Novel structure-engineered amorphous oxide semiconductor thin-film transistors using a solution process to overcome the trade-off between high mobility and other parameters (i.e., on/off ratio, sub-threshold voltage swing, threshold voltage, and so on) are proposed. High performance confining structure-engineered AOS TFTs are successfully demonstrated, which utilize a specially designed layer with ultra-high density and high electron mobility.
Artificial superlattice nanocomposites are successfully prepared by electrostatic heteroassembly of redoxable Co–Al or Co–Ni layered double hydroxide (LDH) nanosheets with graphene. The superlattice electrodes exhibit a high capacity up to ca. 650 F/g, which is approximately 6 times that of pure graphene. The composites are found to be capable of superfast charging and discharging, up to ca. 100 Hz, comparable with the high-power performance of graphene electrodes.
Hybrid nanostructures composed of semiconductor and plasmonic metal components are receiving extensive attention. They display extraordinary optical characteristics that are derived from the simultaneous existence and close conjunction of localized surface plasmon resonance and semiconduction, as well as the synergistic interactions between the two components. They have been widely studied for photocatalysis, plasmon-enhanced spectroscopy, biotechnology, and solar cells. In this review, the developments in the field of (plasmonic metal)/semiconductor hybrid nanostructures are comprehensively described. The preparation of the hybrid nanostructures is first presented according to the semiconductor type, as well as the nanostructure morphology. The plasmonic properties and the enabled applications of the hybrid nanostructures are then elucidated. Lastly, possible future research in this burgeoning field is discussed.
(Plasmonic metal)/semiconductor hybrid nanostructures are currently of increasing interest owing to their rich and attractive physical and chemical properties derived from localized plasmon resonance and semiconduction. In this article, the preparation, properties, and applications of this type of hybrid nanostructure are reviewed. Future directions in this field are also discussed.
Rational bottom-up assembly of nanowire networks may be a way to successfully continue the miniaturization in the semiconductor industry. A generic method is developed that ensures InSb nanowires meet under the optimal angle for the formation of single-crystalline structures, which represents a promising platform for the future random access memories based on Majorana fermions.
As the portable device hardware has been increasing at a noticeable rate, ultrathin thermal conducting materials (TCMs) with the combination of high thermal conductivity and excellent electromagnetic interface (EMI) shielding performance, which are used to efficiently dissipate heat and minimize EMI problems generated from electronic components (such as high speed processors), are urgently needed. In this work, graphene oxide (GO) films are fabricated by direct evaporation of GO suspension under mild heating, and ultrathin graphite-like graphene films are produced by graphitizing GO films. Further investigation demonstrates that the resulting graphene film with only ≈8.4 μm in thickness not only possesses excellent EMI shielding effectiveness of ≈20 dB and high in-plane thermal conductivity of ≈1100 W m-1 K-1, but also shows excellent mechanical flexibility and structure integrity during bending, indicating that the graphitization of GO film could be considered as a new alternative way to produce excellent TCMs with efficient EMI shielding.
The graphitization of graphene oxide films can lead to the formation of graphite-like graphene films, which not only display a remarkable combination of excellent electromagnetic interface (EMI) shielding effectiveness and high in-plane thermal conductivity, but also show excellent mechanical flexibility, indicating a novel promising candidate for excellent thermal conducting materials with efficient EMI shielding.
S. Peng, S. Ramakrishna, Q. Yan, and co-workers demonstrate a solutionbased route for the synthesis of CoS2 and NiS2 hollow spheres with various interiors. The obtained CoS2 hollow spheres display superior performances in supercapacitors and dye-sensitized solar cells. This work provides a promising approach for the design and synthesis of structurally tunable materials with greatly enhanced supercapacitor behavior, which could be applied in energy conversion and storage devices.
Reported here is a bioinspired fabrication of superhydrophobic graphene surfaces by means of two-beam laser interference (TBLI) treatment of graphene oxide (GO) films. Microscale grating-like structures with tunable periods and additional nanoscale roughness are readily created on graphene films due to laser induced ablation effect. Synchronously, abundant hydrophilic oxygen-containing groups (OCGs) on GO sheets can be drastically removed after TBLI treatment, which lower its surface energy significantly. The synergistic effect of micro-nanostructuring and the OCGs removal endows the resultant graphene films with unique superhydrophobicity. Additionally, dual TBLI treatment with 90° rotation is implemented to fabricate superhydrophobic graphene films with two-dimensional grating-like structures that can effectively avoid the anisotropic hydrophobicity originated from the grooved structures. Moreover, the superhydrophobic graphene films become conductive due to the laser reduction effect. Unique optical characteristics including transmission diffraction and brilliant structural color are also observed due to the presence of periodic microstructures. As a mask-free, chemical-free, and cost-effective method, the TBLI processing of GO may open up a new way to biomimetic graphene surfaces, and thus hold great promise for the development of novel graphene-based microdevices.
A bioinspired fabrication of superhydrophobic graphene surfaces by means of laser holographic treatment of graphene oxide (GO) films is presented. Microscale grating-like structures with nanoscale roughness are created on graphene films, and hydrophilic oxygen groups on GO sheets are drastically removed. The synergistic effect endows the resultant graphene films with unique superhydrophobicity and unique optical properties that mimic butterfly wings.
Iron oxide nanoparticles are formidable multifunctional systems capable of contrast enhancement in magnetic resonance imaging, guidance under remote fields, heat generation, and biodegradation. Yet, this potential is underutilized in that each function manifests at different nanoparticle sizes. Here, sub-micrometer discoidal magnetic nanoconstructs are realized by confining 5 nm ultra-small super-paramagnetic iron oxide nanoparticles (USPIOs) within two different mesoporous structures, made out of silicon and polymers. These nanoconstructs exhibit transversal relaxivities up to ≈10 times (r 2 ≈ 835 mm −1 s−1) higher than conventional USPIOs and, under external magnetic fields, collectively cooperate to amplify tumor accumulation. The boost in r 2 relaxivity arises from the formation of mesoscopic USPIO clusters within the porous matrix, inducing a local reduction in water molecule mobility as demonstrated via molecular dynamics simulations. The cooperative accumulation under static magnetic field derives from the large amount of iron that can be loaded per nanoconstuct (up to ≈65 fg) and the consequential generation of significant inter-particle magnetic dipole interactions. In tumor bearing mice, the silicon-based nanoconstructs provide MRI contrast enhancement at much smaller doses of iron (≈0.5 mg of Fe kg−1 animal) as compared to current practice.
Nanoconstructs are realized by confining 5 nm ultra-small superparamagnetic iron oxide nanoparticles (USPIOs) within two different mesoporous structures (silicon and polymers). They exhibit transversal relaxivities up to ≈10 times higher than conventional USPIOs and, under external magnetic fields, collectively cooperate to amplify tumor accumulation in mice to provide MRI contrast enhancement at much smaller doses of iron as compared to current practice.
A spin-cast method is presented for the formation of phosphonic acid functionalized small molecule layers on solution-processed ZnO substrates for use as electron collecting interlayers in organic photovoltaics. Phosphonic acid interlayers modify the ZnO work function and the charge carrier injection barrier at its interface, resulting in systematic control of V OC in inverted bulk heterojunction solar cells. Surface modification is shown to moderate the need for UV light-soaking of the ZnO contact layers. Lifetime studies (30 days) indicate stable and improved OPV performance over the unmodified ZnO contact, which show significant increases in charge extraction barriers and series resistance. Results suggest that enhanced stability using small molecule modifiers is due to partial passivation of the oxide surface to molecular oxygen adsorption. Surface passivation while maintaining work function control of a selective interlayer can be employed to improve net efficiency and lifetime of organic photovoltaic devices. The modified cathode work function modulates V OC via static energetic barriers and modulates contact conductivity by creating reversible and irreversible S-shape current-voltage characteristics as a result of kinetic barriers to charge transport.
Deposition of benzyl phosphonic acids and alkanethiol self-assembled monolayers improve initial device performance, and have beneficial effect at mitigating the light-soaking effect present after aging inverted architecture organic bulk heterojunction devices incorporating ZnO contact layers in air. The effect of a kinetic/transport barrier and a static energetic barrier resulting in formation of S-shaped J–V curves is isolated.
In the present work, MoS2 nanoparticles with fullerene-like structure, and most particularly those doped with minute amounts of rhenium atoms, are used as additive to medical gels in order to facilitate their entry into constricted openings of soft material rings. This procedure is used to mimic the entry of endoscopes to constricted openings of the human body, like urethra, etc. It is shown that the Re-doped nanoparticles reduce the traction force used to retrieve the metallic lead of the endoscope from the soft ring by a factor close to three times with respect to the original gel. The mechanism of the mitigation of both friction and adhesion forces in these systems by the nanoparticles is discussed.
By adding a gold core to silica nanoparticles (BrightSilica), silica-like nanoparticles are generated that, unlike unmodified silica nanoparticles, provide three types of complementary information to investigate the silica nano-biointeraction inside eukaryotic cells in situ. Firstly, organic molecules in proximity of and penetrating into the silica shell in live cells are monitored by surface-enhanced Raman scattering (SERS). The SERS data show interaction of the hybrid silica particles with tyrosine, cysteine and phenylalanine side chains of adsorbed proteins. Composition of the biomolecular corona of BrightSilica nanoparticles differs in fibroblast and macrophage cells. Secondly, quantification of the BrightSilica nanoparticles using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) micromapping indicates a different interaction of silica nanoparticles compared to gold nanoparticles under the same experimental conditions. Thirdly, the metal cores allow the investigation of particle distribution and interaction in the cellular ultrastructure by cryo nanoscale X-ray tomography (cryo-XT). In 3D reconstructions the assumption is confirmed that BrightSilica nanoparticles enter cells by an endocytotic mechanism. The high SERS intensities are explained by the beneficial plasmonic properties due to agglomeration of BrightSilica. The results have implications for the development of multi-modal qualitative and quantitative characterization in comparative nanotoxicology and bionanotechnology.
BrightSilica nanoparticles have a silica surface and a gold core. They provide information about their interaction with biological cells via three different approaches: 1) surface-enhanced Raman scattering for characterization of the biomolecular species interacting with the silica sub-/surface; 2) quantification of the uptake of silica-like nanostructures by mass spectrometric micromapping, and; 3) understanding the 3D subcellular interaction using synchrotron X-ray nanotomography.
Self-aligned graphene grains are precisely controlled on liquid Cu by G. Yu and co-workers, using ambient pressure chemical vapor deposition. Large-scale monolayer graphene arrays are modulated by varying the growth conditions such as the flow rate of the carbon source, growth temperature, and growth time. On page 1664, the as-grown graphene arrays show reasonable mobility and high current density, showing great potential for graphene-based electronics.
The treatment of environmental pollution has become one of the most critical issues in the world. Despite the progress made in the study of semiconductor photocatalysis, it is still a challenge to obtain photocatalysts with high activity through relatively simple fabrication processes. In this work, monodisperse CdS spherical nanoparticles (SNPs) of various sizes and good crystallinity are obtained by only adjusting the starting ratio of reactants and the reaction temperature, exhibiting high photocatalytic performances. The photocatalytic rate constant of the ≈ 100 nm CdS SNPs, especially, is more than double that of P25. Furthermore, 3-mercaptopropyltrimethoxysilane is used to assist the interaction between ≈ 200 nm CdS SNPs and citrate-stabilized Au nanoparticles (NPs). The significant increase of photocatalytic activity is confirmed by the degradation of Rodamine B (RhB) under Xe light irradiation. At the optimal Au concentration (0.5 wt%), the prepared nanohybrids show the highest photocatalytic activity, exceeding that of pure CdS two times. The superior photocatalytic performances of the CdS SNPs-Au nanohybrids can be attributed to the intimate interfacial contact between CdS SNPs and Au NPs, which is a contributing factor to the improvement of transfer and the fate of photogenerated charge carriers from CdS SNPs to Au NPs.
The CdS SNPs-Au NPs hybrids are firstly fabricated through gold-sulfur bonding interaction, which meets the needs for reliable interfacial contact between the semiconductor and Au NPs. This facile strategy can be extended to the synthesis of other binary semiconductor hybrids. The as-fabricated CdS SNPs-Au NPs hybrids are very promising for application in degradation of organic pollutants.
Exciton dissociation at the zinc oxide/poly(3-hexylthiophene) (ZnO/P3HT) interface as a function of nitrogen doping of the zinc oxide, which decreases the electron concentration from approximately 1019 cm−3 to 1017 cm−3, is reported. Exciton dissociation and device photocurrent are strongly improved with nitrogen doping. This improved dissociation of excitons in the conjugated polymer is found to result from enhanced light-induced de-trapping of electrons from the surface of the nitrogen-doped ZnO. The ability to improve the surface properties of ZnO by introducing a simple nitrogen dopant has general applicability.
Nitrogen doping of ZnO is shown to dramatically improve exciton dissociation at the interface between ZnO and a conjugated polymer. The improvements in exciton dissociation and device photocurrent follow from a reduction in the ZnO electron concentration and enhanced light-induced de-trapping of electrons from the surface of the nitrogen-doped ZnO.
Ultrasmall, crystalline, and dispersible NiO nanoparticles are prepared for the first time, and it is shown that they are promising candidates as catalysts for electrochemical water oxidation. Using a solvothermal reaction in tert-butanol, very small nickel oxide nanocrystals can be made with sizes tunable from 2.5 to 5 nm and a narrow particle size distribution. The crystals are perfectly dispersible in ethanol even after drying, giving stable transparent colloidal dispersions. The structure of the nanocrystals corresponds to phase-pure stoichiometric nickel(ii) oxide with a partially oxidized surface exhibiting Ni(iii) states. The 3.3 nm nanoparticles demonstrate a remarkably high turn-over frequency of 0.29 s–1 at an overpotential of g = 300 mV for electrochemical water oxidation, outperforming even expensive rare earth iridium oxide catalysts. The unique features of these NiO nanocrystals provide great potential for the preparation of novel composite materials with applications in the field of (photo)electrochemical water splitting. The dispersed colloidal solutions may also find other applications, such as the preparation of uniform hole-conducting layers for organic solar cells.
Ultrasmall, crystalline, and dispersible NiO nanoparticles are prepared for the first time using a solvothermal reaction in tert-butanol. These nanocrystals can be prepared with sizes tunable from 2.5 to 5 nm and are highly efficient catalysts for electrochemical oxygen generation.
Recent reports have shown that self-assembled monolayers (SAMs) can induce doping effects in graphene transistors. However, a lack of understanding persists surrounding the quantitative relationship between SAM molecular design and its effects on graphene. In order to facilitate the fabrication of next-generation graphene-based devices it is important to reliably and predictably control the properties of graphene without negatively impacting its intrinsic high performance. In this study, SAMs with varying dipole magnitudes/directions are utilized and these values are directly correlated to changes in performance seen in graphene transistors. It is found that, by knowing the z-component of the SAM dipole, one can reliably predict the shift in graphene charge neutrality point after taking into account the influence of the metal electrodes (which also play a role in doping graphene). This relationship is verified through density functional theory and comprehensive device studies utilizing atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and electrical characterization of graphene transistors. It is shown that properties of graphene transistors can be predictably controlled with SAMs when considering the total doping environment. Additionally, it is found that methylthio-terminated SAMs strongly interact with graphene allowing for a cleaner graphene transfer and enhanced charge mobility.
A series of functionalized aromatic self-assembled monolayers (SAMs) are used to systemically control the doping of CVD graphene transistors. A direct correlation between the predicted SAM dipole determined via density functional theory and the charge neutrality point of graphene transistors is found when doping effects due to the metal electrode contacts are taken into account.
Although clean drinking water is a basic human need, freshwater scarcity has been identified as a major global problem of the 21st century. Nature has long served as a source of inspiration for human beings to develop new technology. The cactus in the desert possesses a multifunctional integrated fog collection system originating from the cooperation of a Laplace pressure gradient and the wettability difference. In this contribution, inspired by the cactus, an artificial fog collector on a large scale is first fabricated through integrating cactus spine-like hydrophobic conical micro-tip arrays with the hydrophilic cotton matrix. The novel cactus-inspired fog collector can spontaneously and continuously collect, transport, and preserve fog water, demonstrating high fog collection efficiency and promising applications in the regions with drinking water scarcity. Furthermore, the present approach is simple, time-saving and cost-effective, which provides a potential device and new idea to solve the global water crisis.
Inspired by the fog-harvesting behavior of the cactus, a novel fog collector in large scale is first fabricated through integrating cactus spine-like hydrophobic conical micro-tip arrays with a hydrophilic cotton matrix, which can spontaneously and continuously collect, transport, and preserve fog water.
In the search for better-performing colloidal lightemitting diodes (LEDs), nanocrystals of anisotropic morphologies remain to be explored. On page 295, Z. Chen et al. present the first functional LEDs based on quasi-2D core/shell CdSe/CdZnS nanoplatelets, where quantum confinement takes place in the direction of thickness. These solution-processed hybrid LEDs exhibit extremely narrow electroluminescence under different driving voltages, which is highly promising to achieve superior color purity.
Owing to their small size, biocompatibility, unique and tunable photoluminescence, and physicochemical properties, graphene quantum dots (GQDs) are an emerging class of zero-dimensional materials promising a wide spectrum of novel applications in bio-imaging, optical, and electrochemical sensors, energy devices, and so forth. Their widespread use, however, is largely limited by the current lack of high yield synthesis methods of high-quality GQDs. In this contribution, a facile method to electrochemically exfoliate GQDs from three-dimensional graphene grown by chemical vapor deposition (CVD) is reported. Furthermore, the use of such GQDs for sensitive and specific detection of ferric ions is demonstrated.
A facile and high-yield synthesis method for high quality and strongly photoluminescent graphene quantum dots (GQDs) by electrochemically exfoliating free standing three dimensional graphene foam is demonstrated. The synthesized GQDs are utilized for specific optical detection of ferric ions.
Mesoporous silica nanoparticles (MSNs) have been well-demonstrated as excellent carriers for anticancer drug delivery. Presented here is a cancer-targeted MSNs drug delivery system that allows the direct fluorescence monitoring of the cellular uptake and localization of theranostic agents in cancer cells. Specifically, the anticancer action mechanisms of RGD peptide-functionalized MSNs carrying ruthenium polypyridyl complexes (RuPOP@MSNs) are elucidated in detail. RGD peptide surface decoration significantly enhances the cellular uptake of the nanoparticles through receptor-mediated endocytosis, and increases the selectivity between cancer and normal cells. RuPOP@MSNs exhibits unprecedented enhanced cytotoxicity toward cancer cells overexpressing integrin receptor, which is significantly higher than that of free RuPOP, through induction of apoptosis. The important contribution of extrinsic pathway to cell apoptosis is confirmed by increase in expression levels of death receptors, activation of caspase-8 and truncation of Bid. The internalized nanoparticles release free RuPOP into the cytoplasm, where they modulate the phosphorylation of p53, AKT, and MAPKs pathways to promote cell apoptosis. Moreover, the strong autofluorescence of RuPOP permits the direct monitoring of drug delivery, and extends the power of theranostics to subcellular level. Taken together, this study provides an effective strategy for the design and development of cancer-targeted theranostic agents.
Cancer-targeted MSNs loaded with a novel Ru polypyridyl complex (RuPOP@MSNs) that allows the direct fluorescence monitoring of the cellular uptake and localization of anticancer agents in cancer cells are presented. The internalized RuPOP@MSNs can control the release of free Ru complex to trigger ROS-mediated p53 phosphorylation and to regulate the AKT and MAPKs signaling pathways.
High-quality violet-blue emitting ZnxCd1-xS/ZnS core/shell quantum dots (QDs) are synthesized by a new method, called “nucleation at low temperature/shell growth at high temperature”. The resulting nearly monodisperse ZnxCd1-xS/ZnS core/shell QDs have high PL quantum yield (near to 100%), high color purity (FWHM) <25 nm), good color tunability in the violet-blue optical window from 400 to 470 nm, and good chemical/photochemical stability. More importantly, the new well-established protocols are easy to apply to large-scale synthesis; around 37 g ZnxCd1-xS/ZnS core/shell QDs can be easily synthesized in one batch reaction. Highly efficient deep-blue quantum dot-based light-emitting diodes (QD-LEDs) are demonstrated by employing the ZnxCd1-xS/ZnS core/shell QDs as emitters. The bright and efficient QD-LEDs show a maximum luminance up to 4100 cd m−2, and peak external quantum efficiency (EQE) of 3.8%, corresponding to 1.13 cd A−1 in luminous efficiency. Such high value of the peak EQE can be comparable with OLED technology. These results signify a remarkable progress, not only in the synthesis of high-quality QDs but also in QD-LEDs that offer a practicle platform for the realization of QD-based violet-blue display and lighting.
Violet-blue ZnxCd1-xS/ZnS core/shell quantum dots (QDs) with quantum yields near to 100% are successfully synthesized using a high temperature shell growth method. High bright and efficient deep-blue QD-LED show an maximum luminance up to 4100 cd m-2, and peak external quantum efficiency of 3.8% which can be comparable with state-of-the-art OLED technology.