Pressure-Induced Multidimensional Assembly and Sintering of CuInS₂ Nanoparticles into Lamellar Nanosheets with Band Gap Narrowing

Abstract

Two-dimensional (2D) nanomaterials have fascinating structural, electrical, and optical properties, especially strong excitonic effects due to decreased dielectric screening. However, constructing 2D ultrathin nanomaterials, with the exception of layered materials, remains a challenge. Herein, we successfully realize oriented attachment on guiding one-dimensional chalcopyrite CuInS 2 nanocrystal (NC) formation and 2D assembly into lamellar nanosheets by applying pressure-driven sintering of zero-dimensional CuInS 2 nanoparticles (NPs). We discuss the atomic-level mechanism of such phenomena and illustrate a pressure-driven processing diagram that reveals the sintering process of NPs coordinated by pressure and structural transformation. Optical measurements exhibit that the band gap has a narrowing by 0.21 eV compared with the initial 2.03 eV upon decompression to ambient conditions. Our findings represent a significant step forward in gaining an in-depth understanding of the pressuredriven morphology engineering of nanomaterials and provide a promising strategy to prepare 2D NCs, thereby greatly increasing the choice of materials for various applications.

Pressure-stimulus-responsive behaviors of core–shell InP/ZnSe nanocrystals: remarkable piezochromic luminescence and structural assembly

“…To the best of our knowledge, this is the largest piezochromic PL tuning range in the visible light range for traditional inorganic semiconductor nanomaterials. 26,35,36 Simultaneously, an ultrabroad bandgap tunability range was observed from 1.99 eV (0 GPa) to 2.45 eV (approximately 14.2 GPa). In addition, in situ small-angle synchrotron X-ray scattering (SAXS) measurements and transmission electron microscopy (TEM) images demonstrated that core–shell InP/ZnSe NCs were sintered under high pressure, resulting in the formation of two-dimensional (2D) nanostructures.…”

“…19 Our previous reports have confirmed that InP/ZnS NCs exhibit remarkable piezochromic behavior, where the color changes from orange to green. 26 Compared with the 7.7% lattice mismatch rate between ZnS and InP, the lattice mismatch rate between ZnSe and InP is only 3.2%. 1 Thus, there is a narrow emission spectrum for InP/ ZnSe as compared to InP/ZnS, which ensures the luminescence purity of InP/ZnSe NCs and provides more pronounced color changes for piezochromic behavioral studies.…”

“…[22][23][24] These changes significantly influence their absorption and emission properties. [25][26][27][28][29] Such pressure-stimulus optically responsive characteristics provide powerful means for information acquisition in various applications, from pressure sensing and anticounterfeiting to optoelectronic memory. 29,30 Piezochromic luminescent materials have been mainly used in organic polymers and compounds containing organic molecules because they are unstable under ambient conditions.…”

Effects of Repetitive Pressure on the Photoluminescence of Bare and ZnS-Capped CuInS2 Quantum Dots: Implications for Nanoscale Stress Sensors

“…Quantum dots (QDs) are appealing nanoscale stress/strain sensing materials (SSMs) because of their small size, high photoluminescence (PL) intensity, and tunable band gap governed by the quantum confinement effect. − For example, the potential of QDs applied to detect the pressure induced by explosion, shock, or extreme conditions in experimental biology is enormous due to their GPa-level pressure-sensitive merits. − Moreover, QDs can also be employed for in situ stress/strain detection in highly heterogeneous materials because of their nanometer size . Based on the potential of QDs for stress/strain sensing, the PL responses of QDs related to external pressure under several loading conditions have been studied over the past few years.…”

Pressure Induced Assembly and Coalescence of Lead Chalcogenide Nanocrystals

“…Besides manipulating interatomic distances and inducing structural phase transitions at atomic scales, studies have shown that high pressure has the ability to tune interparticle distances in nanocrystal (NC) assemblies and induce their mesoscale phase transitions and morphological changes. To date, the pressure-induced NC assembly and coalescence process has been successfully applied for synthesis of 1–3D nanostructures for various metal or semiconductor NCs. − …”