductivity.Herein,heterogeneous hollow sphere NiS-Cu_(9)S_(5)/NC(labeled as(NiCu)S/NC)based on Oswald ripening mechanism was prepared through a simple and feasible methodology.From a structural perspective,the hollow structure provides an expansion buffer and raises the electrochemical active area.In terms of electron/ion during the cycles,Na^(+)storage mechanism is optimized by NiS/Cu_(9)S_(5)heterogeneous interface,which increases the storage sites and shortens the migration path of Na^(+).The formation of built-in electric field strengthens the electron/ion mobility.Based on the first principle calculations,it is further proved the formation of heterogeneous interfaces and the direction of electron flow.As the anode for SIBs,the synthesized(NiCu)S/NC delivers high reverse capacity(559.2 mA h g^(-1)at 0.5 A g^(-1)),outstanding rate performance(185.3 mA h g^(-1)at 15 A g^(-1)),long-durable stability(342.6 mA h g^(-1)at 4 A g^(-1)after 1500cycles,150.0 m A h g^(-1)at 10 A g^(-1)after 20,000 cycles with 0.0025%average attenuation rate).The matching cathode electrode Na_(3)V_(2)(PO_(4))_(3)/C is assembled with(NiCu)S/NC for the full-battery that achieves high energy density(253.7 W h kg^(-1))and reverse capacity(288.7 mA h g^(-1)).The present work provides a distinctive strategy for constructing electrodes with excellent capacity and stability for SIBs.

Effect of polytetrafluoroethylene hollow fiber microstructure on formaldehyde carbonylation performance in membrane contactor

Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene(PTFE)membrane contactor has been proved in our previous study. In this paper, the effect of membrane microstructure on process performance was further investigated. Three porous PTFE hollow fibers with different pore sizes and one polydimethylsiloxane(PDMS)/PTFE composite membrane with dense layer were fabricated for comparison. The physical and chemical properties of four membranes, including chemical composition, morphology, contact angle, liquid entry pressure, thermodynamic analysis and gas permeability, were systemically characterized. Experiments of formaldehyde carbonylation under different reaction conditions were conducted. The results indicated that the yield of glycolic acid increased with decreasing pore size for porous membranes, which was due to the improvement of wetting behavior. The dense layer of PDMS in composite hollow fiber could effectively prevent the solvent from entering membrane pores, thus the membrane exhibited the best performance. At reaction temperature of 120℃ and operation pressure of 3.0 MPa, the yield of glycolic acid was always higher than 90% as the mass ratio of trioxane and phosphotungstic acid increased from 0.2:1 to 0.8:1. The highest turnover frequency was up to 26.37 mol·g^(-1)·h^(-1). This study provided a reference for the understanding and optimization of membrane contactors for the synthesis of glycolic acid using solvent with low surface tension.

The Fabrication and SERS Performance of Multi-layer Hollow Au-Ag Alloy Nano Urchins Structure-based SERS Fiber Probe

Novel hollow Au Ag alloy nano urchins were synthesized via Ag seeds growth method,and self-assembly coated on the wall and end-tip of silica fiber for fiber probe fabrication.The nano urchins homogeneously distributed on fiber surface because of fiber silanization.The sizes and tip sharpness of the nano-urchins could be controlled by Ag seeds.The elements distribution analysis indicated there was high Ag content in tip-top for better surface enhance Raman scattering performance.The detectable concentration could be as low as 10-8 M using crystal violet molecules as analyte.Moreover,the fiber probes were stable in air,due to Au in the alloy.This fiber probe could be used for low content single molecular analysis.