I. Abstract of the Paper’s Core Research

This work employs dye-confined ZIF‑7 two‑dimensional luminescent nanosheets (MC blue, F green, RB red) as functional building blocks to formulate toluene‑based stable aerosol inks. It systematically investigates how the number of printing layers, multi‑ink overprinting, and 3D micro‑pillar fabrication modulate luminescent performance, and demonstrates three key functionalities: micro‑patterns, large‑area markings, and white‑light LEDs. The core findings are as follows:

Ultra-thin LMON-specific ink system tailored for aerosols

The two-dimensional MOF nanosheets exhibit a thickness of only 2–5 nm and micrometer-scale lateral dimensions; their 40 mg/mL toluene dispersion remains stably atomized without agglomeration. Low-temperature atomization, combined with a 70°C substrate, yields a consistent single-layer deposition thickness of 0.53 μm, with no nozzle clogging or material settling issues.

Precise control of the number of printed layers to regulate fluorescence intensity.

The film thickness increases linearly from a single layer up to 64 layers, with the emission intensity rising in tandem; however, excessive layering leads to molecular self-quenching. For red and green emitters, the emission intensity peaks at 32 layers, whereas the weakly emitting blue material shows no significant quenching effect. Meanwhile, variations in film thickness can induce slight shifts in the emission peak position.

Layered composite enables a full-color gamut and a white-light emission system.

Blue, green, and red inks are layered sequentially, with the color coordinates precisely calibrated by adjusting the proportion of each layer. A standard overprint configuration of 64 layers of blue, 32 layers of green, and 1 layer of red yields a standard white‑light film, which can be directly encapsulated with a 365 nm UV LED to produce a stable white‑light emitting diode.

Multiscale Digital Micro-Feature Fabrication

Maskless direct writing enables the fabrication of concentric color micro‑dot arrays ranging from 50 to 500 μm, as well as large‑scale, complex logo‑based anti‑counterfeiting patterns up to 2 cm in size. Under different excitation sources, these structures exhibit distinct color responses, enabling wavelength‑based encryption for anti‑counterfeiting.

Aerosol 3D Luminescent Micropillar Fabrication

A low‑focus‑ratio gas‑flow scheme suppresses structural collapse, enabling the fabrication of highly oriented luminescent micropillars with a height of 430 μm. The emitted fluorescence is concentrated along the pillar axis, thereby realizing a directional micro‑light‑emitting array.

II. Complete Preparation Procedure for Luminescent MOF Aerosols

Luminous LMON synthesis: ZIF-7 nanosheets were prepared via the NaCl templating method and subsequently coated with coumarin, fluorescein, and rhodamine B, yielding blue-, green-, and red-emitting nanosheets, respectively.

Ink formulation: Nanosheets were dispersed in toluene, and after ultrasonic treatment for 10 minutes, a stable aerosol ink with a concentration of 40 mg/mL was obtained.

Aerosol device commissioning: UA Max ultrasonic atomization, with a two-stage focusing ratio (initial 1, printing 5–9), nozzle diameter 150 μm, and substrate temperature maintained at 70°C.

Layered Printing Experiment: 1–64-layer gradient monochrome films, three-color overprint composite films, micron‑scale dot arrays, large‑size logos, and 3D micro‑columns;

Post-processing: air-dry at room temperature. , no high-temperature sintering is required, thereby preserving the MOF’s luminescent ligands;

Characterization: Fluorescence confocal microscopy, SEM three-dimensional profiling, spectrometer, and UV‑light‑source LED optoelectronic testing.

III. Five Core Process Advantages of Aerosol-Printed Luminescent MOFs

Compatible with two-dimensional ultrathin MOF nanosheets, addressing the issue of inkjet nozzle clogging in bulk MOFs.

Two-dimensional flaky particles are uniformly dispersed, enabling long-term continuous printing without agglomeration or clogging, thereby overcoming the traditional inkjet printing limitations on MOF particle size.

Maskless digital multi-scale patterning, integrated fabrication from microns to centimeters.

Without lithography or masking templates, it can both print optoelectronic microarrays at the hundred-micrometer scale and mass‑produce large‑area anti‑counterfeiting identifiers.

Layer-by-layer thickness control enables precise regulation of fluorescence intensity and emission color.

The number of printing stations directly determines the film thickness, eliminating the need to reformulate the ink; a single device enables continuous adjustment of patterns from low‑intensity luminescence to high‑brightness.

Multi-ink in-situ layered composite, one-step mixing of RGB tricolor emissive films.

Print red, green, and blue materials in alternating layers and zones—no pre‑mixing of composite pastes required—and enable rapid color‑light iteration with any desired blend ratio.

3D-oriented luminescent micropillars can be fabricated, with compatibility for both planar and three-dimensional architectures.

By regulating the gas‑flow focusing ratio and suppressing structural collapse, vertical light‑emitting microstructures are fabricated, enabling directional light output and compatibility with miniature optical components.

IV. Five Core Technological Innovations of This Study

Innovation 1: A complete process for direct aerosol printing of two-dimensional luminescent MOF nanosheets

Breaking through the limitations of conventional coating and inkjet processing, we have developed LMON‑specific atomized inks and a standardized library of printing parameters.

Innovative Two-Layer Structure – Fluorescence Quantitative Regulation Mechanism

The relationship between film thickness and both luminescence intensity and emission‑peak shift is fully elucidated, and an optimal window for the number of printing layers—free from self‑quenching—is identified.

Innovation: A New Paradigm of White-Light Emission Printing via Three-Color RGB Layered Superposition

By employing layered aerosol deposition to precisely tune the tri-color ratio, white-light-emitting thin films can be fabricated at low cost without requiring a single-component white-light MOF powder.

Innovative Fabrication of Encryption-Based Micro‑Anti‑Counterfeiting Patterns with Four-Wavelength Response

Multicolor micropatterns exhibit distinct colors under different ultraviolet wavelengths, enabling multi-level optical encryption for anti-counterfeiting identification.

Innovative 5‑gas‑controlled 3D luminescent micro‑pillar fabrication technology

Optimized a two-stage sheath‑gas/atomization‑gas flow scheme to address the collapse of the three-dimensional nanosheet architecture, thereby constructing axially oriented luminescent microarrays.

V. Current Industry Challenges and Corresponding Solutions

Challenge 1: Bulk MOF particles are large in size, making them prone to agglomeration during inkjet atomization, which can clog the nozzle.

✅ Utilizes ultra-thin 2–5 nm two-dimensional LMON nanosheets, enabling stable atomization in a toluene-based system and continuous printing without clogging.

Challenge 2: Spin coating can only deposit a uniform film across the entire substrate and cannot pattern color micro‑features in a localized manner.

✅ Aerosol-based digital spot deposition enables partitioned printing on a single substrate, creating independent red, green, and blue emissive regions.

Challenge 3: MOFs are thermally unstable, and lithography and high-temperature processes can degrade the luminescent ligands.

✅ Entire process carried out at room temperature, with no thermal treatment, ensuring no damage to the MOF framework or the fluorescent guest molecules.

Challenge 4: Traditional composite luminescent films require pre-mixing, with fixed ratios that are difficult to adjust.

✅ Layer-by-layer, step-by-step printing allows you to freely adjust the number of layers for each color and dynamically control the emission color coordinates in real time.

Challenge 5: Planar thin-film light emission lacks directional output, and micro-optical devices exhibit low efficiency.

✅ Aerosol-based 3D microcolumn fabrication enables directional fluorescence propagation along the column axis, enhancing the light extraction efficiency of miniature photonic devices.

VI. Future Diversified Industrial Application Scenarios

1 Micro LED pixel emissive layer

Micrometer-scale RGB aerosol printing for color-emitting layers, enabling low-cost fabrication of Mini/Micro LED display chips.

2 Multi-level optical anti-counterfeiting label

Product packaging and identification documents feature centimeter‑level encrypted logos that change color under multi‑wavelength UV light, enabling practical applications in high‑end anti‑counterfeiting.

3 Miniature White LED Chips

White-light MOF thin films directly printed on the surface of UV chips, small indicator lights, and miniature sensing light sources.

4 Biofluorescent Microfluidic Chip

Micrometer-scale partitioned light-emitting array for visualized detection of cells and trace biochemical markers.

5 Miniature Directional Light-Sensing Array

3D luminescent micropillars, miniature optical detectors, and the core functional layer for gas fluorescence sensing.

Image and Text Guide

• (a) : The printing height of the three LMON inks (F/MC/RB@Z7-NS) increases linearly with the number of layers (R² ≈ 0.998), with a maximum thickness of 32–34 μm and consistent layer heights of 0.53 ± 0.01 μm.
• (b) : F@Z7-NS Vertical height profile of wires at each layer—transitioning from a rectangular flat top to a peaked shape.
• (c,d) : Optical image/height map and SEM (corner and edge) of a 500×500 μm² square printed circuit board (4–64 layers).
• (e,f) : The line width decreases from 57 μm to 50 μm as the number of layers increases, while the overspray expands from nearly 0 to 95 μm; the surface roughness first increases and then gradually declines.

• (a–i) : Emission spectra of blue MC@Z7-NS (405 nm excitation), green F@Z7-NS (488 nm), and red RB@Z7-NS (543 nm) as a function of layer number (1–64), along with the corresponding fluorescence/optical microscopy images—patterns are clear, and the outlines become sharper with increasing layer count.
• (j) : The true emission colors of the 32-layer sample under ambient light and 254 nm UV illumination.
• (k) : Emission intensity varies with the number of layers—MC exhibits nearly linear brightening; in contrast, F and RB decrease after 32 layers (and at 64 layers), indicating the presence of Self-absorption/self-quenching threshold 。
• (l–n) : Normalized Gaussian fitting reveals F and RB to be at redshifts of 15±9 and 9±9 nm, respectively—increased layer thickness induces aggregation and reabsorption.

• (a,b) : Blue MC (32 layers) + Red RB (2 layers) → The emission spectrum exhibits blue (λmax 475 nm) and orange‑red (λmax 590 nm), with an average blue-to-red emission ratio of 1:3.
• (c,d) : Blue MC + Yellow F+RB (32 layers each) → Bright green pattern; the blue-to-yellow emission ratio of 1:3.3 achieves color mixing.
• (e–g) : On the 32-layer green F, red RB is added layer by layer—starting with a single red-dominant layer, and after four layers nearly all are red; the color progression from green to yellow to orange to deep orange-red is gradual, with color hue stabilizing after about eight layers.

• (a–d) : The blue MC and the yellow F+RB are printed as concentric squares—when the dimensions are close (300/120 μm), they appear green; when the dimensions are separated (500/120 μm), a blue square and a yellow dot are visible to the naked eye, and the emission spectra show independent emissions.
• (e–g) : Blue/green/red trichromatic 64:32:2 concentric square array—appears pale bluish-white to the naked eye; different excitation wavelengths (405/488/543 nm) can Dynamic Switch Different color components pave the way for miniaturized LEDs (100–200 μm).
• The printed line width reaches 40–50 μm and holds promise for scaling down to sub-100 μm Micro LEDs.

• 2 cm × 2 cm Oxford Laboratory logo—highly detailed elements such as text lines and gear intersections are all crisp and free of smudging.
• The multicolor process prevents color bleeding; the central gear features one layer of yellow ink over red ink, resulting in a brighter orange hue.
• Under UV light within the PET absorption range, the logo emits a uniform white glow—enabling information to be encrypted and decoded using specific wavelengths.

• (a–d) : Cylindrical microcolumn cross-sectional profile (maximum)   430 μm ), 543 nm–excited Z‑stack fluorescence images, FE‑SEM, and emission spectra.
• (e–h) : Photographs and FE-SEM images of microcolumn arrays at different heights under ambient light/UV illumination.
• Dynamic focus adjustment ratio (initial: 0.675 → final: 0.5) prevents collapse and enables continuous additive manufacturing; fluorescence is concentrated at the column’s apex and base‑bottom junctions, exhibiting Waveguide effect Directional emission characteristics.

• (a–c) : Sankeke MC+F+RB@Z7-NS single-layer coating, 365 nm UV LED (3.5×3.5 mm², 3.4 V) — upon illumination, it emits broad-spectrum white light in the 400–800 nm range.
• (d–f) : Blue/green/red are printed in layers at ratios of 64:32:1, 64:16:1, and 32:16:1, with CIE coordinates of   (0.30,0.38), (0.31,0.36), (0.32,0.39) — Emits white light visible to the naked eye, with adjustable warm white and cool white options.