Effects Associated with Nanostructure Fabrication Using In Situ Liquid Cell TEM Technology

We studied silicon,carbon,and SiC xnanostructures fabricated using liquid-phase electron-beam-induced deposition technology in transmission electron microscopy systems.Nanodots obtained from fixed electron beam irradiation followed a universal size versus beam dose trend,with precursor concentrations from pure Si Cl4to 0%SiC l4in CH2Cl2,and electron beam intensity ranges of two orders of magnitude,showing good controllability of the deposition.Secondary electrons contributed to the determination of the lateral sizes of the nanostructures,while the primary beam appeared to have an effect in reducing the vertical growth rate.These results can be used to generate donut-shaped nanostructures.Using a scanning electron beam,line structures with both branched and unbranched morphologies were also obtained.The liquid-phase electron-beaminduced deposition technology is shown to be an effective tool for advanced nanostructured material generation.

Petrogenesis of granitic pegmatite veins:Perspectives from major element and B isotope in tourmalines,Chakabeishan,Northern Tibetan Plateau

The petrogenesis of regionally zoned granitic pegmatite veins remains debated.Because of the economic significance,we carried out a study on the Chakabeishan(CKBS)pegmatite-type Li-Be deposit,eastern North Qaidam Tectonic Belt,Northern Tibetan Plateau,by means of in-situ major element and B isotope compositions of tourmalines in the beryl-bearing and spodumene-bearing pegmatite veins.Tourmalines(Tur-Be)from the beryl-bearing pegmatite are homogeneous schorl with low Mg/(Mg+Fe),high Na/(Na+Ca)and Y Al,suggesting that they are of magmatic origin.Two generations of tourmalines(TurLi)from the spodumene-bearing pegmatite are identified:(i)the crystal cores(mostly elbaite and Lirich schorl with subordinate schorl)are consistent with being of magmatic origin crystallized at the magmatic stage;(ii)the crystal rims(schorl)are best understood as the overgrowth at the later hydrothermal stage.Tur-Be and Tur-Li show an obvious difference in core-to-rim B isotopic variation trend with d11B decrease in Tur-Be and increase in Tur-Li.The core-to-rim d11B decrease in Tur-Be results from degassing during its host pegmatitic melt evolution,whereas the core-to-rim d11B increase in Tur-Li is related to fluid exsolution.The estimated d11B values for the initial melts of the beryl-bearing and spodumenebearing pegmatites are10.46‰and10.78‰,respectively,indicating that they most likely originate from protracted fractional crystallization/differentiation of granitic intrusions rather than partial melting of metapelite.Both Mg/(Mg+Fe)ratios and Li abundances in the cores of Tur-Be are lower than those of Tur-Li,suggesting that Tur-Li crystallizes from chemically more evolved melts.

Direct Observation of Growth and Self-assembly of Pt Nanoclusters in Water with the Aid of a Triblock Polymer Using in situ Liquid Cell Transmission Electron Microscopy （TEM）

Triblock copolymers are playing important roles in nanomaterial synthesis, and the nanomaterial forming mechanisms need to be studied in detail. In situ liquid cell transmission electron microscopy （TEM） is a powerful tool for real time observation of the dynamic growth behavior of nanomaterials in liquid with high resolution, and could be used for the above task. Here we report the observation of the growth and self-assembly of Pt nanoclusters with the aid of an ethylene oxide-propylene oxide-ethylene oxide triblock copolymer （PEO-PPO-PEO） F 127 using in situ liquid cell TEM, with the nanocluster growth and formation procedures being tracked. Nano objects were seen to appear, drift and rotate with time, and then form into certain shaped nanoclusters under the electron beam irradiation. Further interestingly, in the thicker liquid layer region, the nanoclusters appeared to be fluffy, with average size keeping increase with time, while in the thinner region, the clusters were thinner, and got densified with time. The difference in precursor availability due to liquid layer thickness and charging effects is attributed to such a phenomenon.

An acid-triggered porphyrin-based block copolymer for enhanced photodynamic antibacterial efficacy

Bacterial infection, especially multidrug-resistant(MDR) bacterial infection has threatened public health drastically. Here, we fabricate an "acid-triggered" nanoplatform for enhanced photodynamic antibacterial activity by reducing the aggregation of photosensitizers(PSs) in bacterial acidic microenvironment. Specifically, a functional amphiphilic block copolymer was first synthesized by using a pH-sensitive monomer, 2-(diisopropylamino) ethyl methacrylate(DPA) and porphyrin-based methacrylate(TPPC6MA) with poly(oligo(ethylene glycol) methyl ether methacrylate)(POEGMA) as the macromolecular chain transfer agent, and POEGMA-b-[PDPA-co-PTPPC6MA] block copolymer was further self-assembled into spherical nanoparticles(PDPA-TPP). PDPA-TPP nanoparticles possess an effective electrostatic adherence to negatively charged bacterial cell membrane, since they could rapidly achieve positive charge in acidic bacterial media. Meanwhile, the acid-triggered dissociation of PDPA-TPP nanoparticles could reduce the aggregation caused quenching(ACQ) of the photosensitizers, leading to around 5 folds increase of the singlet oxygen(1O2) quantum yield. In vitro results demonstrated that the "acid-triggered" PDPA-TPP nanoparticles could kill most of MDR S. aureus(Gram-positive) and MDR E. coli(Gram-negative) by enhanced photodynamic therapy, and they could resist wound infection and accelerate wound healing effectively in vivo. Furthermore, PDPA-TPP nanoparticles could well disperse the biofilm and almost kill all the biofilm-containing bacteria. Thus, by making use of the bacterial acidic microenvironment, this "acid-triggered" nanoplatform in situ will open a new path to solve the aggregation of photosensitizers for combating broad-spectrum drug-resistant bacterial infection.

A Novel Strategy of Multi-element Nanocomposite Synthesis for High Performance ZnO-CoSe_(2) Supercapacitor Material Development

Developing multi-eleme nt composites is a promisi ng way for high perform a nee supercapacitor material developme nt,and simplifying the synthesis steps is critical for reducing the preparation costs and successful promotion of the materials.A novel one-step selective reaction strategy is developed,and successfully used to prepare four-element ZnO-CoSe_(2)(ZOCS)nano-spherical composites,to be used as supercapacitor materials.Started form nano-spherical glycerate templates,under the optimal synthesis condition,the obtained ZOCS-0.125 electrode material exhibits a specific capacitance of 450.7 F/g at 1 A/g and a good rate performance by keeping 76.8%capacitance at 20 A/g.Moreover,the ZOCS-0.125 electrode exhibits excellent cycle stability of 114.9%capacitance retention after 5000 cycles at 10 A/g.An asymmetric supercapacitor assembled by ZOCS-0.125 and activated carbon electrodes delivers an energy density of 22.35 Wh/kg at 825 W/kg,and a cycle stability of 105.6%capacitance retention after 5000 cycles.This work not only shows the good potential of the facilely prepared ZnO-CoSe_(2) composite electrode material,but also dem on strates a new strategy for low cost and high performance multielement composite material development,that can be used in a wide range of applications.

Research on intelligent judgment method of natural gas hydrate drilling risk

There are many emergency risks in the process of natural gas hydrate(NGH)drilling.In order to ensure the safe and efficient exploitation of NGH,it is urgent to establish an intelligent judgment method for the risks in the process of NGH drilling.In this paper,the response relationship between monitoring parameters and risk categories of NGH while drilling is established.Based on fuzzy analytic hierarchy process(FAHP),the comprehensive weights of 10 risk monitoring parameters are obtained,including gas production,wellbore instability,hydrate ice barrier,drill string fracture,sticking,bit balling,drilling tool piercement,gas seepage,seabed subsidence and seabed landslide.Besides,the comprehensive judgment weight matrix is constructed,and the reasonable fluctuation range of monitoring parameters is formed.Thus,the intelligent judgment method of NGH drilling risk is established.The intelligent judgment and alarm of NGH drilling risks can be realized quickly and accurately by this method,namely,it can monitor the risks in the process of operation and guarantee the construction safety of NGH drilling.

A novel elemental composition based prediction model for biochar aromaticity derived from machine learning

The measurement of aromaticity in biochars is generally conducted using solid state 13C nuclear magnetic resonance spectroscopy,which is expensive,time-consuming,and only accessible in a small number of researchintensive universities.Mathematical modelling could be a viable alternative to predict biochar aromaticity from other much easier accessible parameters(e.g.elemental composition).In this research,Genetic Programming(GP),an advancedmachine learning method,is used to develop newpredictionmodels.In order to identify and evaluate the performance of prediction models,an experimental data set with 98 biochar samples collected from the literature was utilized.Due to the benefits of the intelligence iteration and learning of GP algorithm,a kind of underlying exponential relationship between the elemental compositions and the aromaticity of biochars is disclosed clearly.The exponential relationship is clearer and simpler than the polynomial mapping relationships implicated by Maroto-Valer,Mazumdar,and Mazumdar-Wang models.In this case,a novel exponential model is proposed for the prediction of biochar aromaticity.The proposed exponential model appears better prediction accuracy and generalization ability than existing polynomial models during the statistical parameter evaluation.

具有扭曲D-A-D转子结构的近红外光疗试剂能够同时产生超氧自由基和光热用于消除乏氧肿瘤

肿瘤乏氧微环境严重抑制了肿瘤化疗、放疗及Ⅱ型光动力治疗的疗效.因此,开发非氧气依赖性的肿瘤治疗方式具有重要意义.在此,我们设计了一种超稳定的近红外吸收的光热和超氧自由基(O^(-)_(2)·)供体(TB).由于D-A-D分子结构,在808 nm激光照射下,TB能够产生大量O^(-)_(2)·.此外,由于电子供体同时还充当了转子基元,TB还能够在连续激光照射下产生极强的光热.为了将TB应用于乏氧肿瘤治疗,TB被嵌段共聚物PEG_(45)-b-PLA_(24)封装以制成纳米颗粒(TB NPs).扭曲的分子结构和长烷基链的屏蔽效应有效降低了组装体由于聚集所导致的O^(-)_(2)·淬灭.组装而成的TB NPs仍具有令人满意的O^(-)_(2)·生成能力和较高的光热转化效率,因而TB NPs可被用于乏氧肿瘤治疗.此外,由于TB NPs的光热转换效率较高,其可被用于光声成像和光热成像.在活体抗肿瘤实验中,通过连续光照,TB NPs可以完全消除乏氧肿瘤.本研究为设计非氧依赖性的光疗试剂用于乏氧肿瘤治疗提供了一种全新的策略.

A Study of Electron Beam Induced Deposition and Nano Device Fabrication Using Liquid Cell TEM Technology

SiCx nano dots and nano wires with sizes from 60 nm to approximately 2μm were fabricated using liquid cell transmission electron microscope(TEM)technology.A SiCl_(4)in CH_(2)Cl_(2)solution was sealed between two pieces of Si_(3)N_(4)window grids in an in situ TEM liquid cell.Focused 200 keV electron beams were used to bombard the sealed precursors,which caused decomposition of the precursor materials,and deposition of the nano materials on the Si_(3)N_(4)window substrates.The size of nano dots increased with beam exposure time,following an approximately exponential relationship with the beam doses.Secondary electrons are attributed as the primary sources for the Si and C reduction.A nano device was formed from a deposited nano wire,with its electrical property characterized.