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 PA particles with oxadiazole moieties 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 : µC/cm² PA particles : Charge density : 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”.