Individual Sb-doped ZnO (ZnO:Sb) microwires with durable and reproducible p-type conduction have been synthesized, and by increasing the Sb2O3 weight ratios in the precursor mixtures, tunable p-type conduction characteristics can be obtained. Meanwhile, wavelength-tuning electroluminescence (EL) has been observed by applying bias onto individual ZnO:Sb microwires, in which the ZnO:Sb microwires act as emitting filaments. The as-synthesized p-type ZnO:Sb microwires are applied to fabricate homojunction light-emitting devices. The corresponding p–n junction demonstrates excellent diode characteristics, and strong near band edge emissions can be observed with the dominant EL emission wavelengths centered at 400 nm. The results demonstrated the emitting filament characteristics of ZnO:Sb microwires for the first time, and also demonstrated their applicability in homojunction light-emitting diodes, and thus may offer alluring prospects as compact, efficient, reliable building blocks for microscale light sources.

One dimensional (1D) zinc oxide (ZnO) nano and microwires have been considered as one of the most promising candidates for the fabrication of novel nano and microscale electronic and optoelectronic devices. In this study, individual Ga heavily doped ZnO microwires (GZO MWs) were successfully synthesized via chemical vapor deposition methods. Bright, stable, and near-infrared light-emission from electrically biased individual GZO MWs has been achieved. Mysteriously, alternating current driven near-infrared electroluminescence (EL) devices based on individual GZO MWs can also be realized. Therefore, individual GZO MWs that can be analogous to incandescent sources, provide promising potential applications in future ultracompact near-infrared electronic and optoelectronic devices or systems.

•ZnO films with carrier concentration as low as 5.0 × 1013 cm−3 have been prepared via a lithium and nitrogen codoping method.•Ultraviolet photodetector that can detect weak signal with power density as low as 20 nw/cm2 have been fabricated from the ZnO:(Li,N) films.•The detectivity and noise equivalent power of the photodetector can reach 3.60 × 1015 cmHz1/2/W and 6.67 × 10−18 W−1, both of which are amongst the best values ever reported for ZnO photodetectors.ZnO films with carrier concentration as low as 5.0 × 1013 cm−3 have been prepared via a lithium and nitrogen codoping method, and ultraviolet photodetectors have been fabricated from the films. The photodetectors can be used to detect weak signals with power density as low as 20 nw/cm2, and the detectivity and noise equivalent power of the photodetector can reach 3.60 × 1015 cmHz1/2/W and 6.67 × 10−18 W−1, respectively, both of which are amongst the best values ever reported for ZnO based photodetectors. The high-performance of the photodetector can be attributed to the relatively low carrier concentration of the ZnO:(Li,N) films.

Encryption is of vital importance in both military and civil fields. Although there have been a few attempts to encrypt information and produce anti-counterfeiting techniques employing functional materials, it is still urgently needed to develop advanced encryption routes that cannot be cracked easily. This paper presents a simple strategy for advanced encryption based on the fluorescence quenching of ZnO nanoparticles (NPs) by acid and copper ions. In this strategy, certain patterns are printed onto a ZnO NP pre-coated paper using a CuCl2 aqueous solution as an ink to produce an invisible latent image, which is only visible under ultraviolet (UV) irradiation. For encryption, the patterns can be perfectly concealed by exposure to vinegar vapour, due to the dissolution of the ZnO NPs in acidic conditions, and decryption can be performed via neutralization in an ambient soda vapour environment and subsequent uniform re-coating with ZnO NPs. An additional matrix of pixels with encoded grey levels acquired by tuning the dose of CuCl2 is demonstrated to further enhance the anti-counterfeiting capability. A 4 × 4 micron matrix with a total combination of 1.67 × 108 codes has been enciphered in the latent patterns for demonstration, and this is a huge barrier for counterfeiting. The results reported in this paper provide a simple strategy for advanced encryption, and may inspire versatile applications in the fields of information security and anti-counterfeiting.

Fluorescent carbon dots (CDs) with a size smaller than 10 nm, excellent biocompatibility, and low to no cytotoxicity are considered as a rising star in nanomedicine. In this report, for the first time we demonstrate that green-emitting CDs with a carboxyl-rich surface can be employed as a trackable drug delivery agent for localized cancer treatment in a mouse model. The CDs are conjugated with the cancer drug, Doxorubicin (DOX), via non-covalent bonding, utilizing the native carboxyl groups on CDs and the amine moiety on DOX molecules. The pH difference between cancer and normal cells was successfully exploited as the triggering mechanism for DOX release. Our in vivo study demonstrated that the fluorescent CDs can serve as a targeted drug delivery system for localized therapy, and the stimuli-responsive non-covalent bonding between the nanodot carrier and the drug molecule is sufficiently stable in complex biological systems. Taken together, our work provides a strategy to promote the potential clinical application of CDs in cancer theranostics.

Luminescent ZnO quantum dots (QDs) have been prepared, and the fluorescence intensity of the QDs can be increased greatly with the introduction of carbon nanodots, while the fluorescence lifetime of the QDs decreases significantly. The fluorescence enhancement and lifetime decrement can be attributed to the surface plasmon effect of the carbon nanodots, and the calculated surface plasmon resonance frequency of the nanodots matches well with the fluorescence spectrum of the ZnO QDs.

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.

Graphene-plasmonic hybrid platforms have attracted an enormous amount of interest in surface-enhanced Raman scattering (SERS); however, the mechanism of employing graphene is still ambiguous, so clarification about the complex interaction among molecules, graphene, and plasmon processes is urgently needed. We report that the number of graphene layers controlled the plasmon-driven, surface-catalyzed reaction that converts para-aminothiophenol (PATP)-to-p,p′-dimercaptoazobenzene (DMAB) on chemically inert, graphene-coated, silver bowtie nanoantenna arrays. The catalytic reaction was monitored by SERS, which revealed that the catalytic reaction occurred on the chemical inertness monolayer graphene (1G)-coated silver nanostructures. The introduction of 1G enhances the plasmon-driven surface-catalyzed reaction of the conversion of PATP-to-p,p′-DMAB. The chemical reaction is suppressed by bilayer graphene. In the process of the catalytic reaction, the electron transfer from the PATP molecule to 1G-coated silver nanostructures. Subsequently, the transferred electrons on the graphene recombine with the hot-hole produced by the localized surface plasmon resonance of silver nanostructures. Then, a couple of PATP molecules lost electrons are catalyzed into the p,p′-DMAB molecule on the graphene surface. The experimental results were further supported by the finite-difference time-domain method and quantum chemical calculations.

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.Keywords: accelerated electrons; color-switchable; light-emitting devices; magnesium zinc oxide; ultraviolet; wide-band-gap semiconductors;

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.

Zinc oxide (ZnO) nanocolumns have been prepared by a metal–organic chemical vapor deposition technique, and structural and optical characterization reveal that the nanocolumns have high crystalline and luminescent qualities. Au/MgO/ZnO/In structured Schottky diodes have been fabricated from the nanocolumns. An intense emission can be detected from the diodes under the drive of bias voltage, and the output power can reach 3.7 μW. The intense emission comes from both the high crystalline and luminescent qualities of the ZnO nanocolumns, and the ideal Schottky contact formed in the Au/MgO/ZnO/In structures.

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.

Self-powered, highly spectrum-selective photodetectors have been fabricated from n-ZnO/p-NiO core–shell nanowire arrays. In the structure, the outer-layer of the p-NiO acts as a “filter” which can filter out the photons with short wavelength. In this way, highly spectrum-selective photodetectors that only respond to a narrow spectrum range have been obtained.

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.

In this paper, localized surface plasmon enhanced n-ZnO/i-ZnO/MgO/p-GaN structured light-emitting devices have been designed and constructed. It is found that the electroluminescence of the devices can be enhanced at selective wavelengths that match the localized surface plasmon extinction spectra of the metal nanoparticles.

One dimensional (1D) zinc oxide (ZnO) nano and microwires have been considered as one of the most promising candidates for the fabrication of novel nano and microscale electronic and optoelectronic devices. In this study, individual Ga heavily doped ZnO microwires (GZO MWs) were successfully synthesized via chemical vapor deposition methods. Bright, stable, and near-infrared light-emission from electrically biased individual GZO MWs has been achieved. Mysteriously, alternating current driven near-infrared electroluminescence (EL) devices based on individual GZO MWs can also be realized. Therefore, individual GZO MWs that can be analogous to incandescent sources, provide promising potential applications in future ultracompact near-infrared electronic and optoelectronic devices or systems.

Encryption is of vital importance in both military and civil fields. Although there have been a few attempts to encrypt information and produce anti-counterfeiting techniques employing functional materials, it is still urgently needed to develop advanced encryption routes that cannot be cracked easily. This paper presents a simple strategy for advanced encryption based on the fluorescence quenching of ZnO nanoparticles (NPs) by acid and copper ions. In this strategy, certain patterns are printed onto a ZnO NP pre-coated paper using a CuCl2 aqueous solution as an ink to produce an invisible latent image, which is only visible under ultraviolet (UV) irradiation. For encryption, the patterns can be perfectly concealed by exposure to vinegar vapour, due to the dissolution of the ZnO NPs in acidic conditions, and decryption can be performed via neutralization in an ambient soda vapour environment and subsequent uniform re-coating with ZnO NPs. An additional matrix of pixels with encoded grey levels acquired by tuning the dose of CuCl2 is demonstrated to further enhance the anti-counterfeiting capability. A 4 × 4 micron matrix with a total combination of 1.67 × 108 codes has been enciphered in the latent patterns for demonstration, and this is a huge barrier for counterfeiting. The results reported in this paper provide a simple strategy for advanced encryption, and may inspire versatile applications in the fields of information security and anti-counterfeiting.

In this paper, localized surface plasmon enhanced n-ZnO/i-ZnO/MgO/p-GaN structured light-emitting devices have been designed and constructed. It is found that the electroluminescence of the devices can be enhanced at selective wavelengths that match the localized surface plasmon extinction spectra of the metal nanoparticles.

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.

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.

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.

Fluorescent carbon dots (CDs) with a size smaller than 10 nm, excellent biocompatibility, and low to no cytotoxicity are considered as a rising star in nanomedicine. In this report, for the first time we demonstrate that green-emitting CDs with a carboxyl-rich surface can be employed as a trackable drug delivery agent for localized cancer treatment in a mouse model. The CDs are conjugated with the cancer drug, Doxorubicin (DOX), via non-covalent bonding, utilizing the native carboxyl groups on CDs and the amine moiety on DOX molecules. The pH difference between cancer and normal cells was successfully exploited as the triggering mechanism for DOX release. Our in vivo study demonstrated that the fluorescent CDs can serve as a targeted drug delivery system for localized therapy, and the stimuli-responsive non-covalent bonding between the nanodot carrier and the drug molecule is sufficiently stable in complex biological systems. Taken together, our work provides a strategy to promote the potential clinical application of CDs in cancer theranostics.

Self-powered, highly spectrum-selective photodetectors have been fabricated from n-ZnO/p-NiO core–shell nanowire arrays. In the structure, the outer-layer of the p-NiO acts as a “filter” which can filter out the photons with short wavelength. In this way, highly spectrum-selective photodetectors that only respond to a narrow spectrum range have been obtained.