Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> Large-area ultrathin films of reduced graphene oxide as a transparent and flexible electronic material <s> BIB001 </s> Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> High-performance, transparent and stretchable electrodes are in demand for the development of flexible electronic and optoelectronic applications. Graphene is a candidate as the basis material, because of its excellent optical, electrical and mechanical properties. This paper describes a technique to grow centimetre-scale films using chemical vapour deposition on nickel films and a method to pattern and transfer the films to arbitrary substrates. The electrical conductance and optical transparency are as high as those for microscale graphene films. <s> BIB002 </s> Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> Graphene films with electrical and optical characteristics superior to indium tin oxide are produced in a roll-to-roll process and used to construct devices with flexible touch-screen panels. <s> BIB003 </s> Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> Graphene, a single-atom-thick and two-dimensional carbon material, has attracted great attention recently. Because of its unique electrical, physical, and optical properties, graphene has great potential to be a novel alternative to carbon nanotubes in biosensing. We demonstrate the use of large-sized CVD grown graphene films configured as field-effect transistors for real-time biomolecular sensing. Glucose or glutamate molecules were detected by the conductance change of the graphene transistor as the molecules are oxidized by the specific redox enzyme (glucose oxidase or glutamic dehydrogenase) functionalized onto the graphene film. This study indicates that graphene is a promising candidate for the development of real-time nanoelectronic biosensors. <s> BIB004 </s> Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> We present a low-temperature (300–400 °C), large-area (23 cm×20 cm) and efficient synthesis method for graphene-based transparent conductive films using surface wave plasma chemical vapor deposition. The films consist of few-layer graphene sheets. Their transparency and conductivity characteristics make them suitable for practical electrical and optoelectronic applications, which have been demonstrated by the proper operation of a touch panel fabricated using the films. The results confirm that our method could be suitable for the industrial mass production of macroscopic-scale graphene-based films. <s> BIB005 </s> Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> Abstract A new approach to the development of a single-layer graphene sensor decorated with metal nanoparticles is presented. Chemical vapor deposition is used to grow single layer graphene on copper. Decoration of the single-layer graphene is achieved by electroless deposition of Au nanoparticles using the copper substrate as a source of electrons. Transfer of the decorated single-layer graphene on glassy carbon electrodes offers a sensitive platform for biosensor development. As a proof of concept, 10 units of glucose oxidase were deposited on the surface in a Nafion matrix to stabilize the enzyme as well as to prevent interference from ascorbic acid and uric acid. Amperometric linear response calibration in the μmol l −1 is obtained. The presented methodology enables highly sensitive platforms for biosensor development, providing a scalable roll-to-roll production with a much more reproducible scheme when compared to the graphene biosensors reported previously based on drop-cast of multi-layer graphene suspensions. <s> BIB006 </s> Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> Anticorrosion and antioxidation surface treatments such as paint or anodization are a foundational component in nearly all industries. Graphene, a single-atom-thick sheet of carbon with impressive impermeability to gases, seems to hold promise as an effective anticorrosion barrier, and recent work supports this hope. We perform a complete study of the short- and long-term performance of graphene coatings for Cu and Si substrates. Our work reveals that although graphene indeed offers effective short-term oxidation protection, over long time scales it promotes more extensive wet corrosion than that seen for an initially bare, unprotected Cu surface. This surprising result has important implications for future scientific studies and industrial applications. In addition to informing any future work on graphene as a protective coating, the results presented here have implications for graphene’s performance in a wide range of applications. <s> BIB007 </s> Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> Graphene is a promising candidate in analog electronics with projected operation frequency well into the terahertz range. In contrast to the intrinsic cutoff frequency (fT) of 427 GHz, the maximum oscillation frequency (fmax) of graphene device still remains at low level, which severely limits its application in radio frequency amplifiers. Here, we develop a novel transfer method for chemical vapor deposition graphene, which can prevent graphene from organic contamination during the fabrication process of the devices. Using a self-aligned gate deposition process, the graphene transistor with 60 nm gate length exhibits a record high fmax of 106 and 200 GHz before and after de-embedding, respectively. This work defines a unique pathway to large-scale fabrication of high-performance graphene transistors, and holds significant potential for future application of graphene-based devices in ultra high frequency circuits. <s> BIB008 </s> Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> Lead is a cumulative toxicant, which can induce severe health issues, especially in children’s case due to their immature nervous system. While realizing large-scale monitoring of children blood lead remains challenging by utilizing traditional methods, it is highly desirable to search for alternative techniques or novel sensing materials. Here we report a label-free and portable aptasensor based on graphene field effect transistor (FET) for effective children blood lead detection. With standard solutions of different Pb2+ concentrations, we obtained a dose-response curve and a detection limitation below 37.5 ng/L, which is three orders lower than the safe blood lead level (100 μg/L). The devices also showed excellent selectivity over other metal cations such as, Na+, K+, Mg2+, and Ca2+, suggesting the capability of working in a complex sample matrix. We further successfully demonstrated the detection of Pb2+ ions in real blood samples from children by using our aptasensors, and explored their potential applications for quantification. Our results underscore such graphene FET aptasensors for future applications on fast detection of heavy metal ions for health monitoring and disease diagnostics. <s> BIB009 </s> Graphene-Based Materials for Biosensors: A Review <s> Chemical Vapor Deposition <s> Reliable determination of binding kinetics and affinity of DNA hybridization and single-base mismatches plays an essential role in systems biology, personalized and precision medicine. The standard tools are optical-based sensors that are difficult to operate in low cost and to miniaturize for high-throughput measurement. Biosensors based on nanowire field-effect transistors have been developed, but reliable and cost-effective fabrication remains a challenge. Here, we demonstrate that a graphene single-crystal domain patterned into multiple channels can measure time- and concentration-dependent DNA hybridization kinetics and affinity reliably and sensitively, with a detection limit of 10 pM for DNA. It can distinguish single-base mutations quantitatively in real time. An analytical model is developed to estimate probe density, efficiency of hybridization and the maximum sensor response. The results suggest a promising future for cost-effective, high-throughput screening of drug candidates, genetic variations and disease biomarkers by using an integrated, miniaturized, all-electrical multiplexed, graphene-based DNA array. <s> BIB010
Chemical vapor deposition (CVD) is one of the most popular methods for industrial-scale fabrication of graphene at this moment. Even though graphene provided by this method is very high quality and the number of layers can be precisely controlled, the electronic and structural properties has remained poorer than those of the Scotch-tape graphene. Excellent applications of CVD graphene have been performed in many fields, including electronic transistors BIB008  , transparent conductive electrodes   , corrosion-inhibiting coatings BIB007  and high sensitive sensors  BIB009 BIB010 . CVD is However, to obtain graphene by the Scotch-tape method, the maximum dimensions of the pristine graphene that can be isolated for fundamental studies and basic research that require high quality at only 1 mm 2 . Several synthetic procedures have been established that possess scalability in their different characteristics and are more effective for matching applications. Chemical vapor deposition (CVD) is one of the most popular methods for industrial-scale fabrication of graphene at this moment. Even though graphene provided by this method is very high quality and the number of layers can be precisely controlled, the electronic and structural properties has remained poorer than those of the Scotch-tape graphene. Excellent applications of CVD graphene have been performed in many fields, including electronic transistors BIB008  , transparent conductive electrodes   , corrosion-inhibiting coatings BIB007  and high sensitive sensors  BIB009 BIB010 . CVD is a way to dissolve a gaseous reactant, for example, methane, ethane or propane, into a heated substrate such as Cu or Ni, where the reaction results in graphene film growth on top of the substrate from the nucleation sites during the cooling process as seen in Figure 3b . A large-scale area of single-layer to few-layer graphene films is usually grown on various metal substrates such as Cu, Ni, Pt, Co, Ir and Ru BIB005 BIB002 BIB001 BIB003  . To gain better control of the growth of monolayer or bilayer graphene, Ni and Cu are usually used instead of the other metals which are much higher in cost. The transferred substrate can be either a polymer or metal  where the transfer process may causes damages from tearing and the formation of wrinkles. It is reported that the production of transparent, conductive, and large-area graphene films was achieved by growth on Cu foil by plasma CVD at low temperature of 300-400 • C and transferred to a diagonal width up to 30 inches via roll-to-roll process. The as-prepared graphene films consist of a few-layer sheets with the transparency 97.4% relative to low sheet resistance of 125 Ω/sq which is used in touch screen displays by the touch panel screen industry BIB003 . Alternatively, large-size CVD graphene is introduced into possible biosensor platforms to support Au nanoparticles and then to construct biomolecule receptor patterns BIB006 . Graphene is presented in order to enhance the sensitivity of sensors and biosensors whereas the nanoparticles increase the surface area to bind the analyte. In a glucose or glutamate molecule biosensor BIB004 , the glucose oxidase or glutamic dehydrogenase is functionalized on the graphene surface to monitor the conductance changes in real time. The CVD graphene is usually fabricated as a conducting layer in sensors and biosensors that require a high quality surface platform.