In situ growth of laser-induced graphene micro-patterns on arbitrary substrates

Highly Efficient Laser Bidirectional Graphene Printing: Integration of Synthesis, Transfer and Patterning

Graphene has tremendous potential in future electronics due to its superior force, electrical, and thermal properties. However, the development of graphene devices is limited by its complex, high-cost, and low-efficiency preparation process. This study proposes a novel laser bidirectional graphene printing (LBGP) process for the large-scale preparation of patterned graphene films. In LBGP, a sandwich sample composed of a thermoplastic elastomer (TPE) substrate, carbon precursor powder, and a glass cover is irradiated by a nanosecond pulsed laser. The laser photothermal effect converts the carbon precursor into graphene, with partial graphene sheets deposited directly on the TPE substrate and the remaining transferred to the glass cover via a laser-induced plasma plume. This method simultaneously prepares two face-to-face graphene films in a single laser irradiation, integrating synthesis, transfer, and patterning. The resulting graphene patterns demonstrate good performance in flexible pressure sensing and Joule heating, showcasing high sensitivity (7.7 kPa-1), fast response (37 ms), and good cycling stability (2000 cycles) for sensors, and high heating rate (1 °C s-1) and long-term stability (3000 s) for heaters. It is believed that the simple, low-cost, and efficient LBGP process can promote the development of graphene electronics and laser manufacturing processes.

Smart and emerging point of care electrochemical sensors based on nanomaterials for SARS-CoV-2 virus detection: Towards designing a future rapid diagnostic tool

In the recent years, researchers from all over the world have become interested in the fabrication of advanced and innovative electrochemical and/or biosensors for respiratory virus detection with the use of nanotechnology. These fabricated sensors demonstrated a number of benefits, including precision, affordability, accessibility, and miniaturization which makes them a promising test method for point-of-care (PoC) screening for SARS-CoV-2 viral infection. In order to comprehend the principles of electrochemical sensing and the role of various types of sensing interfaces, we comprehensively explored the underlying principles of electroanalytical methods and terminologies related to it in this review. In addition, it is addressed how to fabricate electrochemical sensing devices incorporating nanomaterials as graphene, metal/metal oxides, metal organic frameworks (MOFs), MXenes, quantum dots, and polymers. We took an effort to carefully compile current developments, advantages, drawbacks, possible solutions in nanomaterials based electrochemical sensors.

Tuning oxygen-containing functional groups of graphene for supercapacitors with high stability

To investigate the relationship between the oxygen-containing functional groups of graphene and the stability of supercapacitors, reduced graphene oxide (rGO) containing different oxygenic functional groups was prepared by varying the reduction time of GO using hydrazine as the reducing agent. TEM, XRD, Raman, and XPS characterizations revealed that, as the reduction time increased, the sp² structure in the rGO sheet was restored and the obtained rGO had good crystallinity accompanied by removal of the oxygenic functional groups. The analysis of the content of the different functional groups also suggested that the reduction rate of the oxygenic functional group was C-O > C[double bond, length as m-dash]O > O-C[double bond, length as m-dash]O. The supercapacitive performance of rGO showed that the oxygenic functional groups contributed to some pseudocapacitance and resulted in a larger specific capacitance. At the same time, however, it is also accompanied by poorer rate performance and durability, which will be improved by removing the oxygenic functional groups by extending the reduction time. With an optimized reaction condition of a reduction time of 24 h, the obtained rGO exhibited excellent stability in floating tests at 3.0 V and 45 °C for 60 days. These findings pave the way for the development of high quality graphene materials for cost-effective and practical graphene supercapacitors.

Effect of Surface Treatment on Performance and Internal Stacking Mode of Electrohydrodynamic Printed Graphene and Its Microsupercapacitor

Microelectronic devices are developing rapidly in portability, wearability, and implantability. This puts forward an urgent requirement for the delicate deposition process of materials. Electrohydrodynamic printing has attracted academic and industrial attention in preparing ultrahigh-density microelectronic devices as a new noncontact, direct graphic, and low-loss thin film deposition process. In this work, a printed graphene with narrow line width is realized by combining the electrohydrodynamic printing and surface treatment. The line width of printed graphene on the hydrophobic treatment surface reduced from 80 to 28 μm. The resistivity decreased from 0.949 to 0.263 Ω·mm. Unexpectedly, hydrophobic treatment can effectively induce random stacking of electrohydrodynamic printed graphene, which avoids parallel stacking and agglomeration of graphene sheets. The performance of printed graphene is thus effectively improved. After optimization, a graphene planar supercapacitor with a printed line width of 28 μm is successfully obtained. Its capacitance can reach 5.39 mF/cm² at 50 mV/s, which is twice higher than that of the untreated devices. The device maintains 84.7% capacitance after 5000 cycles. This work provides a reference for preparing microelectronic devices by ultrahigh precision printing and a new direction for optimizing two-dimensional material properties through stacking adjustment.

Laser-induced photoexcited audible sound effect based on reticular 2-bromo-2-methylpropionic acid modified Fe3O4 nanoparticle aggregates

Reticular 2-bromo-2-methylpropionic acid (BMPA) modified Fe₃O₄ nanoparticle aggregates with novel acoustic properties, namely the photoexcited audible sound (PEAS) effect, were prepared by a laser-induced irradiation method. Their morphology was observed by Lorentz transmission electron microscopy. Their chemical structure, crystal composition, and magnetic properties were analyzed using infrared spectroscopy, X-ray diffraction, and a magnetic property measurement instrument, respectively. It is found that the nanoparticle aggregates appeared reticular, with the size of the BMPA modified Fe₃O₄ nanoparticles being 5.5 ± 0.4 nm. The saturation magnetization values of the BMPA modified Fe₃O₄ nanoparticles and associated aggregates were 59.99 and 63.51 emu g^-1, respectively. The reticular BMPA modified nanoparticle aggregates can produce strong PEAS signals under very weak laser irradiation with great stability and repeatability. The emitted PEAS signals possessed strong specificity, suitable decay time and a large amount of information under a very weak laser power and can be detected by the human ear without any special detection equipment. Subsequently, a heat transfer model was constructed for the simulation of the possible mechanism of the PEAS effect using COMSOL software. The simulation results showed that the aggregates have a fast heat transfer rate with the temperature increasing to 480 K in only 0.25 s and 600 K in 5 s, respectively, meeting the requirements of the vapor explosion mechanism. Therefore, we realized that the possible mechanism of the PEAS effect of the reticular BMPA modified Fe₃O₄ nanoparticle aggregates is laser-induced fast heat transfer and vapor explosion in situ, resulting in the observed audible sound phenomenon. This novel PEAS effect has potential for application in materials science, biomedical engineering and other fields.

Low-voltage-hysteresis aluminum-sulfur battery with covalently functionalized mesoporous graphene

A pyridyl-functionalized mesoporous graphene is developed to accommodate sulfur for Al-S batteries, which can significantly reduce the voltage hysteresis to ∼0.43 V. The reaction kinetics of the Al-S battery are accelerated by the catalyst-free carbon host, ascribed to both the mesoporous graphene structure and the covalently functionalized pyridyl groups.

Hybrid Carbon Nanotubes-Graphene Nanostructures: Modeling, Formation, Characterization

A technology for the formation and bonding with a substrate of hybrid carbon nanostructures from single-walled carbon nanotubes (SWCNT) and reduced graphene oxide (rGO) by laser radiation is proposed. Molecular dynamics modeling by the real-time time-dependent density functional tight-binding (TD-DFTB) method made it possible to reveal the mechanism of field emission centers formation in carbon nanostructures layers. Laser radiation stimulates the formation of graphene-nanotube covalent contacts and also induces a dipole moment of hybrid nanostructures, which ensures their orientation along the force lines of the radiation field. The main mechanical and emission characteristics of the formed hybrid nanostructures were determined. By Raman spectroscopy, the effect of laser radiation energy on the defectiveness of all types of layers formed from nanostructures was determined. Laser exposure increased the hardness of all samples more than twice. Maximum hardness was obtained for hybrid nanostructure with a buffer layer (bl) of rGO and the main layer of SWCNT-rGO(bl)-SWCNT and was 54.4 GPa. In addition, the adhesion of rGO to the substrate and electron transport between the substrate and rGO(bl)-SWCNT increased. The rGO(bl)-SWCNT cathode with an area of ~1 mm² showed a field emission current density of 562 mA/cm² and stability for 9 h at a current of 1 mA. The developed technology for the formation of hybrid nanostructures can be used both to create high-performance and stable field emission cathodes and in other applications where nanomaterials coating with good adhesion, strength, and electrical conductivity is required.