1. Surface characterization and electrochemical behavior of colloidal particles C. PEPIN, S.H FOULGER. E’ ox (V)E ox (V)HOMO (eV)E gap (eV)LUMO (eV) PA particles with carbazole moieties 1.155.55-5.553.5-2.05 PA particles with oxadiazole moieties 1.345.74-5.743.33-2.44 Stability and surface charge density Zeta potential: -electrokinetic potential in colloidal system related to the stability of the colloidal dispersion -calculated at the surface of the shear - calculated from the electrophoretic mobility of the particles Surface charge density: -determine the number of charge at the surface of the particles -use of conductometric titration -calculation of the surface charge density in µC/cm² PS particles : Charge density : 0.0225 µC/cm² PA particles : Charge density : 0.0218 µC/cm² Electrochemical behavior Cyclic Voltammetry: -important technique that can be used to determine the energy profile of an organic material  HOMO -cycling a potential across a sample and measuring the resulting current onset value of oxidation (E’ ox ) E ox = E’ ox +4.4  IP = -e.E ox =HOMO UV-VIS Spectroscopy: -use to determine optically the energy band gap -onset of absorption correspond to the energy needed to promote an electron from the HOMO to the LUMO Onset of absorption= Egap The energy profile of the material : Ionization potential Electron affinity Band gap energy oxidation  charge removal from the HOMO  Ionization potential reduction  charge removal from the LUMO  Electron affinity Study of the redox reactions Conclusion -study of the zeta potential of PA particles; the results show their stability over a range of pH from 9 to 2 - Determination of HOMO, LUMO and energy band gap for PA/AC and PA/AO particles Acknowledgements: Prof. S.H. Foulger, Foulger’s group (Michael, Ali, Ryan and Parul), Prof. K.Richardson and Prof. E. Fargin for the MILMI Master. Introduction “Particle-device” made of Poly(propargyl acrylate) with a hole transporter, an electron transporter and an emissive material colloid core h+h+ e-e- h+h+ e-e- h+h+ e-e- h+h+ e-e- hole transporter Oxadiazole molecule (AO) electron transporter Carbazole molecule (AC) Poly(propargyl acrylate) (PA) -understand the behavior of poly(propargyl acrylate) (PA) particles with surface-attached hole- and electron- transporting moieties -characterize their colloidal stability: Zeta potential and surface charge density -characterize their electrochemical behavior with the determination of the HOMO energy level, LUMO energy level and the energy band gap: Cyclic voltammetry and UV-VIS spectroscopy Objective -Ongoing interest in research focused on developing polymeric organic-light-emitting-devices (OLED) -OLEDs could present better properties such as the ease of device fabrication, low material cost, low environmental impact, facile synthesis routes and high rates of improvement in luminous efficiency -A hole transporting group and an electron transporting group were “clicked” on the surface of a polymer particle to make an individual “particle device”.