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1、NanochemistryIntroduction to the Nanoworld2024/7/30Lecture Outlinel lNanochemistry on Surfaces Surface Chemistry with the STMl lAtomic Scale Chemical Analysisl lPathways to molecular engineeringl lNanoChemistry in Catalysisl lComputing with Molecules2024/7/30LengthScalemicrometernanometerSolid State
2、 PhysicsDevice miniaturizationBiologySelf assembly of complexfunctional unitsChemistryAssembly, macromoleculesNanoscience& Technology“Natures Way”纳米科技是传统学科在纳米尺度上的交差与深入纳米科技是传统学科在纳米尺度上的交差与深入2024/7/30What is nanochemistry? Nanochemistry is the science of tools, technologies, and methodologies for chemi
3、cal synthesis, analysis, and biochemical diagnostics, performed in nanolitre to femtolitre domains. Nanochemistry is the use of synthetic chemistry to make nanoscale building blocks of desired shape, size, composition and surface structure, charge and functionality with an optional target to control
4、 self-assembly of these building blocks at various scale-lengths.2024/7/302024/7/30l The application of a bias voltage between the tip of a scanning probe microscope and a semiconductor surface modifies the bandstructure locally. At a certain bias threshold the redoxpotential of an electrochemical r
5、eaction is reached and thus a local surface reaction may get possible. l This idea is demonstrated on metaldichalcogenides (e.g. WSe2) under ambient conditions. At a tip material dependent bias threshold, the surface is etched locally. It is thought that this is a consequence of a water splitting re
6、action in an adsorbed water film, where nascent oxygen and hydrogen ions are formed. The oxygen modifies the surface towards soluble oxides. Thus nanostructuring can be achieved by applying potential to the tip of scanning probe microscopes. Due to the sharp threshold the bias voltage controls the m
7、odification of the surface and allows such switching between surface modification and surface mapping. 1. 表面纳米化学 - 局部化学反应局部化学反应2024/7/30Nanochemistry on Surfaces lDemonstration of the nanostructuring capabilities 2024/7/30Surface Chemistry with the STMlAdsorbed several C6H5I molecules resting on a t
8、erraced Cu (111) substrate at 20 K.lPried them apart into iodine and phenyl (C6H5) by injecting electrons from the STM tip (a).lUsed the tip to pull the iodine away (b and c) and draw the phenyl molecules closer together (d).lBonding the two by adding another shot of electrons (e).lTo prove that the
9、 phenyls were chemically joined, they pulled one, and the other followed (f).The Ultimate Ullman ReactionPhysical Review Letters 85 (2000) 27772024/7/30ExperimentslThe experiments were performed with a homebuilt UHV-STM operated at 20 K using electrochemically etched W tips. The Cu(111) surface was
10、cleaned by cycles of sputtering with Ne ions and annealing up to 800 K. The iodobenzene (Aldrich 98%) was first purified by several freeze-pump-thaw cycles with liquid nitrogen and then small amounts were dosed onto a cooled Cu(111) sample through an aperture in the radiation shield of the STM.lThe
11、energy transfer from a single electron causes the breaking of the C-I bond. It is not possible to break the C-H and C-C bonds with a single electron process at this voltage2024/7/30 Positioning the STM tip right above the molecule at fixed height and switching the sample bias to 1.5 V for several se
12、conds. Thereby electrons of up to 1.5 eV are injected into the molecule. Association: the bias was raised to 500 mV for 10 s It is not possible to break the C-H and C-C bonds with a single electron process at this voltage, especially as their bond energies are about 2 and 3 times higher than the C-I
13、 bond.Towards Single Molecule Engineering2024/7/30Atomic Scale Bond Breaking & Nanochemistry(a e) C6H5I C6H5 + I, (f) 2C6H5 C12H10S.-W. Hla, L. Bartels, G. Meyer, &Karl-Heinz Rieder, PRL 85(2000)2777The shortestachievable distance between the centers of two phenylsis 3.9 6 , as determined from the S
14、TM images.2024/7/30E.T. Foley, A.F. Kam, J.W. Lyding & P.H. Avouris, PRL 80 (1998)1336STM induced H desorption from Si(100)Hydrogen is not only a prototype absorbate system, but it isused extensively to chemically and electrically passivatesurface and interface dangling bonds.Be attributed to the el
15、ectronic excitation of the Si-H Bond.2024/7/30Atomic EngineeringScientific American: December 1999 MIX-AND-MATCH molecule: Atomic engineers eventually hope to create molecules from scratch, adding atoms exactly as needed to perform specific functions. This molecule, with 18 cesium and 18 iodine atom
16、s, was built-one atom at a time-with a STMA carbon nanotube has been transformed into a writing implement. Using an atomic force microscope with a nanotube tip, researchers at Stanford University removed hydrogen atoms from the top of a silicon base. The exposed silicon oxidized, leaving behind a vi
17、sible tracing.2024/7/30The Art of Atom Manipulation: from IBM to Quantum Corral and Quantum Mirage Fe/Cu(111) M.F. Crommie, C.P. Lutz, D.M. EiglerScience 262 (1993) 218 Co/Cu(111) H.C. Monoharan, C.P. Lutz, D.M. EiglerNature 403 (2000) 512 Xe/Ni(111) D.M. EiglerE.K. SchweizerNature 344(1990) 5242024
18、/7/302. 纳米尺度的化学分析纳米尺度的化学分析2024/7/30Atomic Scale Chemical Analysis (a) STM image (b) vibrational pectrum of single molecules on Cu(100) at 8kB.C. Stipe, M.A. Razaei, & W. Ho, PRL 82 (1999)1724(a) STM image (b) C-D streching image H-C=C-D(c) STM image (d) C-D streching image D-C=C-Hvibrational d2I/dV2
19、 image (b) at 269 mVThe microscope were cooled to 8 K for the experiments.Vibrational excitation of the molecule occurs when tunneling electrons have enough energy to excite a quantized vibrational level. These harmonics are proportional to dI/dV.2024/7/30STM images of acetylene on Cu(100)2024/7/30R
20、eal-Space Identification of Intermolecular Bonding with Atomic Force MicroscopyJ. zhang et al., SCIENCE 342 （2013）6132024/7/303. 分子工程分子工程2024/7/30Pathways to molecular engineeringSingle Atom Manipulation -Xe-Ni(110) at 4 KD.M. Eigler, E.K. Schweizer. Positioning single atoms with a scanning tunnelin
21、g microscope. Nature 344, 524-526 (1990).1. Protein engineering - amino acid sequences that would fold into molecular machines2. Molecular self-assembly - designer molecules that would fit together to make a functional device3. Proximal probes- STMs, AFMs“Molecular gears”2024/7/30DNA- metal and semi
22、conductor nanoparticles l用DNA-基的化学单层和DNA优异的分子识别能力来促成金属和半导体胶体纳米粒子有序化。With this strategy, we have learned how to assemble colloidal Au and CdS particles into well-defined aggregate structures in which the optical, electrical, and mechanical properties can be systematically controlled through choice of
23、 oligonucleotide sequence and length as well as colloidal composition and size. This strategy already has led to the development of a new ultrasensitive and selective detection scheme for DNA (see last reference).l发展新的方法来构筑和评估二维分子基纳米结构。 lDesign of a new class of ligands that provide electrochemical
24、control over stoichiometric and catalytic properties of transition metals. lUsing hemilabile ligands and novel coordination chemistry principles to develop general strategies for preparing supra molecular cage and cylindrical structures (see illustration at top left). The host/guest properties and c
25、atalytic chemistry of these complexes are being evaluated (third reference).2024/7/302024/7/302024/7/3031 nm8 nm2024/7/304. 纳米催化2024/7/30NanoChemistry in Catalysis1. Size of mesoporous materials2. Shape and size selective3. Use of surfactants for example to control composite array structure4. Therma
26、lly stable5. Based on aluminosilicates but other chemicals may be used6. Wide range of functionalisation studies7. Acid sites are important2024/7/30High catalytic activity for CO oxidation of CoHigh catalytic activity for CO oxidation of Co3 3OO4 4nanoparticles in SiOnanoparticles in SiO2 2 nanocaps
27、ules nanocapsulesNan Yan et al., J. Mater. Chem. A, 2013, 1, 6376432024/7/30Reaction-Driven Restructuring of Rh-Pd and Pt-Pd Core-Shell Nanoparticleswww.sciencexpress.org / 9 October 2008 / Page 1 / 10.1126/science.1164170152 nm0.860.03, 1.0nm0.930.03The measured atomic fraction of Rh at surface0.52
28、0.03, 1.6 nmThe observedatomic fraction of Pd in these NPs is 0.840.03, 0.670.03,and 0.520.03 within the MFP distances of 0.7, 1.0, and 1.6 nm, respectively.Lawrence Berkeley National Laboratory, BerkeleyAl K X-rays at 1486.6 eV2024/7/30 X-ray photoelectron spectroscopy (XPS) apparatusx-ray photon e
29、nergies of 645 and 850 eV，1486.6 eV. The mean free paths (MFPs) of Rh3d and Pd3dphotoelectrons excited at these three x-ray energies areapproximately 0.7, 1.0, and 1.6 nm, respectively2024/7/305. 分子器件2024/7/3021st Century Electronics:Transistors at the nano/molecular scaleGateDrainSource100 nmTexas
30、Instruments2000 10 nm?2015 electron flow2024/7/30Computing with Molecules lMark A. Reed and James M. Tour, Computing with Molecules, Scientific American: June 2000 2024/7/30Chemistrynitroamine benzenethiol moleculeNO2NH22024/7/30Molecular Electronics:the marriage of electronics with chemistryMark Re
31、ed Group (Yale)electron flow2024/7/30From molecular structure to electronic functionNO2NH2NH2 onlyN02VoltageVoltageCurrentCurrentJ. Chen, et al., Yale2024/7/30From Theory to ExperimentVDIS2S1Contact m1Contact m2Ss Voltage (V) Current (nA) DithiolS. Datta, et al., Purdue2024/7/30 Consider a molecule
32、of phenyl dithiol sandwiched between two gold electrodes as shown in Fig.1. The molecular energy levels consist of a set of occupied levels separated by a gap from a set of unoccupied levels. At equilibrium, the Fermi energy is typically located in the gap between the highest occupied molecular orbi
33、tal (HOMO) and the lowest unoccupied molecular orbital (LUMO), but when a bias is applied, the Fermi energy in the right contact (m2) floats up by eV relative to the Fermi level in the left contact (m1). The molecule conducts when the bias is large enough that one or more of the molecular energy lev
34、els lie between m1 and m2.Create energy levels lie between contact 1 and 22024/7/30Gigascale Circuits3000100020000.10.30.20.40.5 0.0VDS (V)IDS (mA/mm)VG = 0VGT = 0.52024/7/30 Molecular MotorslThe moving part of ATPase(腺苷三磷酸酶 ) is a central protein shaft (or rotor, in electric-motor terms), less than
35、 12 nanometers in diameter, that rotates in response to electrochemical reactions with each of the molecules three proton channels (comparable to the electromagnets in the stator coil of an electric motor). lATP (adenosine triphosphate) is the fuel for the molecular motors motion. Energy becomes ava
36、ilable when atomic bonds between phosphate atoms are broken during hydrolysis, converting ATP into ADP (adenosine diphosphate). During hydrolysis, the shaft rotates in a counterclockwise direction, whereas it rotates clockwise during ATP synthesis from ADP.lWhen the scientists switched on their moto
37、r-by bathing it in a solution of ATP-the rotor spun for 40 minutes at 3 to 4 revolutions per second, (September issue of Nanotechnology).2024/7/30Nanomachines in MedicineMICROMACHINES like the ones envisioned here could someday serve as tiny mechanical doctors. These miniature devices would roam bet
38、ween the red cells of the bloodstream, seeking out and destroying harmful viruses (shown here as green geometric solids). The moving parts of the micromachines would be built around gears no bigger than a protein molecule.Waiting for Breakthroughs, by Gary Stix; Scientific American, April 1996.2024/7/30The end 谢谢 谢！谢！
