Kodaira Tetsuya, Ikeda Takuji
National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
National Institute of Advanced Industrial Science and Technology (AIST), 4-2-1 Nigatake, Miyagino, Sendai, 983-8551, Japan.
Nanoscale. 2025 Jan 23;17(4):1959-1969. doi: 10.1039/d4nr04272g.
Cationic sodium (Na) clusters incorporated into a dehydrated Na-form LTA (Na-LTA) zeolite by the adsorption of Na atoms exhibit diamagnetism regardless of their adsorption amount. These clusters preferentially form in β-cages under the condition of dilute adsorption. In this study, photochromism was observed on the dilute Na-adsorbed Na-LTA, which showed a color change from yellow-green to dark blue-green at room temperature. This phenomenon resulted in dissociation of the diamagnetic Na clusters in β-cages upon light irradiation and thereby in the formation of two metastable Na clusters with symmetry in α-cages from the photoabsorption and electron spin resonance spectra. We also observed photochromism in a sample of insufficiently dehydrated Na-LTA with dilute Na adsorption-, the initial white color changed to blue, then blue-green and finally dark moss-green upon irradiation with UV light. This phenomenon consists of two steps. First, products in the β-cages, formed by the reaction of residual water molecules with adsorbed Na atoms, release electrons upon irradiation. The electrons transfer to the α-cages, forming the metastable Na clusters. Next, the diamagnetic Na clusters are formed in vacant β-cages by the thermal transfer of electrons from the Na clusters in the α-cages. Na clusters including multiple electrons were also formed in the α-cages by long exposure to UV light irradiation, which had a similar effect to increasing the adsorption amount of Na atoms onto the dehydrated Na-LTA. After termination of irradiation, the sample required a week to change its color to light yellow.
通过吸附钠原子而纳入脱水钠型LTA（Na-LTA）沸石中的阳离子钠（Na）簇，无论其吸附量如何，均表现出抗磁性。在稀吸附条件下，这些簇优先在β笼中形成。在本研究中，在稀钠吸附的Na-LTA上观察到光致变色现象，该样品在室温下呈现从黄绿色到深蓝绿色的颜色变化。这种现象导致光照时β笼中的抗磁性Na簇解离，从而根据光吸收和电子自旋共振光谱在α笼中形成两个具有对称性的亚稳Na簇。我们还在稀钠吸附的脱水不足的Na-LTA样品中观察到光致变色现象，用紫外光照射时，初始白色先变为蓝色，然后变为蓝绿色，最后变为深苔绿色。这种现象包括两个步骤。首先，由残留水分子与吸附的钠原子反应在β笼中形成的产物在光照时释放电子。电子转移到α笼中，形成亚稳Na簇。接下来，通过电子从α笼中的Na簇热转移，在空的β笼中形成抗磁性Na簇。通过长时间暴露于紫外光照射，α笼中也形成了包含多个电子的Na簇，这与增加钠原子在脱水Na-LTA上的吸附量具有相似的效果。照射终止后，样品需要一周时间才能将颜色变回浅黄色。
