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1、Nanochemistry,Introduction to the Nanoworld,2023/2/1,Lecture Outline,Nanochemistry on Surfaces Surface Chemistry with the STMAtomic Scale Chemical AnalysisPathways to molecular engineeringNanoChemistry in CatalysisComputing with Molecules,2023/2/1,纳米科技是传统学科在纳米尺度上的交差与深入,2023/2/1,What is nanochemistry
2、?,Nanochemistry is the science of tools,technologies,and methodologies for chemical 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 surf
3、ace structure,charge and functionality with an optional target to control self-assembly of these building blocks at various scale-lengths.,2023/2/1,2023/2/1,The application of a bias voltage between the tip of a scanning probe microscope and a semiconductor surface modifies the bandstructure locally
4、.At a certain bias threshold the redoxpotential of an electrochemical reaction is reached and thus a local surface reaction may get possible.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
5、 is thought that this is a consequence of a water splitting reaction 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.
6、Due to the sharp threshold the bias voltage controls the modification 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,2023/2/1,Nanochemistry on Surfaces,Demonstration of the nanostructuring capabilities,2023/2/1,Surface Chemistry with the ST
7、M,Adsorbed several C6H5I molecules resting on a terraced Cu(111)substrate at 20 K.Pried them apart into iodine and phenyl(C6H5)by injecting electrons from the STM tip(a).Used the tip to pull the iodine away(b and c)and draw the phenyl molecules closer together(d).Bonding the two by adding another sh
8、ot of electrons(e).To prove that the phenyls were chemically joined,they pulled one,and the other followed(f).,The Ultimate Ullman Reaction,Physical Review Letters 85(2000)2777,2023/2/1,Experiments,The experiments were performed with a homebuilt UHV-STM operated at 20 K using electrochemically etche
9、d W tips.The Cu(111)surface was 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 radia
10、tion shield of the STM.The 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 voltage,2023/2/1,Positioning the STM tip right above the molecule at fixed height and switching the sample bi
11、as to 1.5 V for several seconds.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 tim
12、es higher than the C-I bond.,Towards Single Molecule Engineering,2023/2/1,Atomic Scale Bond Breaking&Nanochemistry,(a e)C6H5I C6H5+I,(f)2C6H5 C12H10S.-W.Hla,L.Bartels,G.Meyer,&Karl-Heinz Rieder,PRL 85(2000)2777,The shortestachievable distance between the centers of two phenylsis 3.9 6,as determined
13、from the STM images.,2023/2/1,E.T.Foley,A.F.Kam,J.W.Lyding&P.H.Avouris,PRL 80(1998)1336,STM 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
14、 electronic excitation of the Si-H Bond.,2023/2/1,Atomic 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 atoms
15、,was built-one atom at a time-with a STM,A 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 visible
16、 tracing.,2023/2/1,The 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)524,2023/2/1,2.纳米尺度的化学分析,2023/2/
17、1,Atomic 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-H,vibrational d2I/dV2 image(b)at 269 mV,The microscope were cooled to
18、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.,2023/2/1,STM images of acetylene on Cu(100),2023/2/1,Real-Space Identification of Intermolecular Bondi
19、ng with Atomic Force Microscopy,J.zhang et al.,SCIENCE 342（2013）613,2023/2/1,3.分子工程,2023/2/1,Pathways to molecular engineering,Single Atom Manipulation-Xe-Ni(110)at 4 KD.M.Eigler,E.K.Schweizer.Positioning single atoms with a scanning tunneling microscope.Nature 344,524-526(1990).,1.Protein engineeri
20、ng-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”,2023/2/1,DNA-metal and semiconductor nanoparticles,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。W
21、ith 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 oligonucleotide sequence and length as well as colloidal composition an
22、d size.This strategy already has led to the development of a new ultrasensitive and selective detection scheme for DNA(see last reference).发展新的方法来构筑和评估二维分子基纳米结构。Design of a new class of ligands that provide electrochemical control over stoichiometric and catalytic properties of transition metals.Usi
23、ng 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 catalytic chemistry of these complexes are being evaluated(third reference).,2023/
24、2/1,2023/2/1,2023/2/1,31 nm8 nm,2023/2/1,4.纳米催化,2023/2/1,NanoChemistry in Catalysis,1.Size of mesoporous materials2.Shape and size selective3.Use of surfactants for example to control composite array structure4.Thermally stable5.Based on aluminosilicates but other chemicals may be used6.Wide range o
25、f functionalisation studies7.Acid sites are important,2023/2/1,High catalytic activity for CO oxidation of Co3O4nanoparticles in SiO2 nanocapsules,Nan Yan et al.,J.Mater.Chem.A,2013,1,637643,2023/2/1,Reaction-Driven Restructuring of Rh-Pd and Pt-Pd Core-Shell Nanoparticles,www.sciencexpress.org/9 Oc
26、tober 2008/Page 1/10.1126/science.1164170,152 nm,0.860.03,1.0nm,0.930.03,The measured atomic fraction of Rh at surface,0.520.03,1.6 nm,The 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 Natio
27、nal Laboratory,Berkeley,Al K X-rays at 1486.6 eV,2023/2/1,X-ray photoelectron spectroscopy(XPS)apparatus,x-ray photon energies 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,respectively,20
28、23/2/1,5.分子器件,2023/2/1,21st Century Electronics:Transistors at the nano/molecular scale,Gate,Drain,Source,100 nm,Texas Instruments2000,10 nm,?,2015,electron flow,2023/2/1,Computing with Molecules,Mark A.Reed and James M.Tour,Computing with Molecules,Scientific American:June 2000,2023/2/1,Chemistry,n
29、itroamine benzenethiol molecule,NO2,NH2,2023/2/1,Molecular Electronics:the marriage of electronics with chemistry,Mark Reed Group(Yale),electron flow,2023/2/1,From molecular structure to electronic function,NO2,NH2,NH2 only,N02,Voltage,Voltage,Current,Current,J.Chen,et al.,Yale,2023/2/1,From Theory
30、to Experiment,VD,I,S2,S1,Ss,Voltage(V),Current(nA),Dithiol,S.Datta,et al.,Purdue,2023/2/1,Consider a molecule 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.
31、At equilibrium,the Fermi energy is typically located in the gap between the highest occupied molecular orbital(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
32、).The molecule conducts when the bias is large enough that one or more of the molecular energy levels lie between m1 and m2.,Create energy levels lie between contact 1 and 2,2023/2/1,Gigascale Circuits,2023/2/1,Molecular Motors,The moving part of ATPase(腺苷三磷酸酶)is a central protein shaft(or rotor,in
33、electric-motor terms),less than 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).ATP(adenosine triphosphate)is the fuel for the molecular motors m
34、otion.Energy becomes available 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.When the scientists swit
35、ched on their motor-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).,2023/2/1,Nanomachines in Medicine,MICROMACHINES like the ones envisioned here could someday serve as tiny mechanical doctors.These miniature devi
36、ces would roam between 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.,2023/2/1,The end,谢 谢！,
