A simple and facile method for obtaining patterned graphene under ambient conditions on the surface of diverse materials ranging from renewable precursors such as food, cloth, paper, and cardboard to high-performance polymers like Kevlar or even on natural coal would be highly desirable. Here, we report a method of using multiple pulsed-laser scribing to convert a wide range of substrates into laser-induced graphene (LIG). With the increased versatility of the multiple lase process, highly conductive patterns can be achieved on the surface of a diverse number of substrates in ambient atmosphere. The use of a defocus method results in multiple lases in a single pass of the laser, further simplifying the procedure. This method can be implemented without increasing processing times when compared with laser induction of graphene on polyimide (Kapton) substrates as previously reported. In fact, any carbon precursor that can be converted into amorphous carbon can be converted into graphene using this multiple lase method. This may be a generally applicable technique for forming graphene on diverse substrates in applications such as flexible or even biodegradable and edible electronics.

Graphene based materials have profoundly impacted research in nanotechnology, and this has significantly advanced biomedical, electronics, energy, and environmental applications. Laser-induced graphene (LIG) is made photothermally and has enabled a rapid route for graphene layers on polyimide surfaces. However, polysulfone (PSU), poly(ether sulfone) (PES), and polyphenylsulfone (PPSU) are highly used in numerous applications including medical, energy, and water treatment and they are critical components of polymer membranes. Here we show LIG fabrication on PSU, PES, and PPSU resulting in conformal sulfur-doped porous graphene embedded in polymer dense films or porous substrates using reagent- and solvent-free methods in a single step. We demonstrate the applicability as flexible electrodes with enhanced electrocatalytic hydrogen peroxide generation, as antifouling surfaces and as antimicrobial hybrid membrane-LIG porous filters. The properties and surface morphology of the conductive PSU-, PES-, and PPSU-LIG could be modulated using variable laser duty cycles. The LIG electrodes showed enhanced hydrogen peroxide generation compared to LIG made on polyimide, and showed exceptional biofilm resistance and potent antimicrobial killing effects when treated with Pseudomonas aeruginosa and mixed bacterial culture. The hybrid PES-LIG membrane-electrode ensured complete elimination of bacterial viability in the permeate (6 log reduction), in a flow-through filtration mode at a water flux of ∼500 L m h (2.5 V) and at ∼22 000 L m h (20 V). Due to the widespread use of PSU, PES, and PPSU in modern society, these functional PSU-, PES-, and PPSU-LIG surfaces have great potential to be incorporated into biomedical, electronic, energy and environmental devices and technologies.

Prevention of fouling on surfaces is a major challenge that broadly impacts society. Water treatment technologies, hospital infrastructure, and seawater pipes exemplify surfaces that are susceptible to biofouling. Here we show that laser-induced graphene (LIG) printed on a polyimide film by irradiation with a CO infrared laser under ambient conditions is extremely biofilm resistant while as an electrode is strongly antibacterial. We investigated the antibacterial activity of the LIG surface using LIG powder in suspension or deposited on surfaces, and its activity depended on the particle size and oxygen content. Remarkably, the antimicrobial effects of the surface were greatly amplified when voltages in the range of 1.1-2.5 were applied in an electrode configuration in bacterial solutions. The bactericidal mechanism was directly observed using microscopy and fast photography, which showed a rapid bacterial movement toward the LIG surface and subsequent bacterial killing. In addition, electrochemical generation of HO was observed; however, the bacterial killing mechanism depended strongly on the physical and electrical contact of the bacterial cells to the surfaces. The anti-biofilm activity of the LIG surfaces and electrodes could lead to efficient protection of surfaces that are susceptible to biofouling in environmental applications by incorporating LIG onto the surfaces.

Laser-induced graphene (LIG) is a platform material for numerous applications. Despite its ease in synthesis, LIG’s potential for use in some applications is limited by its robustness on substrates. Here, using a simple infiltration method, we develop LIG composites (LIGCs) with physical properties that are engineered on various substrate materials. The physical properties include surface properties such as superhydrophobicity and antibiofouling; the LIGCs are useful in antibacterial applications and Joule-heating applications and as resistive memory device substrates.

The oxidation of DNA resulting from reactive oxygen species generated during aerobic respiration is a major cause of genetic damage that, if not repaired, can lead to mutations and potentially an increase in the incidence of cancer and aging. A major oxidation product generated in cells is 8-oxoguanine (oxoG), which is removed from the nucleotide pool by the enzymatic hydrolysis of 8-oxo-2′-deoxyguanosine triphosphate and from genomic DNA by 8-oxoguanine-DNA glycosylase. Finding and repairing oxoG in the midst of a large excess of unmodified DNA requires a combination of rapid scanning of the DNA for the lesion followed by specific excision of the damaged base. The repair of oxoG involves flipping the lesion out of the DNA stack and into the active site of the 8-oxoguanine-DNA glycosylase. This would suggest that thermodynamic stability, in terms of the rate for local denaturation, could play a role in lesion recognition. While prior X-ray crystal and NMR structures show that DNA with oxoG lesions appears virtually identical to the corresponding unmodified duplex, thermodynamic studies indicate that oxoG has a destabilizing influence. Our studies show that oxoG destabilizes DNA (ΔΔG of 2–8 kcal mol−1 over a 16–116 mM NaCl range) due to a significant reduction in the enthalpy term. The presence of oxoG has a profound effect on the level and nature of DNA hydration indicating that the environment around an oxoG•C is fundamentally different than that found at G•C. The temperature-dependent imino proton NMR spectrum of oxoG modified DNA confirms the destabilization of the oxoG•C pairing and those base pairs that are 5′ of the lesion. The instability of the oxoG modification is attributed to changes in the hydrophilicity of the base and its impact on major groove cation binding.

Graphene nanomaterials can feature both superb electrical conductivity and unique physical properties such as extreme surface wettability, which are potentially applicable for many purposes including water treatment. Laser-induced graphene (LIG) is an electrically conductive three-dimensional porous carbon material prepared by direct laser writing on various polymers in ambient conditions with a CO2 laser. Low-fouling LIG coatings in water technology have been reported; however, the mechanical strength and the separation properties of LIG-coated membranes are limited. Here, we show mechanically robust electrically conductive LIG–poly­(vinyl alcohol) (PVA) composite membranes with tailored separation properties suitable for ultrafiltration processes. PVA has outstanding chemical and physical stability with good film-forming properties and is a biocompatible and nontoxic polymer. Compared to LIG-coated filters, the PVA–LIG composite membrane filters exhibited up to 63% increased bovine serum albumin rejection and up to ∼99.9% bacterial rejection, which corresponded well to the measured molecular weight cutoff ∼90 kDa. Compared to LIG fabricated on a polymer membrane control, the composite membranes showed similar excellent antifouling properties including low protein adsorption, and the antibiofilm effects were more pronounced at lower PVA concentrations. Notably for the antibacterial capabilities, the LIG-supporting layer maintained its electrical conductivity and a selected LIG–PVA composite used as electrodes showed complete elimination of mixed bacterial culture viability and indicated that the potent antimicrobial killing effects were maintained in the composite. This work demonstrates that the use of LIG for practical industrial filtration applications is possible.

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Biofilm formation on surfaces in technology and the environment is a problem that can lead to high costs and can endanger human lives. Namely, infrastructure, medical implants, and food processing units, as well as oil refineries, ship hulls, and membrane technology for water treatment, are affected and underline the importance of identifying low fouling surfaces. Recently, surfaces coated with laser-induced graphene (LIG) were shown to strongly resist biofilm formation. Here we investigated the role of LIG texture and surface chemistry on biofilm formation and showed that the rough LIG surface texture correlated to enhanced biofilm inhibition. Fabrication conditions of LIG led to rough surfaces containing carbon nanofibers (250−750 nm diameter), and micropores (1−25 μm), which were shown to inhibit the attachment and proliferation of bacterial cells. In contrast, LIG surfaces with crushed nanofibers and covered micropores resisted biofilm formation less effectively. By oxidizing the LIG surface using oxygen plasma, we rendered the LIG more hydrophilic (contact angle was zero), but this chemical modification had negligible effects on the biofilm formation. After biofilm growth experiments, SEM images revealed that the morphology of Psudomonas aeruginosa cells adhered to poly(ether sulfone) substrate surfaces were rod-like in contrast to more spherical shaped cells on the LIG surfaces, which suggested distress. This study gives evidence of the importance of surface texture in antifouling applications and desirable design features such as nanofibers for effective antifouling LIG surfaces in energy, environmental, and biomedical fields.