Impact of Chemistry [16:160:127]

Transcription

1 Impact of Chemistry [16:160:127] 2. Introduction to Nanotechnology Chemistry and Chemical Biology Dept. Rutgers University KiBum Lee, Ph.D.

2 Notice There will be no case study # 3. Research Presentation (Drug delivery to brain tumor cells and Stem Cells) on next Thurs (10/13) Lecture notes will be posted on the Sakai (from the next week)

3 Review What is nanoscience? New physics, chemistry and technology Two visions of nanofabrication What is a role of Chemist? Size, Shape, Compositions, and Crystalline

4 What is nanotechnology? Nanotechnology is research and technology development at the atomic, molecular or macromolecular levels, in the length scale of approximately nm National Science Foundation 1 nanometer = 10-9 m Human hair = 50,000 nm Smallest thing seeable with the naked eye = 10,000 nm Hydrogen atom = 0.1 nm Nanoscience: the study of fundamental principles of molecules and structures with a least one dimension roughly between 1 and 100 nm (nanostructure). Nanotechnology: the application of these nanostructures into nanoscale devices

5 A Different Kind of Small At the macroscale: chemical & physical properties of materials are not size dependent As we cut a bulk of gold down to smaller pieces, the properties (gold, yellow, shiny, electrically conductive metal, melting point..) will be exactly the same until we reach the nanoscale. At nanoscale: everything will change, including color, melting points, and chemical properties Due to the nature of the interaction among the atoms Interactions are not averaged out as in bulk material Nano gold doesn t act like bulk gold

6 Surface area of NPs: a simple model

7 Science: New Tools

8 Science: New Physics

9 Science: New Chemistry

10 Science: New Biology

11 Approaches to nanoscale structures

12 What is a role of Chemistry?

13 Contents Review the previous lecture 0, 1 and 3 dim. nanomaterials Self-Assembly Monolayers (SAMs) Specific Topics in nanochemistry

14 The most-cited researchers in Chemistry

15 To find a good reference Search Engine: SciFinder Web of Science ( MEDLINE ( Impact Factors: Science, Nature, and Cell Nature*, Advanced Materials, Nano Letters JACS, Angewante Chem Other Specific Journals

16

17 Fundamental Science

18 Zero dimensional (0D) growth Terri Odom (Northwestern)

19 Arrested precipitation: general approach

20 Arrested precipitation: metallic colloids Aqueous reduction of metal salts (Ag, Au) in the presence of citrate ions Chemisorption of organic ligands for handling Distribution varies > 10% Higher temperature reduction of metal salts (Co, Ni) in the presence of stabilizing agents Metal NCs nucleate and grow until the reagent is consumed No Ostwald ripening is observed NC size is coarsely tunable by the ratio of capping groups to metal salt Schmid G Chem. Rev.92:

21 Arrested precipitation: metallic colloids Terri Odom (Northwestern)

22 Arrested precipitation: semiconducting NCs

23 One dimensional (1D) growth Y. Xia et al., Adv. Mat. 15, 353 (2003)

24 Electrodeposition scheme Porous template Silver component growth gold component growth Removal of template

25 Preparation of Anodic Aluminum Oxide template + D.C Power - Wate r in circulator Wate r out Al Electro-polishing PCA: EtOH Anodization 0.3M oxalic acid Anodization 0.3M oxalic acid Etching Chromium oxide +phosphoric acid

26 SEM image AFM image Particles Lattice mismatches

27 Titanium Oxide Nanotubes (NTs)

28 Titanium Oxide Nanotubes (NTs)

29 Titanium Oxide NanoTubes (NTs)

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31 Electrodeposition within nanoporous membranes

32 Three dimensional (3D) nanostructures photo-induced conversion kinetic control DNA-based assembly

33 Self-Assembled Monolayers In 1946 Zisman published the preparation of a monomolecular layer by adsorption (self-assembly) of a surfactant onto a clean metal surface. J. Colloid Interface Sci.1946, 1, 513.

34 Formation of SAMs on Gold In 1983Nuzzoand Allara showed that SAMs of alkanethiolates on gold can be prepared by adsorption of di-n-alkyl disulfide from dilute solutions. J. Am. Chem. Soc.1983, 105, the most studied SAMs to date SAMs are ordered molecular assemblies formed by the adsorption of an active surfactanton a solid surface. The order in these 2D system is produced by a spontaneous chemical synthesis at the interface, as the system approaches equilibrium. proposed mechanism (still controversial): oxidative addition of the S-H bond to the gold surface, followed by a reductive elimination of the hydrogen R-S-H + Au o n R-S-Au + Au o n + 1/2H 2 on the basis of the bond energies of RS-H, H-H, and RS-Au (87, 104, and 40 kcal/mol, respectively), the net energy for adsorption of alkanethiolates on gold would be ca. 5 kcal/mol, which is exothermic. cf. J. Am. Chem. Soc.2002, 124, 1132.

35 Formation of SAMs on different substrates

36 Self-Assembled Monolayers (SAMs)

37 Self-Assembled Monolayers (SAMs)

38 Tailoring the composition of the SAM on Nanoparticles

39 SAMs on Silicon Oxide alkylchlorosilanes and alkylalkoxysilanes require hydroxylated surfaces in situ formation of polysiloxane, which is connected to surface silanol groups (-SiOH) via Si-O-Si bonds

40 SAMs on Silicon Oxide not easy to produce, mainly because of the need to carefully control the amount of water in solution incomplete monolayers are formed in the absence of water excess water results in facile polymerization in solution and polysiloxane deposition of the surface for the formation of closely packed monolayers, a moisture quantity of 0.15mg/100mL of solvent was suggested as the optimum condition temperature: the threshold temperature below which an ordered monolayer is formed. The threshold temperature is a function of the chain length (higher for octadecyl 18 o C than for tetradecyl chain 10 o C).

41 SAMs: Reactivity Issues Solvent Effect: Solvation of functional groups embedded in a monolayer and the local concentration of dissolved reagents near the surface may be different from the bulk. Steric Effect: Sterically demanding reactions or reactions requiring penetration of a reagent through a well-packed monolayer may be hindered at surfaces. On the other hand enforced favorable orientation or conformation of monolayer-embedded functional group could promote certain reactions. Electronic Effect: Functional groups adjacent to the reaction center in the monolayer may affect reactivity. Bulk vs. Monolayer pk1/2 Values