(1)血基質分子在二氧化鈦奈米粒子上的光化學(2)鋅二價席夫鹼錯合物的光物理

Abstract

被修飾於二氧化鈦奈米粒子上的血基質分子(iron(III)protoporphyrin)，經可見光激發後，可傳遞電子到二氧化鈦奈米粒子的傳導帶，此電子流可被外接安培計偵測。藉由連接外電路，電子流可被導入另一內含甲基藍(methylene blue)的電極，並將甲基藍還原成leucomethylene blue。可由其在265 nm處生成的吸收峰證明。電子傳遞後的血基質分子，在水中會氧化2,2'-azino-di-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS)成ABTS自由基。可由其在414 nm處生成的吸收峰證明。氧化的血基質在有機溶劑中，與guaiacol反應，會在350 nm處生成一吸收峰，但目前無法判斷產物。血基質分子修飾的二氧化鈦奈米粒子一旦和含有酸基的反應物接觸，血基質分子就會從二氧化鈦上脫落。 十個鋅二價席夫鹼錯合物受光激發後，會進行n到Pi*的躍遷，其吸收峰約在380 nm，並由單重激發態放光，其放光的位置約在460 nm。它們的放光量子產率很高，其中有些達到了0.5，生命期則約為5 ns，這都是從單重激發態放光的結果。這些錯合物在相對於標準氫電極(NHE)約1 V之處有不可逆的氧化電位。它們比席夫鹼容易氧化，差距約為200 mV。Hemin (iron(III) protoporphyrin) was convently attached to TiO2 nanoparticle through ester bond from propanic acid and the TiO2 surface hydroxyl group. Upon visible-light excitation, hemin injected an electron into the conduction band of TiO2 nanoparticle. The electron flow is evidenced by the reduction of methylene blue to leucomethylene blue (abs. max = 265 nm) through outer circuit to a separate compartment. The current can be measured by an amperometer. After electron transfer, oxidized hemin can oxidize ABTS (2,2’-azino-di-(3-ethylbenzthiazoline- 6-sulphonic acid)) to its radical (abs. max = 414 nm) in water. In organic solvent, oxidized hemin reacts with guaiacol to give unidentified products (abs. max = 350 nm). Hemin falls off from TiO2 while contacts with reagents containing acid groups. Ten Zinc(II) Schiff-base complexes exhibit n to Pi* transition around 380 nm, which leads to emission around 460 nm. High emission quantum yield (~ 0.5) and short lifetime (~ 5 ns) are typical for a singlet excited state emission. These complexes exhibit irreversible oxidation potential about 1.0 V verses NHE. All complexes are easier to be oxidized than free bases by about 200 mV.