TM Vol. 3, No. 1 3-D Nano and Micro Structures Inks for Direct-Write 3-D Assembly Colloidal Crystal Templating Small Structures Inspiring Electrospinning Big Technologies Quantum Dots: Nanoscale Synthesis and Micron-Scale Applications 2 Introduction TM Welcome to the first 2008 issue of Material Matters™, focusing on 3-dimensional (3D) micro- and nanostructures. New techniques to create materials ordered at micro- Vol. 3 No. 1 and nanoscale drive scientific and technological advances in many areas of science and engineering. For example, 3D-patterned metal oxides could enable construction of micro-fuel cells and high-capacity batteries smaller and more energy efficient compared to presently available devices. Ordered porous materials with exceedingly large surface areas are good candidates for highly efficient catalysts and sensors. Aldrich Chemical Co., Inc. New methods for periodic patterning of semiconductor materials are fundamental Sigma-Aldrich Corporation to next-generation electronics, while individual nanoscale semiconductor structures, 6000 N. Teutonia Ave. known as quantum dots (QDs), have remarkable optical properties for optoelectronics Milwaukee, WI 53209, USA and imaging applications. And biomedical engineers are using tailored nanofibers and patterned polymeric structures to develop tissue-engineering scaffolds, drug-delivery devices and microfluidic networks. To Place Orders The broad diversity of potentially relevant material types and architectures underscores Telephone 800-325-3010 (USA) the need for new approaches to make 3D micro- and nanostructures. In this issue, FAX 800-325-5052 (USA) Introduction Professor Jennifer Lewis (University of Illinois at Urbana-Champaign) describes direct- write printing of 3D periodic arrays. This work depends on formulation of suitable Customer & Technical Services inks, many of which can be prepared using particles and polyelectrolytes available Customer Inquiries 800-325-3010 from Sigma-Aldrich®. Researchers from the University of Minnesota write about Technical Service 800-231-8327 colloidal templating of 3D-ordered materials. A sol-gel precursor selection table and SAFC® 800-244-1173 an application note on making colloidal templates accompany the article. Custom Synthesis 800-244-1173 Dr. Jingwei Xie and Professor Younan Xia (Washington University, St. Louis) describe Flavors & Fragrances 800-227-4563 electrospinning — a versatile technique for preparation of precise nanoscale polymer International 414-438-3850 and ceramic fibers. The article is accompanied by a selection of polymer products that 24-Hour Emergency 414-438-3850 can be electrospun into nanofibers. Finally, researchers from Nanoco Technologies, Web site sigma-aldrich.com Ltd. (Manchester, UK), describe methods for reproducible high-volume synthesis of Email [email protected] colloidal QDs. Through the partnership between Nanoco and Sigma-Aldrich, these high-quality QD nanostructures are now available to help you work toward new structured materials and applications. Subscriptions We hope that the articles and Sigma-Aldrich products featured in this issue will help you in your work. Please contact Aldrich Materials Science at [email protected] if you To request your FREE subscription to need a material that you cannot find in this issue or in our catalog. Material Matters, please contact us by: Phone: 800-325-3010 (USA) Ilya Koltover, Ph.D. Materials Science Mail: Attn: Marketing Communications Sigma-Aldrich Corporation Aldrich Chemical Co., Inc. Sigma-Aldrich Corporation P.O. Box 355 Milwaukee, WI 53201-9358 Email: [email protected] International customers, please contact your local Sigma-Aldrich office. For worldwide contact information, please see back cover. Material Matters is also available in PDF format on the Internet at sigma-aldrich.com/matsci. Aldrich brand products are sold through Sigma-Aldrich, Inc. Sigma-Aldrich, Inc. warrants that its products conform to the information contained in this and other Sigma-Aldrich publications. Purchaser About Our Cover must determine the suitability of the product for its particular use. See reverse side of invoice or packing Photonic band gap (PBG) materials are an exciting application of 3D nanostructures. Periodic PBGs are designed to affect motion of photons in a similar way that periodic semiconductor crystals affect electrons, slip for additional terms and conditions of sale. allowing only propagation of light with certain wavelengths or along defined directions. Potential PBG applications include omni-directional mirrors and low-loss-waveguides that will become building blocks All prices are subject to change without notice. of future all-optical integrated circuits. PBGs are made from dielectric or metallo-dielectric nanostructures, such as the titanium dioxide lattice shown on the cover of this issue. This lattice was made using a direct- write technique developed by Prof. Jennifer Lewis (see article on p. 4) and using titanium diisopropoxide Material Matters (ISSN 1933–9631) is a publication of bis(acetylacetonate) precursor (molecule on the right-side of the cover) purchased from Aldrich Chemical Co., Inc. Aldrich is a member of the Sigma-Aldrich. Sigma-Aldrich Group. © 2008 Sigma-Aldrich Co. US $ 3 “Your Materials Matter.” Do you have a compound that you wish Sigma-Aldrich® could list to help materials research? If it is needed to accelerate your research, it matters—please send your suggestion to [email protected] and we will be happy to give it careful consideration. Joe Porwoll, President Aldrich Chemical Co., Inc. Introduction 1,3,5-Tris(4-carboxyphenyl)benzene: Building Block for Metal Organic Frameworks Dr. Channing Ahn of the California Institute of Technology kindly suggested that we make 1,3,5-tris(4-carboxyphenyl)- O OH benzene (BTB) — a building block for Metal Organic Frameworks (MOFs). MOFs are a class of 3D-microporous materials with potential applications in adsorption and separation technologies.1–3 BTB can be used as a linker to make MOFs with very high surface area, such as MOF-177: a hydrogen absorbing material with an extremely high storage capacity of 7.5% at 77K.3 HO OH O O References: (1) Kubas, G. J., Chem. Rev. 2007, 107, 4152 (2) Walton, K. S.; Millward, A. R.; Dubbeldam, D.; Frost, H.; Low, J. J.; 1,3,5-Tris(4-carboxyphenyl)benzene, (BTB) Yaghi, O. M.; Snurr, R. Q. J. Am. Chem. Soc., 2008, 130, 406. 686859-1G 1 g 150.00 (3) Wong-Foy A. G., Matzger A.J., Yaghi O. M. J. Am. Chem. Soc. 2006, 128, 3494. Materials and Synthetic Tools for 3D-Structures Featured in This Issue Materials Category Content Page Micro-and Nanoscale Powders Ceramic and metal particulate materials for syntehsis of 3D micro- and 7 nanostructures. Polyelectrolytes Anionic and cationic polymers with various molecular weights and charged 8 functional groups. Sol-Gel Precursors Alkoxide, acetylacetonate and acetate precursors for structured metal oxides. 14 Oxalate Salts Metal oxalate salts for thermal synthesis of structured metal oxides, carbonates 16 and metals. Mesoporous Materials Silica and alumina mesoporous molecular sieves. 18 Structure Directing Amphiphiles Surfactants and block copolymers for templated synthesis of ordered structures. 18 Polymers for Electrospinning Synthetic, biodegradable and natural polymers suitable for electrospinning of 22 nanofibers. Quantum Dots New core-shell luminescent semiconductor nanocrystals. 27 For questions, product data, or new product suggestions, please contact Aldrich Materials Science at [email protected]. 4 Novel Inks for Direct-Write Assembly of 3-D Periodic Structures a single or multi-nozzle array. The filament diameter is determined by the nozzle diameter, ink rheology, and deposition speed. The component dimensions, minimum feature size, and build times are dictated in part by the lateral (x-y) and vertical (z) translation distances, resolution, and speed. We have recently implemented two 3-axis, motion-controlled stages in our laboratory, as shown in Figure 1. They range from the highest precision stage, which is mounted on an inverted fluorescence microscope Prof. Jennifer A. Lewis and has maximum x-y-z travel distances of 300 µm with nanometer resolution and travel speeds of ~ 1 mm/sec, to a Materials Science and Engineering Department larger area stage, in which the maximum x-y travel distances Frederick Seitz Materials Research Laboratory exceed several centimeters with a resolution of a tens of University of Illinois at Urbana-Champaign nanometers and travel speeds of up to 30 mm/s. These vastly different capabilities allow us to pursue applications Novel Inks for Introduction that range from photonic crystals to self-healing composites. New methods for materials fabrication at the micro- and nanoscale will drive scientific and technological advances in areas of materials science, chemistry, physics, and biology. Direct-Write Assembly Direct-Write The broad diversity of potentially relevant materials, length scales, and architectures underscores the need for flexible of 3-D Periodic Structures patterning approaches. One important example is the fabrication of 3D periodic structures composed of colloidal,1 polymeric,2–4 or semiconductor5 materials. These structures may find potential application as sensors,6 microfluidic networks,7 self-healing materials,8 photonic band gap materials,9 and tissue engineering scaffolds.10 Several strategies have recently emerged for precisely assembling 3D periodic arrays,1–5 including colloidal epitaxy,1 litho-5 and holographic,3 and direct-write techniques.2–4