Graphene oxide scrolls on hydrophobic substrates fabricated by molecular combing and their application in gas sensing

Biomaterials science and surface engineering strategies for dental peri-implantitis management

Peri-implantitis is a bacterial infection that causes soft tissue inflammatory lesions and alveolar bone resorption, ultimately resulting in implant failure. Dental implants for clinical use barely have antibacterial properties, and bacterial colonization and biofilm formation on the dental implants are major causes of peri-implantitis. Treatment strategies such as mechanical debridement and antibiotic therapy have been used to remove dental plaque. However, it is particularly important to prevent the occurrence of peri-implantitis rather than treatment. Therefore, the current research spot has focused on improving the antibacterial properties of dental implants, such as the construction of specific micro-nano surface texture, the introduction of diverse functional coatings, or the application of materials with intrinsic antibacterial properties. The aforementioned antibacterial surfaces can be incorporated with bioactive molecules, metallic nanoparticles, or other functional components to further enhance the osteogenic properties and accelerate the healing process. In this review, we summarize the recent developments in biomaterial science and the modification strategies applied to dental implants to inhibit biofilm formation and facilitate bone-implant integration. Furthermore, we summarized the obstacles existing in the process of laboratory research to reach the clinic products, and propose corresponding directions for future developments and research perspectives, so that to provide insights into the rational design and construction of dental implants with the aim to balance antibacterial efficacy, biological safety, and osteogenic property.

Nanoparticle Assembly: From Self-Organization to Controlled Micropatterning for Enhanced Functionalities

Nanoparticles form long-range micropatterns via self-assembly or directed self-assembly with superior mechanical, electrical, optical, magnetic, chemical, and other functional properties for broad applications, such as structural supports, thermal exchangers, optoelectronics, microelectronics, and robotics. The precisely defined particle assembly at the nanoscale with simultaneously scalable patterning at the microscale is indispensable for enabling functionality and improving the performance of devices. This article provides a comprehensive review of nanoparticle assembly formed primarily via the balance of forces at the nanoscale (e.g., van der Waals, colloidal, capillary, convection, and chemical forces) and nanoparticle-template interactions (e.g., physical confinement, chemical functionalization, additive layer-upon-layer). The review commences with a general overview of nanoparticle self-assembly, with the state-of-the-art literature review and motivation. It subsequently reviews the recent progress in nanoparticle assembly without the presence of surface templates. Manufacturing techniques for surface template fabrication and their influence on nanoparticle assembly efficiency and effectiveness are then explored. The primary focus is the spatial organization and orientational preference of nanoparticles on non-templated and pre-templated surfaces in a controlled manner. Moreover, the article discusses broad applications of micropatterned surfaces, encompassing various fields. Finally, the review concludes with a summary of manufacturing methods, their limitations, and future trends in nanoparticle assembly.

Sodium titanate: A proton conduction material for ppb-level NO2 detection with near-zero power consumption

Constrained by the traditional charge transfer sensing mechanism, it is quite challenging to fabricate NO2 sensors that simultaneously exhibit high sensitivity, rapid response/recovery, and low power consumption. Herein, sodium titanate (NTO), a layered material with abundant surface-rooted OH groups (OHR), is demonstrated to be a promising NO2 sensing material. To understand the sensing behavior of NTO, the influences of operating temperature, applied voltage, and relative humidity are investigated, and a novel OHR-enabled proton conduction sensing mechanism is proposed. The sensing process mainly involves selective NO2 adsorption on OHR, thereby lowering the activation energy for proton transportation along the NTO surface. Meanwhile, the moderate intermolecular interaction makes NO2 both easily adsorbed and desorbed at room temperature. Hence, NTO exhibits a highly sensitive, rapid, and fully recoverable response (∼5.7-1 ppm NO2 within 3 s), wide detection range (1 ppb-20 ppm), good stability (>2 months), and near-zero power consumption (0.5 nW). Finally, we demonstrate that NTO has an excellent practical indoor/outdoor NO2 sensing ability. This work offers a new pathway to resolve the inherent conflicts in available NO2 sensors by using NTO via the OHR-enabled proton conduction sensing mechanism, which may also provide insight into designing high-performance sensors for other gases.

Spontaneous formation of MoS2 nanoscrolls from flat monolayers with sulfur vacancies: a molecular dynamics investigation

The unique physical properties exhibited by one-dimensional nanoscrolls assembled from nanosheets have propelled them into the spotlight of two-dimensional materials research. However, the self-scrolling mechanism of transition metal dichalcogenides has not been unveiled with an appropriate theoretical approach. In this paper, we systematically investigate the spontaneous formation of MoS2 nanoscrolls from flat monolayers by molecular dynamics simulations based on a reactive force field. The sulfur vacancies on one side break the atomic symmetry and the reconstruction acts as the driving force for the curling of the flat nanoribbon. If sulfur vacancies are arranged in a line, clear bending angles of the nanoribbon can be obtained and the angle relies on the direction of the line vacancy. With random sulfur vacancies on the top, spontaneous curling and a time-dependent scrolling process of the nanoribbon can be observed. The interplay between dangling bonds and van der Waals (vdW) interactions plays a pivotal role in the formation process of MoS2 nanoscrolls. With an increasing density of sulfur vacancies, the curvature of the nanoscrolls increases. Meanwhile, the scrolling rate accelerates and the time required for the formation of vdW structures decreases. These results provide theoretical insights into the fabrication of nanoscrolls and pave avenues for tailoring nanoscrolls with different morphologies.

Direct Synthesis of MoS2 Nanosheets in Reduced Graphene Oxide Nanoscroll for Enhanced Photodetection

Due to their unique tubular and spiral structure, graphene and graphene oxide nanoscrolls (GONS) have shown extensive applications in various fields. However, it is still a challenge to improve the optoelectronic application of graphene and GONS because of the zero bandgap of graphene. Herein, ammonium tetrathiomolybdate ((NH₄)₂MoS₄) was firstly wrapped into the ((NH₄)₂MoS₄@GONS) by molecular combing the mixture of (NH₄)₂MoS₄ and GO solution on hydrophobic substrate. After thermal annealing, the (NH₄)₂MoS₄ and GO were converted to MoS₂ nanosheets and reduced GO (RGO) simultaneously, and, thus, the MoS₂@RGONS was obtained. Raman spectroscopy and high-resolution transmission electron microscopy were used to confirm the formation of MoS₂ nanosheets among the RGONS. The amount of MoS₂ wrapped in RGONS increased with the increasing height of GONS, which is confirmed by the atomic force microscopy and Raman spectroscopy. The as-prepared MoS₂@RGONS showed much better photoresponse than the RGONS under visible light. The photocurrent-to-dark current ratios of photodetectors based on MoS₂@RGONS are ~570, 360 and 140 under blue, red and green lasers, respectively, which are 81, 144 and 35 times of the photodetectors based on RGONS. Moreover, the MoS₂@RGONS-based photodetector exhibited good power-dependent photoresponse. Our work indicates that the MoS₂@RGONS is expected to be a promising material in the fields of optoelectronic devices and flexible electronics.

Metallic phase WSe2 nanoscrolls for the hydrogen evolution reaction

Nanostructured metastable metallic phase transition-metal dichalcogenides (TMDs) have attracted tremendous attention due to their promising practical applications in the hydrogen evolution reaction (HER).

Nitrogen Dioxide Gas Sensor Based on Ag-Doped Graphene: A First-Principle Study

High-performance tracking trace amounts of NO2 with gas sensors could be helpful in protecting human health since high levels of NO2 may increase the risk of developing acute exacerbation of chronic obstructive pulmonary disease. Among various gas sensors, Graphene-based sensors have attracted broad attention due to their sensitivity, particularly with the addition of noble metals (e.g., Ag). Nevertheless, the internal mechanism of improving the gas sensing behavior through doping Ag is still unclear. Herein, the impact of Ag doping on the sensing properties of Graphene-based sensors is systematically analyzed via first principles. Based on the density-functional theory (DFT), the adsorption behavior of specific gases (NO2, NH3, H2O, CO2, CH4, and C2H6) on Ag-doped Graphene (Ag–Gr) is calculated and compared. It is found that NO2 shows the strongest interaction and largest Mulliken charge transfer to Ag–Gr among these studied gases, which may directly result in the highest sensitivity toward NO2 for the Ag–Gr-based gas sensor.

Two-Dimensional, Few-Layer MnPS3 for Selective NO2 Gas Sensing under Ambient Conditions

In this study, two-dimensional few-layer MnPS₃ is introduced as a selective and reversible NO₂ gas sensor in dry nitrogen (N₂) under ambient conditions. The solvent exfoliation technique is utilized to exfoliate bulk MnPS₃ into a few layers, which are further assembled as thin films by the vacuum filtration method. The films are subsequently transferred onto a sensing device and used for NO₂ sensing. Exfoliated MnPS₃ shows excellent sensitivity toward NO₂ gas with a low detection limit of a few tens of ppb at 25 °C. A sensitivity of 9530% is obtained at 35 ppm concentration of NO₂ with the theoretical limit of detection calculated to be ∼9.5 ppb. The sensor is highly selective toward NO₂ gas (with respect to interferents NO, NH₃, H₂, CO, CO₂, C₂H₂, and O₂) and is fully reversible under ambient conditions. The time constant is determined to be in the range of 30-160 s for adsorption and desorption processes. Raman spectroscopy reveals that the mechanism of sensing is based on charge transfer interactions between the sensor and analyte. This study opens up ways to fabricate gas sensors using few-layer metal phosphochalcogenides (MPX₃).

Impact of pH on Regulating Ion Encapsulation of Graphene Oxide Nanoscroll for Pressure Sensing

Recently, graphene oxide nanoscroll (GONS) has attracted much attention due to its excellent properties. Encapsulation of nanomaterials in GONS can greatly enhance its performance while ion encapsulation is still unexplored. Herein, various ions including hydronium ion (H₃O⁺), Fe³⁺, Au³⁺, and Zn²⁺ were encapsulated in GONSs by molecular combing acidic graphene oxide (GO) solution. No GONS was obtained when the pH of the GO solution was greater than 9. A few GONSs without encapsulated ion were obtained at the pH of 5–8. When the pH decreased from 5 to 0.15, high-density GONSs with encapsulated ions were formed and the average height of GONS was increased from ~50 to ~190 nm. These results could be attributed to the varied repulsion between carboxylic acid groups located at the edges of GO nanosheets. Encapsulated metal ions were converted to nanoparticles in GONS after high-temperature annealing. The resistance-type device based on reduced GONS (rGONS) mesh with encapsulated H₃O⁺ showed good response for applied pressure from 600 to 8700 Pa, which manifested much better performance compared with that of a device based on rGONS mesh without H₃O⁺.

Transforming Monolayer Transition-Metal Dichalcogenide Nanosheets into One-Dimensional Nanoscrolls with High Photosensitivity

One-dimensional (1D) nanoscrolls derived from two-dimensional (2D) nanosheets own unusual physical and chemical properties that arise from the spiraled 1D morphology and the atomic thin 2D building blocks. Unfortunately, preparation of large-sized nanoscrolls of transition-metal dichalcogenides (TMDCs) remains a big challenge, which greatly restricts the fabrication of single-scroll devices for their fundamental studies and further applications. In this work, we report a universal and facile method, by making use of the evaporation process of volatile organic solvent, to prepare TMDC (e.g., MoS₂ and WS₂) nanoscrolls with lengths of several tens to one hundred micrometers from their 2D precursors presynthesized by chemical vapor deposition on Si/SiO₂. Both atomic force microscopy and electron microscopy characterizations confirmed the spirally rolledup structure in the resulting nanoscrolls. An interlayer spacing of as small as ∼0.65 nm was observed, suggesting the strong coupling between adjacent layers, which was further evidenced by the emergence of new breathing mode peaks in the ultralow frequency Raman spectrum. Importantly, compared with the photodetector fabricated from a monolayer MoS₂ or WS₂ nanosheet, the device based on an MoS₂ or WS₂ nanoscroll showed the much enhanced performance, respectively, with the photosensitivity greatly increased up to 2 orders of magnitude. Our work suggests that turning 2D TMDCs into 1D scrolls is promising in achieving high performances in various electronic/optoelectronic applications, and our general method can be extended to the preparation of large-sized nanoscrolls of other kinds of 2D materials that may bring about new properties and phenomena.

Rolling up graphene oxide sheets through solvent-induced self-assembly in dispersions

Herein we report a new approach to fabricating nanoscrolls through the self-assembly of graphene oxide (GO) sheets in a dispersion. The assembly process for GO nanosheets was induced by the dropwise addition of an appropriate organic solvent such as N,N-dimethylformamide (DMF) into the aqueous dispersion. The results show that nanoscrolls were gradually formed from the GO sheets by rolling-up in a piece-by-piece manner with the increase of the DMF content. The transmission electron microscopic analysis indicates that for a typical case, the nanoscrolls have an average diameter of 242 ± 102 nm at the central part and the interlayer spacing between adjacent GO layers is 0.58 nm. The scrolls were estimated to have 207 turns and include on average 42 pieces of GO sheets per scroll. By this method, GO sheets with different sizes and oxidation degrees were proved to be able to form GO nanoscrolls in a similar way. Moreover, it is interesting that the diffraction efficiency of surface-relief-gratings photoinduced on the film of azo molecular glass was significantly enhanced by doping the GO nanoscrolls with a very low content (0.5 wt%); this suggests a possible new application for the GO scrolls in optical devices. This facile approach, which is also feasible by using other organic solvents such as ethanol, can be used to fabricate GO nanoscrolls for large scale applications in supercapacitors, sensors and other devices.

Architecting Graphene Oxide Rolled-Up Micromotors: A Simple Paper-Based Manufacturing Technology

A graphene oxide rolled-up tube production process is reported using wax-printed membranes for the fabrication of on-demand engineered micromotors at different levels of oxidation, thickness, and lateral dimensions. The resultant graphene oxide rolled-up tubes can show magnetic and catalytic movement within the addition of magnetic nanoparticles or sputtered platinum in the surface of graphene-oxide-modified wax-printed membranes prior to the scrolling process. As a proof of concept, the as-prepared catalytic graphene oxide rolled-up micromotors are successfully exploited for oil removal from water. This micromotor production technology relies on an easy, operator-friendly, fast, and cost-efficient wax-printed paper-based method and may offer a myriad of hybrid devices and applications.

UV-Activated MoS2 Based Fast and Reversible NO2 Sensor at Room Temperature

Two-dimensional materials have gained considerable attention in chemical sensing owing to their naturally high surface-to-volume ratio. However, the poor response time and incomplete recovery at room temperature restrict their application in high-performance practical gas sensors. Herein, we demonstrate ultrafast detection and reversible MoS₂ gas sensor at room temperature. The sensor's performance is investigated to NO₂ at room temperature, under thermal and photo energy. Incomplete recovery and high response time of ∼249 s of sensor are observed at room temperature. Thermal energy is enough to complete recovery, but it is at the expense of sensitivity. Further, under photo excitation, MoS₂ exhibits an enhancement in sensitivity with ultrafast response time of ∼29 s and excellent recovery to NO₂ (100 ppm) at room temperature. This significant improvement in sensitivity (∼30%) and response time (∼88%) is attributed to the charge perturbation on the surface of the sensing layer in the context of NO₂/MoS₂ interaction under optical illumination. Moreover, the sensor shows reliable selectivity toward NO₂ against various other gases. These unprecedented results reveal the potential of 2D MoS₂ to develop a low power portable gas sensor.

Scrolling up graphene oxide nanosheets assisted by self-assembled monolayers of alkanethiols

We report a simple and novel method for the fabrication of high-quality nanoscrolls of graphene oxide (GO) and graphene oxide decorated with silver nanoparticles (GO-Ag) on a gold substrate through a scrolling process assisted by the self-assembly of alkanethiol monolayers. The yield and rate of the scrolling process were highly dependent on the lengths of the alkanethiol molecules, and could be well described by power law functions. Importantly, compared to nanosheets, nanoscrolls of GO and GO-Ag showed superior performance in humidity sensing due to their unique scrolled structures.

Selenium-Functionalized Graphene Oxide That Can Modulate the Balance of Reactive Oxygen Species

Graphene oxide (GO) is an important two-dimensional material since it is water-soluble and can be functionalized to adapt to different applications. However, the current covalent functionalization methods usually require hash conditions, long duration, and sometimes even multiple steps, while noncovalent functionalization is inevitably unstable, especially under a physiological environment where competing species exist. Diselenide bond is a dynamic covalent bond and can respond to both redox conditions and visible light irradiation in a sensitive manner. Thus, in this work by combining the stimuli response of diselenide bond and the oxidative/radical attackable nature of GO, we achieved the in situ covalent functionalization of GO simply by stirring GO with diselenide-containing molecules in aqueous solution. The covalent functionalization was proved by Fourier transform infrared, time-of-flight secondary ion mass spectrometry, atomic force microscopy, thermogravimetric analysis, and so forth, and the functionalization mechanism was deduced to involve both redox reaction and radical addition reaction according to the X-ray photoelectron spectrscopy, atomic emission spectroscopy, and Raman spectroscopy. Moreover, we modified GO with a biocompatible diselenide-containing polymer (mPEGSe)₂ and found selenium-functionalized GO could modulate the balance of reactive oxygen species (ROS). GOSe could decrease ROS level by accelerating the reduction of peroxides when the ROS concentration is high while boosting the ROS level by in situ generating ROS when its concentration is relatively low.

Nitrogen-Doped Graphene Nanoscroll Foam with High Diffusion Rate and Binding Affinity for Removal of Organic Pollutants

A nitrogen-doped 3D graphene foam assembled with nanoscroll structure is constructed via a facile mild-heating methodology using a polar molecule of formamide as the driving regent. The as-prepared graphene nanoscroll foam exhibits promising performance in organic pollutant removal with improved adsorption rate and high binding affinity, and is thought to be a novel adsorption material.

Graphene oxide scroll meshes encapsulated Ag nanoparticles for humidity sensing

rGO–Ag scroll meshes shows 3 orders of magnitude higher humidity response compared to that of rGO scroll meshes.

Two-dimensional nanomaterial-based field-effect transistors for chemical and biological sensing

This review highlights the recent progress in graphene-, 2D transition metal dichalcogenide-, and 2D black phosphorus-based FET sensors for detecting gases, biomolecules, and water contaminants.

Fabrication and morphology tuning of graphene oxide nanoscrolls

Here we report the synthesis of graphene oxide nanoscrolls (GONS) with tunable dimensions via low and high frequency ultrasound solution processing techniques. GONS can be visualized as a graphene oxide (GO) sheet rolled into a spiral-wound structure and represent an alternative to traditional carbon nano-morphologies. The scrolling process is initiated by the ultrasound treatment which provides the scrolling activation energy for the formation of GONS. The GO and GONS dimensions are observed to be a function of ultrasound frequency, power density, and irradiation time. Ultrasonication increases GO and GONS C-C bonding likely due to in situ thermal reduction at the cavitating bubble-water interface. The GO area and GONS length are governed by two mechanisms; rapid oxygen defect site cleavage and slow cavitation mediated scission. Structural characterization indicates that GONS with tube and cone geometries can be formed with both narrow and wide dimensions in an industrial-scale time window. This work paves the way for GONS implementation for a variety of applications such as adsorptive and capacitive processes.

Mass production of graphene nanoscrolls and their application in high rate performance supercapacitors

The output of graphene nanoscrolls (GNSs) has been greatly enhanced to the gram-level by using an improved spray-freeze-drying method without damaging the high transforming efficiency (>92%). The lowest bulk density of GNS foam reaches 0.10 mg cm(-3). Due to the unique morphology and high specific surface area (386.4 m(2) g(-1)), the specific capacitances of the GNSs (90-100 F g(-1) at 1 A g(-1)) are all superior to those of multiwalled carbon nanotubes meanwhile maintaining excellent rate capabilities (60-80% retention at 50 A g(-1)). For the first time, all-graphene-based films (AGFs) are fabricated via the intercalation of GNSs into graphene layers. The AGF exhibits a capacitance of 166.8 F g(-1) at 1 A g(-1) and rate capability (83.9% retention at 50 A g(-1)) better than those of pure reduced graphene oxide (RGO) films and carbon nanotubes/graphene hybrid films (CGFs).

Physisorption-Based Charge Transfer in Two-Dimensional SnS2 for Selective and Reversible NO2 Gas Sensing

Nitrogen dioxide (NO2) is a gas species that plays an important role in certain industrial, farming, and healthcare sectors. However, there are still significant challenges for NO2 sensing at low detection limits, especially in the presence of other interfering gases. The NO2 selectivity of current gas-sensing technologies is significantly traded-off with their sensitivity and reversibility as well as fabrication and operating costs. In this work, we present an important progress for selective and reversible NO2 sensing by demonstrating an economical sensing platform based on the charge transfer between physisorbed NO2 gas molecules and two-dimensional (2D) tin disulfide (SnS2) flakes at low operating temperatures. The device shows high sensitivity and superior selectivity to NO2 at operating temperatures of less than 160 °C, which are well below those of chemisorptive and ion conductive NO2 sensors with much poorer selectivity. At the same time, excellent reversibility of the sensor is demonstrated, which has rarely been observed in other 2D material counterparts. Such impressive features originate from the planar morphology of 2D SnS2 as well as unique physical affinity and favorable electronic band positions of this material that facilitate the NO2 physisorption and charge transfer at parts per billion levels. The 2D SnS2-based sensor provides a real solution for low-cost and selective NO2 gas sensing.

Comparative Study of Potential Applications of Graphene, MoS2, and Other Two-Dimensional Materials in Energy Devices, Sensors, and Related Areas

Novel properties of graphene have been well documented, whereas the importance of nanosheets of MoS2 and other chalcogenides is increasingly being recognized over the last two to three years. Borocarbonitrides, BxCyNz, with insulating BN and conducting graphene on either side are new materials whose properties have been attracting attention. These two-dimensional (2D) materials contain certain common features. Thus, graphene, MoS2, and borocarbonitrides have all been used in supercapacitor applications, oxygen reduction reactions (ORRs), and lithium-ion batteries. It is instructive, therefore, to make a comparative study of some of the important properties of these layered materials. In this article, we discuss properties related to energy devices at length. We examine the hydrogen evolution reaction facilitated by graphene, MoS2, and related materials. We also discuss gas and radiation sensors based on graphene and MoS2 as well as gas storage properties of graphene and borocarbonitrides. The article should be useful in making a judicious choice of which 2D material to use for a particular application.

Elasticity of MoS2 Sheets by Mechanical Deformation Observed by in Situ Electron Microscopy

MoS₂ has been the focus of extensive research due to its potential applications. More recently, the mechanical properties of MoS₂ layers have raised interest due to applications in flexible electronics. In this article, we show in situ transmission electron microcsopy (TEM) observation of the mechanical response of a few layers of MoS₂ to an external load. We used a scanning tunneling microscope (STM) tip mounted on a TEM stage to induce deformation on nanosheets of MoS₂ containing few layers. The results confirm the outstanding mechanical properties on the MoS₂. The layers can be bent close to 180°. However, when the tip is retrieved the initial structure is recovered. Evidence indicates that there is a significant bond reconstruction during the bending with an outstanding capability to recover the initial bond structure. The results show that flexibility of three layers of MoS₂ remains the same as a single layer while increasing the bending modulus by 3 orders of magnitude. Our findings are consistent with theoretical calculations and confirm the great potential of MoS₂ for applications.

Graphene field-effect transistor and its application for electronic sensing

Graphene, because of its excellent mechanical, electrical, chemical, physical properties, sparked great interest to develop and extend its applications. Particularly, graphene based field-effect transistors (GFETs) present exciting and bright prospects for sensing applications due to their greatly higher sensitivity and stronger selectivity. This Review highlights a selection of important topics pertinent to GFETs and their application in electronic sensors. This article begins with a description of the fabrications and characterizations of GFETs, and then introduces the new developments in physical, chemical, and biological electronic detection using GFETs. Finally, several perspective and current challenges of GFETs development are presented, and some proposals are suggested for further development and exploration.

Flexible and transparent gas molecule sensor integrated with sensing and heating graphene layers

Graphene leading to high surface-to-volume ratio and outstanding conductivity is applied for gas molecule sensing with fully utilizing its unique transparent and flexible functionalities which cannot be expected from solid-state gas sensors. In order to attain a fast response and rapid recovering time, the flexible sensors also require integrated flexible and transparent heaters. Here, large-scale flexible and transparent gas molecule sensor devices, integrated with a graphene sensing channel and a graphene transparent heater for fast recovering operation, are demonstrated. This combined all-graphene device structure enables an overall device optical transmittance that exceeds 90% and reliable sensing performance with a bending strain of less than 1.4%. In particular, it is possible to classify the fast (≈14 s) and slow (≈95 s) response due to sp(2) -carbon bonding and disorders on graphene and the self-integrated graphene heater leads to the rapid recovery (≈11 s) of a 2 cm × 2 cm sized sensor with reproducible sensing cycles, including full recovery steps without significant signal degradation under exposure to NO2 gas.

Photosensitive graphene transistors

High performance photodetectors play important roles in the development of innovative technologies in many fields, including medicine, display and imaging, military, optical communication, environment monitoring, security check, scientific research and industrial processing control. Graphene, the most fascinating two-dimensional material, has demonstrated promising applications in various types of photodetectors from terahertz to ultraviolet, due to its ultrahigh carrier mobility and light absorption in broad wavelength range. Graphene field effect transistors are recognized as a type of excellent transducers for photodetection thanks to the inherent amplification function of the transistors, the feasibility of miniaturization and the unique properties of graphene. In this review, we will introduce the applications of graphene transistors as photodetectors in different wavelength ranges including terahertz, infrared, visible, and ultraviolet, focusing on the device design, physics and photosensitive performance. Since the device properties are closely related to the quality of graphene, the devices based on graphene prepared with different methods will be addressed separately with a view to demonstrating more clearly their advantages and shortcomings in practical applications. It is expected that highly sensitive photodetectors based on graphene transistors will find important applications in many emerging areas especially flexible, wearable, printable or transparent electronics and high frequency communications.

Graphene oxide architectures prepared by molecular combing on hydrophilic-hydrophobic micropatterns

A novel graphene oxide (GO) architecture is fabricated on hydrophilic-hydrophobic patterned alkanethiol self-assembled monolayers on Au by molecular combing of GO sheets. With hydrazine reduction, the reduced GO architecture-based device is demonstrated to detect NO2 gas. This simple method shows the potential to control the shape, orientation and position of GO sheets over large areas.

Synthesis of graphene-conjugated polymer nanocomposites for electronic device applications

Graphene-based polymer nanocomposites have attracted increasing interest because of their superior physicochemical properties over polymers. Semiconductor conjugated polymers (CPs) with excellent dispersibility and stability, and efficient electronic and optical properties have been recently integrated with graphene to form a new class of functional nanomaterials. In this minireview, we will summarize the recent advances in the development of graphene-CP nanocomposites for electronic device applications.