Laser-scribed graphene for sensors: preparation, modification, applications, and future prospects

Sensors are widely used to acquire biological and environmental information for medical diagnosis, and health and environmental monitoring. Graphene is a promising new sensor material that has been widely used in sensor fabrication in recent years. Compared with many other existing graphene preparation methods, laser-scribed graphene (LSG) is simple, low-cost, environmentally friendly, and has good conductivity and high thermal stability, making it widely used in the sensor field. This paper summarizes existing LSG methods for sensor fabrication. Primary LSG preparation methods and their variants are introduced first, followed by a summary of LSG modification methods designed explicitly for sensor fabrication. Subsequently, the applications of LSG in stress, bio, gas, temperature, and humidity sensors are summarized with a particular focus on multifunctional integrated sensors. Finally, the current challenges and prospects of LSG-based sensors are discussed

Doping of Laser-Induced Graphene and Its Applications

Laser-induced graphene (LIG) has attracted extensive attention owing to its facile preparation of graphene and direct engraving patterns for devices. Various applications are demonstrated such as sensors, supercapacitors, electrocatalysis, batteries, antimicrobial, oil and water separation, solar cells, and heaters. In recent years, doping has been employed as a significant strategy to modulate the properties of LIG and thereby improve the performance of LIG devices. Due to the patternable manufacture, controllable morphologies, and the synergistic effect of doped atoms and graphene, the doped LIG devices exhibit a high sensitivity of sensing, pseudocapacitance performance, and biological antibacterial. This paper reviews the latest novel research progress of heteroatom and nanoparticles doped LIG in synthesis, properties, and applications. The fabrications of LIG and typical doping approaches are presented. Special attention is paid to two doping processes of LIG: the one-step laser irradiation method and the two-step laser modification consisting of deposition, drop-casting, and duplicated laser pyrolysis. Doped LIG applications with improved performance are mainly highlighted. Taking advantage of doped LIG's properties and device performances will provide excellent opportunities for developing artificial intelligence, data storage, energy, health, and environmental applications.</p

Direct laser writing of graphene oxide for ultra-low power consumption memristors in reservoir computing for digital recognition

A memristor is a promising candidate of new electronic synaptic devices for neuromorphic computing. However, conventional memristors often exhibit complex device structures, cumbersome manufacturing processes, and high energy consumption. Graphene-based materials show great potential as the building materials of memristors. With direct laser writing technology, this paper proposes a lateral memristor with reduced graphene oxide (rGO) and Pt as electrodes and graphene oxide (GO) as function material. This Pt/GO/rGO memristor with a facile lateral structure can be easily fabricated and demonstrates an ultra-low energy consumption of 200 nW. Typical synaptic behaviors are successfully emulated. Meanwhile, the Pt/GO/rGO memristor array is applied in the reservoir computing network, performing the digital recognition with a high accuracy of 95.74%. This work provides a simple and low-cost preparation method for the massive production of artificial synapses with low energy consumption, which will greatly facilitate the development of neural network computing hardware platforms

All-Optical Diffractive Deep Neural Networks Enabled Laser-Reduced Graphene Oxide Tactile Sensor for Braille Recognition

All-optical diffractive deep neural networks (D2NNs) show a wide range of applications in image recognition and artificial vision due to their advantages of high-speed parallel processing, low energy consumption, and excellent anti-interference ability. However, there is relatively limited research applying D2NNs for tactile perception. In this study, we propose an automatic Braille recognition method based on D2NNs and tactile sensors. A flexible molybdenum disulfide-doped laser-reduced graphene oxide (LRGO/MoS2) tactile sensor was fabricated with the laser direct writing method. The LRGO/MoS2 tactile sensor shows a sensitivity of 9.8 kPa-1, with a response/recovery time of 0.14/0.10 s and excellent cyclic stability. The tactile sensor can be employed to capture Braille character information in real time and convert it into digital signals as inputs for all-optical D2NNs. The automatic recognition of Braille characters is achieved in the all-optical D2NNs with five diffraction layers, and the system finally can realize a recognition accuracy of 100% for Braille recognition. The strategy of integrating flexible tactile sensors with all-optical deep learning paves a path for realizing a low-cost, fast, accurate, and efficient tactile recognition system.</p

Photo-electrochemical effects in topological insulator Sb2Te3 thin films

Topological insulators have attracted increased attention owing to their fascinating properties and important applications, such as spintronic devices, quantum computers, and optoelectronic devices. In this study, we demonstrated the photo-electrochemical properties of a typical topological insulator material, Sb2Te3 thin film. Sb2Te3 thin films were grown on a glass substrate using atomic layer deposition subsequently, samples or thin films were characterized using Raman spectroscopy, scanning electron microscopy, X-ray diffraction, and atomic force microscopy. The as-fabricated Sb2Te3 thin films have continuous and coarse surfaces with high crystallization. The photo-electrochemical effects of Sb2Te3 electrodes were observed. We show that the Sb2Te3 films have potential in photocatalytic water splitting application

Plasmon-Enhanced Surface-State Emission of CdSe Quantum Dots and Its Application to Microscale Luminescence Patterns

In this paper, we report distinct enhancement of surface-state emissions (SSEs) of colloidal CdSe quantum dots (QDs) via coupling to localized plasmons (LPs) in Ag nanostructures. The roles of oleic acid (OA) ligand on QDs in the formation of Ag nanostructures and in the intense enhancement of SSEs of CdSe QDs are explored. We find that OA ligand on CdSe QDs plays a critical role in modifying the morphology of the contacted Ag, which consequently impacts the coupling of QD emitters with LPs in Ag. A systematic study of size effect of QDs on coupling of SSEs with LPs shows that as-deposited small Ag particles favorably enhance the SSEs of small-size CdSe QDs. The OA ligand on QDs yields better Ag crystallinity and clear corners during the annealing process; therefore, it promotes reshaping of small Ag particles into larger ones, favorable to enhance the SSEs of large-size CdSe QDs. The annealed QDs/Ag hybrid structures are more stable than the unannealed ones due to the loss of the OA ligand in the heating process. The selective coupling of QD emitters with LPs in Ag nanostructures allows feasible realization of microscale fluorescent color patterns. The approach of OA-assisted modification of plasmonic properties of Ag nanostructures provides a new route to synthesizing bright luminescence materials and devices that use colloidal QDs