STABILITY OF ZNO PARTICLES IN AQUEOUS SUSPENSIONS UNDER UV ILLUMINATION
STABILITY OF ZNO PARTICLES IN AQUEOUS SUSPENSIONS UNDER UV ILLUMINATION
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DOI：
10.1021/j100278a031
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发表时间：
1986-03-13
影响因子：
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通讯作者：
PRIETO, A
中科院分区：
文献类型：
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作者：
DOMENECH, J;PRIETO, A
结果在黑暗中，氧化锌在搅拌的水溶液(每30毫升水0.25克，pH 6.5)中有部分溶解，锌(II)的平衡浓度为0.05 mM(图1)。在光照条件下，锌离子浓度较高。锌离子浓度随着辐照时间的增加而增加(图1)。另一方面，在辐照后的悬浮液中检测到H202的形成。H_2O_2的产生量随照射时间的延长而增加，光照5分钟后达到0.05 mm左右的极限浓度。在无氧条件下，通过在悬浮液中鼓泡氮气，也可以检测到氧化锌的光分解。在此条件下，没有检测到H202的痕迹。在pH为10的条件下，氧化锌不发生光腐蚀。在这种情况下，确定了锌(II)的平衡浓度约为0.01 mM，这肯定对应于暗化学攻击。在酸性pH低于4.5的条件下，即使在黑暗中，氧化锌也完全溶解。实验结果表明，随着半导体质量的增加，溶液中锌离子的浓度增大。然而，半导体光解的初始速率d[Zn-(II)]/dR与悬浮液中氧化锌的质量无关。溶液中氧化还原物种的存在，原则上可以更有效地与半导体粒子的光生空穴反应，从而防止半导体的光氧化。考虑到这一点，我们研究了水相悬浮液中的氧化锌粒子在Cl-™、Br-™、I-™和CH3COO~+存在下的稳定性。图2显示了在浓度为0.1M的溶液中，当溶液中存在不同的阴离子时，锌(II)的浓度随照射时间的变化。在给定的照射时间下，氧化锌的稳定性
Results In the dark, some dissolution of ZnO in stirred aqueous sus-pensions (0.25 g per 30 mL of water, pH 6.5) was noted, yielding an equilibrium concentration of Zn (II) of 0.05 mM (Figure 1). A greater concentration of Zn (II) was found when the samples were illuminated. The Zn (II) concentration increases with in-creasing irradiation time (Figure 1). On the other hand, formation of H202 in the irradiated suspensions was detected. Thequantity of H202 produced increases with increasing irradiation time, attaining a limiting concentration of about 0.05 mM after 5 min of illumination. Photodecomposition of ZnO was also detected in the absence of oxygen, by bubbling nitrogen through the suspension. Under these conditions, no traces of H202 were detected. At pH 10, no photocorrosion of ZnO takes place. In this case, an equilibrium concentration of approximately 0.01 mM for Zn (II) was determined, which certainly corresponds to the dark chemical attack. At acid pH, lower than 4.5, the dissolution of ZnO is complete even in the dark. It was observed that the concentration of Zn (II) in solution augments with increasing mass of semiconductor. However, the initial rate of the semiconductor photodecomposition (d [Zn-(II)]/dr) is independent of the mass of ZnO in the suspension. The presence in solution of redox species which, in principle, can react more efficiently with the photogenerated holes of the semiconductor particlewill prevent the photooxidation of the semiconductor. With this in mind, the stability of ZnO particles in aqueous suspensions under illumination in the presence of Cl™, Br™, I™, and CH3COO~ ions was investigated. The concentration of Zn (II) as a function of irradiation timein the presence of the different anions in solution at a concentration of 0.1 M is shown in Figure 2. At a given irradiation time, the stability of ZnO