This study explores the optical properties of a close-packed monolayer composed of core/shell-alloyed CdSeS/ZnS quantum dots (QDs) of two different sizes and compositions. The monolayers were self-assembled in a stacked configuration at the water/air interface using Langmuir–Blodgett (LB) techniques. Under continuous 532 nm laser illumination on the red absorption edge of the blue-emitting smaller QDs (QD450), the red-emitting larger QDs (QD645) exhibited oscillatory temporal dynamics in their photoluminescence (PL), characterized by a pronounced blueshift in the emission peak wavelength and an abrupt decrease in peak intensity. Conversely, excitation by a 405 nm laser on the blue absorption edge induced a drastic redshift in the emission wavelength over time. These significant shifts in emission spectra are attributed to photon- and anisotropic-strain-assisted interlayer atom transfer. The findings provide new insights into strain-driven atomic rearrangements and their impact on the photophysical behavior of QD systems.

This study explores the self-assembly and optical properties of close-packed quantum dots (QDs) within Langmuir-Blodgett (LB) films, focusing on strain-driven interactions and potential inter-atom diffusion. Monolayers of yellow-emitting QD450 and red-emitting QD645 were subjected to continuous laser illumination, revealing significant inter-dot coupling effects and time-dependent photoluminescence (PL) dynamics. The exponential shifts in PL peak positions and broadening of emission spectra suggest strain-induced modulation of optical properties. Differences in Se/S mole ratios and anisotropic strain at the core/shell interfaces of the QDs are proposed to drive inter-atom diffusion, leading to localized structural and electronic changes. Additionally, nonlinear variations in band-gap energy under varying laser intensities highlight a complex interplay between strain, optical excitation, and material properties. These findings provide insights into strain-driven atomic rearrangements and their impact on the photophysical behavior of QD systems.

Fulgides are a class of organic compounds that have been extensively investigated because of their photochromic properties and the wide range of applications arising from them. Fulgimides, an important subclass of fulgides, contain a succinimide moiety in place of the succinic anhydride functionality found in fulgides. Isofulgimides are constitutional isomers of fulgimides in which the succinimide ring is replaced by a 5-iminodihydrofuran-2(3H)-one moiety. Although isofulgimides also exhibit photochromism, their synthesis and photochromic behavior have received considerably less attention than those of other fulgide derivatives. Reports on isofulgimides remain scarce, and crystallographic investigations are particularly limited. As part of our ongoing efforts to develop novel photochromic compounds, we synthesized a unique dimeric isofulgimide featuring an N–N single-bond linkage. Herein, we report its synthesis, crystal structure, and photochromic properties.

Isofulgimides, characterized by a 5-iminodihydrofuran-2(3H)-one moiety, constitute a subgroup of fulgide derivatives that have received comparatively limited attention despite their potential photochromic applications. Herein, we report the synthesis, crystal structure, and preliminary photochromic characterization of a structurally unique dimeric isofulgimide in which two conjugated systems are connected through a single N–N bond to form a more extensively conjugated system. The compound crystallizes in the centrosymmetric triclinic space group P-1, with disorder of the phenyl groups in close intermolecular contact and strong interactions, including strong π-π stacking. the molecular structure of each half of the dimer closely superimposes on that of the starting fulgide. In solution, irradiation with a low-power 405 nm laser produced a new broad absorption band centered at approximately 510 nm, indicating photoinduced isomerization. After irradiation was discontinued, this band gradually disappeared within approximately 42 min, demonstrating thermal recovery of the initial form. Because isofulgimides remain relatively uncommon and crystallographic studies of dimeric isofulgimides have not previously been reported, these findings provide new structural and preliminary photochemical insights into this understudied class of photochromic compounds.