Laser‐Induced Carbonization of Natural Organic Precursors for Flexible Electronics

Abstract

replace toxic, expensive, or conflict materials with environmentally and socially more benign CNMs. Therefore, they are still considered promising candidates for a range of future applications in electronics, optoelectronics, or catalytic systems. Laser-fabrication methods have been investigated as fast, energy-saving, low-cost, and precise material processing techniques in both science and industry and even a new "age of photon-driven materials manufacturing" has been prognosed. [5] In industry, laser-processing techniques are mainly used for cutting, welding, cladding, or surface processing. [6] It allows for high-precision materials modifications with unprecedented accuracy, not only spatially but also temporally, which is of particular interest for the manufacturing of future small-scale electronic and photonic products. Also direct laser-induced materials synthesis has become an active field of research. For example, laser-induced ablation of graphite, discovered in the 1990s, is commonly used for the targeted synthesis of CNMs. [7,8] Highpower laser pulses hit a graphite target and create a carbon plasma above the surface, which reacts to crystalline nanocarbons. These laser-assisted synthesis methods differ from conventional thermal methods in the reaction timescales. Heat transfer within micro-or milliseconds allows for reactions different to conventional heating methods. Moreover, the precise spatial control with nano-to micrometer resolutions allows also for the fine patterning of materials. Generally, laser-patterning describes the micro-structuring of organic materials like polymers or plastics by evaporating material from their surface. [9] Directed 2D-film patterning by laser-induced material conversion evolved in the past years as a new synthetic fabrication method. [10] In particular, the uncomplicated access to laser-assisted patterning of graphene oxide and their relatives has given the field a significant push. [11-18] In most cases, graphene is produced by laser-induced reduction of graphene oxide (GO). Another famous laser-patternable material is polyimide (PI), which carbonizes at high temperatures. [19-21] Vast research efforts have been conducted on the characterization and application of laser-patterned GO or PI films. [22-24] However, the starting materials used are rather expensive and the modification of the resulting materials properties is limited since the starting materials are polymeric. Other materials could be used as precursor like paper or wood but without the possibility of choosing the initial substrate. [25] A precursor ink for carbon laser-patterning is developed using inexpensive, naturally abundant molecular compounds, namely citric acid and urea, and used to fine-print conductive carbon circuits on a flexible substrate. The precursor in the ink consists of organic nanoparticles obtained from the thermal treatment of citric acid and urea. This precursor is thoroughly characterized chemically and structurally. A simple recipe for the ink is then described for the creation...

In Situ Synthesis of Molybdenum Carbide Nanoparticles Incorporated into Laser‐Patterned Nitrogen‐Doped Carbon for Room Temperature VOC Sensing

“…The CNFA was prepared according to a previously published protocol. [ 15 ] In brief: citric acid and urea were annealed at 300 °C in a chamber oven for 2 h. After annealing, the black reaction product was dispersed in deionized H 2 O and stirred at 95 °C for 24 h. The dispersion was centrifuged to obtain a black precipitate and a brown supernatant. The supernatant was removed and the washing process was repeated four times.…”

Upgrading carbonaceous materials: Coal, tar, pitch, and beyond

“…Doping, in general, is a sensitive and crucial process for determining the band structure and conductivity of materials and can be deployed by lasing with additives that decompose to supply targeted dopants. 121 A next step would be to employ continuous manufacturing of HCM-based films with properties tailored for a given target application. Laser integrated roll-to-roll manufacturing is highly customizable for thin-film electronics, while a few recent works by Luong et al 5,120 show that flash heating can produce graphene solid products at gram scale.…”

On‐Chip Direct Laser Writing of PAN‐Based Carbon Supercapacitor Electrodes

“…[13] We and others have previously reported on laser-induced carbonization of PAN-based carbon-fibers and other carbonprecursors. [14][15][16][17][18] Conventional carbonization of PAN is performed in convection ovens at temperatures >1000 °C. [19,20] By contrast, laser-induced carbonization is beneficial, as heat is locally produced in the focus of the laser, preventing exposure to high temperatures in undesired areas.…”