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Spatially patterned dielectric materials are ubiquitous in electronic, photonic, and optoelectronic devices. These patterns are typically made by subtractive or additive approaches utilizing vapor-phase reagents. On the other hand, recent advances in solution-phase synthesis of oxide nanomaterials have unlocked a materials library with greater compositional, microstructural, and interfacial tunability. However, methods to pattern and integrate these nanomaterials in real-world devices are less established. In this work, we directly optically pattern oxide nanoparticles (NPs) by mixing them with photosensitive diazo-2-naphthol-4-sulfonic acid and irradiating with widely available 405 nm light. We demonstrate the direct optical lithography of ZrO2, TiO2, HfO2, and ITO NPs and investigate the chemical and physical changes responsible for this photoinduced decrease in solubility. Micron-thick layers of amorphous ZrO2 NPs were patterned with micron resolution and shown to allow 2π phase control of visible light. We also show multilayer patterning and use it to fabricate features with different thicknesses and distinct structural colors. Upon annealing at 400 °C, the deposited ZrO2 structures have excellent optical transparency across a wide wavelength range (0.3-10 μm), a high refractive index (n = 1.84 at 633 nm), and are optically smooth. We then fabricate diffractive optical elements, such as binary phase diffraction gratings, that show efficient diffractive behavior and good thermal stability. Different oxide NPs can also be mixed prior to patterning, providing a high level of material tunability. This work demonstrates a general patterning approach that harnesses the processability and diversity of colloidal oxide nanomaterials for use in photonic applications.

Rational structure design of carbon nanomaterials including modulation of interlayer spacing and control of order degree, has been adopted to improve their electrochemical properties for high performance lithium-ion batteries (LIBs). Here, we construct three-dimensional (3D) architectures composed of intercrossed 1D graphitized-carbon nanotubes (g-CNTs) via a simple template synthesis. The g-CNT with high aspect ratio, can be viewed as a thin graphitized carbon sheet rolled up into a large hollow nanotube (average diameter: 222 nm). Its thin tube wall (3–4 nm) with multi-layered structure and relatively large interlayer spacing (3.73 nm) in short range can conduct fast diffusion of lithium ions (Li+), accommodate increased volume expansion and facilitate reversible Li+ intercalation/extraction. Particularly, heteroatoms like N and O are also doped in C patterns and would provide more active insertion or adsorption sites. Thus, the porous architectures are enabled to serve as freestanding anodes for LIBs, exhibiting a high specific capacity of ∼624 mA h/g at current density of 100 mA/g, stable long-term cycle stability, as well as good rate capability. Due to their larger tube cavity and 3D structures, our g-CNT architectures are further exploited as conductive frameworks to dual-load MnO2 nanoflowers, and would speed up the development of next-generation rechargeable LIBs.

Direct optical lithography of functional inorganic nanomaterials (DOLFIN) is a photoresist-free method for high-resolution patterning of inorganic nanocrystals (NCs) that has been demonstrated using deep UV (DUV, 254 nm) photons. Here, we expand the versatility of DOLFIN by designing a series of photochemically active NC surface ligands for direct patterning using various photon energies including DUV, near-UV (i-line, 365 nm), blue (h-line, 405 nm), and visible (450 nm) light. We show that the exposure dose for DOLFIN can be ∼30 mJ/cm2, which is small compared to most commercial photopolymer resists. Patterned nanomaterials can serve as highly robust optical diffraction gratings. We also introduce a general approach for resist-free direct electron-beam lithography of functional inorganic nanomaterials (DELFIN) which enables all-inorganic NC patterns with feature size down to 30 nm, while preserving the optical and electronic properties of patterned NCs. The designed ligand chemistries and patterning techniques offer a versatile platform for nano- and micron-scale additive manufacturing, complementing the existing toolbox for device fabrication.

Thorough understanding of intergranular cracking mechanism is essential and important for developing superior layered cathodes. As a chemomechanical failure, crack's nucleation and evolution are affected mainly by cycling protocols, but it is still lacking direct and accurate observations. Herein, we develop an experimental protocol to visualize the cracking evolution process by tracing the same secondary particles. Further combining large area cross-sectional observations, we identify two distinctive cracking mechanisms due to different state of charge (SOC). At low SOC, chronic fatigue cracking is dominant. At high SOC, particle bursting makes intergranular cracks quickly saturated during the initial cycles, causing battery rapid performance decay in the beginning. We further validate that cracks are nucleated at the end of charging process and it is the discharging that leads to high density of cracks. Managing individual secondary particle below the critical SOC to prevent particle bursting is essential for achieving high cycling stability of Ni-rich layered cathodes.

Precise patterning of quantum dot (QD) layers is an important prerequisite for fabricating QD light-emitting diode (QLED) displays and other optoelectronic devices. However, conventional patterning methods cannot simultaneously meet the stringent requirements of resolution, throughput, and uniformity of the pattern profile while maintaining a high photoluminescence quantum yield (PLQY) of the patterned QD layers. Here, a specially designed nanocrystal ink is introduced, "photopatternable emissive nanocrystals" (PENs), which satisfies these requirements. Photoacid generators in the PEN inks allow photoresist-free, high-resolution optical patterning of QDs through photochemical reactions and in situ ligand exchange in QD films. Various fluorescence and electroluminescence patterns with a feature size down to ≈1.5 µm are demonstrated using red, green, and blue PEN inks. The patterned QD films maintain ≈75% of original PLQY and the electroluminescence characteristics of the patterned QLEDs are comparable to thopse of non-patterned control devices. The patterning mechanism is elucidated by in-depth investigation of the photochemical transformations of the photoacid generators and changes in the optical properties of the QDs at each patterning step. This advanced patterning method provides a new way for additive manufacturing of integrated optoelectronic devices using colloidal QDs.