Two-dimensional graphene offers interesting electronic,thermal,and mechanical properties that are currently being explored for advanced electronics,membranes,and composites.Here we synthesize and explore the biologica...Two-dimensional graphene offers interesting electronic,thermal,and mechanical properties that are currently being explored for advanced electronics,membranes,and composites.Here we synthesize and explore the biological applications of nano-graphene oxide(NGO),i.e.,single-layer graphene oxide sheets down to a few nanometers in lateral width.We develop functionalization chemistry in order to impart solubility and compatibility of NGO in biological environments.We obtain size separated pegylated NGO sheets that are soluble in buffers and serum without agglomeration.The NGO sheets are found to be photoluminescent in the visible and infrared regions.The intrinsic photoluminescence(PL)of NGO is used for live cell imaging in the near-infrared(NIR)with little background.We found that simple physisorption viaπ-stacking can be used for loading doxorubicin,a widely used cancer drug onto NGO functionalized with antibody for selective killing of cancer cells in vitro.Owing to its small size,intrinsic optical properties,large specifi c surface area,low cost,and useful non-covalent interactions with aromatic drug molecules,NGO is a promising new material for biological and medical applications.展开更多
A graphene/TiO_(2) nanocrystals hybrid has been successfully prepared by directly growing TiO_(2) nanocrystals on graphene oxide(GO)sheets.The direct growth of the nanocrystals on GO sheets was achieved by a two-step ...A graphene/TiO_(2) nanocrystals hybrid has been successfully prepared by directly growing TiO_(2) nanocrystals on graphene oxide(GO)sheets.The direct growth of the nanocrystals on GO sheets was achieved by a two-step method,in which TiO_(2) was first coated on GO sheets by hydrolysis and crystallized into anatase nanocrystals by hydrothermal treatment in the second step.Slow hydrolysis induced by the use of EtOH/H2O mixed solvent and addition of H2SO4 facilitates the selective growth of TiO_(2) on GO and suppresses growth of free TiO_(2) in solution.The method offers easy access to the GO/TiO_(2) nanocrystals hybrid with a uniform coating and strong interactions between TiO_(2) and the underlying GO sheets.The strong coupling gives advanced hybrid materials with various applications including photocatalysis.The prepared graphene/TiO_(2) nanocrystals hybrid has superior photocatalytic activity to other TiO_(2) materials in the degradation of rhodamine B,showing an impressive three-fold photocatalytic enhancement over P25.It is expected that the hybrid material could also be promising for various other applications including lithium ion batteries,where strong electrical coupling to TiO_(2) nanoparticles is essential.展开更多
Aligned graphene nanoribbon (GNR) arrays have been made by unzipping of aligned single-walled and few-walled carbon nanotube (CNT) arrays. Nanotube unzipping was achieved by a polymer-protected Ar plasma etching metho...Aligned graphene nanoribbon (GNR) arrays have been made by unzipping of aligned single-walled and few-walled carbon nanotube (CNT) arrays. Nanotube unzipping was achieved by a polymer-protected Ar plasma etching method, and the resulting nanoribbon array can be transferred onto any chosen substrate. Atomic force microscope (AFM) imaging and Raman mapping on the same CNTs before and after unzipping confirmed that ~80% of CNTs were opened up to form single layer sub-10 nm GNRs. Electrical devices made from the GNRs (after annealing in H2 at high temperature) showed on/off current (Ion/Ioff) ratios up to 103 at room temperature, suggesting the semiconducting nature of the narrow GNRs. Novel GNR-GNR and GNR-CNT crossbars were fabricated by transferring GNR arrays across GNR and CNT arrays, respectively. The production of such ordered graphene nanoribbon architectures may allow for large scale integration of GNRs into nanoelectronics or optoelectronics.展开更多
Chemically derived and noncovalently functionalized graphene sheets(GS)were found to self-assemble onto patterned gold structures via electrostatic interactions between the functional groups and the gold surfaces.This...Chemically derived and noncovalently functionalized graphene sheets(GS)were found to self-assemble onto patterned gold structures via electrostatic interactions between the functional groups and the gold surfaces.This afforded regular arrays of single graphene sheets on large substrates,which were characterized by scanning electron microscopy(SEM),Auger microscopy imaging,and Raman spectroscopy.This represents the fi rst time that self-assembly has been used to produce on-substrate and fully-suspended graphene electrical devices.Molecular coatings on the GS were removed by high current“electrical annealing”,which restored the high electrical conductance and Dirac point of the GS.Molecular sensors for highly sensitive gas detection using the self-assembled GS devices are demonstrated.展开更多
基金by NIH-NCI funded CCNE TR at Stanford University.We are grateful to Drs.Alice Fan and Dean Felsher for providing the antibodies used in this work.
文摘Two-dimensional graphene offers interesting electronic,thermal,and mechanical properties that are currently being explored for advanced electronics,membranes,and composites.Here we synthesize and explore the biological applications of nano-graphene oxide(NGO),i.e.,single-layer graphene oxide sheets down to a few nanometers in lateral width.We develop functionalization chemistry in order to impart solubility and compatibility of NGO in biological environments.We obtain size separated pegylated NGO sheets that are soluble in buffers and serum without agglomeration.The NGO sheets are found to be photoluminescent in the visible and infrared regions.The intrinsic photoluminescence(PL)of NGO is used for live cell imaging in the near-infrared(NIR)with little background.We found that simple physisorption viaπ-stacking can be used for loading doxorubicin,a widely used cancer drug onto NGO functionalized with antibody for selective killing of cancer cells in vitro.Owing to its small size,intrinsic optical properties,large specifi c surface area,low cost,and useful non-covalent interactions with aromatic drug molecules,NGO is a promising new material for biological and medical applications.
基金This work was supported in part by Intel,MARCO-MSD,and ONR.
文摘A graphene/TiO_(2) nanocrystals hybrid has been successfully prepared by directly growing TiO_(2) nanocrystals on graphene oxide(GO)sheets.The direct growth of the nanocrystals on GO sheets was achieved by a two-step method,in which TiO_(2) was first coated on GO sheets by hydrolysis and crystallized into anatase nanocrystals by hydrothermal treatment in the second step.Slow hydrolysis induced by the use of EtOH/H2O mixed solvent and addition of H2SO4 facilitates the selective growth of TiO_(2) on GO and suppresses growth of free TiO_(2) in solution.The method offers easy access to the GO/TiO_(2) nanocrystals hybrid with a uniform coating and strong interactions between TiO_(2) and the underlying GO sheets.The strong coupling gives advanced hybrid materials with various applications including photocatalysis.The prepared graphene/TiO_(2) nanocrystals hybrid has superior photocatalytic activity to other TiO_(2) materials in the degradation of rhodamine B,showing an impressive three-fold photocatalytic enhancement over P25.It is expected that the hybrid material could also be promising for various other applications including lithium ion batteries,where strong electrical coupling to TiO_(2) nanoparticles is essential.
基金This work was supported by MARCO-MSD,Intel,ONR and graphene-MURI.
文摘Aligned graphene nanoribbon (GNR) arrays have been made by unzipping of aligned single-walled and few-walled carbon nanotube (CNT) arrays. Nanotube unzipping was achieved by a polymer-protected Ar plasma etching method, and the resulting nanoribbon array can be transferred onto any chosen substrate. Atomic force microscope (AFM) imaging and Raman mapping on the same CNTs before and after unzipping confirmed that ~80% of CNTs were opened up to form single layer sub-10 nm GNRs. Electrical devices made from the GNRs (after annealing in H2 at high temperature) showed on/off current (Ion/Ioff) ratios up to 103 at room temperature, suggesting the semiconducting nature of the narrow GNRs. Novel GNR-GNR and GNR-CNT crossbars were fabricated by transferring GNR arrays across GNR and CNT arrays, respectively. The production of such ordered graphene nanoribbon architectures may allow for large scale integration of GNRs into nanoelectronics or optoelectronics.
文摘Chemically derived and noncovalently functionalized graphene sheets(GS)were found to self-assemble onto patterned gold structures via electrostatic interactions between the functional groups and the gold surfaces.This afforded regular arrays of single graphene sheets on large substrates,which were characterized by scanning electron microscopy(SEM),Auger microscopy imaging,and Raman spectroscopy.This represents the fi rst time that self-assembly has been used to produce on-substrate and fully-suspended graphene electrical devices.Molecular coatings on the GS were removed by high current“electrical annealing”,which restored the high electrical conductance and Dirac point of the GS.Molecular sensors for highly sensitive gas detection using the self-assembled GS devices are demonstrated.
