1、Subscriber access provided by Stockholm University Libraryis published by the American Chemical Society. 1155 Sixteenth Street N.W.,Washington, DC 20036Published by American Chemical Society. Copyright American Chemical Society.However, no copyright claim is made to original U.S. Government works, o
2、r worksproduced by employees of any Commonwealth realm Crown government in the courseof their duties.Interfaces: Adsorption, Reactions, Films, Forces, Measurement Techniques, ChargeTransfer, Electrochemistry, Electrocatalysis, Energy Production and StorageUltrathin uniform platinum nanowires via a f
3、acile routeusing an inverse hexagonal surfactant phase templateSamina Akbar, Jacob Boswell, Carys Worsley, Joanne M Elliott, and Adam M. SquiresLangmuir, Just Accepted Manuscript DOI: 10.1021/acs.langmuir.7b03970 Publication Date (Web): 21 May 2018Downloaded from http:/pubs.acs.org on May 21, 2018Ju
4、st Accepted“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are postedonline prior to technical editing, formatting for publication and author proofing. The American ChemicalSociety provides “Just Accepted” as a service to the research community to expedite the
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6、y theDigital Object Identifier (DOI). “Just Accepted” is an optional service offered to authors. Therefore,the “Just Accepted” Web site may not include all articles that will be published in the journal. Aftera manuscript is technically edited and formatted, it will be removed from the “Just Accepte
7、d” Website and published as an ASAP article. Note that technical editing may introduce minor changesto the manuscript text and/or graphics which could affect content, and all legal disclaimers andethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors orconseq
8、uences arising from the use of information contained in these “Just Accepted” manuscripts. Figure 3. TEM micrographs of Pt-nanowires fabricated from the HII phase of phytantriol in the presence of 0 % (left) and 4.1 % (right) (w/w) tricosene at 55 and 25 C respectively. The fabrication time was 6 ho
9、urs. 683x1113mm (72 x 72 DPI) Page 1 of 23ACS Paragon Plus EnvironmentLangmuir123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 1Ultrathin uniform platinum nanowires via a facile route using an inverse hexagonal surfactant phase template
10、Samina Akbar,a,b Jacob Boswell,c Carys Worsley,c Joanne M. Elliott,*a and Adam M. Squires*ac a Department of Chemistry, University of Reading, Whiteknights, Reading, RG6 6AD. Fax: (+)44 (0)118 378 6331, E-mail: a.squiresbath.ac.uk, j.m.elliottreading.ac.uk, Homepage: http:/www.reading.ac.uk/chemistr
11、y/chem-home.aspx b Department of Basic Sciences and Humanities, University of Engineering and Technology, KSK Campus, GT Road Lahore, Pakistan. c Department of Chemistry, University of Bath, Bath BA2 7AY, UK KEYWORDS. Self assembly, Inverse Hexagonal, Templating, Platinum, Nanowires ABSTRACT. In thi
12、s paper, we present an attractive method for the fabrication of long, straight, highly crystalline ultra-thin platinum nanowires. The fabrication is simply achieved using an inverse hexagonal (HII) lyotropic liquid crystal phase of the commercial surfactant phytantriol as a template. A platinum prec
13、ursor dissolved within the cylindrical aqueous channels of the liquid crystal phase is chemically reduced by galvanic displacement using stainless steel. We demonstrate the production of nanowires using the HII phase in the phytantriol/water system Page 2 of 23ACS Paragon Plus EnvironmentLangmuir123
14、456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 2which we obtain either by heating to 55 C, or at room temperature by the addition of a hydrophobic liquid, 9-cis-tricosene, to relieve packing frustration. The two sets of conditions produce
15、d high aspect nanowires with diameters of 2.5 nm and 1.7 nm respectively, at least hundreds of nanometers in length, matching the size of the aqueous channels in which they grow. This versatile approach can be extended to produce highly uniform nanowires from a range of metals. INTRODUCTION. Nanostr
16、uctured platinum materials have been investigated for a wide range of high-surface-area applications. Some of these technologies are driven by the need to meet the increasing demand for renewable energy, for example, in fuel cells1 and solar cells2. Other applications include sensors3 and chemical c
17、atalysts4-5. The use of nanowires rather than the commonly used supported nanoparticles brings a number of advantages, overcoming several problems associated with the latter especially in fuel cells, such as support degradation, particle sintering, and limitations on catalyst loading1. Ultrathin pla
18、tinum nanowires have been shown to exhibit higher electrochemical surface area activity than supported nanoparticles6, and greater electrochemical durability under voltage cycling5. In other applications, platinum nanowires bring new optical7, magnetic8 and catalytic properties9-10. More generally,
19、ultrathin nanowires from other metals have applications in transparent conducting electrodes11. A number of approaches have been used to produce ultrathin (10 nm diameter) platinum nanowires. Non-templating routes through chemical reduction generally give rise to shorter, more disordered wires6 alth
20、ough Xia et al.12 have reported the synthesis of 3 nm diameter ultralong nanowires in a template-free solvothermal route taking 1-2 days, and involving temperatures of 170 C. Longer, straight ultrathin platinum nanowires are more commonly Page 3 of 23ACS Paragon Plus EnvironmentLangmuir1234567891011
21、12131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 3produced by growing the metal within the cylindrical pores of a template such as mesoporous silica13, carbon nanofibers14, insulin fibrils5 and metal organic frameworks15. However, the assembly and su
22、bsequent removal of these templates are associated with complex, multi-step processes, often involving harsh conditions and reagents. Platinum nanomaterials with different morphologies showing periodicity in two or three dimensions have been produced by electrodeposition within highly ordered hexago
23、nal or cubic lyotropic liquid crystalline phases16-18. They generally represent a much more attractive route than the templates mentioned in the previous paragraph. However, such lyotropic phases have not until now been used to produce straight ultra-thin nanowires (although inverse micelles have be
24、en used to grow nanowires which are much larger10 or more disordered19. In this study, inverse hexagonal lyotropic liquid crystal phases (HII) formed from self-assembly of the readily available lipid phytantriol (3,7,11,15-tetramethyl-1,2,3trihydroxy-hexadecane) are used for the template synthesis o
25、f ultra-thin, straight platinum nanowires. HII phases contain arrays of straight aqueous channels a few nm in diameter, and have mainly been researched for pharmaceutical applications20. In the few cases where these have been used as templates, in the synthesis of metals21 and semiconductor22-23 nan
26、owires, the nanowires produced are typically tens of nanometres in diameter; these dimensions are much larger than the diameter of the channels (indicating that the process has not faithfully templated the channel dimension) and of the ultrathin nanowires we report in this paper. The HII phase is th
27、e thermodynamically favoured phase for phytantriol in excess water above 45 C24. Addition of a hydrophobic liquid such as 9-cis-tricosene (as here) or hexadecane25 relieves packing frustration by filling voids between the monolayer cylinders allowing the HII phase to form at room temperature. Page 4
28、 of 23ACS Paragon Plus EnvironmentLangmuir123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 4EXPERIMENTAL. Materials and Equipment: 3,7,11,15-tetramethyl-1,2,3-hexadecanetriol (C20H42O3), commonly known as phytantriol, was kindly donated
29、by Adina Cosmetics Ingredients. Hexachloroplatinic acid (HCPA) solution (8 wt % in water) and 9-cis-tricosene were purchased from Aldrich. 0.5 M sulfuric acid was prepared from Merck p.a.-grade concentrated acid. Laboratory reagent grade acetone was purchased from Fischer Scientific. 6 M HCl was pre
30、pared by diluting the laboratory reagent grade HCl (36 %) from Fischer Scientific. All of the compounds were used as received. All solutions were prepared in purified water, which was prepared by passing deionized, distilled water through a Milli-Q water purification system. Stainless steel sheet (2
31、 mm thick), purchased from Inspired steel limited, was cut down to 0.3-1 cm2 pieces by the in-house mechanical workshop. Preparation of liquid crystal templates: The binary mixture of phytantriol containing 4.1 % (w/w) 9-cis-tricosene was prepared by weighing appropriate amounts of phytantriol and 9
32、-cis-tricosene in a capped glass vial. The mixture was vigorously stirred at room temperature with the help of a glass rod or polypropylene spatula. The glass vial containing the mixture was sealed and heated in water bath at 40 oC for 20 min and then cooled down to room temperature. The sample was
33、stirred again. After mixing, the sample was allowed to stand for 1-2 hours to remove air bubbles. Phytantriol and the binary mixture of phytantriol/9-cis-tricosene were each dissolved in ethanol in 1:1 or 1:2 ratios by weight for SAXS analysis or platinum deposition on stainless steel respectively.
34、Fabrication of Pt-nanowires: For the fabrication of Pt-nanowires, a thick layer (1-2 mm) of phytantriol or binary mixture of phytantriol/9-cis-tricosene (dissolved in ethanol) was placed on the steel plate in a Teflon cell. The Teflon cell was left for 1-2 hour to allow the ethanol to Page 5 of 23AC
35、S Paragon Plus EnvironmentLangmuir123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 5evaporate. The Teflon cell was then sealed and placed inside a Pyrex water jacketed cell attached to a thermostat water bath for temperature control. Aft
36、er equilibration at the required temperature for 30-60 mins, HCPA solution was added drop wise to the top of the surfactant layer. It was allowed to stand for 4-8 hours until the mixture became fully black. Chemical deposition of Pt-nanowires from HII phase of phytantriol without the presence of tri
37、cosene was carried out at 55 C. In the presence of 4.1 wt % tricosene, deposition was carried out at 25 oC. Once the process was completed, the chemical deposits were removed from the substrate and transferred to a glass vial followed by washing (see below). Washing of chemical deposits: Washing of
38、chemical deposits was carried out with acetone (20 ml), water (10 ml), 6 M HCl (10 ml), water (10 ml), acetone (10 ml) and finally with water. After washing, the nanostructured platinum powder was kept moist in order to avoid inhalation risks associated with dry powders. Characterization: Structural
39、 investigations were carried out by small angle X-ray scattering (SAXS) and transmission electron microscope (TEM) whereas electrochemical analysis was carried out by cyclic voltammetry. Small Angle X-Ray Scattering (SAXS) analysis: Small angle X-ray scattering patterns were recorded using a Small A
40、ngle X-Ray System V 4.1.35 Bruker AXS operating at 45 kV and 650 A. Silver behenate CH3 (CH2)20COOAg was used as a calibrant using d001 = 5.8380 nm26. Scattering patterns were obtained with a wavelength of 0.154 nm. During analysis the optics and the sample chamber were under vacuum to minimize the
41、air scatter. 2-D scattering patterns were subsequently integrated and converted into one dimensional d-spacing intensity profiles by using Image J software with macros written in-house. The sample to detector distance was 107 cm Page 6 of 23ACS Paragon Plus EnvironmentLangmuir12345678910111213141516
42、1718192021222324252627282930313233343536373839404142434445464748495051525354555657585960 6(extended beam path) or 67 cm (short beam path). All the temperature controlled measurements were performed using an mri Physikalische Gerate GmbH high temperature heating stage (mri-0065151/heating stage). Sam
43、ple preparation of nanostructured platinum materials: Small amounts of the Pt-nanowire powder were wrapped in polyimide sticky tape with the help of a spatula and attached to a metal frame for SAXS analysis. Sample preparation of liquid crystals with incorporated platinum: During the chemical fabric
44、ation process, a small amount of a liquid crystal template along with the platinum replica was removed from the steel plate and a sandwich cell was prepared. A sample was sandwiched between two layers of a polyimide paper supported by a silicon rubber sheet attached together by double sided sticky t
45、ape. For temperature control, the cell was placed between two metal plates screwed together and then fixed into the heating stage. Preparation of liquid crystal samples under excess hydration conditions: Thin coatings of phytantriol with or without the presence 9-cis-tricosene were deposited on the
46、inside of open-ended thin-walled glass capillary tubes from their ethanolic solutions (w/w ratio of 1:1) followed by drying with compressed air ( 15 min) and then kept under ambient conditions for not less than an hour. Drying time with compressed air was extended to 30 min for immediate use (in thi
47、s case, it was not kept for another hour under ambient conditions). During this time, the ethanol evaporated leaving a thin film (21 5 m thick) of phytantriol with or without the presence of tricosene. The capillary was then filled with water or HCPA solution, sealed and fixed into the heating stage
48、. TEM Analysis: The surface morphology of the Pt-nanowires was revealed by taking images using Philips CM20 Analytical TEM and JEOL JEM-2010 HR TEM operated at 200 kV. For Page 7 of 23ACS Paragon Plus EnvironmentLangmuir12345678910111213141516171819202122232425262728293031323334353637383940414243444
49、5464748495051525354555657585960 7TEM analysis, 2 ml of isopropyl ether or acetone was added to the sample in a glass vial and sonicated for 5 min to make a suspension of the Pt-nanowires. 1-2 drops of the suspension was placed on a copper grid with supporting carbon film (300 mesh) with the help of
50、a dropper. The copper grid was placed on the sample holder and loaded inside the sample chamber for analysis. Electrochemical characterisation: All electrochemical experiments were carried out on a purpose built electrochemical workstation and software, interfaced to a personal computer using a CIO-
