Keith Johnston Research Group Email: [email protected] Synthesis and Assembly of Nanocrystals with Supercritical Fluids –Assembly on unpatterned and patterned

Keith Johnston Research GroupEmail: [email protected]

• Synthesis and Assembly of Nanocrystals with Supercritical Fluids– Assembly on unpatterned and patterned substrates

– Si and Ge nanocrystals, nanowires (high T)

• Controlled release of nanoparticle pharmaceuticals (oral, depot, pulmonary)– Poorly water soluble drugs

– Peptides and proteins- (stability and release)

Keith Johnston

SCF- low viscosity and surf tensiontunableexcellent penetration and uniform filmshigh T crystallization

Fast Nanocrystal Evaporation w/o Dewetting

Lin et al. J. Phys. Chem. B, 2001.

Ag/FOMA/CO2

Control supersaturation during evaporation of liq. CO2

Shah et al. 2003

Keith Johnston

organized nanocrystals- metal and insulator behaviordisorganized- insulator only

Nanocrystal Assembly on Surfaces

1. Nanocoatings1. Nanocoatings 2. Photonic crystals2. Photonic crystals 3. Inverse opals3. Inverse opals

4. Patterned structures4. Patterned structures 5. Microwires5. Microwires 6. Nanodevices6. Nanodevices

Keith Johnston

1. moisture resistance, optical coatings, 2.-3. light guides, light filters, photonic micropolis (web) http://ab-initio.mit.edu/photons/4. lasers, switching devices5. 6. sensors, light emitters, biosensors,

A

B

• Significant blue-shift compared to bulk silicon band gap

• Discrete features in PLE spectra Room T quantum yield of 23%

• Size dependent luminescence

• UV, green light- displays/sensors

• Future- control size, yield, contamination, measure optoelectronic properties

Silicon PLE and PL (Ge also)

Keith Johnston

Room-temperature PL (solid lines, excitation energydenoted by solid arrows) and PLE (dashed lines, detection energydenoted by dashed arrows) spectra of Si nanocrystals. Photographic image of the luminescent Si nanocrystalsexcited at 320 nm in hexane: (A) 15 Å diameter Si nanocrystals and(B) 25-40 Å diameter nanocrystals. The smaller nanocrystals emit inthe near-UV and appear deep blue, whereas the larger particles appearblue-green.

High Dissolution Rates for Poorly Water Soluble Drug Nanoparticles

• Solution based nucleation– Antisolvent (2 processes)

– Evaporation

– freezing (2 processes)

• Control nucleation, growth and stabilization

• Animal tests- bioavailability

2 nm danazol domains mixed with PVP (spray freezing)

www.bioaqueous.com (Dow Chemical)

Nanostructured particles by rapid nucleation and surfactant stabilization

)( CCsh

DS

dt

dm

D rug m o le c ule s

Surfac tant dif fus io n

N uc le i

Agglo m e ratio n

W ate r phaseO rganic phase

D iffus io n

Stabilizatio n o f drug par tic le s by surfac tants

Interface orients surfactantHigh surface area, wettability, dissol. rates and bioavailabilityHigh drug:surfactant ratios

Destination of PhD Students

• DixonS. Dakota S. Mines

• Gupta Auburn• Balbuena U. S. Carol.• Luna-Barcenas

CINVESTAV Res. Inst.• Meredith Ga. Tech.• Yates U. Rochester• Da Rocha Wayne State U.• Lee U. S. California

• McFann Unilever• Condo 3M• Harrison TI• Mawson Union Carbide• Li* Cardinal

Health• Young Dow (Pharma)• Psathas Schering-

Plough• Rogers Dow (Pharma)• Sirard Lam Research

Documents

Keith Johnston Research Group Email: [email protected] Synthesis and Assembly of Nanocrystals with Supercritical Fluids –Assembly on unpatterned and patterned