Keith Johnston Research GroupEmail: kpj@che.utexas.edu

• 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)

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

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

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)

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