Microshell Arrays Enhanced Sensitivity in Detection of Specific Antibody for Reduced Graphene Oxide Optical Sensor.

Protein-protein interactions play an important role in the investigation of biomolecules. In this paper, we reported on the use of a reduced graphene oxide microshell (RGOM)-based optical biosensor for the determination of goat anti-rabbit IgG. The biosensor was prepared through a self-assembly of monolayers of monodisperse polystyrene microspheres, combined with a high-temperature reduction, in order to decorate the RGOM with rabbit IgG. The periodic microshells allowed a simpler functionalization and modification of RGOM with bioreceptor units, than reduced graphene oxide (RGO). With additional antibody-antigen binding, the RGOM-based biosensor achieved better real-time and label-free detection. The RGOM-based biosensor presented a more satisfactory response to goat anti-rabbit IgG than the RGO-based biosensor. This method is promising for immobilizing biomolecules on graphene surfaces and for the fabrication of biosensors with enhanced sensitivity.

Reduced graphene oxide nanoshells for flexible and stretchable conductors.

Graphene has been extensively investigated for its use in flexible electronics, especially graphene synthesized by chemical vapor deposition (CVD). To enhance the flexibility of CVD graphene, wrinkles are often introduced. However, reports on the flexibility of reduced graphene oxide (RGO) films are few, because of their weak conductivity and, in particular, poor flexibility. To improve the flexibility of RGO, reduced graphene oxide nanoshells are fabricated, which combine self-assembled polystyrene nanosphere arrays and high-temperature thermal annealing processes. The resulting RGO films with nanoshells present a better resistance stabilization after stretching and bending the devices than RGO without nanoshells. The sustainability and performance advances demonstrated here are promising for the adoption of flexible electronics in a wide variety of future applications.

Ultrasensitive flow sensing of a single cell using graphene-based optical sensors.

On the basis of the polarization-dependent absorption of graphene under total internal reflection, we designed a graphene-based optical refractive index sensor with high resolution of 1.7 × 10(-8) and sensitivity of 4.3 × 10(7) mV/RIU, as well as an extensive dynamic range. This highly sensitive graphene optical sensor enables label-free, live-cell, and highly accurate detection of a small quantity of cancer cells among normal cells at the single-cell level and the simultaneous detection and distinction of two cell lines without separation. It provides an accurate statistical distribution of normal and cancer cells with fewer cells. This facile and highly sensitive sensing refractive index may expand the practical applications of the biosensor.

Flexible graphene saturable absorber on two-layer structure for tunable mode-locked soliton fiber laser.

Using a two-layer structure consisting of polyethylene terephthalate (PET) and polydimethylsiloxane (PDMS) to support graphene grown by chemical vapor deposition (CVD), we demonstrate a flexible integrated graphene saturable absorber (SA) on microfiber for passive mode-locked soliton fiber laser. This method can optimize the light-graphene interaction by using evanescent field in the integration structure. Moreover, the fiber laser with the in-line microfiber-to-graphene SA can realize the tunabilities of both the 3dB bandwidth of output optical spectrum and the pulse width of soliton. This tunable mode-locked soliton laser has potential applications in optical communication, optical microscopy, and so on.

Large tunable optical absorption of CVD graphene under total internal reflection by strain engineering.

We have developed a method to tune polarization-dependent optical absorption of large-scale chemical vapor deposition (CVD) graphene under total internal reflection (TIR) by strain engineering. Through control of the strain direction, the optical absorption of graphene for transverse magnetic or transverse electric waves can be separately tuned. Strain-induced modulation of the optical absorption has been theoretically expected when light is normally incident through graphene. Under TIR, however, we experimentally observed a significant increase in the strain-induced tunability of optical absorption for CVD graphene, with the modulation efficiency of optical absorption in monolayer graphene increasing by a factor of three times that for normal incidence. We conclude that the strain sensitivity of optical absorption of graphene under TIR offers significant potential for application in many areas such as ultra-thin optical devices and strain sensors.

Graphene and its Derivatives-Based Optical Sensors.

Being the first successfully prepared two-dimensional material, graphene has attracted extensive attention from researchers due to its excellent properties and extremely wide range of applications. In particular, graphene and its derivatives have displayed several ideal properties, including broadband light absorption, ability to quench fluorescence, excellent biocompatibility, and strong polarization-dependent effects, thus emerging as one of the most popular platforms for optical sensors. Graphene and its derivatives-based optical sensors have numerous advantages, such as high sensitivity, low-cost, fast response time, and small dimensions. In this review, recent developments in graphene and its derivatives-based optical sensors are summarized, covering aspects related to fluorescence, graphene-based substrates for surface-enhanced Raman scattering (SERS), optical fiber biological sensors, and other kinds of graphene-based optical sensors. Various sensing applications, such as single-cell detection, cancer diagnosis, protein, and DNA sensing, are introduced and discussed systematically. Finally, a summary and roadmap of current and future trends are presented in order to provide a prospect for the development of graphene and its derivatives-based optical sensors.

Novel yellow solid-state fluorescent-emitting carbon dots with high quantum yield for white light-emitting diodes.

Fluorescence quenching of carbon dots (CDs) occurs in their aggregated state ascribed to direct π-π interactions or excessive resonance energy transfer (RET). Thus, CDs have been severely restricted for applications requiring phosphors that emit in the solid state, such as the fabrication of white light-emitting diodes (WLEDs). In this report, novel CDs with bright solid-state fluorescence (SSF) were synthesized by simple microwave-assisted synthesis method, using 1,4,7,10-tetraazacyclododecane (cyclen) and citric acid as precursors. Under 365 nm UV light, these CDs emit bright yellow SSF, indicating they successfully overcome the aggregation-induced fluorescence quenching (ACQ) effect. When the excitation wavelength (λex) is fixed at 450 nm, the emission peak of the CDs is centered at 546 nm with the Commission Internationale de l'Eclairage chromaticity (CIE) coordinates of (0.43, 0.55), which means that they can be combined with a blue-emitting chip in order to fabricate WLEDs. More importantly, the absolute quantum yield (QY) of these CDs powder reached 48% at λex of 450 nm, which was much higher than many previously reported SSF-emitting CDs and indicating their high light conversion ability in solid-state. Thanks to the excellent optical property of these CDs powder, they were successfully used in the preparation of high-performance WLEDs. This study not only enriches SSF-emitting CD-based nanomaterials with good prospects for application, but also provides valuable reference for subsequent research on the synthesis of solid-state fluorescent CDs.

Fast Growth and Broad Applications of 25-Inch Uniform Graphene Glass.

A unique ethanol-precursor-based LPCVD route is developed for the fast (4 min, improved 20 times) and scalable (25 inch, improved six times) growth of high-quality graphene glass. The obtained graphene glass presents high uniformity across large areas and is demonstrated to be an excellent material for constructing switchable windows and biosensor devices, owing to its excellent transparency and conductivity.

High-Precision Twist-Controlled Bilayer and Trilayer Graphene.

Twist-controlled bilayer graphene (tBLG) and double-twisted trilayer graphene (DTTG) with high precision are fabricated and their controllable optoelectronic properties are investigated for the first time. The successful fabrication of tBLG and DTTG with designated θ provides an attractive starting point for systematic studies of interlayer coupling in misoriented few-layer graphene systems with well-defined geometry.

The selective transfer of patterned graphene.

We demonstrate a selective microcleaving graphene (MG) transfer technique for the transfer of graphene patterns and graphene devices onto chosen targets using a bilayer-polymer structure and femtosecond laser microfabrication. In the bilayer-polymer structure, the first layer is used to separate the target graphene from the other flakes, and the second layer transfers the patterned graphene to the chosen targets. This selective transfer technique, which exactly transfers the patterned graphene onto a chosen target, leaving the other flakes on the original substrate, provides an efficient route for the fabrication of MG for microdevices and flexible electronics and the optimization of graphene's performance. This method will facilitate the preparation of van der Waals heterostructures and enable the optimization of the performance of graphene hybrid devices.