Effects from various initial molar ratios of aniline (AN), ammonium peroxydisulfate (APS) and HCl ( [AN]: [APS]: [HCl]) on the polymerization of AN were investigated. First, a scheme derived from a molecular point of view was proposed to distinguish formation mechanisms based on their initial conditions. Thereafter, by choosing a relatively low ratio of Keywords: aniline; formation mechanism; phenazine-like oligomers; polyaniline INTRODUCTION Polyaniline (PANI) is one of the most important conducting and semi-conducting polymers widely used in organic optoelectronic devices and has attracted considerable attention recently because of its tunable electrical conductivity, easy preparation from common chemicals and excellent thermal and environmental stabilities. 1,2 The electrical properties of PANI are sensitively dependent on its oxidation and protonation states, of which the emeraldine state (see Figure 1) with a wide range of electrical conductivity can be achieved by simple doping/dedoping chemistry based on acidic/basic reactions. 1-3 The conventional chemical oxidative polymerization of aniline (AN) is carried out in a strong acidic solution and initiated by adding an oxidant (such as ammonium peroxydisulfate, APS). 3 From a technical point of view, the above-mentioned preparation for PANI is a simple process, but the formation mechanism involves an intricate interplay of consecutive chemical and physical reactions. [3][4][5][6][7][8][9][10][11][12] To account for the formation of PANI, the following basic mechanisms were reported. The redox reaction of neutral ANs with APS produces AN radicals. 4 Under a neutral or alkaline condition, the mixed ortho-para coupling of AN radicals together with oxidative intramolecular cyclization forms AN oligomers with phenazine-like structures at the initial stage (see Figures 2a and b for phenazine and phenazine-like trimer). 9-13 The oxidation of AN and AN oligomers with APS both release protons, and the pH of the solution falls. [12][13][14][15][16][17][18][19][20] In a strong acidic environment, the formation of a para-coupled structure

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Reduced graphene oxide (rGO) sheets are synthesized and tunneling junction devices are fabricated with an aluminum oxide layer inserted in between electrodes and rGO sheets. Differential conductances, revealing density of states (DOS), of rGO sheets are measured in a wide voltage range. A difference in DOS of rGO sheets with different thickness is identified. For the single-layer rGO, the DOS shows a whole band with band edges in line with theoretical predictions, and gating DOS is used to estimate electron's Fermi velocity. Disorder effects on conductance and DOS of rGO sheets are explored and compared with each other. V

Various Cu-phthalocyanine (CuPc) films were grown from physical vapor deposition on top of indium-tinoxide glass substrates by controlling substrate temperature (T sub ), source temperature (T sou ), and growth time. From side-view SEM pictures, the growth rates for these CuPc films are estimated and can be categorized into three regions. From the Arrhenius plot of growth rate versus 1/T sub , the activation energy E A can be obtained. As T sou = 390 °C, for region (A) with T sub < 140 °C, the growth of CuPc films is dominated by the adhesion process with E A = 810 meV. For region (B) with 140 °C < T sub < 320 °C, the growth is then limited by the steric character associated with the organic molecular solids with E A = 740 meV. For region (C) with T sub > 320 °C, the re-evaporation of the CuPc adhered molecules from the interface becomes dominant.

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