Showing papers in "Advanced Materials in 2012"
TL;DR: This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials, and highlights crucial issues that should be addressed in future research activities.
Abstract: Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.
3,265 citations
TL;DR: Optical, microscopic and electrical measurements suggest that the synthetic process leads to the growth of MoS(2) monolayer, and TEM images verify that the synthesized MoS (2) sheets are highly crystalline.
Abstract: Large-area MoS(2) atomic layers are synthesized on SiO(2) substrates by chemical vapor deposition using MoO(3) and S powders as the reactants. Optical, microscopic and electrical measurements suggest that the synthetic process leads to the growth of MoS(2) monolayer. The TEM images verify that the synthesized MoS(2) sheets are highly crystalline.
3,088 citations
TL;DR: The recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed andp-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed.
Abstract: Transparent electronics is today one of the most advanced topics for a wide range of device applications. The key components are wide bandgap semiconductors, where oxides of different origins play an important role, not only as passive component but also as active component, similar to what is observed in conventional semiconductors like silicon. Transparent electronics has gained special attention during the last few years and is today established as one of the most promising technologies for leading the next generation of flat panel display due to its excellent electronic performance. In this paper the recent progress in n- and p-type oxide based thin-film transistors (TFT) is reviewed, with special emphasis on solution-processed and p-type, and the major milestones already achieved with this emerging and very promising technology are summarizeed. After a short introduction where the main advantages of these semiconductors are presented, as well as the industry expectations, the beautiful history of TFTs is revisited, including the main landmarks in the last 80 years, finishing by referring to some papers that have played an important role in shaping transparent electronics. Then, an overview is presented of state of the art n-type TFTs processed by physical vapour deposition methods, and finally one of the most exciting, promising, and low cost but powerful technologies is discussed: solution-processed oxide TFTs. Moreover, a more detailed focus analysis will be given concerning p-type oxide TFTs, mainly centred on two of the most promising semiconductor candidates: copper oxide and tin oxide. The most recent data related to the production of complementary metal oxide semiconductor (CMOS) devices based on n- and p-type oxide TFT is also be presented. The last topic of this review is devoted to some emerging applications, finalizing with the main conclusions. Related work that originated at CENIMAT|I3N during the last six years is included in more detail, which has led to the fabrication of high performance n- and p-type oxide transistors as well as the fabrication of CMOS devices with and on paper.
2,440 citations
TL;DR: The in vitro and in vivo biocompatibility and biotranslocation of MSNs are discussed in relation to their chemophysical properties including particle size, surface properties, shape, and structure.
Abstract: In the past decade, mesoporous silica nanoparticles (MSNs) have attracted more and more attention for their potential biomedical applications. With their tailored mesoporous structure and high surface area, MSNs as drug delivery systems (DDSs) show significant advantages over traditional drug nanocarriers. In this review, we overview the recent progress in the synthesis of MSNs for drug delivery applications. First, we provide an overview of synthesis strategies for fabricating ordered MSNs and hollow/rattle-type MSNs. Then, the in vitro and in vivo biocompatibility and biotranslocation of MSNs are discussed in relation to their chemophysical properties including particle size, surface properties, shape, and structure. The review also highlights the significant achievements in drug delivery using mesoporous silica nanoparticles and their multifunctional counterparts as drug carriers. In particular, the biological barriers for nano-based targeted cancer therapy and MSN-based targeting strategies are discussed. We conclude with our personal perspectives on the directions in which future work in this field might be focused.
2,251 citations
TL;DR: Recent advances in strategies for advanced metal oxide-based hybrid nanostructure design are reviewed, with the focus on the binder-free film/array electrodes that can provide larger electrochemically active surface area, faster electron transport and superior ion diffusion, thus leading to substantially improved cycling and rate performance.
Abstract: Metal oxide nanostructures are promising electrode materials for lithium-ion batteries and supercapacitors because of their high specific capacity/capacitance, typically 2-3 times higher than that of the carbon/graphite-based materials. However, their cycling stability and rate performance still can not meet the requirements of practical applications. It is therefore urgent to improve their overall device performance, which depends on not only the development of advanced electrode materials but also in a large part "how to design superior electrode architectures". In the article, we will review recent advances in strategies for advanced metal oxide-based hybrid nanostructure design, with the focus on the binder-free film/array electrodes. These binder-free electrodes, with the integration of unique merits of each component, can provide larger electrochemically active surface area, faster electron transport and superior ion diffusion, thus leading to substantially improved cycling and rate performance. Several recently emerged concepts of using ordered nanostructure arrays, synergetic core-shell structures, nanostructured current collectors, and flexible paper/textile electrodes will be highlighted, pointing out advantages and challenges where appropriate. Some future electrode design trends and directions are also discussed.
2,176 citations
TL;DR: Nitrogen-doped carbon nanofiber webs (CNFWs) with high surface areas are successfully prepared by carbonization-activation of polypyrrole nan ofiber webs with KOH, which exhibit a superhigh reversible capacity and porous nanostructure.
Abstract: Nitrogen-doped carbon nanofiber webs (CNFWs) with high surface areas are successfully prepared by carbonization-activation of polypyrrole nanofiber webs with KOH. The as-obtained CNFWs exhibit a superhigh reversible capacity of 943 mAh g(-1) at a current density of 2 A g(-1) even after 600 cycles, which is ascribed to the novel porous nanostructure and high-level nitrogen doping.
1,516 citations
TL;DR: The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established and Insight is given into what the authors can expect from this rapidly expanding field and future challenges will be addressed.
Abstract: The advent of negative index materials has spawned extensive research into metamaterials over the past decade. Metamaterials are attractive not only for their exotic electromagnetic properties, but also their promise for applications. A particular branch–the metamaterial perfect absorber (MPA)–has garnered interest due to the fact that it can achieve unity absorptivity of electromagnetic waves. Since its first experimental demonstration in 2008, the MPA has progressed significantly with designs shown across the electromagnetic spectrum, from microwave to optical. In this Progress Report we give an overview of the field and discuss a selection of examples and related applications. The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established. Insight is given into what we can expect from this rapidly expanding field and future challenges will be addressed.
1,419 citations
TL;DR: The recent research activities in the synthesis of metal oxide hollow nanostructures with controlled shape, size, composition, and structural complexity, as well as their applications in LIBs are summarized.
Abstract: Metal oxide hollow structures have received great attention because of their many promising applications in a wide range of fields. As electrode materials for lithium-ion batteries (LIBs), metal oxide hollow structures provide high specific capacity, superior rate capability, and improved cycling performance. In this Research News, we summarize the recent research activities in the synthesis of metal oxide hollow nanostructures with controlled shape, size,composition, and structural complexity, as well as their applications in LIBs. By focusing on hollow structures of some binary metal oxides (such as SnO 2 ,TiO 2 , Fe 2 O 3 , Co 3 O 4 ) and complex metal oxides, we seek to provide some rational understanding on the effect of nanostructure engineering on the electrochemical performance of the active materials. It is thus anticipated that this article will shed some light on the development of advanced electrode materials for next-generation LIBs.
1,391 citations
TL;DR: This method has been successfully applied to determine Cu(2+) in real water samples and shows good results in terms of particle size and quantum yield.
Abstract: Dr. S. Liu , J. Tian , L. Wang , Zhang , Dr. . Y X. Qin , Luo , . Y Prof. X. Sun State Key Lab of Electroanalytical Chemistry Changchun Institute of Applied Chemistry Changchun 130022, Jilin, China; Fax: ( + 86) 431-85262065 E-mail: sunxp@ciac.jl.cn J. Tian Graduate School of the Chinese Academy of Sciences Beijing 100039, China Prof. A. M. Asiri , A. O. Al-Youbi , Prof. X. Sun Chemistry Department, Faculty of Science King Abdulaziz University Jeddah 21589, Saudi Arabia Prof. A. M. Asiri , A. O. Al-Youbi , Prof. X. Sun Center of Excellence for Advanced Materials ResearchKing Abdulaziz University Jeddah 21589, Saudi Arabia
1,295 citations
TL;DR: Several challenges remain in developing ASSSs, such as to: i) explore high-performance electrode materials, ii) enhance the interfacial compatibility between electrode and solid-state electrolyte, and iii) simplify the device fabrication process.
Abstract: carbide-derived carbon, [ 12 ] carbon nanotubes (CNTs), [ 14–17 ] and graphene, [ 6 , 7 , 10 , 18 , 19 ] possess notable features including high surface area, high electrical conductivity, and good chemical stability, and therefore they have been widely explored as thinfi lm electrode materials for ASSSs. However, the fabrication of ASSSs generally involves complex solution processing, highpressure pressing, high-temperature sintering, and sputtering techniques. [ 11 , 12 , 14–17 ] Moreover, polymer binders and conductive additives are required to enhance the adhesion between electrode materials and substrates as well as to improve the conductivity of the electrode, which unavoidably leads to decreased energy density of the devices. [ 6 , 20 ] Therefore, several challenges remain in developing ASSSs, such as to: i) explore high-performance electrode materials, ii) enhance the interfacial compatibility between electrode and solid-state electrolyte, and iii) simplify the device fabrication process. Graphene aerogels (GAs) represent a new class of ultralight and porous carbon materials that are associated with high
1,260 citations
TL;DR: The developments in stability/degradation of OPVs in the last five years are reviewed, such as inverted device structures of the bulk heterojunction geometry device, which allows for more stable metal electrodes, the choice of more photostable active materials, the introduction of interfacial layers, and roll-to-roll fabrication.
Abstract: Organic photovoltaics (OPVs) evolve in an exponential manner in the two key areas of efficiency and stability. The power conversion efficiency (PCE) has in the last decade been increased by almost a factor of ten approaching 10%. A main concern has been the stability that was previously measured in minutes, but can now, in favorable circumstances, exceed many thousands of hours. This astonishing achievement is the subject of this article, which reviews the developments in stability/degradation of OPVs in the last five years. This progress has been gained by several developments, such as inverted device structures of the bulk heterojunction geometry device, which allows for more stable metal electrodes, the choice of more photostable active materials, the introduction of interfacial layers, and roll-to-roll fabrication, which promises fast and cheap production methods while creating its own challenges in terms of stability.
TL;DR: This Review focuses on manipulation of the electronic and atomic structural features which makes up the thermoelectric quality factor, and the principles used are equally applicable to most good thermoeLECTric materials that could enable improvement of thermoelectedric devices from niche applications into the mainstream of energy technologies.
Abstract: Lead chalcogenides have long been used for space-based and thermoelectric remote power generation applications, but recent discoveries have revealed a much greater potential for these materials. This renaissance of interest combined with the need for increased energy efficiency has led to active consideration of thermoelectrics for practical waste heat recovery systems—such as the conversion of car exhaust heat into electricity. The simple high symmetry NaCl-type cubic structure, leads to several properties desirable for thermoelectricity, such as high valley degeneracy for high electrical conductivity and phonon anharmonicity for low thermal conductivity. The rich capabilities for both band structure and microstructure engineering enable a variety of approaches for achieving high thermoelectric performance in lead chalcogenides. This Review focuses on manipulation of the electronic and atomic structural features which makes up the thermoelectric quality factor. While these strategies are well demonstrated in lead chalcogenides, the principles used are equally applicable to most good thermoelectric materials that could enable improvement of thermoelectric devices from niche applications into the mainstream of energy technologies.
TL;DR: Materials that are both conductive and stretchable could enable a spectrum of applications such as stretchable displays, stretchable radiofrequency antennas, artifi cial muscles and conformal skin sensors.
Abstract: IO N Materials that are both conductive and stretchable could enable a spectrum of applications such as stretchable displays, [ 1 ] stretchable radiofrequency antennas, [ 2 ] artifi cial muscles [ 3 ] and conformal skin sensors. [ 4–7 ] A variety of such materials have been recently developed, such as wavy thin metals, [ 8 , 9 ] metal-coated net-shaped plastic fi lm, [ 10 ] graphene fi lms [ 11 ] and carbon nanotube (CNT)-based composites. [ 12–19 ] But several limitations typically exist in these materials including low conductivity, [ 13 , 15 , 16 , 19 ]
TL;DR: An overview of TMO-based device architectures ranging from transparent OLEDs to tandem OPV cells is given, and various TMO film deposition methods are reviewed, addressing vacuum evaporation and recent approaches for solution-based processing.
Abstract: During the last few years, transition metal oxides (TMO) such as molybdenum tri-oxide (MoO3), vanadium pent-oxide (V2O5) or tungsten tri-oxide (WO3) have been extensively studied because of their exceptional electronic properties for charge injection and extraction in organic electronic devices. These unique properties have led to the performance enhancement of several types of devices and to a variety of novel applications. TMOs have been used to realize efficient and long-term stable p-type doping of wide band gap organic materials, charge-generation junctions for stacked organic light emitting diodes (OLED), sputtering buffer layers for semi-transparent devices, and organic photovoltaic (OPV) cells with improved charge extraction, enhanced power conversion efficiency and substantially improved long term stability. Energetics in general play a key role in advancing device structure and performance in organic electronics; however, the literature provides a very inconsistent picture of the electronic structure of TMOs and the resulting interpretation of their role as functional constituents in organic electronics. With this review we intend to clarify some of the existing misconceptions. An overview of TMO-based device architectures ranging from transparent OLEDs to tandem OPV cells is also given. Various TMO film deposition methods are reviewed, addressing vacuum evaporation and recent approaches for solution-based processing. The specific properties of the resulting materials and their role as functional layers in organic devices are discussed.
TL;DR: Multilayer MoS(2) phototransistors further exhibit high room temperature mobilities, near-ideal subthreshold swings, low operating gate biases, and negligible shifts in the threshold voltages during illumination.
Abstract: Phototransistors based on multilayer MoS(2) crystals are demonstrated with a wider spectral response and higher photoresponsivity than single-layer MoS(2) phototransistors. Multilayer MoS(2) phototransistors further exhibit high room temperature mobilities (>70 cm(2) V(-1) s(-1) ), near-ideal subthreshold swings (~70 mV decade(-1) ), low operating gate biases (<5 V), and negligible shifts in the threshold voltages during illumination.
TL;DR: A novel vulcanized polyaniline nanotube/sulfur composite was prepared successfully via an in situ vulcanization process by heating a mixture of polyAniline Nanotube and sulfur at 280 °C.
Abstract: Applications of rechargeable batteries are diverse and range from storing energy from renewable resources such as wind generators and solar arrays , powering electric vehicles and portable electronic devices. Significant R&D efforts have focused on achieving high energy density, long cycling life, low cost, and safety.1 Among all known rechargeable battery systems, lithium-sulfur (Li-S) batteries have attracted considerable attention.2, 3 Elemental sulfur is abundant, and is a very attractive cathode material for lithium batteries because of its high theoretical capacity (1672 mAh g-1) and specific energy (2600 Wh kg-1), assuming complete reaction of lithium with sulfur to form Li2S.
TL;DR: A simple and general fabrication method for helical swimming micromachines by direct laser writing and e-beam evaporation is demonstrated and the magnetic helical devices exhibit varying magnetic shape anisotropy, yet always generate corkscrew motion using a rotating magnetic field.
Abstract: A simple and general fabrication method for helical swimming micromachines by direct laser writing and e-beam evaporation is demonstrated. The magnetic helical devices exhibit varying magnetic shape anisotropy, yet always generate corkscrew motion using a rotating magnetic field. They also exhibit good swimming performance and are capable of pick-and-place micromanipulation in 3D. Cytotoxicity of the devices was investigated using mouse myoblasts. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
TL;DR: The progress made in the properties of dielectric nanosheets is reviewed, highlighting emerging functionalities in electronic applications and a perspective on the advantages offered by this class of materials for future nanoelectronics.
Abstract: Two-dimensional (2D) nanosheets, which possess atomic or molecular thickness and infinite planar lengths, are regarded as the thinnest functional nanomaterials. The recent development of methods for manipulating graphene (carbon nanosheet) has provided new possibilities and applications for 2D systems; many amazing functionalities such as high electron mobility and quantum Hall effects have been discovered. However, graphene is a conductor, and electronic technology also requires insulators, which are essential for many devices such as memories, capacitors, and gate dielectrics. Along with graphene, inorganic nanosheets have thus increasingly attracted fundamental research interest because they have the potential to be used as dielectric alternatives in next-generation nanoelectronics. Here, we review the progress made in the properties of dielectric nanosheets, highlighting emerging functionalities in electronic applications. We also present a perspective on the advantages offered by this class of materials for future nanoelectronics.
TL;DR: These PEDOT:PSS films with conductivity and transparency comparable to ITO can replace ITO as the transparent electrode of optoelectronic devices.
Abstract: The conductivity of PEDOT:PSS films was significantly enhanced from 0.3 S cm(-1) to 3065 S cm(-1) through a treatment with dilute sulfuric acids. PEDOT:PSS films with a sheet resistance of 39 Ω sq(-1) and transparency of around 80% at 550 nm are obtained. These PEDOT:PSS films with conductivity and transparency comparable to ITO can replace ITO as the transparent electrode of optoelectronic devices.
TL;DR: The elastic deformation of few layers (5 to 25) thick freely suspended MoS2 nanosheets is studied by means of a nanoscopic version of a bending test experiment, carried out with the tip of an atomic force microscope.
Abstract: We study the elastic deformation of few layers (5 to 25) thick freely suspended MoS2 nanosheets by means of a nanoscopic version of a bending test experiment, carried out with the tip of an atomic force microscope. The Young's modulus of these nanosheets is extremely high (E = 0.33 TPa), comparable to that of graphene oxide, and the deflections are reversible up to tens of nanometers.
TL;DR: The stretchable metal electrode from very long metal nanowires demonstrated high electrical conductivity and mechanical compliance at the same time and is expected to overcome the performance limitation of the current stretchable electronics such as graphene, carbon nanotubes, and buckled nanoribbons.
Abstract: A highly stretchable metal electrode is developed via the solution-processing of very long (>100 μm) metallic nanowires and subsequent percolation network formation via low-temperature nanowelding. The stretchable metal electrode from very long metal nanowires demonstrated high electrical conductivity (~9 ohm sq(-1) ) and mechanical compliance (strain > 460%) at the same time. This method is expected to overcome the performance limitation of the current stretchable electronics such as graphene, carbon nanotubes, and buckled nanoribbons.
TL;DR: The structural reformation of graphene, from pore generation to morphology transformation, is receiving growing attention, because the reconstruction of graphene could potentially result in localized highly reactive regions and thus unexpected properties for specifi c applications.
Abstract: Continuous scientifi c endeavors have been directed toward the optimization of graphene by manipulating its electronic, mechanical, chemical, and structural properties, such as surface area, pore geometry, and functional sites, in order to advance various potential applications, including nanoelectronics, energy storage/conversion, and catalysis. [ 1 ] The structural reformation of graphene, from pore generation to morphology transformation, is receiving growing attention, because the reconstruction of graphene could potentially result in localized highly reactive regions and thus unexpected properties for specifi c applications. [ 2 ] For instance, it was reported that crumpled graphene allows for the fabrication of polymer-graphene nanocomposite fi lms with low O 2 permeability and effective reduction of transparency. [ 3 ] Chemical functionalization of graphene (e.g., graphene oxide or GO) is another effective method for manipulating physical and chemical properties of graphene, because enriched reactive oxygen functional groups in GO can provide ample covalent bonding sites for the chemical functionalization. The functionalized GO can be easily converted to graphene-like materials through chemical or thermal reduction of GO. [ 4 ] For instance, nitrogen-doped graphene (NG) can be synthesized through thermal annealing of GO in ammonia, and the resulting NG showed some unique properties including improved conductivity and excellent catalytic activity. Actually, NG has been intensively investigated as electrode materials for lithium-ion batteries, catalysts for oxygen reduction reac-
TL;DR: With doxorubicin hydrochloride loaded, Au@SiO(2)-DOX show two light-mediated therapeutic modes: low power density laser-triggered drug release for chemotherapy, and high powerdensity laser-induced hyperthermia, which suggest the potential for in-vivo applications.
Abstract: X. Wu, C. Chen, and co-workers develop mesoporous silica-coated gold nanorods (Au@ SiO2) as a versatile platform for imaging, chemotherapeutics, and hyperthermia. The Au@ SiO2 thus keeps both the unique functions of mesoporous silica nanoparticles and gold nanorods, and also provides a new functionality: lightcontrolled drug release. With integrated functions, such multifunctional theranostic systems are critical to optimize therapeutic efficacy and to improve safety of therapeutic regimes. They will provide more opportunities for on-demand therapy, paving the way to personalized medicine.
TL;DR: Graphene-TiO(2) nanoparticles possess excellent photocatalytic properties under visible light for the degradation of methylene blue and a red-shift of the band-edge and a significant reduction of theBandgap.
Abstract: Highly photoactive, graphene-wrapped anatase TiO(2) nanoparticles are synthesized through one-step hydrothermal reduction of graphene oxide (GO) and TiO(2) crystallization from GO-wrapped amorphous TiO(2) NPs. Graphene-TiO(2) nanoparticles exhibit a red-shift of the band-edge and a significant reduction of the bandgap (2.80 eV). Graphene-TiO(2) nanoparticles possess excellent photocatalytic properties under visible light for the degradation of methylene blue.
TL;DR: Using this theranostic nanoprobe, in-vivo triple modal fluorescence, photoacoustic, and magnetic resonance imaging are carried out, uncovering high passive tumor targeting, which is further used for effective photothermal ablation of tumors in mice.
Abstract: In this work, a nanoscale reduced graphene oxide-iron oxide nanoparticle (RGO-IONP) complex is noncovalently functionalized with polyethylene glycol (PEG), obtaining a RGO-IONP-PEG nanocomposite with excellent physiological stability, strong NIR optical absorbance, and superparamagnetic properties. Using this theranostic nanoprobe, in-vivo triple modal fluorescence, photoacoustic, and magnetic resonance imaging are carried out, uncovering high passive tumor targeting, which is further used for effective photothermal ablation of tumors in mice.
TL;DR: This paper reviews the chemical sensors and biosensors based on two types of OTFTs, including organic field-effect transistors (OFETs) and organic electrochemical transistor (OECTs), mainly focusing on the papers published in the past 10 years.
Abstract: Organic thin-film transistors (OTFTs) show promising applications in various chemical and biological sensors. The advantages of OTFT-based sensors include high sensitivity, low cost, easy fabrication, flexibility and biocompatibility. In this paper, we review the chemical sensors and biosensors based on two types of OTFTs, including organic field-effect transistors (OFETs) and organic electrochemical transistors (OECTs), mainly focusing on the papers published in the past 10 years. Various types of OTFT-based sensors, including pH, ion, glucose, DNA, enzyme, antibody-antigen, cell-based sensors, dopamine sensor, etc., are classified and described in the paper in sequence. The sensing mechanisms and the detection limits of the devices are described in details. It is expected that OTFTs may have more important applications in chemical and biological sensing with the development of organic electronics.
TL;DR: The relationship between the photovoltaic performance and the structure of perylene imides is discussed and perylene imides-based copolymers or oligomers play an important role in single junction devices.
Abstract: Perylene imides have been an object of research for 100 years and their derivatives are key n-type semiconductors in the field of organic electronics. While perylene diimides have been applied in many electronic and photonic devices, their use can be traced back to the first efficient organic solar cell. By functionalizing different positions of the in total 12 positions (four peri, four bay, and four ortho-positions) on the perylene core, perylene imides with significantly different optical, electronic and morphological properties may be prepared. Perylene imides and their derivatives have been used in several types of organic photovoltaics, including flat-, and bulk-heterojunction devices as well as dye-sensitized solar cells. Additionally perylene imides-based copolymers or oligomers play an important role in single junction devices. In this review, the relationship between the photovoltaic performance and the structure of perylene imides is discussed.
TL;DR: In this Review, the importance of graphene-based electrodes, their fabrication techniques, and application areas are discussed.
Abstract: Graphene, the thinnest two dimensional carbon material, has become the subject of intensive investigation in various research fields because of its remarkable electronic, mechanical, optical and thermal properties. Graphene-based electrodes, fabricated from mechanically cleaved graphene, chemical vapor deposition (CVD) grown graphene, or massively produced graphene derivatives from bulk graphite, have been applied in a broad range of applications, such as in light emitting diodes, touch screens, field-effect transistors, solar cells, supercapacitors, batteries, and sensors. In this Review, after a short introduction to the properties and synthetic methods of graphene and its derivatives, we will discuss the importance of graphene-based electrodes, their fabrication techniques, and application areas.
TL;DR: Preparation of freestanding multilayered graphene fi lms by vacuum-assisted fi ltration based on the effective prevention of graphene intersheet restacking and the formation of a 3D graphene hydrogel by a hydrothermal method are reported.
Abstract: For instance, freestanding graphene macroscopic structures have shown unique catalytic, electrochemical, and mechanical properties together with potential applications in chemical fi lters and electrodes for energy storage devices. [ 6–8 , 11 , 30 ] However, in most cases, during the process of assembling nanometerscale building blocks into macroscopic paper-like structures, the large accessible surface area of 2D graphene sheets is lost. The reason for this is that the individual graphene sheets tend to irreversibly aggregate and restack owing to the strong π π stacking and van der Waals force between the planar basal planes of graphene sheets. This reduces the potential applications of graphene materials in electrochemical electrodes, composite materials, and so on. [ 20 ] Therefore, preventing aggregation of graphene sheets in the macroscopic structures, such that the properties of the individual graphene sheets are not compromised, is a critical challenge in constructing functional graphene-based macroscopic structures. Currently, a number of strategies for preventing aggregation have been developed, which include adding spacers (e.g., surfactants, nanoparticles, polymers), [ 27–36 ] template-assisted growth, [ 37 ] and crumpling the graphene sheets. [ 18 , 38 ] Alternatively, several groups have reported the formation of freestanding 3D graphene-based macroscopic structures without the assistance of any spacers or templates. [ 7 , 39,40 ] For instance, Li and coworkers reported the preparation of freestanding multilayered graphene fi lms by vacuum-assisted fi ltration based on the effective prevention of graphene intersheet restacking. [ 7 ] Shi and coworkers demonstrated the formation of a 3D graphene hydrogel by a hydrothermal method. [ 39 ] However, preparing freestanding and fl exible graphene fi lms with large accessible surface area but
TL;DR: Drug delivery studies suggest the promise of these UCNPs as drug carriers for intracellular drug delivery and eventually as a multifunctional nanoplatform for simultaneous diagnosis and therapy.
Abstract: Pure dark red emission (650-670 nm) of NaYF(4):Yb/Er upconversion nanoparticles (UCNPs) is achieved by manganese ions (Mn(2+)) doping. In addition, the Mn(2+)-doping can also control the crystalline phase and size of the resulting UCNPs simultaneously. Drug delivery studies suggest the promise of these UCNPs as drug carriers for intracellular drug delivery and eventually as a multifunctional nanoplatform for simultaneous diagnosis and therapy.