Nanomaterials and their Optical Applications

Transcription

1 Nanomaterials and their Optical Applications Winter Semester 2013 Lecture 05

2 Module enrolment & Exams 2 Do not forget: module enrolment ( within few weeks) Exam form: oral or written, it depends on the number of students Examinations date: Tuesday 11 of February h30 Website for Lecture Materials Labwork / HiWi position Send me your CV / transcript of record and motivations!

3 Topics oral presentation 3 Topics 1 Nanodiamonds 2 PALM & STORM 3 STED 4 Optical to plasmon tweezers 5 Optofluidics for Energy 6 Quantum dots and computing 7 Lotus Effects 8 Nanowire as biosensors 9 Molecura beam epitaxy and MOCVD for semiconductor nanowires growth 10 Blue laser diode 11 Upconversion nanoparticles 12 Solid-state nanopores 13 SPASER : surface plasmon laser? 14 Sensing with SNOM 15 Sensing with whispering gallery modes.

4 Oral presentation 4 15 minutes presentation + 3 minutes question Account for 40% of your grade You will be noted on the following criteria Quality of the slides: clear and comprehensive, references included Timing: no more than 15 minutes and not less either Oral expression: fluent Scientific content: Answer to questions: precise and short

5 Possible time for the presentations 5 Date Room Time Speaker Title of the talk IAP IAP IAP

6 Outline: Plasmonics 6 1. Plasmonics vs Electronics and Photonics a) Definitions: plasmon, polariton b) Surface plasmon polariton: Drude Model c) Localized surface plasmon: nanoparticles, nanorods, nanoshells d) Theoretical modelling : light scattering theory (Rayleigh and Mie) 2. Fabrication of Plasmonics nanostructures 3. Applications of plasmonics: Stained glass, Notre Dame de Paris, 1250

7 Why plasmonics? 7 The speed of photonics The size of electronics High transparency of dielectrics like optical fibre Data transport over long distances Very high data rate Nanoscale data storage Limited speed due to interconnect Delay times Brongersma, M.L. & Shalaev, V.M. The case for plasmonics. Science 328, (2010). To replace slow electronic with fast photonic devices

8 Definition of Plasmonics 8 Metallic nanostructures = the field of plasmonics Not the confinment of electrons or holes as in semiconductors dots but Electrodynamics effect Modification of the dielectric environment How does plasmonic material look like? Metallic thin film Metallic nanoparticle Metallic nanorod Metallic nanoshell Different point of view of SURFACE PLASMON: Lycurgus cup (British Museum, London, UK). Electrodynamic: surface wave like in radiowave propagation along the earth Optics: modes of an interface Solid-state physics: collective oscillations of electrons

9 Concept of polariton 9 Elementary excitations: Phonons (lattice vibrations) Plasmons (collective electron oscillations) Polaritons: Commonly called coupled state between an elementary excitation and a photon = light-matter interaction In metal: coupled state between a plasmon and a photon= plasmon polariton In ionic crystal : coupled state between a phonon and a photon = phonon polariton In semiconductor: coupled state between an electron-hole pair = exciton polariton plasmon polariton resonance positions in vaccum Bulk metal Metal surface Localized surface of a metal particle Some materials are taken from lectures located on L. Novotny s group website: rachel.grange@uni-jena.de Lecture 05

10 Bulk Plasmon 10 Lecture 05

11 Bulk Plasmon 11 Lecture 05

12 The dielectric constant 12 ω > ω p ε m 1 volume plasmon polariton ω < ω p ε m < 0 wavevector of light in the medium is imaginary no propagating electromagnetic modes in bulk

13 Drude model (1900) 13 The model, which is an application of kinetic theory, assumes that the microscopic behavior of electrons in a solid may be treated classically and looks much like a pinball machine, with a sea of constantly jittering electrons bouncing and re-bouncing off heavier, relatively immobile positive ions Dielectric constant: Strong frequency dependence meaning dispersion 1/γ is the relaxation time of 10 fs for noble metals For a non-lossy model γ = 0 The damping constant γ is related to the average collision time interactions with the lattice vibrations: electron-phonon scattering. rachel.grange@uni-jena.de Introduction to surface plasmon theory, J.-J. Greffet Lecture 05

14 Concept of polariton 14 plasmon polariton resonance positions in vaccum Bulk metal Metal surface

15 Surface Plasmon Polariton (SPP) 15 Special case when the charges are confined to the surface of a metal SPP only exist for TM (p) polarization rachel.grange@uni-jena.de Lecture 05

16 Plasmon 16 Lecture 05

17 Plasmon 17 Terahertz range : ( Hz), and the low frequency edge of the far-infrared light band, 3000 GHz ( Hz) rachel.grange@uni-jena.de Lecture 05

18 Plasmon = collective oscillations of electrons 18 n free electron per unit volume Gauss theorem: Newton equation: ON: Displacement of electrons which cancel the field inside the metal OFF: electrons inside the metal accelerated by the surface charges Plasma frequency for a film infinite surface oscillations For a nanosphere Oscillations due to an electric field caused by all the electrons

19 Non lossy Drude model (1900) 19 Semi-infinite geometry: Energy and momentum must be conserved : light cannot be coupled directly. Finite geometry: Momentum conservation is possible when light is coupled to the localized plasmon excitations of a small metal particle = optical antennas resonances

20 Coupling of light into surface plasmon is then tricky 20

21 From bulk to surface plasmons 21 plasmon polariton resonance positions in vaccum Bulk metal Metal surface Localized surface of a metal particle Surface Plasmon polariton SPP are 2D, dispersive EM waves propagating at the interface conductor-dielectric Localized surface plasmon LSP are non-propagating excitations of the conduction electrons of a metallic nanostructure coupled to an EM field.

22 From bulk to surface plasmons 22 plasmon polariton resonance positions in vaccum Localized surface of a metal particle The curved surface of the nanostructure allows the excitation of the LSP by 3D light The resonance falls into the visible region for Au and Ag nanoparticles Localized surface plasmon LSP are non-propagating excitations of the conduction electrons of a metallic nanostructure coupled to an EM field.

23 23

24 Localized surface plasmon in nanoparticles 24 No wavevector or special geometry, but absorption of light with the right plasmon band 1. Spheres Absorption within a narrow wavelength range The maximum of absorption depends on the size, the shape of the nanoparticles and the surrounding medium Small shift for particle smaller than 25 nm, red shift for bigger nanoparticles J. a Fan, C. Wu, K. Bao, J. Bao, R. Bardhan, N. J. Halas, V. N. Manoharan, P. Nordlander, G. Shvets, and F. Capasso, Self-assembled plasmonic nanoparticle clusters., Science, vol. 328, no. 5982, pp , May 2010.

25 Absorption & Scattering 25 Light passing through a typical 30nm spherical silver (Ag) colloid appears yellow-green due to the fact that silver particles of this size absorb light in the violet-blue region. Spherical gold (Au) nanoparticle colloids of similar sizes appear red, absorbing light maximally in the green region (Stockman Physics Today 2011). Extinction = absorption + scattering but scattering dominate for small particle Ag Au 400 nm (blue) 530nm (green) Wavelength Dark field image : only the light that is scattered Direct light image : the resonant color is absorbed, thus the rest is transmitted

26 Absorption & Scattering 26 A famous example is the Lycurgus cup (Roman empire, 4 th century AD)f green color when observing in reflecting light it shines in red in transmitting light conditions Dark field image : only the light that is scattered Direct light image : the resonant color is absorbed, thus the rest is transmitted

27 Localized surface plasmon in nanoparticles Spheres From classical electrodynamic: resonance condition Polarizability of a sphere: εr = -2, true in the visible range for noble metal Microscopic view: 1 atom Take the simplest atom: hydrogen Macroscopic view: N atoms You end up with a dipole moment Put it into an electric field p = α E where α is the answer of the atom to electric field the macroscopic dipole moment (per unit volume) is called the POLARIZATION : P = χε E 1 0 Electric susceptibility is a measure of how easily a dielectric material can be polarized = εr -1

28 Localized surface plasmon in nanoparticles Wires, rods or rices Prolate spheroid a, b as axis εr = -2 (wavelength of 400 nm) to =-21.5 (wavelength of 700 nm) Two plasmon bands for nanorods: long and short axis Transverse mode is close to nanoparticles and longitudinal mode is red shifted

29 Localized surface plasmon in nanoparticles 29 No wavevector or special geometry, but absorption of light with the right plasmon band 2. Wires, rods or rices Two plasmon bands for nanorods: long and short axis Transverse mode is close to nanoparticles and longitudinal mode is red shifted

30 Localized surface plasmon in nanoparticles Nanoshell 60 nm core radius 20 to 5 nm shell thickness For a constant core, a thinner shell shift the plasmon resonance to the red For a constant core/shell ratio, small particles predominantly aborbs light and big particles scattered light. Over the dipole limit, multiple plasmon resonance occurs A broad spectral region is covered

31 Type of nanoantennas 31

32 Theoretical models to calculate the radiated field 32 Dipole approximation (or quasi-static) Mie scattering

33 Light Scattering and Absorption Theory 33 Extinction cross-section (cm 2 ) = absorption cs + sctattering cs 1. Dipole approximation (or quasi-static) particle much smaller than the wavelength σ scat σ abs total scattered or removed energy rate

34 Light Scattering and Absorption Theory Mie scattering Maxwell's equations are solved in spherical co-ordinates through separation of variables The incident plane wave is expanded in Legendre polynomials so the solutions inside and outside the sphere can be matched at the boundary Bessel and Hankel functions are solution are also used in the complex expression for simplification Legendre polynomials Bessel and Hankel functions

35 Concept of polariton 35 plasmon polariton resonance positions in vaccum Bulk metal Metal surface Localized surface of a metal particle

36 Outline: Plasmonics Fabrication of Plasmonics nanostructures Chemical synthesis Single nanoparticles Self assembly of nanoparticles Nanofabrication 3. Applications of plasmonics: Field enhancement by plasmon coupling Optical antennas Field enhanced vibrational spectroscopy Nano-tools for medicine Stained glass, Notre Dame de Paris, 1250

37 Liquid chemical synthesis 37 Before the addition of the reducing agent, the gold is in solution in the Au +3 form. When the reducing agent is added, gold atoms are formed in the solution, and their concentration rises rapidly until the solution exceeds saturation. Particles then form in a process called nucleation. The remaining dissolved gold atoms bind to the nucleation sites and growth occurs.

38 Liquid chemical synthesis 38 Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion. Turkevich method hot chlorauric acid with small amounts of sodium citrate solution The colloidal gold will form because the citrate ions act as both a reducing agent, and a capping agent. J. Turkevich, P. C. Stevenson, J. Hillier, "A study of the nucleation and growth processes in the synthesis of colloidal gold", Discuss. Faraday. Soc. 1951, 11, 55-75

39 Under different reactions conditions 39 Temperature : 120 to 190, transition between regular and irregular shapes Molar ratio between the materials Surfactants: organic compounds that are amphiphilic, meaning they contain both hydrophobic groups (their tails) and hydrophilic groups (their heads), lower the surface tension of a liquid, e. g. CTAB Precursors: chemical compound preceding another, like the GOLD SEEDS SCIENCE VOL DECEMBER 2002 p. 2177

40 Seed-mediated growth method 40 J. Phys. Chem. C 2010, 114,

41 Seed-mediated growth method 41 J. Phys. Chem. C 2010, 114,

42 Self-assembly method 42 Possible Forces Covalent : sharing a pair of electrons Ionic: transfer of electrons Metallic: strong bond Hydrogen: simplest covalent bond coordination bonds van der Waals : electrostatic forces casimir, π-π hydrophobic colloidal capillary forces

43 Self-assembly method At an interface: water-oil, and let one of the liquid evaporate 2. Molecular linkers J. Nanosci. Lett. 2012, 2: 10 Linking agent or linkers 1790 Analyst, 2009, 134,

44 Self-assembly method Molecular linkers J. Nanosci. Lett. 2012, 2: 10

45 Self-assembly method Molecular linkers J. Nanosci. Lett. 2012, 2: 10

46 Self-assembly method Biomediated self-assembly DNA, proteins, Viruses, Bacteria 4. Template directed self-assembly external forces that had been placed by design elements are used in forming the self-assembled structures J. Nanosci. Lett. 2012, 2: 10

47 Self-assembly method Stimuli responsive self-assembly Temperature, ph, light, solvent polarity ACS Nano, VOL. 4 NO

48 Nanofabrication: Direct writing method Focused ion beam milling: drill holes 2. Electron beam lithography direct-writing, 2D arrays Three-Dimensional Plasmon Rulers Nature Photonics, 5, (2011) SCIENCE, p VOL JUNE 2011 Low throughput, expensive, no large scale fabrication for industry

49 Nanofabrication: Templates Lithography Optical Lithography Diffraction limited More expensive for extreme UV

50 Nanofabrication: Templates Lithography Optical lithography: Plasmonic Nanolithography Plasmonic Nanolithography, Werayut Srituravanich,Nicholas Fang,Cheng Sun,Qi Luo, and, and Xiang Zhang, Nano Letters (6),

51 Nanofabrication: Templates Lithography 51 PDMS = polydimethylsiloxane Soft stamp, transparent, chip Biocompatible, Parallelism Simplicity, Flexibility J. Nanotechnol. 2011, 2,

52 Nanofabrication: Templates Lithography 52 Muhannad S. Bakir, Microelectronics Research Center Georgia Institute of Technology Lecture 05

53 Nanofabrication: Templates Lithography 53 Plasmonic waveguides metal V-grooves metal V-grooves Muhannad S. Bakir, Microelectronics Research Center Georgia Institute of Technology Lecture 05

54 Outline: Plasmonics Fabrication of Plasmonics nanostructures Chemical synthesis Single nanoparticles Self assembly of nanoparticles Nanofabrication 7. Applications of plasmonics: Field enhancement by plasmon coupling Optical antennas Field enhanced vibrational spectroscopy Nano-tools for medicine Stained glass, Notre Dame de Paris, 1250

55 Applications 1. Field enhancement by plasmon coupling 55 Interaction of a gold nanoparticle with a single molecule Plasmon resonance = local enhancement of the electric field, increased absorption of a molecule Non planar field distribution matching a molecular assembly Fluorescence lifetime is decreased thus the molecule returns sooner to its ground state S. Kühn, U. Håkanson, L. Rogobete, and V. Sandoghdar, Enhancement of Single-Molecule Fluorescence Using a Gold Nanoparticle as an Optical Nanoantenna, Physical Review Letters, vol. 97, no. 1, pp. 1-4, Jul

56 Applications: 2. Nanoantennas 56 Yagi-Uda antennas EM antenna = transducer between electromagnetic waves and electric currents Purpose: convert the energy of free propagating radiation to localized energy, and vice versa Antenna = transducer between free radiation and localized energy HF to UHF bands (about 3 MHz to 3 GHz) High gain: 10 db

57 Applications: 2. Nanoantennas 57 Characteristic dimensions of an antenna are of the order of the radiation wavelength Optical antennas on the order of nanometers For a cell phone: λ/100 (for a cell phone, λ ~ 30 cm, for optics 5 nm) Bow-tie antennas Yagi-Uda antennas Antennas for light, L. Novotny, Niek van Hulst, Nature Photonics 5, 83 90(2011)

58 Applications: 2. Nanoantennas 58 all parts of the antennas are multiple or fraction of the em radiation λ electrons in metals do not respond to the wavelength λ of the incident radiation but to an effective wavelength λ eff : Geometric constant: n1 n2 Plasma wavelength Metal not ideal (conductivity drops at the nanoscale) but carbon nanotubes or graphene 1. Photodetection and photovoltaics Increased absorption cross-section thus reduce the dimension, power consumption 2. Nanoimaging 3. Building blocks for data processing

59 Applications: 3. Surface enhanced Raman spectroscopy (SERS) 59 What is Raman scattering? Rayleigh = elastic scattering of a photon Raman = inelastic scattering of a photon

60 Applications: 3. Surface enhanced Raman spectroscopy (SERS) 60 What is Raman scattering? inelastic scattering of a photon

61 Applications: 3. Surface enhanced Raman spectroscopy (SERS) 61 What is Raman scattering? The Raman effect corresponds to the absorption and subsequent emission of a photon via an intermediate quantum state of a material. The intermediate state can be either a "real", or a virtual state. The Raman interaction leads to two possible outcomes: the material absorbs energy and the emitted photon has a lower energy than the absorbed photon. This outcome is labeled Stokes Raman scattering. the material loses energy and the emitted photon has a higher energy than the absorbed photon. This outcome is labeled anti-stokes Raman scattering.

62 Applications: 3. Surface enhanced Raman spectroscopy (SERS) 62 Raman scattering Fluorescence Infrared absorption Term paper for Physics 598 OS, Shan Jiang, University of Illinois Fluorescence : the incident light is completely absorbed and the system is transferred to an excited state from which it can go to various lower states only after a certain resonance Raman effect : can take place for any frequency of the incident light not a resonant effect

63 Applications: 3. Surface enhanced Raman spectroscopy (SERS) 63 Internal total reflection for the momentum conservation 15 orders of magnitude enhancement From an enhanced electric field = plasmon resonance Chemical enhancement too (factor of 200 on non metallic substrate)! Term paper for Physics 598 OS, Shan Jiang, University of Illinois

64 Applications: 4. Nanotools for medicine 64 Two combined effects: 1. Optical property: plasmon resonance 2. Thermal property : remaining energy HEAT Heat generated in four different colloidal gold nanoparticles of same volume and fixed intensity Metal particle = point-like sources of either light or heat

65 Applications: 4. Nanotools for medicine Temperature mapping Technique to locally probe the stationary temperature of the medium surrounding nano heat-sources including those formed by plasmonic nanostructures 2 March 2009 / Vol. 17, No. 5 / OPTICS EXPRESS 3291

66 Applications: 4. Nanotools for medicine Plasmonics biosensors Engineering nanosilver as an antibacterial, biosensor and bioimaging material, Current Opinion in Chemical Engineering Volume 1, Issue 1, October 2011, Pages 3 10

67 Applications: 4. Nanotools for medicine Plasmonics biosensors Binding of molecules between plasmon structures ACS Nano, 2009, 3 (5), pp

68 Applications: 4. Nanotools for medicine Plasmon-based optical trapping Nature Physics 3, (2007) Towards an integrated plasmonic platform for bio-analysis Low fluid volumes (less waste, lower reagents costs and less required sample Faster analysis and response times due to short diffusion distances, fast heating, high surface to volume ratios, small heat capacities. Compactness Massive parallelization, highthroughput Lower fabrication costs, Safer platform for chemical, radioactive or biological studies because of integration of functionality, smaller fluid volumes and stored energies Plasmon nano-optical tweezers, Nature Photonics, 5, 349, 2011

69 Applications: 4. nanotools for medicine Thermal therapy Kennedy et al. Gold-Nanoparticle- Mediated Thermal Therapies, Small, 2010

70 Outlook 70 J. a Fan, C. Wu, K. Bao, J. Bao, R. Bardhan, N. J. Halas, V. N. Manoharan, P. Nordlander, G. Shvets, and F. Capasso, Selfassembled plasmonic nanoparticle clusters., Science, vol. 328, no. 5982, pp , May S. Kühn, U. Håkanson, L. Rogobete, and V. Sandoghdar, Enhancement of Single-Molecule Fluorescence Using a Gold Nanoparticle as an Optical Nanoantenna, Physical Review Letters, vol. 97, no. 1, pp. 1-4, Jul Choose your topic and the date of the presentation Discuss it at the seminar next week H. Atwater, The promis of Plasmonics, Scientific Amercian, 2007 Brongersma, M.L. & Shalaev, V.M. The case for plasmonics. Science 328, (2010). D. W. Hahn, Light scattering theory, Notes, July 2009

71 Non lossy Drude model (1900) 71 Dispersion relation = solution of Maxwell equation with boundary conditions o Negative permittivity o SPP wavevector always larger than photon ->coupling of light is then tricky in planar structure to match the wave vector : Subwavelength scatterer Periodic grating Evanescent field o Large tunability of the dispersion but propagation losses Dispersion of photon Surface plasmon polariton