Jaehan Jung

Humidity sensors are widely employed in diverse fields such as healthcare, agriculture, construction, and the storage of food and pharmaceuticals. In these areas, accurate and reliable humidity monitoring is essential to ensure appropriate environmental conditions and prevent material degradation or device malfunction. Recently, organic–inorganic hybrid materials have emerged as promising platforms for humidity sensing, as they integrate the complementary properties of both organic and inorganic components. Notably, hybrid materials with three-dimensional architectures have received growing attention owing to their large specific surface area, which affords enhanced reactivity and improved sensing performance. In this review, recent progress in humidity sensors based on organic–inorganic hybrid materials is summarized, with particular emphasis on three-dimensional hybrid architectures. The analysis suggests that 3D hybrid architectures can enhance sensing performance by improving water adsorption and charge transport pathways. Overall, the potential and significance of organic–inorganic hybrid architectures for the development of high-performance humidity sensors are critically discussed.

We report a facile one-pot synthetic strategy for producing CdSe/Cd_1−xZn_xS core/shell nanoplatelets (NPLs) with a chemical composition gradient, enabled by the introduction of halide ions, which promote the formation of a uniform-thickness shell. The use of a compositionally graded shell eliminates abrupt interfaces between the core and shell, leading to both high photoluminescence quantum yield and enhanced photostability. This graded shell architecture also induces significant Stokes shift, particularly due to heterogeneous growth of the NPL vertices, thereby effectively suppressing self-absorption. By varying the halide precursor concentration, both the emission wavelength and shell uniformity can be finely tuned, while the Auger recombination rate is significantly reduced with increasing shell thickness. Furthermore, we introduce an Al-doped ZnS outer shell that functions as a robust inorganic diffusion barrier, markedly enhancing resistance to photo-oxidation by effectively blocking oxygen and moisture penetration. Together, the halide-assisted graded shell and Al-doped outer passivation enable the direct synthesis of thick NPLs with optimized electronic structure and long-term stability, making them promising candidates for optoelectronic applications such as light-emitting diodes and laser devices.

Organic–inorganic hybrid nanocomposites comprising conjugated polymers in close contact with inorganic nanocrystals (NCs) were crafted via a catalyst-free click reaction. It highlights simple, robust, yet effective sodium azide treatment to effectively detach all of the insulating aliphatic ligands, including covalently bonded ones, from NC surfaces as well as to introduce covalently bonded azide functional sites, yielding azide-terminated NCs for click coupling. Subsequently, ethynyl-terminated organics (e.g., 1-octyne and ethynyl-terminated poly­(3-hexylthiophene) (–P3HT)) were tethered with azide-functionalized NCs via catalyst-free azide–alkyne cycloaddition, yielding semiconducting organic–inorganic nanocomposites (e.g., 1-octyne–CdSe/ZnS quantum dots and P3HT–CdSe tetrapod nanocomposites). The success of the click reaction was substantiated by Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopies. A significant reduction in the ethynyl proton signal after the click reaction and decreased azide absorption in FTIR spectra strongly support the anchoring of ethynyl-terminated organics (e.g., 1-octyne and –P3HT) with azide-functionalized NCs. This strategy for the preparation of functional organic-tethered nanocrystals enables the direct introduction of reactive azide sites onto bare NCs, eliminating the need for redundant organic bifunctional ligands or tedious multistep procedures, and may offer a promising route to functional nanocomposites for optoelectronic applications.

3D printing has garnered significant attention across academia and industry due to its capability to design and fabricate complex architectures. Applications such as those requiring intricate geometries or custom designs, including footwear, healthcare, energy storage, and electronics applications, greatly benefit from exploiting 3D printing processes. Despite the recent advancement of structural 3D printing, its use in functional devices remains limited, requiring the need for the development of functional materials suitable for 3D printing in device fabrication. In this review, we briefly introduce various 3D printing techniques, including material extrusion and vat polymerization, and highlight the recent advances in 3D printing for energy and biomedical devices. A summary of future perspectives in this area is also presented. By highlighting recent developments and addressing key challenges, this review aims to inspire future directions in the development of functional devices.

Photocurable hybrid organic–inorganic composites were prepared via surface modification and 3D-patterned structures were fabricated by utilizing a continuous roll-to-roll manufacturing strategy. The surfaces of nanocrystals were engineered with a bifunctional ligand that is a 2-carboxyethyl acrylate, which possesses a carboxylic acid moiety at one end and an acrylate functionality moiety at the other end, yielding acrylate-functionalized nanocrystals. Micro-scale 3D patterns (protruding pyramidal shapes with each side measuring 147 μm) were continuously manufactured at a speed of 2.5 m/min via UV curing with a soft engraved mold. The surface properties of the functionalized nanocrystals and their UV curing condition were explored with Fourier transform infrared spectroscopy. The morphology of the 3D film was measured using scanning electron microscopy. A pin-on-disk tribometer measurement revealed an improved interaction between the functionalized particles and resins.