New Insights into CdS Quantum Dots in Zeolite−Y

Abstract

When dry Cd 2+-exchanged zeolites Y are exposed to dry H 2 S under a rigorously anhydrous condition, CdS quantum dots (QDs) are formed in the supercages of zeolite-Y regardless of the loading levels of CdS from 0.01% to 32% and regardless of the Si/Al ratio of zeolite-Y between 1.8 and 2.5. The absorptions with the maximums (λ max ) e 290 nm are assigned as those arising from isolated CdS QDs with the sizes smaller than or equal to the size of a supercage (1.3 nm); the absorptions with λ max between 290 and 380 nm are assigned as those arising from interconnected CdS QDs that were formed by the interconnection of isolated CdS QDs through the supercage windows; and the absorptions with λ max > 400 nm are assigned as those arising from mesosized (3-10 nm) CdS QDs residing in or on the surfaces of amorphous aluminosilicate. The H + ions alone, which are generated during the formation of CdS, do not destruct the zeolite-Y framework causing the formation of amorphous aluminosilicate. Instead, the water-induced agglomeration of isolated and interconnected CdS QDs to mesosized CdS QDs in the presence of H + ions leads to the destruction of the zeolite-Y framework. The size of the interconnected CdS QD which is formed by moisture adsorption increases as the loaded amount of CdS increases for a given zeolite and as the size of the zeolite host increases. The presence of a tetraethylammonium ion in each supercage not only gives rise to the formation of very small QDs within zeolites Y but also prevents the zeolite framework from destruction.

Facile Two‐Step Synthesis of All‐Inorganic Perovskite CsPbX3 (X = Cl, Br, and I) Zeolite‐Y Composite Phosphors for Potential Backlight Display Application

“…Nevertheless, we clearly observe fringes spaced by 14.0 Å, corresponding to the distance between (111) lattice planes in faujacite (JCPDF #00-043-0168). [61] Elemental mapping of the composite crystal of Figure 3a by means of energydispersive X-ray spectroscopy reveals that CsPbBr 3 is present throughout (Figure 3c,d; separate maps in Figure S2d-i in the Supporting Information). It is difficult to evaluate the domain size of these small perovskite crystallites from HRTEM, but those observables in Figure 3b appear to be a few nanometer long at least in one dimension.…”

“…To minimize electron-beam-induced damage of the fragile zeolite particles, the image had to be recorded in less than 10 s and at a low operating voltage of 120 kV. [52,61] Figure S2b,c (Supporting Information) shows cases of nearly spherical nanometer-sized CsPbBr 3 crystallites, but possibly residing on the surface of zeolite-Y. In addition, the images reveal fringes separated by 3.6 Å (Figure 3b), matching the (111) lattice distance of the CsPbBr 3 perovskite crystal structure.…”

Supramolecular Organization in Confined Nanospaces

“…In particular, the improvement of synthesis and characterization techniques [441][442][443][444][445] combined with insight from computational studies [446][447][448] fostered this decade's tremendous progress. [43,449] Common synthetic strategies for confined nanoclusters are vapor deposition of suitable precursors, [14,16] or "ship-in-abottle" [450,451] approaches allowing for the in-situ synthesis of compounds in a host matrix. In the latter case, the reactants are molecules and ions sufficiently small to penetrate inside the host nanochannels, leading to products too large to escape from the cavities.…”

Nonlinear Optical Zeolite Films for Second and Third Harmonic Generation

“…[28][29][30][31][32][33][34][35][36][37][38][39] However, their sensitivities have not yet reached the degree that is sufficient for practical applications. Zeolites are also excellent hosts for QDs [40][41][42][43][44][45][46][47][48][49][50][51] and have many advantages over glass and polymers due to the followings. The zeolite-encapsulated QDs are usually smaller than 1.5 nm, their sizes are highly uniform, and they exist very regularly within the crystalline hosts.…”