Impact of Heating on Quantum Yield Quantum yield as a function of heating time. (Inset is heating times after 30 min.) Quantum yield as a function of time after 8 months of TIO- CdSe QDs.  Used by 9 th century artisans for pottery  Wires  Resistors  Switches  Transistors  Diodes  Capacitors  Chemical sensors 1  Optoelectronics 2  Photovoltaics 3  Fluorescent display devices 3  Light-mediated binding & release of biomolecules 3 Relative Quantum Yield Equation 5 Ф X = Quantum yield of QDs Ф ST = Quantum yield of standard η = Refractive index Grad = Slope of integrated intensities from the plot Reaction Mixture  Metal perchlorate: Cd(ClO 4 ) 2 ·H 2 O, Zn(ClO 4 ) 2 ·6H 2 O or Pb(ClO 4 ) 2 ·3H 2 O in Type 1 water.  Water-soluble thiols added in 2.4:1 thiol:metal ratio Procedure  The pH is adjusted to ≥ 11 using 1 M NaOH while stirring  Mixture was deaerated for ~30 minutes with N 2  Selenium source comes from either Al 2 Se 3 or NaHSe  Mixture was allowed to reflux over a period of time Impact of Structure on Quantum Yield Previous research explored quantum yields of CdSe quantum dots produced using Al 2 Se 3 (t HEAT = 0). Note: Different excitations were used QDs with ZnSe and CdSe core and different thiols (t HEAT = 0). Project Overview Water-Soluble, Monolayer-Protected QDs Monolayer-Protected Gold Nanoparticles A study of quantum yield in water–soluble, monolayer- protected quantum dots (QDs) was completed. The study examined the changes in quantum yield from the effects of heating, method of selenide addition, type of surrounding thiol, and material lifetime. Subsequent modifications of the QD surface were characterized using electrochemistry. Monolayer-protected gold nanoparticles were prepared using several different synthetic methods. The nanoparticles were characterized by UV-visible spectroscopy, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and mass spectrometry. Different thiols were used in the synthetic scheme in order to monitor differences in surface chemistry. KIM Synthesis 8  Add HAuCl 4 ·3H 2 O to a solution of Oct 4 NBr in toluene  Remove aqueous phase  Add 1-hexanethiol in 5:1 ratio thiol/gold ratio  Cool to 0°C, reduce with NaBH 4, and stir for 30 min  Collect black organic phase and wash 4x with Type 1 H 2 O  Remove solvent under reduced pressure  Add slowly DMSO to the MPC and allow to stand overnight  Collect black product  Add acetone to the flask to extract Au 25  Remove acetone with reduced pressure  Wash with acetonitrile and ethanol 1) J.W. Grate et al. Anal. Chem. 2003, 75, ) Kamat, P.V. J. Phys. Chem. B 2002, 106, ) Thomas, K.G.; Kamat, P.V. Acc. Chem. Res. 2003, 36, ) N.Gaponik et al. J. Phys. Chem. B 2002, 106, ) M.Grabolle et al. Anal. Chem. 2009, 81, ) M. Brust et al. J. Chem. Soc. Chem. Commun. 1995, ) M. S. Devadas et al. J. Phys. Chem. C, 2010, 114 (51), ) J. Kim et al. Langmuir. 2007, 23 (14), ) Z.Wu et al. Adv. Funct. Mater. 2011, 21, NSF CHE , Faculty Research Grants, Academic Initiatives, Conduff Scientific Grants, and Croom Beatty Chemistry Research Internship References/Acknowledgements DEVADAS Synthesis 7  Make solution of 3:1 thiol/HAuCl 4 ·3H 2 O ratio  Reduce with NaBH 4 and stir for 30 min  Obtain Au 25 by stepwise recrystallization with methanol  Centrifuge at 3000 rpm for 10 minutes  Wash with a 4:1 H 2 O:methanol mixture WU Synthesis 9  Dissolve HAuCl 4 ·3H 2 O in H 2 O, and cool to 0°C for 30 min  Add thiol to solution in a 4:1 ratio with gold and stir for 1.5 hr  Solution was reduced with NaBH 4 and stirred for >12 hours  Add methanol to reaction mixture  Collect precipitate by centrifugation (3800 rpm, 10 minutes)  Wash solid with MeOH/H 2 O and wash repeatedly w/ MeOH  Dry under reduced pressure for 4 days DPV of ferrocene modified TGL-CdSe QDs and ferrocene monomer. Surface Modification of QDs The Synthesis and Analysis of Metallic and Semiconducting Nanoparticles Water-Soluble Thiols Elizabeth M. Henry and Deon T. Miles The University of the South, Department of Chemistry, Sewanee, TN Applications Brust/Schiffrin MPC Synthesis 6 [Au(I)SR] n 0 ºC AuCl 4 – + RSH Au III Au I Au 0 3X 10X BH 4 – Small core of Au atoms that are stabilized by a monolayer of chemisorbed alkanethiolate ligands Monolayer-Protected NanoCluster (MPC) Synthetic Methods for Au 25 MPCS Spectral and Electrochemical Analysis DPV CYS-Au 25 MPC (Wu Synthesis) in 0.05 M tetra-n- butylammonium bromide/H 2 O using Pt WE, Pt CE UV-vis spectrum of MSA-Au 25 MPC (Wu Synthesis) Au 140 Synthesis of QDs 4 Image: Professor. Miles Elizabeth Mass Spectrum of CYS-Au 25 MPC (Wu Synthesis) Anticipated MW = 5173 Da Aliquots were collected based on visible change in color. Color change progresses towards red region.