Search

We have demonstrated the fast-speed and high-rejection-ratio solar-blind ultraviolet (UV) photodetectors based on amorphous Ga2O3 (a-Ga2O3) films grown by atomic layer deposition. The effect of the annealing under oxygen atmosphere on the performance of a-Ga2O3 photodetectors is investigated. By the oxygen annealing at 500 °C, the 90-10% decay time of a-Ga2O3 photodetector can be decreased to ∼150 ns, and the UV/Visible rejection ratio of the photodetector can reach as high as 2.74×105, due to the significant suppression of the visible light response. Moreover, the dark current of the 500 °C-annealed photodetector is only 9.43 pA at 10 V bias. These phenomena can be explained by the decrease in oxygen vacancy concentration of the a-Ga2O3 films after the oxygen annealing. The combination of high rejection ratios and fast operating speeds offers a viable way for facile and scalable fabrication of the oxide semiconductor solar-blind UV detectors.

A novel self-powered solar-blind ZnGa2O4 ultraviolet (UV) photodetector has been constructed by fabricating asymmetric pairs of Au Schottky electrodes on the ZnGa2O4 film. The current-voltage curve of the device exhibits an obvious rectifying characteristic with a rectification ratio of 11.3 at ±8 V. At 0 V bias, the peak responsivity of our device at 246 nm is about 22.2 mA/W with an UV–vis rejection ratio of 1.3× 10 4 , indicating the excellent self-powered solar-blind UV photodetector performance. More interestingly, the rise time and decay time of the device are only 10 ns and 30 ns, respectively, which are much faster than that of any other previously reported self-powered solar-blind UV photodetectors to the best of our knowledge. The ultra-fast response speed of the device should be attributed to the asymmetric Schottky junctions and the high crystalline quality of our ZnGa2O4 film with low trap density. Our work provides a new method to constructing high-performance self-powered solar-blind UV photodetectors.

Doping wide-band-gap semiconductor with impurities always accompanied spontaneous compensation of opposite charged intrinsic defects, which lead to invalid control of the type of free carriers. We demonstrate an effectual route to overcoming such detrimental defects formation during doping by suppressing Fermi level shifting using non-equilibrium carriers gathering on the polar epitaxial surfaces. Non-equilibrium carriers are generated by ultraviolet light excited interband transitions (photon energy greater than bandgap). Because the p-type dopants are compensated by non-equilibrium electrons at metal-polar surfaces, donor-type native defects are inhibited. This new doping strategy provides an attractive solution to self-compensation problems in wide–band-gap semiconductors with spontaneous polarization of the future.

Semiconducting micro/nanostructures possessing naturally optical waveguiding behaviors and Fabry-Perot (F-P) like resonances are emerging as versatile building blocks for the assembly of photonic and optoelectronic devices, such as photodetectors, light-emitting diodes, lasers and so on. Individual ZnO micro/nanowires with a rectangular cross-section, such as microwires and microbelts possessing naturally smooth facets along both sides for good optical feedback, can be employed as an underlying F-P mode microcavity whilst as the gain medium for light amplification. In this context, electrically pumped F-P mode microlasers comprising a single ZnO:Ga microbelt and p-GaN substrate have been realized. By treating as the precondition, electrically driven exciton-polariton light-emitting behavior was achieved from the heterojunction diodes, which could be ascribed to strong exciton-photon coupling and waveguided nature of the synthesized microbelts. Once the applied bias exceeded the threshold value, an electrically pumped F-P mode lasing behavior could be observed, the lasing peaks centered at 410.5 nm and 450.5 nm respectively, accompanied with a dramatic narrowing of the spectral line-width to be around 1.0 nm emerging on the waveguided emission spectrum. Therefore, the realization of electrically pumped F-P mode lasing using single microbelt based heterojunction diodes opens the door not only to the fabrication of coherent light sources and model systems for waveguided resonators, but also affords a competitive candidate to develop electrically pumped and ultralow threshold polariton lasers.

Recent investigations indicate that the performance of organic-inorganic perovskite optoelectronic devices can be improved by combining the perovskites and the inorganic materials. However, very few studies have focused on the investigation of perovskites/inorganic semiconductor hybrid UV photodetectors and their detailed performance-enhancement mechanism is still not very clear. In this work, a CH

Thermal-treatment controlled room temperature phosphorescence is realized by embedding either originally synthesized carbon dots (CDs) or 200 °C thermal-treated CDs into a polyvinylalcohol (PVA) matrix through post-synthetic thermal annealing at 200 or 150 °C. The thermal-treatment controlled phosphorescence is attributed to the transfer of photoexcitation from the excited singlet state to the triplet state through intersystem crossing, followed by radiative transition to the ground state, which is due to decrease of quenchers (oxygen) in the CDs and suppression of the vibrational dissipations through the chemical bonding of CDs in the PVA matrix. Multilevel fluorescence/phosphorescence data encryption is demonstrated based on the thermal-treatment controlled phosphorescence from CD@PVA composites.

Van der Waals heterostructures (vdWHs) have opened new avenues for fundamental scientific studies and design of novel devices. Although numerous reports have demonstrated vdWH optoelectronic devices, no report on vdWH lasers can be found to date. In this paper we demonstrated electrically driven vdWH lasers for the first time, and the lasers were realized from ZnO microwire/MgO/p-GaN structures. By coating Ag films on the top surfaces of the ZnO microwires, the current injection and lasing directionality of the vdWH lasers have been improved significantly, and this improvement can be attributed to the high conductivity and reflectivity of the Ag film. The output power of the device can reach 2.41 μW under 14 mA drive current, which is among the highest values ever reported for ZnO based lasers. Our results may provide a promising way to electrically pumped lasers based on micro/nano-structures.

A strategy of achieving efficient orange emissive carbon nanodots (CNDs) with large sized conjugated sp(2) -domain is achieved in a solvothermal synthetic route using dimethylformamide as solvent, which is the basis of orange bandgap emission; enhanced orange emission with photoluminescent quantum yield of 46% is realized through surface charges engineering by surface metal-cation-functionalization.

Carrier multiplication is one process for improving the performance of deep ultraviolet (DUV) photodetectors. Conduction band discontinuity can make electrons obtain additional kinetic energy by potential energy (equal to ΔEC) reducing, and then have sufficient energy to impact a lattice generating electron–hole pairs to increase the internal photocurrent. An active layer consisting of four-period graded bandgap MgZnO with a steep MgxZn1−xO/MgyZn1−yO heterointerface, in which an impact ionization process takes place, has been demonstrated. The fabricated photodetector shows a DUV detection capability with a cutoff wavelength at ∼280 nm. The peak responsivity at about 250 nm nonlinearly increases with the applied reverse bias.

A series of low cost and easily prepared supra-(carbon nanodots (CNDs)) were developed by injecting CND ethanol solutions into toluene under vigorous stirring to induce nano-sized aggregates. Water-jet printing of luminescent patterns and mapping of human sweat pore patterns can be realized on the supra-CND-coated paper. With the application of two kinds of supra-CNDs, dual-encrypted luminescence information was constructed through water-jet printing and hand writing. We found that the low-cost and easily prepared supra-CNDs can be expected to show considerable potential to achieve multi-level encryption in anti-counterfeiting and information security.

Mixed-phase ZnMgO (m-ZMO) thin films with a single absorption edge tuning from ∼3.9 to ∼4.8 eV were realized on a-face sapphire (a-Al2O3) by plasma-assisted molecular beam epitaxy. The small lattice mismatch of both ZnO and MgO with a-Al2O3 should be responsible for the single and controllable absorption edge. Metal-semiconductor-metal (MSM) photodetectors were fabricated based on these m-ZMO films, and the devices have the single cutoff wavelength, which can be tuned from 335 to 275 nm. These devices possess low dark current (78 pA for m-Z0.67M0.33O, 11 pA for m-Z0.59M0.41O, and 4 pA for m-Z0.39M0.61O at 40 V) and high responsivity (434 A/W for m-Z0.67M0.33O, 89.8 A/W for m-Z0.59M0.41O, and 3.7 A/W for m-Z0.39M0.61O at 40 V). Further response study reveals that the 90-10% decay time of m-Z0.67M0.33O, m-Z0.59M0.41O, and m-Z0.39M0.61O is around 37, 30, and 0.7 ms, respectively. Large amounts of heterojunction interfaces between wurtzite ZMO and cubic rock-salt ZMO could be responsible for the low dark current and high responsivity of our mixed-phase devices. The excellent comprehensive performance of m-ZMO UV photodetectors on a-Al2O3 suggests that m-ZMO UV photodetectors should have great applied potential.

A facile pulse laser ablation approach for preparing black titanium oxide nanospheres, which could be used as photocatalysts under visible light, is proposed. The black titanium oxide nanospheres are prepared by pulsed-laser irradiation of pure titanium oxide in suspended aqueous solution. The crystalline phases, morphology, and optical properties of the obtained nanospheres are characterized by means of X-ray diffraction (XRD), field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), and UV-vis-NIR diffuse reflectance spectroscopy. It is shown that high-energy laser ablation of titanium oxide suspended solution benefited the formation of Ti(3+) species and surface disorder on the surface of the titanium oxide nanospheres. The laser-modified black titanium oxide nanospheres could absorb the full spectrum of visible light, thus exhibiting good photocatalytic performance under visible light.

Owing to the special properties and wide applications, UV photodetectors based on wide-band-gap semiconductors have drawn an increasing interest during the last two decades. However, practical UV photodetectors are required two contradictory performances: high internal gain and fast recovery speed, because high internal gain is achieved by long life time of photoexcited carriers and fast recovery needs their fast decay. Their slow decay in wide-band-gap semiconductors has been known as a persistent photoconductivity (PPC) problem and hinders applications. In this paper, a good solution to the above contradictory problem is demonstrated on a single SnO2 microrod photoconductor, which shows both high photoconductive gain (≈1.5 × 109) and quick recovery speed ( 1 d), which is induced by a novel “reset” process: bending and straightening the microrod and subsequently applying a voltage pulse. This result suggests that SnO2 microrods have potential applications in high-performance UV photodetecting devices.

In this work, photoinduced charge separation behaviors in non-long-chain-molecule-functionalized carbon nanodots (CDs) with visible intrinsic absorption (CDs-V) and TiO2 composites were investigated. Efficient photoinduced electron injection from CDs-V to TiO2 with a rate of 8.8 × 108 s−1 and efficiency of 91% was achieved in the CDs-V/TiO2 composites. The CDs-V/TiO2 composites exhibited excellent photocatalytic activity under visible light irradiation, superior to pure TiO2 and the CDs with the main absorption band in the ultraviolet region and TiO2 composites, which indicated that visible photoinduced electrons and holes in such CDs-V/TiO2 composites could be effectively separated. The incident photon-to-current conversion efficiency (IPCE) results for the CD-sensitized TiO2 solar cells also agreed with efficient photoinduced charge separation between CDs-V and the TiO2 electrode in the visible range. These results demonstrate that non-long-chain-molecule-functionlized CDs with a visible intrinsic absorption band could be appropriate candidates for photosensitizers and offer a new possibility for the development of a well performing CD-based photovoltaic system.

Novel luminescent "nano-bombs" based on a self-assembled system of carbon-nanodots, termed supra-CDs, are developed. The luminescence of these luminescent "nano-bombs" depends strongly on water contact; they show weak emission in toluene and decompose in contact with water, resulting in strong photoluminescence. Paper coated with these "nano-bombs" is successfully applied for water-jet printing of luminescence patterns and the mapping of human sweat-pore patterns.

We carried out a nitrogen plasma treatment process to obtain N-doped ZnO single crystal. The treated sample showed an acceptor related emission located at 3.354 eV when excited by a 325-nm He–Cd laser at 85 K. Raman spectra revealed the formation of a bond between Zn and N atoms. The surface work function indicated increasing of hole concentration of the N-plasma-treated ZnO. By constructing a ZnO-based homojunction, the I–V curve displayed perfect rectification performance.

Thermal decomposition of single-crystal SiC is one of the popular methods for growing graphene. However, the mechanism of graphene formation on the SiC surface is poorly understood, and the application of this method is also hampered by its high growth temperature. In this study, based on the ab initio calculations, we propose a vacancy assisted Si-C bond flipping model for the dynamic process of graphene growth on SiC. The fact that the critical stages during growth take place at different energy costs allows us to propose an energetic-beam controlled growth method that not only significantly lowers the growth temperature but also makes it possible to grow high-quality graphene with the desired size and patterns directly on the SiC substrate.

Vertically aligned ZnO nanowires have been prepared, and intense electroluminescence (EL) has been observed with holes injected into the nanowires from p-type ZnO prepared via a high pressure high temperature route. The emission can be attributed to the radiative recombination between the electrons in the nanowires and the injected holes, and the power of the EL can reach about 10 μW when the injection current is 20 mA. The intense emission is believed to be resulted from both the relatively high quality of the nanowires and injection of the holes from the p-type ZnO.

Well-aligned ZnO nanowire arrays have been prepared, and p-MgZnO has been deposited onto the nanowires to form core–shell heterostructures. Transmission electron microscopy confirms the formation of n-ZnO/p-MgZnO core–shell nanowire heterostructures. Under injection of a continuous current, random lasing with a threshold current of around 15 mA has been observed from the heterostructures. The low threshold may be due to the relatively high crystalline quality of the ZnO nanowires as well as the carrier confinement in the heterostructures.

Cubic ZnMgO (c-ZnMgO) with a band gap in the ultraviolet-B (UVB) region was deposited for the first time on the a-face sapphire substrate by molecular beam epitaxy using a thin low-Zn-content ZnMgO film as the buffer layer. The metal–semiconductor–metal photodetectors were demonstrated on this c-ZnMgO with different finger gaps, and their cut-off wavelength is around 320 nm. At 10 V, the device with a finger gap of 2 μm shows a low dark current of 3 pA, and its peak responsivity at 302 nm is ∼5.188 A W−1. A further temporal photoresponse study reveals that the c-ZnMgO UVB photodetectors display a fast response speed (90–10% decay time is around 24 μs) with good reproducibility and stability. Our findings indicate that the present c-ZnMgO UVB photodetectors are very promising for future optoelectronic device applications.

By taking semiconductors with different band-gap energies as the active layers and controlling the electron-hole recombination region through the electric field, bias-polarity dependent ultraviolet/visible switchable light-emitting devices have been realized in Au/MgO/Mg0.49Zn0.51O/MgxZn1-xO/n-ZnO structures, of which the emission bands can be switched from the ultraviolet region to the orange region by changing the polarity of the applied bias. The results reported here may provide a feasible idea to multicolor-switchable light-emitting devices.

The collective oscillation of electrons located in the conduction band of metal nanostructures being still energized, with the energy up to the bulk plasmon frequency, are called nonequilibrium hot electrons. It can lead to the state-filling effect in the energy band of the neighboring semiconductor. Here, we report on the incandescent-type light source composed of Au nanorods decorated with single Ga-doped ZnO microwire (AuNRs@ZnO:Ga MW). Benefiting from Au nanorods with controlled aspect ratio, wavelength-tunable incandescent-type lighting was achieved, with the dominating emission peaks tuning from visible to near-infrared spectral regions. The intrinsic mechanism was found that tunable nonequilibrium distribution of hot electrons in ZnO:Ga MW, injected from Au nanorods, can be responsible for the tuning emission features. Apart from the modification over the composition, bandgap engineering, doping level, etc., the realization of electrically driving the generation and injection of nonequilibrium hot electrons from single ZnO:Ga MW with Au nanostructure coating may provide a promising platform to construct electronics and optoelectronics devices, such as electric spasers and hot-carrier-induced tunneling diodes.

We propose a simple rule for finding Dirac cone electronic states in solids, that is neglecting those lattice atoms inert to the particular electronic bands, and pursuing the two dimensional (2D) graphene-like quasi-atom lattices with s- and p-bindings by considering the equivalent atom groups in the unit cell as quasi-atoms. With CsPbBr$_3$ and Cs$_3$Bi$_2$Br$_9$ bilayers as examples, we demonstrate the effectiveness and generality of this rule with the density functional theory (DFT) calculations. We demonstrate that both bilayers have Dirac cones around the Fermi level and reveal that their corresponding Fermi velocities can reach as high as $\sim$ 0.2$\times$10$^6$m/s. That makes these new 2D layered materials very promising in making new ultra-fast ionic electronic devices., Comment: 3 pages, 3 figures, 2 SI figures

We demonstrate a novel type of ZnO self-powered photodetector based on the asymmetric metal-semiconductor-metal (MSM) structure: one Au interdigitated electrode with wide fingers and the other one with narrow fingers. These ZnO photodetectors exhibit attractive photovoltaic characteristics at 0 V bias. More interestingly, with increasing the asymmetric ratio (the width of wide fingers : the width of narrow fingers) of the interdigitated electrodes, the responsivity of the ZnO self-powered UV photodetectors was enhanced obviously, reaching as high as 20 mA W−1 when the asymmetric ratio was 20 : 1. A physical model based on band energy theory was developed to illustrate the origin of the photoresponse at 0 V in our device. Our findings provide a new route to realizing self-powered photodetectors.

The coupling interaction among metal nanoparticles can cause asymmetric distribution of the surface charges, which can lead to the cleavage of surface plasmon resonance. Higher order resonance modes in plasmonic nanostructures exhibit sharp resonance and dramatic line shape shifts. These unique resonant behaviours existing in nanostructures can be used to improve the performance of wide band gap semiconductor devices, such as increasing the output power of lasers. According to the theoretical calculation and simulation, silver nanoparticles have been prepared experimentally, and the corresponding extinction spectra were also tested to verify the simulation results. It is found that the hybrid quadrupolar resonance can indeed occur in the short wavelength region.

Unravelling the factors influencing photoluminescence (PL) quantum yield of the carbon nanoparticles (CNPs) is the prerequisite for preparing highly luminescent CNP-based materials. In this work, an easy and effective method is reported for preparing highly luminescent CNP-based materials. Water-soluble luminescent CNPs (CNP-Cs) with large size distribution (1-60 nm) with PL quantum yields of 22% are synthesized through a microwave pyrolysis approach. Energy transfer (ET) is confirmed to occur from small size CNPs (CNP-Ss:1-7 nm, blue emitters) to large size CNPs (CNP-Ls:10-60 nm, green emitters). Further centrifugally separating CNP-Cs resulted in an enhancement of the PL quantum yield up to 39% of CNP-Ss aqueous solution. The PL quantum yield of CNP-Ss could even be further improved in high-viscosity solvents. PL quantum yield higher than 90% is achieved in films of commercial glue water embedded with the CNP-Ss at embedding ratio lower than 3 wt%. By contrast, the yield is greatly decreased in the CNP-C-embedding films with embedding ratio higher than 1 wt%, which is due to self-absorption, as well as enhanced ET between CNP-Ss and CNP-Ls. High-viscosity solvents and polymer matrix are proposed to act as surface passivation reagents to enhance PL quantum yield of CNPs.

Hybrid plasmonic waveguides have achieved rapid advancement in plasmonics, which has given rise to remarkable field enhancement, light harvest, light-transport capabilities, bridging the gap between electronics and photonics by routing and manipulating light at sub-wavelength regions and so on. However, the development of plasmonic waveguides is hindered by lack of devices that can adjust coherent plasmonic fields. In this letter, hybridized planar multilayer insulator metal insulator metal insulator heterostructures are proposed, and it is demonstrated that their unique capabilities can be used to adjust the mode characteristics by means of varying the thickness of the insulator spacer layer inserted between two metal films, such as the shift of the surface plasmon resonance wavelength. This type of hybrid plasmonic waveguides opens up opportunities for the tunability of mode characteristics, adjustment of resonant energy transfer processes, that have a potential for designing novel optical micro/nano resonance cavities.

Double hetero-structured n-Mg0.13Zn0.87O/i-ZnO/p-Mg0.13Zn0.87O light-emitting devices (LEDs) have been fabricated, and the p-type Mg0.13Zn0.87O layer was obtained via a lithium–nitrogen codoping method. Obvious emission at around 400 nm has been observed from the LEDs under forward bias. To increase the light extraction from the LEDs, a distributed Bragg reflector whose reflectivity is 98% at 400 nm was bonded on the back side of the device, and the emission of the device was enhanced by around 1.6 times with the reflector.

In this work, the optical properties of carbon nanoparticles (CNPs) can be modulated by the dopant-N atom and sp(2) C-contents. CNPs prepared with the low urea mass ratio of 0.2:1 (CNP1) exhibit blue emission (maximum PL quantum yield: 15%). Increasing sp(2) C- and dopant-N atom contents, as determined in CNPs prepared with high urea mass ratio of 2:1 (CNP2), lead to green emission (maximum PL quantum yield up to 36% in ethanol aqueous solution). Amplified spontaneous emission (ASE) can be observed only in CNP2 ethanol aqueous solution. Green lasing emission is achieved from CNP2 ethanol aqueous solution in a linear long Fabry-Perot cavity, indicating the potential of CNP2 as a gain medium for lasing. CNP2 shows superior photostability compared with C545T dye. The green emission from CNP2 is speculated to arise from electron-hole recombination (intrinsic state emission). The high PL quantum yield and small overlap between absorption and emissions of CNP2 ethanol aqueous solution are the key factors in realizing lasing emission.

The tunable hybridized quadrupole plasmons and their strong coupling with excitons have been demonstrated in ZnMgO/Ag nanoclusters (NCs) system. By adjusting the density of the random Ag NCs, the hybridized quadrupole resonance with strong intensity can be obtained due to the asymmetry Fano-like interference. Owing to a good energy match between hybridized quadrupole plasmons and excitons of ZnMgO, a giant near-band-edge UV emission enhancement was realized. The finite difference time-domain method was used to demonstrate the formation of the tunable hybridized quadrupole resonance in the short wavelength range. This novel method for enhancing the UV emission, associated with the hybridized quadrupole plasmons, may pave the way for the further development of high-efficiency UV light-emitting diodes and laser diodes.

In this paper, we report a vertical Schottky ultraviolet photodetector based on the MgZnO:Al transparent electrode. The vertical MgZnO:Al/MgZnO/Au photodetector was fabricated on the sapphire substrate, which shows a good Schottky contacting character. The transparent and conducting MgZnO:Al thin film was developed by magnetron sputtering and annealed to fit the request of our detection. The device is structured vertically in an order of sapphire/MgZnO:Al/MgZnO/Au. The device shows a good Schottky contacting character. The maximum responsivities of the photodetector are 0.0266 mA/W at 0 V bias and 13.31 mA/W under 10 V backward bias, respectively. The peak response wavelength is located at 340 nm and cut-off is at the wavelength of 355 nm. The turn-on voltage is 2.0 V and the breakdown voltage is 40 V. The leakage current is less than 70 pA at a reverse bias of 15 V.

We have comparatively investigated the electroluminescence (EL) performance from the asymmetric p-Mg0.05Zn0.95O/i-ZnO/n+-GaN and p-Mg0.05Zn0.95O/i-ZnO/n+- Si double-heterojunction light emitting diodes (LEDs) grown on different lattice mismatch substrates. The I-V curve measurements show clear rectification characteristics with a threshold voltage of 3.8 and 6 V for the p-Mg0.05Zn0.95O/i-ZnO/n+-GaN and p-Mg0.05Zn0.95O/i-ZnO/n+-Si double heterojunctions, respectively. A strong violet-ultraviolet EL emission and no deep-level emission were observed for the p-Mg0.05Zn0.95O/i-ZnO/n+-GaN double heterojunction grown on small lattice-mismatched n+-GaN substrate. In comparison, a dominant visible emission band and a weak ultraviolet emission peak were observed for p-Mg0.05Zn0.95O/i-ZnO/n+-Si double heterojunction grown on large lattice-mismatched n+-Si substrate. The difference between both LEDs is due to different quality of the MgZnO and ZnO layers grown on different lattice mismatch substrates. 2013 Elsevier B.V. All rights reserved.

Nitrogen (N)-doped ZnO films (ZnO:N) grown on the a-/c-plane sapphire substrates (a-/c-Al2O3) by plasma-assisted molecular beam epitaxy were investigated. It was found that the content of N in the ZnO films grown on c-Al2O3 is higher than that of the films grown on a-Al2O3. The ZnO:N films grown on c-Al2O3 have lower carrier concentration and larger intensity ratio of the DAP/D degrees X emission compared with those of the ZnO:N films grown on a-Al2O3 under the same growth conditions, which indicates higher incorporation efficiency of N in the ZnO films grown on c-Al2O3. (C) 2013 Elsevier B.V. All rights reserved.

Gold nanoparticles (NPs) of various shapes were synthesized by a one-step method at ambient temperature in the presence of NaCl. 2-mercaptosuccinic acid (MSA) was used as both reducing agent and stabilizing agent. The shapes of gold NPs were controllable by simply tuning S/Au ratio (S is from MSA molecule, and S/Au ratio is controlled by tuning the volume of added MSA solution), and triangle, polygonal and spherical nanoparticles were obtained. This result suggested a new way to consider the effects of MSA on the growth of nanoparticles, which showed that MSA is a strong capping agent and facilitates more uniform growth of nanoparticles in every dimension. And other important factors on nanoparticles growth including NaCl and temperature were discussed. Furthermore, a typical probe molecule, 4-aminothiophenol (4-ATP) was used to test the surface-enhanced Raman scattering (SERS) activity of these gold NPs and the results indicated good Raman activity on these substrates. And the enhancement factor (EF) at 1078 cm−1 (a1) was estimated to be as large as 6.3 × 104 and 5.5 × 104 for triangular plates and truncated particles, respectively.

We proposed and demonstrated Ag nanoparticles (NPs)-decorated ZnO photodetectors for UV light sensing. After decoration of their surface with random Ag NPs, the dark current density of ZnO UV photodetectors decreases obviously. Moreover, the device exhibits an obvious increase in peak responsivity at around 380 nm, which can be attributed to the narrow-band quadrupole plasmon resonance of Ag NPs in the UV range. Meanwhile, the responsivity at the other wavelengths decreases a lot. As a result, the response peak becomes more significant, and the response of the devices presents an excellent wavelength selectivity after covering with Ag NPs. The detailed mechanism for this phenomenon was explained. We believe that our findings would open a way to harness the high-order plasmon modes in the field of UV optoelectronic devices.

In this paper, n-ZnO/i-ZnO/MgO/p-GaN structured light-emitting devices have been designed and constructed, and Ag nanoparticles whose surface plasmon resonance absorption spectrum overlaps well with the electroluminescence (EL) of the structure were employed to improve the emission characteristics of the devices. A noticeable enhancement in the EL intensity has been obtained, and the enhancement can be attributed to the resonant coupling between the electron hole pairs in the structure and the surface plasmons of the Ag nanoparticles. (c) 2012 Elsevier B.V. All rights reserved.

Electrically pumped random lasing has been realized in Au/MgO/ZnO structures. By incorporating Ag nanoparticles, whose extinction spectrum overlaps well with the emission spectrum of the structures, the threshold of the random lasing can be decreased from 63 mA to 21 mA. The decrease in the threshold has been attributed to the resonant coupling between the carriers in the active layer of the structures and the surface plasmon of the Ag nanoparticles.

Ag nanoparticle surface plasmon enhanced ZnO homojunction light-emitting devices (LEDs) have been constructed. It is found that the Ag nanoparticles can increase the emission of the devices greatly, and the Ag nanoparticle decorated LEDs degrade little after placing in ambient air for three months, revealing their good stability.

Paper, as one of the most important information carriers, has contributed to the development and transmission of human civilization greatly. Meanwhile, a serious problem of environmental sustainable development caused by the production and utilization of paper has been resulted to modern society. Therefore, a simple and green route is urgently demanded to realize rewritable painting on paper. Herein, a simple route to rewritable painting on copy paper has been demonstrated by using eco-friendly ZnO nanoparticles (NPs) as fluorescent ink, and vinegar and soda that are frequently used in kitchen as erasing and neutralizing agents. Words or patterns written using the ZnO NPs as ink can be erased by vinegar vapour within five seconds, and after a neutralizing process in the ambient of soda vapour, the paper can be used for writing again. It is worth noting that the resolution and precision of the patterns produced via the above route degrade little after ten rewriting cycles, and the quality of the patterns produced using the ZnO NPs as ink fades little after being storage for several months, which promises the versatile potential applications of the rewriting route proposed in this paper. ispartof: SCIENTIFIC REPORTS vol:7 ispartof: location:England status: published

Carbon nanodots (CNDs)@BaSO

This study demonstrates significant improvements of ZnO nanowire lasers by the piezophototronic effect. The laser output power can be enhanced by a factor of 4.96, and the threshold voltage can be decreased from 48 to 20 V by applying pressure. The mechanism of the improved performance can be attributed to the enhanced carrier injection and recombination due to the piezophototronic effect.

Black-colored ZnO nanowires have been prepared in a metal-organic chemical vapor deposition system by employing a relatively low growth temperature and oxygen-deficient conditions. X-ray photoelectron spectroscopy reveals the incorporation of carbon into the nanowires. The photocatalytic hydrogen evolution activity of the black-colored ZnO nanowires is over 2.5 times larger than that of the pristine ZnO nanowires under simulated solar illumination conditions, and the enhanced photocatalytic activity can be attributed to the higher absorption of visible light by the black color and better carrier separation at the ZnO/carbon interface.

We reported a simple method to synthesize ZnO–Au nanocomposites (hybrid A) by combining hydrothermal and electric beam evaporation deposition method. It was found that Au deposition time takes an important role in the generation of Au nanoparticles. Changing Au deposition time makes the thickness of Au formed on ZnO nanorods increase from 10 nm to 70 nm. On the other hand, white-emitting ZnO–Au nanocomposites (hybrid B) were obtained after treating hybrid A with HCl solution. Thanks to the covering of Au film and acid etching, it induces many defects on the surface of ZnO NRs, and largely enhances the visible emission of surviving ZnO and finally generates white emission on Au mesocrystals (hybrid B). Both of the ZnO–Au hybrids (A and B) can be applied as substrates in surface-enhanced Raman scattering (SERS) measurement. A typical probe molecule, 4-ATP was used to test the SERS activity of the ZnO–Au composites and the results indicated good Raman activity on the substrates.