A novel and facile wet-chemical method for synthesis of silver microwires

A novel and facile wet-chemical method for synthesis of silver microwires was developed.The well-defined particles were prepared by adding an iron（Ⅱ） sulfate heptahydrate solution into a silver nitrate solution containing citric acid drop by drop at 50 °C.The resulting products were characterized by scanning electron microscopy and X-ray diffraction.It was found that the particles consisted of numerous silver microwires.The reaction temperature greatly affected the morphologies of the as-prepared particles.Both of the mean length and width of the silver microwires increased with the decrease of the concentration of silver nitrate.And the lower concentration was unfavorable for the formation of more silver microwires.Similar findings were also observed when the concentration of iron（Ⅱ） sulfate was decreased.The amount of citric acid also greatly affected the shape of the as-prepared particles.It was concluded that citric acid was the key role in the formation of silver microwires via the Oswald ripening mechanism.

A novel wet-chemical method for preparation of silver flakes

A novel wet-chemical method for the preparation of silver flakes was studied. The well-defined particles were prepared by directly adding FeSO4 solution into AgNO3 solution containing citric acid at an agitation speed of 150 r/min at room temperature. The products were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The results show that particles are irregular thin silver flakes. And the sizes of them range from 2 to 10 μm. It is found that citric acid plays an important role in the formation of sliver flakes. There is an optimum amount of citric acid for the preparation of silver flakes by this method. It is also found that high reduction rate is favorable for the formation of silver flakes.

Preparation and optical characteristics of ZnO films by chelating sol-gel method

The effect of different annealing temperatures on the structure, morphology,and optical properties of ZnO thin films prepared by the chelating sol-gel method was investigated.Zinc-oxide thin films were coated on quartz glass substrates by dip coating. Zinc nitrate, absoluteethanol, and citric acid were used as precursor, solvent, and chelating agent, respectively. Theresults show that ZnO films derived from zinc-citrate have lower crystallization temperature (below400℃), and that the crystal structure is wurtzite. The films, treated over 500℃, consist ofnano-particles and show to be porous at 600℃. The particle size of the film increases with theincrease of the annealing temperature. The largest particle size is 60 nm at 600℃. The opticaltransmittances related to the annealing temperatures become 90% higher in the visible range. Thefilm shows a starting absorption at 380 nm, and the optical band-gap of the thin film (fired at500℃) is 3.25 eV and close to the intrinsic band-gap of ZnO (3.2 eV).

Preparation of Spherical Tungsten Particles Assisted by Hydrothermal Method

We presented a strategy to prepare spherical tungsten powder by the combination of hydrothermal method and H2reduction process.In hydrothermal process,the micelle of tetraethylammonium bromide(TEAB)act as spherical templates for the deposition of tungsten oxide,whereas the excessive TEAB inhibit the formation of spherical tungsten oxide due to the dense molecular layer of TEAB on the tungsten oxide particles.Citric acid(CA)can control the formation rate and structure of the tungsten oxide when its concentration is more than 0.2 mol/L,because of its ability to coordinate with tungsten atoms.The synergistic effect of TEAB and CA facilitates the formation of spherical tungsten oxide with nanorod crown.After being treated by H_(2)at 600 and 650℃,the tungsten oxide particles are reduced to tungsten particles,which maintain the spherical structure of tungsten oxide and have porous structure.

Improved activity of Ni-Mo/SiO_(2) bimetallic catalyst synthesized via sol-gel method for methylcyclohexane cracking

To improve the cracking behavior of hydrocarbon,Ni-Mo/SiO_(2) bimetallic catalysts were synthesized by different preparation methods(sol-gel,co-impregnation and single-impregnation) and added the additives(citric acid,polyethylene glycol and cetyltrimethylammonium bromide) based on the most suitable method above.The cracking reaction of methylcyclohexane under supercritical conditions was performed as the probe reaction to estimate the catalytic performance,and the properties of Ni-Mo/SiO_(2) catalyst were characterized by N_(2) absorption-desorption,XRD,XPS,H_(2)-TPR,NH_(3)-TPD,in-situ IR of NH_(3) desorption,HRTEM and STEM-mapping so as to study the structure-activity relationship.The catalyst synthesized via sol-gel method showed the best conversion and heat sink,being 81.8% and 3.81 MJ/kg,which was closely related to strong mutual effect between active components and SiO_(2) as well as strong acid sites.Besides,the introduction of additives by sol-gel method has an affirmative influence on properties of Ni-Mo/SiO_(2) catalysts,being that the acidity(more L and B acid sites) was modulated and organic groups interact with metal to suppress the aggregation of metal species(Ni and Mo),thereby enhancing the catalytic activity.At 750℃,the conversion(89.3%) as well as heat sink(3.99 MJ/kg) of MCH cracking obtained an optimum over Ni-Mo/SiO_(2) catalyst with addition of citric acid.

Preparation and electrochemical performance of Li_2Mn_(0.5)Fe_(0.5)SiO_4 cathode material with sol-gel method for lithium ion batteries

Li2Fe0.5Mn0.5SiO4 material was synthesized by a citric acid-assisted sol-gel method. The influence of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+) on the electrochemical properties of Li2Fe0.5Mn0.5SiO4 was studied. The final sample was identified as Li2Fe0.5Mn0.5SiO4 with a Pmn21 monoclinic structure by X-ray diffraction analysis. The crystal phases components and crystal phase structure of the Li2Fe0.5Mn0.4SiO4 material were improved as the increase of the stoichiometric ratio value of n(citric acid) to n(Fe2+-Mn2+). Field-emission scanning electron microscopy verified that the Li2Fe0.5Mn0.5SiO4 particles are agglomerates of Li2Fe0.5Mn0.5SiO4 primary particles with a geometric mean diameter of 220 nm. The Li2Fe0.5Mn0.5SiO4 sample was used as an electrode material for rechargeable lithium ion batteries, and the electrochemical measurements were carried out at room temperature. The Li2Fe0.5Mn0.5SiO4 electrode delivered a first discharge capacity of 230.1 mAh/g at the current density of 10 mA/g in first cycle and about 162 mAh/g after 20 cycles at the current density of 20 mA/g.

不同提取工艺对刺梨中维生素C提取量的影响研究

本文以柠檬酸为提取剂,分别采用浸提法、超声辅助法、微波辅助法提取刺梨果肉中维生素C,并利用紫外分光光度计测定维生素C提取量。结果表明,超声辅助提取法的提取率最高,在超声功率为80 W、超声时间为8 min条件下,维生素C的提取量为35.9 mg·g^(-1)。

酸热法提取黑水虻鲜幼虫油脂工艺研究

【目的】构建黑水虻油脂的快速、高效的新型提取工艺,解决传统提取工艺中因乳化作用和细胞破碎不足导致油脂提取率较低的问题,为黑水虻油脂的提取及黑水虻油脂的规模化发展提供新思路。【方法】使用酸热法提取黑水虻鲜幼虫油脂,通过控制变量法选取黑水虻鲜幼虫油脂的预处理方法和提取溶剂,经单因素试验和正交试验对提取工艺进行优化,分析黑水虻鲜幼虫油脂的理化指标,并通过高效气相色谱仪分析其脂肪酸组成。【结果】酸热法提取黑水虻鲜幼虫油脂的最佳预处理方法为添加质量分数5.0%的柠檬酸溶液匀浆破碎(m(鲜幼虫/g)∶V(溶液/mL)=1∶1),最佳提取溶剂为石油醚,提取工艺条件为柠檬酸溶液质量分数5.0%、料液比m(鲜幼虫/g)∶V(石油醚/mL)=1∶5、提取时间60 min和提取温度50℃。在此条件下,油脂提取率达到94.67%,且耗时4 h便可得到黑水虻鲜幼虫油脂。黑水虻鲜幼虫油脂的酸值为9.30 mg·g-1,过氧化值为1.74 mmol·kg^(-1),皂化值为227.23 mg·g-1。鲜幼虫油脂共检测出20种脂肪酸,其中,亚油酸与月桂酸的含量最高,分别为32.72%和30.75%。【结论】酸热法能快速、高效地提取黑水虻鲜幼虫油脂,既节省了干燥成本,又保证了油脂的品质和脂肪酸组成。

净制对乌梅质量的影响及乌梅肉质量标准的研究

目的:研究净制对乌梅质量的影响,完善乌梅肉质量标准。方法:首先采用蒸与润2种方法分别净制3批乌梅肉样品,比较其产率、浸出物以及枸橼酸含量差异,确定净制方法;根据确定的净制方法,对12批乌梅药材进行净制,比较乌梅肉和核中浸出物及枸橼酸含量差异,探讨净制对乌梅质量的影响。对21批乌梅肉饮片的外观性状、显微、薄层鉴别、水分、水溶性浸出物和枸橼酸含量分别按照药典要求进行测定,拟定乌梅肉质量标准限度。结果:蒸法与润法净制乌梅质量(产率、水分、枸橼酸及浸出物)无显著性差异,但蒸法所用时间为30 min,远短于润法润制过夜。乌梅肉的浸出物及枸橼酸的含量72.5%、33.1%远高于乌梅核17.9%、8.0%,二者存在极显著差异。乌梅肉的平均水分为(11.0±1.4)%;浸出物为(72.0±3.4)%;枸橼酸含量为(33.8±4.5)%。结论:乌梅净制可以去除非药用部位,提高枸橼酸及浸出物含量,具有科学道理,蒸法和润法2种净制方法均可行,蒸法更易操作。

亲水性CIT-NaYF_(4)∶Yb^(3+),Ho^(3+)纳米粒子的制备及其发光性能研究

采用溶剂热法制备了油溶性稀土掺杂上转换纳米粒子NaYF_(4)∶Yb^(3+),Ho^(3+),并利用TEM、XRD、IR、荧光光谱法等考察了反应温度、反应时间、掺杂比等反应条件对纳米粒子形貌、结构、发光性能的影响。结果表明,在反应温度为300℃、反应时间为50 min、稀土离子掺杂比为NaYF_(4)∶20%Yb^(3+),2%Ho^(3+)条件下,制备出的油溶性NaYF_(4)∶Yb^(3+),Ho^(3+)纳米粒子呈标准六方晶型,尺寸均一、单分散性好,平均粒径为31.55 nm。通过表面配体交换法成功将柠檬酸修饰在其表面,转为亲水性CIT-NaYF_(4)∶Yb^(3+),Ho^(3+)纳米粒子。

溶胶-凝胶法合成钛酸锌锂负极材料

以溶胶-凝胶法制备锂离子电池Li_(2)ZnTi_(3)O_(8)(LZTO)负极材料,考察退火温度和退火时间对LZTO电化学性能的影响,得到了最佳工艺条件:退火温度为700℃,退火时间为3 h。在最佳工艺条件下制备的LZTO中添加络合剂柠檬酸进行了改性。结果表明,当金属离子与柠檬酸的物质的量比为2.00∶1.50时,制备的样品LZTO-2/1.50颗粒小、分散均匀,表现出良好的电化学性能;当电流密度为0.5 A/g时,恒流充放电300次后放电比容量为203.6 mA·h/g。

基于溴酸钾氧化酚藏花红的荧光猝灭法测定柠檬酸

在稀H_(2)SO_(4)介质中,用柠檬酸活化钒(V)可催化溴酸钾氧化酚藏花红,导致酚藏花红的荧光猝灭,由此建立了荧光猝灭法测定柠檬酸的新方法。探讨了硫酸、溴酸钾、偏钒酸铵、酚藏花红用量、反应温度、反应时间对体系的影响,优化了测定条件。在最佳实验条件下,方法的线性范围为0.833~3.750μg·mL^(-1),线性方程为ΔF=-2.359+67.483ρ,相关系数R^(2)为0.9929,检出限为0.42μg·mL^(-1)。该方法用于饮料中柠檬酸的测定,测定结果的回收率为95.5%~108%,RSD为3.5%~4.1%,表明本分析方法可行。

低剂量两段法局部枸橼酸抗凝对高危出血风险患者行含钙透析液血液透析的影响研究

目的探讨低剂量两段法局部枸橼酸抗凝对高危出血风险患者行含钙透析液血液透析的影响。方法选择纳入我院2020.7-2022.7收治的80例高危出血风险患者行含钙透析液血液透析患者,按照随机法将其分为对照组与研究组,每组各40例,均采用局部枸橼酸抗凝和标准含钙透析液,其中对照组注入常规剂量,设定前段4%枸橼酸钠溶液输注量为血流量的1.5倍;研究组注入低剂量,设定输注量改为1.0倍,比较两组实际抗凝效果。结果两组基线资料对比,差异无统计学意义(P>0.05)。在枸橼酸抗凝不同剂量下,研究组透析器和静脉壶的抗凝有效率均高于对照组(P<0.05),两组干预前凝血功能指标比较无明显差异(P>0.05);两组干预后凝血功能各指标均有所改善,但组间对比不存在统计学差异(P>0.05),研究组透析器前和静脉壶的枸橼酸溶液输注量以及实际血流量均高于对照组(P<0.05)。结论在两段法局部枸橼酸抗凝的基础上,选择低剂量抗凝,不仅能够达到理想的抗凝效果,同时也明显提高透析充分性,是一种安全有效可行的抗凝方案。

TiO_2/YFeO_3复合光催化剂的制备、表征及其对气相苯的降解(英文)

利用共沉淀法和柠檬酸法制备YFeO3,并以其为载体,将TiO2溶胶负载在其表面,制备了复合光催化剂TiO2/YFeO3.在紫外灯的照射下,考察对气相苯的降解效果并利用N2吸附、X射线衍射(XRD)、拉曼光谱、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、UV-Vis漫反射光谱等手段对催化剂进行了表征.结果表明,以共沉淀法制备的YFeO3为载体的复合催化剂,180min内苯的降解率达到44.7%,表现出更好的光催化活性.两种方法制备的YFeO3均为斜方晶相,TiO2分散在载体的表面,并与YFeO3存在一定的相互作用;两种复合催化剂均具有较窄的带隙能.

溶胶-凝胶法制备纳米氧化镁

以六水硝酸镁为前驱体,采用柠檬酸溶胶-凝胶法合成了不同粒径(10-100nm)和结晶度的纳米MgO粉末。研究了柠檬酸的作用机理、不同的工艺条件(水、无水乙醇、柠檬酸的加入量)对溶胶-凝胶稳定性的影响以及焙烧温度对粉末晶体粒径、结晶度的影响。结果表明:未引入柠檬酸时,凝胶的稳定性较差,氧化镁产物粒径较大且团聚较严重。引入柠檬酸后,并当水:六水硝酸镁:柠檬酸:乙醇=100:9:9:2:1(摩尔比)时可形成稳定的凝胶体系。焙烧温度对制得的MgO粉末的化学成分和晶体形貌基本无影响,但对粉末结晶度和粒径有显著的影响。500℃焙烧制得的纳米氧化镁粉末粒径为10nm左右,结晶度低,粒子间有一定的团聚;600℃的粉末粒径为30-60nm,结晶度有所提高,粒子的分散性较好;900℃的粉末粒径为50-100nm,结晶度更高,晶相更完整。

超细层状材料A_2La_2Ti_3O_(10)(A=Na,K)的低温合成及表征

s: Ultrafine A2La2Ti3O10 (A=K, Na) powders with laminar structure were successfully synthesized by citric acid sol-gel method using ANO3(A=K, Na)?La(NO3)3?Ti(OBu)4 and citric acid as starting precursors. The crystalline phase of A2La2Ti3O10 can be obtained by thermal decomposition of citrate complex precursors at a relatively low temperature of 800 ℃ (600 ℃ for A=Na), about 300 ℃(500 ℃ for A=Na) lower than that of conventional solid state reaction process. The properties of the citrate precursors and the calcined powders were characterized by Infrared spectroscopy (IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal-gravimetric-differential thermal analysis (TG-DTA), inductively coupled plasma (ICP) and Brunauer-Emmett-Teller (BET) techniques. Results show that the average size of A2La2Ti3O10 powders obtained by citric acid sol-gel route was reduced to 200 nm×250 nm and the specific surface area was up to 19 m2·g-1. At the same time, the product was with more regular morphological characteristics. The synthesis process and the formation of A2La2Ti3O10 were also discussed. The obtained A2La2Ti3O10 was found to be transformed from A2La2Ti3O9.5 during the formation process.

溶胶-凝胶法制备Bi_2WO_6微纳米材料及其光催化性能

为了开发可见光响应型光催化剂,以柠檬酸为络合剂,采用溶胶-凝胶法制备前驱体,通过煅烧得到了Bi2WO6微纳米材料。采用X-射线衍射(XRD)、场发射扫描电镜(FESEM)、紫外-可见光漫反射谱(UV-vis DRS)等技术对其进行表征,考察了制备条件对样品晶相结构的影响。结果表明,在煅烧温度450℃、煅烧时间3 h、柠檬酸与Bi3+的物质的量比为3∶1、前驱液的pH=1、分散剂为PEG-4000的条件下制备的Bi2WO6样品为斜方晶系Bi2WO6结构,由粒径为50 nm左右的小薄片堆积而成。所得的Bi2WO6样品具有优良的光催化性能,在可见光照射(200 W点钨灯)及H2O2助剂的存在下,对10 mg/L罗丹明B溶液的光降解率可达82.0%。研究结果可为高效Bi2WO6光催化材料的制备提供新的思路。

柠檬酸溶胶凝胶法制备LiCoO_2电极材料及其表征

LiCoO2 precursors of the cathode material for lithium ion batteries were prepared from lithium hydroxide, basic cobalt carbonate and citric acid by a sol gel method. The LiCoO2 samples were obtained by sintering the gel precursors at different temperatures and for different times. The thermal decomposition behavior of the gel precursors was examined by means of thermo gravimetric analysis and differential thermal analysis using a PCT IA thermal analyzer system. Their structures and morphologies were characterized by powder XRD and SEM techniques. It was found that using citric acid realized that the formation of LiCoO2 crystal can be clearly differentiated to the nucleation and growth processes of the crystals; furthermore, the crystal size can be controlled. Electrochemical tests using the LAND BT1 10 test system showed the electrochemical performance of the material is affected by its integrity and stability.

柠檬酸微波加热法合成纳米二氧化锡

以SnCl4·5H2O为原料,用柠檬酸微波加热法制备了金红石结构的纳米SnO2粒子。用DSC、TGA、XRD、TEM和IR等技术对SnO2粒子进行了表征。结果表明,焙烧温度、金属与柠檬酸摩尔比对粒径影响较大,而焙烧时间、微波加热时间对粒径影响较小,对结晶度影响较大;在600℃,Sn4+与柠檬酸的摩尔比为1∶2时,制备的SnO2粒子平均晶粒尺寸为17.4nm,平均颗粒尺寸为22nm。

阻抑动力学荧光法测定柠檬酸

基于在高氯酸介质中柠檬酸能抑制铁 (Ⅲ )催化H2 O2 氧化吡咯红Y的反应 ,建立了一种测定柠檬酸的动力学荧光分析法。方法的线性范围为 0 .1 2～2 .4μg/mL ,检出限为 0 .0 5 μg/mL。将方法用于汽水中柠檬酸的测定 ,回收率为97%～ 1 0 6%。