The Status of SolidState Chemistry Societal Impact Nanoscience

The Status of Solid-State Chemistry: Societal Impact Nanoscience, Health, Energy, National Security, Technology, Environment Panelists: Bill Buhro (Wash. U. ) – panel chair Dan Giammar (Wash. U. ) – environment Jennifer Hollingsworth (LANL) – national defense and nanoscience Dave Johnson (U. of OR) – thermoelectrics and semiconductor tech. Art Nozik (NREL) – solar energy and nanoscience Xiaogang Peng (U. of AR) – nanoscience

Sony to Unveil First Blu-ray Laptop Tue May 16, 2006, 12: 30 AM ET Sony Corp will release the first laptop capable of playing, editing and recording next -generation, high-definition videos in the Bluray DVD format. • Blu-ray = 25/50 GB/disc • DVD = 4. 7/8. 5 GB/disc h Sony, which led the development of the Bluray format, said Tuesday the new VAIO AR TD Premium model will be available this summer for $3, 500. Besides the Blu-ray DVD drive, the entertainment-oriented notebook computer features a 17 -inch display, an integrated TV In-rich In. Ga. N QDs tuner, and Microsoft Corp. 's Windows Media Ga-rich In. Ga. N matrix Center Edition operating system. • Blu-ray = 405 -nm emission from nanostructured, phase-separated Inx. Ga 1 -x. N quantum wells

Societal Impact of Solid State Chemistry • Solid-state chemistry • Nanoscience • Semiconductor Technology • Nanoelectronics • Quantum-dot light-emitting devices • Energy • Environment • National Defense • Health

Societal Impact: Semiconductor Technology Cu - caused fundamental changes in processing Solid-state chemists needed: • More elements now used • Number increasing rapidly • New materials needed High-K dielectrics Low-K dielectrics Diffusion barriers Inorganic photoresists Nanostructured

The shrinking scale of microelectronics Chip data from Intel See also: D. Normile Science 2001 G. Moore • Moore’s Law: transistors per chip doubles every 1. 5 – 2. 0 years… • through shrinking feature sizes… • until photolithographic patterning reaches its minimum-size limit; when’s that? • What’s next?

1 D nanostructures for nanoelectronics C-nanotube logic gate (NOT gate, V inverter) Ph. Avouris et al. Nano Lett. 2001 Crossed-nanowire FET array (Si nanowires; “address decoder”) C. M. Lieber et al. Science 2003 • Current interest exists in C nanotubes and semiconductor nanowires for nanoelectronic interconnects and devices … • FETs, SETs, p-n diodes, rectifiers, logic circuits, etc. • Nanoelectronics by assembly of nanoscale components is in a proof-ofconcept stage

Jack Kilby: Tyranny-of-numbers problem • Currently, nanoelectronic devices are fabricated in a serial, one-at-time manner… • whereas a massively parallel approach for integration and interconnection is required • No clear strategy yet exists for the massively parallel integration of nanoelectronics • Lieber – Langmuir-Blodgett assembly, statistical interconnection • Until this problem is solved assembly-based nanoelectronics is just a dream US Patent 3, 138, 743 • Jack Kilby – Texas Instruments • Nobel Prize for Physics, 2000 • Co-inventor of the monolithic integrated circuit (1958) – became the Si microchip

Nanocrystals and Colloidal Quantum Nanostructures II-VI and III-V Semiconductor Nanocrystals Cd. E: JACS 2001, 2002 Nano. Lett 2001, 2006 Angew Chem 2002 Chem. Mater. 2003 In. P/As: Nano Lett 2002 Zn. E: Nano Lett 2004 Jana et al, JACS 2003 Synthesis: Performance, rational and green Oxide Semiconductor Noble Metal Nanocrystals Magnetic Oxide Nanocrystals Ag Jana et al. , Chem. Mater. 2004 Chen et al, JACS 2005

Highly Emissive and Green Quantum Dots (QDs) Similar Emission Color Range Zn. Se Cu-Zn. Se. Mn-Zn. Se Outstanding Stability Cu: Zn. Se 200 o. C Mn: Zn. Se 220 o. C • QD Photoluminescence quantum efficiencies 50 – 90%

QD Light-Emitting Devices Electroluminescence from QD devices (Bawendi, 2002) Note also social impact of Solid. State Chemistry in solid-state lighting (LEDs) and laser diodes Stimulated emission (lasing) from QDs (Klimov, Hollingsworth, Bawendi, 2000)

Societal Impact: Quantum Dots Build Knowledge-Based Industry http: //www. nn-labs. com Conference Presentations Highest quality • APS March Meeting, 2002 -2005 Broadest wavelength range • Narrow Gap Semiconductors, 2003 Large quantities Involve K-12, and Undergrad. Students

Societal Impact: Energy • Thermoelectrics • Fuel Cells – ordered intermetallic catalysts (Pt. Bi) • Solar-energy conversion (photovoltaics) • Solid-state inorganic • Si, Cu. In. Se 2 cells • Semiconductor liquidjunction cells • Nanostructured: • Dye-sensitized (Grätzel) cells • Hybrid semiconductororganic cells • Multiple Exciton Generation (MEG) in QDs

Societal Impact: Thermoelectric Materials Thermoelectrics have both cooling and power generation uses Currently used in small cooling applications and remote power generation (space probes) Potentially large impact if new materials with enhanced efficiency can be found Two challenges; Optimize electrical properties Minimize thermal conductivity

Societal Impact: Thermoelectric Materials Fundamental challenges: • parameters interrelated • Current models present synthetic challenges: • Phonon-glass/electroncrystal model • Complex unit cells • Nanostructured materials • Ag. Pb 10 Sb. Te 12 • ZT > 2 (> 700 K) • Kanatzidis (2004)

Projected Need for Carbon-Free Primary Power Hoffert et. al. Nature 395, 881, 1998; and Science 298, 981, 2002 Bottom Line: New “disruptive” energy technology is needed

PV Power Costs as Function of Module Efficiency and Cost From Martin Green min BOS Ultimate Thermodynamic limit at 1 sun Shockley. Queisser limit For PV or PEC to provide the full level of C-free energy required for electricity and fuel—solar power cost needs to be ~2 cents/k. Wh ($0. 40/Wp)

Consequences of Size Quantization in Semiconductor QDs § Dramatic variation of optical and electronic properties § Large blue shift of absorption edge § Discrete energy levels/structured absorption and photoluminescence spectra § Enhanced photoredox properties for photogenerated electrons and holes § PL blinking in single QDs § Slowed relaxation and cooling (~10 X) of photogenerated hot electrons and holes (excitons) § Enhanced Auger processes (including exciton multiplication) § Conversion of indirect § § § semiconductors to direct semiconductors or vice versa Greatly enhanced exciton absorption at 300 K Greatly enhanced oscillator strength per unit volume (absorption coefficient) Greatly enhanced non-linear optical properties Greatly modified pressure dependence of phase changes and direct to indirect transitions Efficient anti-Stokes luminescence

3 rd Generation Photon Conversion Valid Thermodynamic Approaches to Achieve Photon Conversion Efficiencies > 32% (Exceeds the Shockley-Queisser Limit at low cost) 1. 2. 3. 4. 5. Tandem Cells (exceed S-Q limit but very expensive) Hot Carrier Conversion a. Extract, collect, and utilize hot carriers b. Impact ionization/multiple exciton generation (MEG)* Intermediate Band Solar Cell Thermophotonic Solar Cells Down conversion and upconversion of incident photons (M. Green and P. Wuerfel) See: M. Green, “Third Generation Photovoltaics”. Springer, 2003 A. Marti and A. Luque, “Next Generaton Photovoltaics”, Inst. Of Physics Series in Optics and Optoelectronics, 2002 Red ≡ Nanostructures (quantum dots) can provide a path, and * indicates recent breakthrough

MEG and quantum efficiencies in QDs NREL LANL • Pb. Se and Pb. S QDs • Generation of 7 concurrent excitons – which is not the limit • Predict much higher solar-cell efficiencies if these carriers can be separated and collected

Configurations for QD and nanowire solar cells Nozik, 2005 • Zn. O-nanowire dyesensitized cell (P. Yang, 2005) • Enhance electron diffusion length by replacing nanoparticle film with oriented single-crystal wires

Environmental Impacts: Size Effects on Environmental Behavior Large Surface Area/Mass Benefits Interfacial Reactions (solid-water and solid-gas) Ti. O 2 ; Density = 4. 2 g/cm 3 – adsorption – oxidation-reduction – catalysis Nanoscale Size Affects Chemical Reactions – quantum effects on (photo)catalysis – altered surface regions dominant – enhanced apparent solubility Nanoscale Size Enables New Applications – transport solid reactants in subsurface (e. g. , groundwater) – incorporation in membranes – sensors for environmental systems Banfield and Zhang, 2001, in Nanoparticles and the Environment,

Environmental Impacts: Applications of Nanostructure Materials Treatment and Remediation – engineered reactors • adsorbents for water and exhaust gas treatment – higher capacity (mass basis) but not necessarily greater affinity • photocatalytic degradation of contaminants – in situ remediation • deliver of zero-valent iron nanoparticles to groundwater to reduce contaminants – transport requires surface-modifications for stability – hybrid inorganic-organic membranes • improve flux and inhibit fouling Pollution Prevention (Life-Cycle Analysis) – reduce material and energy inputs in manufacturing – minimize volume of waste stream Environmental Risk Assessment – enhanced surface reactions and transport may pose new risks – avoid past mistakes (e. g. , CFCs, DDT, tetraethyl lead) – early studies indicate few unusual risks Masciangioli and Zhang, 2003 Environmental Science & Technology

Environmental Impacts: Challenges and Opportunities Match the Scales of Reaction and Transport – access to reactive surfaces can be limited by diffusion • example: adsorbents must facilitate water flow and provide access to surface area – delivery of nanoparticles to environmental field sites • example: zero valent iron for reduction of chlorinated solvents and other contaminants – stabilization of nanoparticles to enhance transport can inhibit reactivity; deliver reactivity to optimal locations Elucidate Reaction Mechanisms in Environmental Systems – underlying mechanisms for presence or absence of size effects remain elusive • example: why do nanoparticles have lower adsorption capacities and affinities than largerscale materials? – integrated experimental evaluation of reactions, material characterization, and molecular simulation – aquatic and atmospheric environments are complex multi-component systems Dynamic Nature of Nanostructured Materials in Aqueous Systems – crystalline phase changes with time • phase transformations influenced by interfacial energetics – nanoparticle aggregation • aggregates may not exhibit chemical or physical nanoscale properties and • can inititiate phase transformation

National Security: Intelligence Community Utilizes Nanoscience • Intelligence Community requires new means for monitoring assets and collecting/ analyzing data Ø Optical/acoustic receivers Ø Chem/bio sensors Ø Micro power supplies Ø Enhanced computing Ø Stealth communication • CIA-sponsored Postdoctoral Research Fellowship Program turns, in part, to nanoscience: Ø Fluorescent Nano-Particles for High Efficiency, Portable Bio/Chem Sensors: using nanometal-enhanced fluorescence Ø Spectrally Adaptive Nanoscale IR Sensors: QD-based mid-IR sensors for monitoring chemical agent production facilities, identifying geographical terrain, etc. Ø Quantum Dot Stability and Emission Efficiency: Optical markers for tagging a variety of physical assets Ø High Frequency Applications of Carbon Nanotubes (from rf to microwave frequencies): Nanoscale antennas for wireless connection between a nanoscale device and a macroscopic one Ø Nano- to Micro-Scale Power Sources: Portable electronics, e. g. , distributed sensing and communications technology limited by the power source, requires new micro-fuel cells, micro-photovoltaic cells, or microthermoelectric cells. Ø Nanoscale Spectroscopy of Qubits for a Solid-State Quantum Computer: Searching databases and factoring large numbers (Qubit = a nanoscale object – e. g. , the charge on a quantum dot, the polarization of a photon, or the nuclear spin state of an individual atom)

Defense Community Sponsors Nanoscience Research • MIT charged by U. S. Army to create a 21 st century battlesuit that “combines hightech capabilities with light weight and comfort” (2002 $50 million contract) • Research areas: Ø Energy Absorbing Materials (polymers) Ø Mechanically Active Materials and Devices (adaptive/multifunctional; polymer+magnetic actuators) Ø Sensing and Counteraction (dendrimer+nanocrystal chem/bio sensors+neutralizers) Ø Biomaterials and Nanodevices for Soldier Medical Technology (sensing+auto delivery of medications, load-transfer+variableimpedence devices) Ø Processing and Characterization - The Nanofoundries (enabling fiber, microfluidics+ layer deposition technologies) Ø Modeling and Simulation of Materials and Processes (of new materials+processes) Ø Systems Design, Hardening, and Integration (intra-team+team-army communication) Institute for Soldier Nanotechnologies

Nanoscience Supports DOE Mission: National, Economic, and Energy Security • Five new nanoscience centers for the “synthesis, processing, fabrication, and analysis of materials at the nanoscale: ” Ø The Center for Integrated Nanotechnologies at Sandia and Los Alamos National Laboratories Ø Lawrence Berkeley National Laboratory's Molecular Foundry Ø The Center for Functional Nanomaterials at BNL Ø The Center for Nanophase Materials Sciences at Oak Ridge National Laboratory Ø The Center for Nanoscale Materials at Argonne National Lab • E. g. , Nanocrystal Quantum Dots find national-security relevant applications at LANL: High efficiency solar cells Solid state lighting Assets marking/detection

Societal Impact: Health Biological labeling and detection with QDs. Uses: • Immunofluorescent probes for Her 2 breast-cancer marker • In immunoassays microbial toxins • Labels in cancer-cell-motility studies • During surgery to map lymph nodes • Virus detection: • Respiratory Syncytial Virus (RSV) • D. W. Wright, Nano Lett. 2005 1 h QD RSV detection fast and sensitive: • QD detection in 1 h • Western blot: > 96 h • Real-time PCR: early response near detection limit 96 h

Societal Impact of Solid State Chemistry • Solid-state chemistry • Nanoscience • Semiconductor Technology • Nanoelectronics • Quantum-dot light-emitting devices • Energy • Environment • National Defense • Health