•A novel non-enzymatic H2O2 sensor was fabricated by electrodepositing 5–16 nm AuNPs onto porous GaN electrode.•As far as I know, this is the first time to report porous GaN based electrochemical H2O2 biosensor.•Our work focuses on the design of simply prepared and good practicability H2O2 biosensor. There is no doubt that our work has wider societal impact.Here we report the electrodeposition of gold nanoparticles (AuNPs) onto porous GaN electrode obtained by photoelectrochemical etching planar GaN to fabricate a non-enzymatic hydrogen peroxide (H2O2) sensor. SEM images revealed porous GaN has uniformly high-porosity structure and the diameter of AuNPs is 5–16 nm. The AuNPs/porous GaN electrode exhibited good electrocatalytic activity toward the reduction of H2O2 and performed as amperometric sensor for the detection of H2O2. The AuNPs/porous GaN electrode showed linear amperometric responses for H2O2 in the concentration range from 10 to 100 μM with the sensitivity of 281.5 μA mM−1. The limit of detection (LOD) is 2 μM with a signal-to-noise ratio of 3. In addition, the AuNPs/porous GaN electrode exhibited good repeatability, reproducibility, selectivity and long-term stability for H2O2 detection, in the meanwhile, AuNPs showed excellent adhesive capacity to the porous GaN electrode, which was tested by continually sonicating the AuNPs/porous GaN electrode for 3 h. Above results demonstrated this simply prepared H2O2 sensor has good practicability and is promising to measure the analyte in practical applications.A novel non-enzymatic H2O2 sensor was fabricated by electrodepositing 5–16 nm AuNPs onto porous GaN electrode. The AuNPs/porous GaN sensor exhibited good sensitivity, repeatability and long-term stability towards H2O2 detection.Download high-res image (159KB)Download full-size image

Rationally solution-processed organic electronics are expected to pave the way for low-cost and large-area devices with new and exciting applications. In this study, a non-halogenated solvent was employed for the first time for the one-step and scalable synthesis of extremely high aspect ratio organic semiconducting nanowires of copper octaethylporphyrin (CuOEP) using a cast assembly method under a solvent atmosphere. Remarkably, these single crystalline nanowires exhibited excellent photoswitching effects with reliable reproducibility and superior stability, indicating their potential for application in high-performance optoelectronic devices.

•Porous GaN electrode was applied for trace Ag(I) detection for the first time.•Crystal defects are the active sites for depositing Ag.•The detection limit is as low as 0.5 ppb.Here we demonstrate porous GaN electrode can be applied for trace Ag(I) detection. Compared to traditional planar electrodes, porous GaN electrode can detect lower concentration of Ag(I) as it possesses more deposition sites (crystal defects) and larger surface area. Under the optimum conditions, porous GaN electrode shows a linear voltammetric response in the Ag(I) concentration range from 1 to 100 ppb with the detection limit of 0.5 ppb. Such an unmodified, high-porosity and chemically stable electrode is promising to operate in real samples.Porous GaN electrode was used for trace Ag(I) detection. Porous GaN electrode shows a linear response in the Ag(I) concentration range from 1 to 100 ppb with the detection limit of 0.5 ppb.

•3D AuNPs/GaN NFs and AgNPs/GaN NFs were designed for SERS substrates.•3D GaN NFs supports were fabricated by metal-assisted photochemical etching.•AuNPs were in situ electrodeposited on the 3D GaN NFs support.•AgNPs were in situ photodeposited on the 3D GaN NFs support.•3D GaN NFs based SERS substrates have good biocompatibility for detecting BSA.Three-dimensional (3D) metal-semiconductor nanostructures as surface-enhanced Raman scattering (SERS) substrates were designed by in situ electrodeposition of gold nanoparticles (AuNPs) or in situ photodeposition of silver nanoparticles (AgNPs) on gallium nitride (GaN) nanoflowers (NFs) supports fabricated by metal-assisted photochemical etching of single crystalline GaN. 3D AuNPs/GaN NFs and AgNPs/GaN NFs substrates exhibit excellent enhancement effect for Rhodamine 6G (R6G) due to more “hot spots” in the same probing volume compared to 2D GaN based substrates. The enhancement factors of the AuNPs/GaN NFs and AgNPs/GaN NFs substrates are up to 2.1 × 107 and 5.9 × 107, respectively, and the corresponding detection limits of R6G are 10−8 and 10−10 M, respectively. Moreover, further study reveals both substrates have good reproducibility and long-term stability. The performance of the prepared substrates for biological application was demonstrated by the detection of bovine serum albumin (BSA). A series of characteristic bands of amides suggest BSA can be well adsorbed on the surface of the AuNPs/GaN NFs and AgNPs/GaN NFs substrates, which demonstrates our substrates have good biocompatibility and are promising candidates for SERS biosensors.Download high-res image (153KB)Download full-size image3D metal-semiconductor nanostructures as SERS substrates were designed by in situ electrodeposition of AuNPs or in situ photodeposition of AgNPs on GaN nanoflowers supports fabricated by metal-assisted photochemical etching of single crystalline GaN.

•A free-standing film of nickel phthalocyanine (NiPc) was successfully prepared on ionic liquid surface via a physical vapor deposition method.•The good transferability of the film make it can be easily transferred onto any substrate for further device applications.•The device based on these films shows good photoelectrical property, high stability and high photosensitivity.In this study, we report for the preparation of nickel phthalocyanine (NiPc) free-standing films on ionic liquid (IL) surface by a physical vapor deposition method. Different from on the solid substrate, the as-obtained film is α phase and with a 2D network structure. In addition, the good transferability of the film make it can be easily transferred onto any substrate for further device applications. The device based on these films shows good photoelectrical property, high stability and high photosensitivity.Free-standing film of nickel phthalocyanine were fabricated on the surface of 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate by a physical vapor deposition method. Moreover, the device based on the as-obtained NiPc film shows good photoelectrical property, high stability and high photosensitivity.Download high-res image (148KB)Download full-size image

•GaN surface was etched by EDTA-2Na.•GaN may be dissolved into EDTA-2Na by forming Ga–EDTA complex.•We propose the complexation dissolution mechanism for the first time.Gallium nitride (GaN) surface was etched by 0.3 M ethylenediamine tetraacetic acid disodium (EDTA-2Na) via photoelectrochemical etching technique. SEM images reveal the etched GaN surface becomes rough and irregular. The pore density is up to 1.9 × 109 per square centimeter after simple acid post-treatment. The difference of XPS spectra of Ga 3d, N 1s and O 1s between the non-etched and freshly etched GaN surfaces can be attributed to the formation of Ga–EDTA complex at the etching interface between GaN and EDTA-2Na. The proposed complexation dissolution mechanism can be broadly applicable to almost all neutral etchants under the prerequisite of strong light and electric field. From the point of view of environment, safety and energy, EDTA-2Na has obvious advantages over conventionally corrosive etchants. Moreover, as the further and deeper study of such nearly neutral etchants, GaN etching technology has better application prospect in photoelectric micro-device fabrication.GaN surface was etched by 0.3 M EDTA-2Na. The proposed complexation dissolution mechanism can be applicable to almost all neutral etchants under the prerequisite of strong light and electric field.Download high-res image (49KB)Download full-size image

Blend films with long nanowires of zinc octaethylporphyrin (ZnOEP) embedded in an insulating polymer of poly(methyl methacrylate) (PMMA) have been successfully fabricated by a one-step spin-coating process. Concerning photoactive blends based on small-molecule semiconductors, this is quite a novel strategy and allows us to greatly reduce the issues related to low device performance, such as phase-separation, poor connectivity of the semiconducting layer, and higher densities of interfacial defects. Intensive studies on the correlation between the film morphology and device performance have revealed that excellent photodetector performance is derived from efficient charge transport and good connectivity observed in highly crystalline, interconnected ZnOEP nanowires embedded in an insulating PMMA matrix. To the best of our knowledge, this is the first demonstration of a blend-film-based organic photodetector, which exhibits high sensitivity, high stability, high Ion/Ioff ratio, excellent mechanical flexibility, and a broadband responsivity region extending up to 1050 nm. The unique characteristics of facile fabrication, high sensitivity, excellent mechanical stability, and broadband responsivity can make the blend film of ZnOEP and PMMA promising in large-area flexible photodetectors.

All solution-processed large-area patterned flexible photodetectors were successfully fabricated by utilizing small-molecule organic semiconductor/polymer hybrid film as an active layer and patterned printed Ag electrodes. The large-area hybrid film could be fabricated by a direct solution-process self-assembly method and had a wide absorption spectrum and improved charge transport ability, resulting in high photoresponsivity. Moreover, the device displayed fast response time, high stability and broadband spectral response. Importantly, the device exhibited high flexibility, good folding strength and electrical stability on shafts with different curvature radiuses and after bending. Even after 500 bending cycles, the device still showed good photodetector and photoswitching properties. The facile low-cost large-area fabrication process and excellent performance gives potential applications in large-scale flexible electronic devices.

Large-size single crystalline nanosheets of 9,10-bis(phenylethynyl)-anthracene were prepared by a facile solution process and were fully characterized. The prototype photodetector was then fabricated on the basis of a single nanosheet and exhibited superior performance with the largest photoresponse ratio up to ca. 105. Moreover, the nanosheets show obvious light emission anisotropy.

Single-crystalline 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP) microrods were prepared by a facile solution process. The PPCP microrods with smooth surfaces could absorb excitation light and propagate the photoluminescence (PL) emission. They showed excellent properties in the low optical loss of a single rod and feasible transfer between neighboring rods. Moreover, PPCP displayed typical aggregation-induced emission enhancement (AIEE) characteristics in the solution state.

The electrodeposition of Ni on single-crystal n-GaN(0001) film from acetate solution was investigated using scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, atomic force microscopy, and electrochemical techniques. The as-deposited Ni/n-GaN(0001) had a flat band potential of Ufb = −1.0 V vs. Ag/AgCl, which was much lower than that of bare GaN(0001). That is, a more feasible charge-transfer process occurred at the Ni/n-Ga(0001) interface. On the basis of a Tafel plot, an exchange current density of ∼1.66 × 10−4 mA cm−2 was calculated. The nuclei density increased when the applied potential was varied from −0.9 V to −1.2 V and, eventually the whole substrate was covered. In addition, the current transient measurements revealed that the Ni deposition process followed instantaneous nucleation in 5 mM Ni(CH3COO)2 + 0.5 M H3BO3.

A phase-transformation method has been developed for the precise growth of charge-transfer (CT) co-crystals with varied stoichiometries. Perylene·TCNQ (P1T1) microrods, pyrene·perylene·TCNQ (PyPeT) microrods and (perylene)3·TCNQ (P3T1) microsheets were successfully constructed. The phase transformation can not only happen from P1T1 or P3T to PyPeT, but also from P3T1 to P1T1, which can be controlled by changing the solute concentration. Due to the additional pyrene in PyPeT compared to P1T1, devices based on PyPeT microrods show slightly lower electron mobility and much larger positive threshold than P1T1 microrods. In addition, both of them can be used as phototransistors with a maximum Ion/Ioff ratio of ca. 1000.

This work presents a facile approach toward the synthesis of platinum octaethylporphyrin crystalline aggregates with wires, leaves, plates, and four-leaf clover like architectures by exploitation of intriguing ionic liquid-mediated solution self-assembly. Moreover, the well-defined microwires exhibit highly reproducible and sensitive photo-response characteristics.

•Porous GaN was fabricated using ionic liquid as the etchant.•PECE has better etching effect than ECE.•Holes are regarded as the etching centers.•The photocurrent of porous GaN is 5 times larger than that of planar GaN.Here we report an environment-friendly approach to fabricate porous GaN photoelectrode using ionic liquid as the etchant. SEM images revealed photo-assisted electrochemical etching (PECE) has better etching effect than electrochemical etching (ECE). Furthermore, Raman spectra demonstrated porous GaN obtained by PECE has better lattice integrity than that obtained by ECE. The photocurrent of porous GaN prepared by PECE is six times and two times of planar and porous GaN fabricated by ECE, respectively. Above results indicated porous GaN obtained by PECE can be a promising photoelectrode for optoelectronic applications.

•Hybrid heterostructure of p-type CuPc and n-type porous GaN was fabricated by electrophoretic deposition.•The influence of concentration, electric field intensity, and deposition time on the growth of CuP film was explored.•Prototype devices of CuPc/PGaN heterostructures showed photovoltaic response.•The biggest Ion/Ioff ratio of CuPc/PGaN hybrid heterostructure can reach 162.A new hybrid heterostructure of p-type copper phthalocyanine (CuPc) and n-type porous GaN (PGaN) has been fabricated by electrophoretic deposition. The influence of CuPc concentration, electric field intensity, and deposition time on the growth of CuPc film has been explored. The as-prepared CuPc films are made of numerous nanorods. The X-ray diffraction (XRD) spectra revealed that the CuPc films are the β phase and amorphous type on pristine and porous GaN, respectively. Moreover, the prototype devices were fabricated on the basis of the CuPc/PGaN heterostructures. The devices exhibited excellent photodetector performance under ultraviolet (UV) light illumination.

Ultralong zinc octaethylporphyrin (ZnOEP) nanowires were successfully prepared by a facile solution-phase precipitative method and fully characterized. Specifically, ionic liquids (ILs) were employed, for the first time, as “poor” solvents and chloroform as a “good” solvent of ZnOEP. Furthermore, the influence of the type of ILs, the volume ratio of chloroform/ILs, and the concentration of ZnOEP on the growth of nanowires was investigated. The results indicated that the as-obtained nanowires are ultralong, highly pure, and single crystalline. Both anions and cations of ILs were found to play important roles in the final morphology and aspect ratio of nanowires. In addition, the as-obtained ZnOEP nanowires were directly used for the construction of a prototype photodetector exhibiting excellent performance. This advancement might pave the green way for preparing nano/micro structures of organic small-molecular materials.

Coronene·TCNQ cocrystal microrods, coronene microrods, and TCNQ microsheets were constructed by a drop-casting method. Prototype devices were fabricated and their field-effect-transistor (FET) performances were investigated. It is found that coronene·TCNQ microrods had exhibited an n-type characteristic and showed better FET performances than TCNQ microsheets.

Well-defined single-crystalline nanobelts of butoxy-substituted copper phthalocyanine (CuPcOC4) have been rapidly prepared by a facile and reliable non-solvent nucleation method without any template. Remarkably, the nanobelt film exhibited an excellent electrical conductivity of up to 5.2 S m−1, which is one of the highest values reported for organic semiconducting materials.

Au nanoparticles, with an ultra low-loading of Pt and Pd atoms, supported on n-GaN were prepared using electrochemical atomic layer deposition and surface-limited redox replacement. The as-prepared electrocatalysts showed an enhanced performance for formic acid oxidation, and the mass activity reached 3.5 mA μgPtPd−1. The active sites of the PtChem-O species were found to play a key role in formic acid oxidation.

We develop a facile approach for the one-step growth of ultralong and high-quality NiOEP nanowires in a large area, through a solvent-induced self-assembly method without using any structure directing agents. The size of the nanowires can be controlled by changing the composites of solvent mixtures. Being assembled in visible-light sensors, these nanowires exhibit a fast, reversible, and stable response. The highest Ion/Ioff ratio and photoresponsivity of photodiodes could reach 681 and 10.1 mA W−1, respectively, which could be attributed to the perfect single crystal quality, large surface to volume ratio, and fewer recombination barriers within the nanostructures. The facile fabrication and good photoresponse make NiOEP nanowires promising in optoelectronic applications.

•Nanoporous GaN was generated by PEC in 0.5 M H2SO4.•Hierarchical Ag was deposited on porous GaN and used as SERS substrate.•Hierarchical Ag/GaN presented SERS response with an EF of 107.Nanoporous GaN generated by photo-assisted electrochemical etching was used as template for electrodeposition of hierarchical Ag. The multilevel structures of deposits were confirmed by SEM, and further structurally characterized by XRD. Moreover, surface enhanced Raman scattering characterization revealed a low detection limit of 10−12 M for Rhodamine 6G and an enhancement factor of ~107 by using the as-fabricated hierarchical Ag/GaN substrates.

Foreign ions are of significant importance in controlling and modulating the morphology of semiconductor nanocrystals during the colloidal synthesis process. Herein, we demonstrate the potential of foreign metal ions to simultaneously control the morphology and crystal phase of chalcogenide semiconductors. The results indicate that the introduction of Al3+ ions can induce the structural transformation from monoclinic CuClSe2 microribbons (MRs) to klockmannite CuSe nanosheets (NSs) and the growth of large-sized CuSe NSs. The as-prepared micrometer-sized CuSe NSs exhibit a high-conducting behavior, long-term durability, and environment stability. The novel properties enable CuSe NSs to open up a bright prospect for printable electrical interconnects and flexible electronic devices.

A facile and rapid microwave-assisted method was developed to synthesize uniform single-crystalline Sb2Se3 nanowires in high yields. The as-prepared Sb2Se3 nanowires were directly used for fabricating prototype photodetectors. The device displayed a remarkable response to light intensity with an on/off ratio larger than 150, short response/recovery times (0.2/1.2 s), and long-term durability. The high sensitivity and robust environmental stability of the devices demonstrate the bright prospects for Sb2Se3 nanowires in highly efficient photodetectors for practical use.

Nano/microstructures of copper octaethylporphyrin (CuOEP, donor)–tetracyanoquinodimethane (TCNQ, acceptor) cocrystals with controlled stacking were prepared by a facile solution method and fully characterized. The as-prepared CuOEP–TCNQ cocrystals were either nanoribbons of TCNQ·2CuOEP or microrods of TCNQ·CuOEP, which had DDA(DDA)nDDA and DA(DA)nDA stacking, respectively. For the first time, a phase transformation was found to occur from nanoribbons of TCNQ·2CuOEP to microrods of TCNQ·CuOEP, which was mainly controlled by the concentration of TCNQ. Moreover, prototype devices were fabricated to investigate their photoresponse properties. The results demonstrated that the DDA(DDA)nDDA stacking had much better photoresponse than the DA(DA)nDA stacking.

Dendritic Pd nanoarchitectures were electrochemically deposited on single-crystal n-GaN(0001) by cyclic voltammetry and employed as anode electrocatalyst for direct formic acid fuel cells. The Pd deposition on n-GaN(0001) was found to commence at 0.2 V vs. Ag/AgCl without underpotential deposition process and follow the typical instantaneous nucleation in large overpotential region. High-resolution transmission electron microscope images revealed that numerous small branches were formed around the trunk of dendritic structures and grew along the <111> directions. The as-obtained dendritic Pd nanoarchitectures showed good catalytic performance for formic acid and the oxidation peak potential appeared at 0.45 V vs. Ag/AgCl. The maximum current density and mass activity were 19.7 mA cm−1 and 904 mA mg−1, respectively, for the dendritic Pd nanocrystals obtained by cycling the potentials from -0.25 to 1.0 V for 5 times.

The ultralong nanobelts of N,N-bis-(1-propylimidazole)-3,4,9,10-perylene tetracarboxylic diimide (PI-PTCDI) were fabricated by a one-step solution process. The prototype devices based on the PI-PTCDI nanobelts exhibited excellent photodetector and photoswitching performance. The highest Ion/Ioff ratio and photoresponsivity of photodiodes could reach 240 and 5.6 mA W−1, respectively.

Single-crystal microsheets of platinum octaethylporphyrin (PtOEP) were fabricated by a facile solution process and fully characterized. The as-fabricated microsheets had well-defined shapes and smooth surfaces, and could act as active optical waveguides. The prototype photodetector based on a single microsheet showed high reproducibility and photosensitivity with an Ion/Ioff ratio of ∼500.

A microwave-assisted method was developed to synthesize novel single-crystalline CuClSe2 microribbons (MRs) in high yield. Their phase transformation and stability to thermal irradiation were systematically studied. The single CuClSe2 MR-based device showed a favorable photosensitivity and long-term environmental stability. This implies good prospects for CuClSe2 MRs in low-cost and high-performance photodetectors for practical use.

Ultrasensitive surface enhanced Raman scattering substrates have been fabricated by electrodepositing Au nanoparticles onto porous gallium nitride. A detection limit of ∼10−16 M rhodamine 6G, approximating single-molecule detection, can be achieved.

•Hybrid films of ZnOEP/ZnO were fabricated by a facile solution process.•The devices based on hybrid films showed excellent photoresponse and photoswitching.•The enhanced photoresponse was attributed to the formation of ZnOEP/ZnO heterojunctions.Hybrid heterojunction films of zinc octaethylporphyrin/zinc oxide (ZnOEP/ZnO) were fabricated by a facile solution process, in which ZnO nanoparticles were directly added to ZnOEP nanowire networks. The devices based on the as-fabricated films displayed high sensitivity and stable photoswitching. The largest Ion/Ioff switching ratio of the phototransistor devices was over 103. Moreover, the ZnOEP/ZnO heterojunctions could effectively prevent the photogenerated charge carrier recombination and prolong the photocarrier lifetime. Therefore, higher photocurrent or photoresponsivity of hybrid photodetectors were obtained. The excellent performance associated with facile, large-scale, and cost-effective fabrication process of ZnOEP/ZnO heterojunctions is promising for photodetector and photoswitch application.Graphical abstract

Hierarchical assembly of 2-aminooctane-functionalized naphthalenediimide (NDI) was investigated via a solvent displacement method. That is, a good solvent (ethyl acetate) of NDI was fast dispersed into a poor solvent (methanol, methanol + water, or water). The NDI assemblies with varied scale, shape, and aggregation were formed and fully characterized by SEM, TEM, EDX, UV-vis, and fluorescence. The results demonstrated that the use of a mixture of two poor solvents can provide fine-tuning of intermolecular interactions. In addition, to reveal the structure–property correlation, the I–V characteristics of the as-obtained NDI architectures were explored.

•Hybrid heterostructure of p-type PPy and GaN was fabricated by electrodeposition.•The GaN substrate had an obvious enhancement of Raman scattering of the PPy.•The excitonic emission and recombination were quenched at PPy/GaN interface.•Prototype devices of PPy/GaN heterostructures showed photovoltaic response.A new hybrid organic/inorganic heterostructure of p-type polypyrrole (PPy) and n-type gallium nitride (GaN) was fabricated by means of electrodeposition and characterized. The Raman spectra indicated that the GaN substrate had an obvious enhancement of Raman scattering of the PPy, and the PL spectra revealed that the excitonic emission and recombination were partially quenched at the PPy/GaN interface. Moreover, the prototype devices were fabricated on the basis of the PPy/GaN heterostructures. The current–voltage characteristics of the devices in dark and under ultraviolet light illumination showed obvious photovoltaic response.Graphical abstract

Co-crystal microrods of dibenzotetrathiafulvalene (DBTTF) and tetracyanoquinodimethane (TCNQ) molecules with the mixed-stack structure were prepared via a facile solution process and fully characterized. The as-prepared microrods were directly used for fabricating prototype devices, which exhibited typical ambipolar charge transport characteristics. The result indicated that the co-crystal microrods of DBTTF-TCNQ were potentially useful for miniaturized devices.

An interconnected network of ultralong zinc octaethylporphyrin (ZnOEP) nanowires was fabricated via a solution process and directly used for constructing prototype photodetectors. The device exhibited high reproducibility and sensitivity with the largest photoswitching ratio over 104. The facile fabrication process and the superior performance made ZnOEP an ideal candidate for photodetector applications.

Nanowire networks of zinc octaethylporphyrin (ZnOEP) were printed using an aerosol-jet printer on a poly(ethylene terephthalate) (PET) flexible substrate. The prototype photodetector based on the as-printed network exhibited high photosensitivity, fast photoresponse, and excellent mechanical stability.

Nanoparticles of platinum (Pt) were directly prepared on n-GaN(0001) by a potentiostatic electrodeposition in 0.5 M H2SO4 + 8 mM H2PtCl6 solution and fully characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive X-ray analysis (EDAX). The as-deposited nanoparticles, whose morphology and size were dependent on the applied potential and time, were made of platinum. The real surface area and catalytic properties of Pt nanoparticles prepared at different potentials were estimated by cyclic voltammetry in 0.5 M H2SO4 and by chronoamperometry in 0.5 M H2SO4 + 0.2 M CH3OH solutions, respectively. The maximum of real surface area and the best catalytic activity of Pt nanoparticles were obtained at the potential of −0.7 V.

•Single-crystalline MoO3 nanosheets were prepared by a facile PVD method.•The as-deposited MoO3 nanosheets were single crystals and had smooth surfaces.•Prototype devices were fabricated on the basis of individual MoO3 nanosheets and exhibited promising photoconductive response.Molybdenum trioxide (MoO3) nanosheets were synthesized on Si substrate by a facile physical vapor deposition method and fully characterized by means of scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, energy dispersive X-ray spectroscopy, and Raman spectroscopy. The characteristic spectra of both Raman and XRD demonstrated that the as-deposited nanosheets are highly pure and have perfect crystallinity of the orthorhombic-phase MoO3. Moreover, prototype devices based on individual MoO3 nanosheets were fabricated and exhibited promising photoconductive response upon the white light illumination. The result indicated that the as-deposited MoO3 nanosheets were of potential applications in optoelectronic devices.Graphical abstractSingle-crystalline MoO3 nanosheets were prepared by a facile PVD method. The as-deposited MoO3 nanosheets were single crystals and had smooth surfaces. The prototype devices were fabricated on the basis of individual MoO3 nanosheets and exhibited promising photoconductive response.

Micro-patterned composite films consisting of bowl-like tin dioxide (SnO2) microparticles with smooth surfaces and well-defined shapes were prepared by the breath figures method using a homogeneous solution of tin (IV) chloride/polystyrene/chloroform (SnCl4/PS/CHCl3). The samples were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. The shape and size of SnO2 microparticles could be adjusted by varying parameters of concentration and relative humidity. A possible mechanism was proposed for illustrating the formation of composite films with bowl-like SnO2 microparticles. The present strategy for the fabrication of bowl arrays offers new prospects for the application in biosensors, microreactor, and microfluidic devices.Highlights► Micro-patterned composite films with bowl-like SnO2 microparticles were prepared. ► The microparticles possess smooth surfaces and well-defined shapes. ► Possible mechanism was proposed for the formation of composite films. ► Shape and size of microparticles were dependent on the concentration and relative humidity.

Hierarchical flower-shaped NPB architectures are prepared via a facile solvent evaporation method and investigated by means of SEM, TEM, FT-IR, and XRD. The results indicate that each NPB flower is composed of a number of randomly oriented nanoflakes, which are single crystals and connect with each other. Furthermore, time-dependent experiments reveal that the NPB flowers are formed via a heterogeneous nucleation, coupled with “Ostwald ripening”. The densely packed films of NPB flowers, which can withstand extreme conditions, e.g., high temperature, strong acid, and strong alkali possess a durable water-repellent property.

A facile and rapid route for the synthesis of uniform single-crystal copper nanowires by a microwave-assisted method is demonstrated. The as-prepared copper nanowires exhibit excellent conductivity, which is comparable with electrospun copper nanofibers.

Micro rings of organic NPB have been prepared by evaporating chloroform solution on a silicon surface, which is assisted with a template of water droplets. The topography and optical properties of NPB rings were investigated by microscopy techniques. It is found that the polarized fluorescence microscope images of rings show pronounced polarization related to their central angle Φ. This indicates that the NPB molecules within a ring are ordered. Systematic investigation indicates that the water droplets condensed on silicon are essential for the ring formation. Such strategy is available for other small molecules, e.g., fullerene, porphyrin, and phthalocyanine.Graphical abstractHighlights► Micro rings of organic NPB have been prepared by evaporating chloroform solution on a silicon surface. ► The polarized fluorescence microscope images of rings show pronounced polarization related to their central angle Φ. ► The NPB molecules within a ring are highly ordered. ► Systematic investigation discloses that the water droplets condensed on silicon are essential for the ring formation.

Tri-component nanostructures of C60/m-xylene/thiophene were synthesized via a solvent-induced self-assembly method and characterized by SEM, TEM, XRD, FT-IR, and Raman. The shapes of nanostructures were dependent on the concentration of C60, the volume ratio of thiophene to m-xylene, and the volume ratio of mixture solvent to isopropanol. High-resolution TEM image and SAED pattern revealed that twisted nanorods of C60 were single crystals and had an hcp structure. The EDX and FT-IR analysis confirmed the existence of thiophene. The results indicated that the twisted nanorods consisted of pristine C60, m-xylene, and thiophene molecules. In addition, thiophene molecules were assumed to partially replace m-xylene molecule in the C60/m-xylene lattice. Such tri-component nanorods of C60 are ideal building blocks for fabricating novel nanodevices.Highlights► Tri-component twisted nanorods of C60/m-xylene/thiophene were fabricated by a solvent-induced self-assembly method. ► The EDX and FT-IR analysis confirm the existence of thiophene. ► Moreover, thiophene molecules are assumed to partially replace m-xylene molecule in the C60/m-xylene lattice.

Surface-bound nanowires of tris(8-hydroxyquinoline) aluminum (Alq3) have been fabricated by an adsorbent-assisted physical vapor deposition method and investigated by scanning electron microscopy, transmission electron microscopy, and UV–vis spectroscopy. The as-deposited Alq3 nanowires are the single crystals, which are monodispersed. Moreover, the cathode luminescence spectrum of Alq3 nanowires exhibits a strong fluorescence emission at 497 nm. The conductive atomic force microscopy images reveal that the current flow along the physically contacted probe increases monotonically with the bias voltage above a critical value of 3.0 V. The point current can reach up to 500 pA when the bias voltage is set at 5 V. The results imply that the surface-bound Alq3 nanowires are of potential in organic photonic and electronic applications.Highlights► Alq3 nanowires were fabricated by an adsorbent-assisted PVD. ► The as-deposited nanowires are surface-bound and single crystalline. ► The CL spectrum exhibits a strong fluorescence emission at 497 nm. ► The CAFM image reveals a high electron-transporting ability.

Helical nanowires of cobalt phthalocyanine (CoPc) were fabricated on Si substrate by a physical vapor deposition (PVD) method and characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and ultraviolet‐visible spectroscopy. The results indicated that the morphology, size, and crystal structure of CoPc helical nanowires were dependent on the substrate temperature. The deposited CoPc helical nanowires showed a perfect crystalline feature. Moreover, the CoPc helical nanowire-based devices were fabricated and the drain-source current exhibited obvious dependence on the gate voltage, implying that CoPc helical nanowires were of potential in the application fields of optoelectronic devices.Highlights► Helical CoPc nanowires are controllably synthesized by PVD. ► Helical CoPc nanowires show a perfect crystalline feature. ► Single nanowire devices exhibit obvious transistor characteristic.

Nickel-phthalocyanines (NiPc) with planar aromatic structures are ideal building blocks for organic nanostructures. They can self-assemble into stacks through π–π interaction, exhibit high thermal and chemical stabilities, and possess outstanding electrical and optical properties. Herein, single-crystal NiPc nanorods were synthesized by a facile vapor transfer deposition method. Their nanostructures and compositions were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) in detail. The deposited NiPc nanorods were found to be the β-phase single crystals. Moreover, the NiPc nanorod-based devices were fabricated and exhibited high photocurrent upon white-light illumination. This indicates that the NiPc nanorods can be considered as a candidate material for fabricating photoelectric devices.Single-crystal NiPc nanorods were synthesized by a facile vapor transfer deposition method. The devices based on individual NiPc nanorod exhibited high photocurrent upon white-light illumination.Research Highlights► NiPc nanorods are controllably synthesized by PVD. ► NiPc nanorods are the b-phase single crystals. ► Single nanorod devices exhibit high photocurrent.

Electrocrystallization of Ga on Au(111) in two different ionic liquid electrolytes has been investigated by in situ electrochemical STM imaging with partly nanometer resolution. In chlorogallate-containing melts underpotential deposition (UPD) leads to surface alloying whereby a Ga−Au surface layer is formed on top of Au(111). In AlCl3−[C4mim]Cl + 5 mM GaCl3 melts, 2D-electrochemical phase formation is driven by conventional nucleation and growth of 2D Ga islands. Prior to the UPD processes anion adsorption of GaCl4− and AlCl4−, respectively, occurs which is characterized by well-ordered anion layer structures with comparable lattice constants. At potentials negative of the UPD region, 3D Ga clusters are formed. On the basis of their shape and the coexistence of small and large clusters in contact, it is concluded that the clusters in the size range 5−30 nm are solid. Taking into account that the temperatures during electrodeposition ranged up to 313 K—above the melting point of α-Ga of 303 K—this observation is remarkable.

The electrodeposition of Pb onto Au(1 1 1) from a Lewis acidic ionic liquid, 1-methyl-3-butylimidazolium chloride–aluminum chloride has been investigated by STM. In the UPD range, STM imaging shows three different processes: terrace expansion at 0.8 V, island growth at 0.73 V, and monolayer formation with triangular vacancies at 0.5 V. High-resolution STM images reveals a Moiré-like pattern of Pb adatoms. Moreover, a smooth surface can be formed when potentials are changed progressively. Therefore, a quasi-equilibrium process can be expected. These results indicate that Pb UPD is diffusion-controlled. In the overpotential deposition (OPD) range, the nucleation of 3D Pb crystal occurs.Nanoscale electrodeposition of Pb on Au(1 1 1) from an acidic chloroaluminate ionic liquid has been studied by in situ STM. Triangular-shaped vacancies of Pb cofined to a monoatomic height have been grown controllably.

The electrodeposition of Sb on Au(111) in an acidic chloroaluminate ionic liquid has been investigated by cyclic voltammetry and scanning tunneling microscopy (STM). In situ STM imaging has revealed an ordered structure of the adsorbed SbCl2+ at 1.1 V vs Al/Al(III), which has further compressed into a Moiré-like pattern at 1.05 V. In the UPD range of Sb, a sudden smoothing of surface has been observed at 1.0 V, which is similar to those in BMIBF4. In the later stage, the nucleation process begins to occur and is followed by the formation of 2D-nanostripe architectures. Instead of width, the number and the length of Sb nanostripes increase with time. When the potential goes more negative, clusters are formed on the top of close-packed Sb nanostripes. These results are different from the Sb UPD in the neutral melt, implying that the acidicity of ionic liquid might play an important role in the deposition of Sb.

•Porous GaN layers were fabricated by wet etching technique.•High-density PtNPs or AuNPs were electrodeposited onto GaN to act as metal catalysts.•A detailed mechanism for metal-assisted photochemical etching is proposed.Porous gallium nitride (PGaN) layers were fabricated by metal-assisted photochemical etching (MaPCE) using electrodeposited platinum nanoparticles (PtNPs) or gold nanoparticles (AuNPs) as catalysts. After identification of a suitable negative potential and appropriate cyclic voltammetry (CV) conditions, high-density PtNPs or AuNPs were deposited onto a planar GaN substrate. Based on the concrete numerical values of energy levels, the generation, transfer and consumption of electrons and holes, and the assumption that localized galvanic cells are formed, an etching mechanism was proposed which may provide theoretical guidance for future work on etching of GaN and other semiconductor materials.Based on the concrete numerical values of energy levels, the generation, transfer and consumption of electrons and holes, and the presumption of the formation of localized galvanic cells, we propose the detailed etching mechanism of metal-assisted photochemical etching for the first time.

Ultralong zinc octaethylporphyrin (ZnOEP) nanowires were successfully prepared by a facile solution-phase precipitative method and fully characterized. Specifically, ionic liquids (ILs) were employed, for the first time, as “poor” solvents and chloroform as a “good” solvent of ZnOEP. Furthermore, the influence of the type of ILs, the volume ratio of chloroform/ILs, and the concentration of ZnOEP on the growth of nanowires was investigated. The results indicated that the as-obtained nanowires are ultralong, highly pure, and single crystalline. Both anions and cations of ILs were found to play important roles in the final morphology and aspect ratio of nanowires. In addition, the as-obtained ZnOEP nanowires were directly used for the construction of a prototype photodetector exhibiting excellent performance. This advancement might pave the green way for preparing nano/micro structures of organic small-molecular materials.

Nano/microstructures of copper octaethylporphyrin (CuOEP, donor)–tetracyanoquinodimethane (TCNQ, acceptor) cocrystals with controlled stacking were prepared by a facile solution method and fully characterized. The as-prepared CuOEP–TCNQ cocrystals were either nanoribbons of TCNQ·2CuOEP or microrods of TCNQ·CuOEP, which had DDA(DDA)nDDA and DA(DA)nDA stacking, respectively. For the first time, a phase transformation was found to occur from nanoribbons of TCNQ·2CuOEP to microrods of TCNQ·CuOEP, which was mainly controlled by the concentration of TCNQ. Moreover, prototype devices were fabricated to investigate their photoresponse properties. The results demonstrated that the DDA(DDA)nDDA stacking had much better photoresponse than the DA(DA)nDA stacking.

An interconnected network of ultralong zinc octaethylporphyrin (ZnOEP) nanowires was fabricated via a solution process and directly used for constructing prototype photodetectors. The device exhibited high reproducibility and sensitivity with the largest photoswitching ratio over 104. The facile fabrication process and the superior performance made ZnOEP an ideal candidate for photodetector applications.

The ultralong nanobelts of N,N-bis-(1-propylimidazole)-3,4,9,10-perylene tetracarboxylic diimide (PI-PTCDI) were fabricated by a one-step solution process. The prototype devices based on the PI-PTCDI nanobelts exhibited excellent photodetector and photoswitching performance. The highest Ion/Ioff ratio and photoresponsivity of photodiodes could reach 240 and 5.6 mA W−1, respectively.

The electrodeposition of Ni on single-crystal n-GaN(0001) film from acetate solution was investigated using scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, atomic force microscopy, and electrochemical techniques. The as-deposited Ni/n-GaN(0001) had a flat band potential of Ufb = −1.0 V vs. Ag/AgCl, which was much lower than that of bare GaN(0001). That is, a more feasible charge-transfer process occurred at the Ni/n-Ga(0001) interface. On the basis of a Tafel plot, an exchange current density of ∼1.66 × 10−4 mA cm−2 was calculated. The nuclei density increased when the applied potential was varied from −0.9 V to −1.2 V and, eventually the whole substrate was covered. In addition, the current transient measurements revealed that the Ni deposition process followed instantaneous nucleation in 5 mM Ni(CH3COO)2 + 0.5 M H3BO3.

Large-size single crystalline nanosheets of 9,10-bis(phenylethynyl)-anthracene were prepared by a facile solution process and were fully characterized. The prototype photodetector was then fabricated on the basis of a single nanosheet and exhibited superior performance with the largest photoresponse ratio up to ca. 105. Moreover, the nanosheets show obvious light emission anisotropy.

Single-crystalline 1,2,3,4,5-pentaphenyl-1,3-cyclopentadiene (PPCP) microrods were prepared by a facile solution process. The PPCP microrods with smooth surfaces could absorb excitation light and propagate the photoluminescence (PL) emission. They showed excellent properties in the low optical loss of a single rod and feasible transfer between neighboring rods. Moreover, PPCP displayed typical aggregation-induced emission enhancement (AIEE) characteristics in the solution state.

Co-crystal microrods of dibenzotetrathiafulvalene (DBTTF) and tetracyanoquinodimethane (TCNQ) molecules with the mixed-stack structure were prepared via a facile solution process and fully characterized. The as-prepared microrods were directly used for fabricating prototype devices, which exhibited typical ambipolar charge transport characteristics. The result indicated that the co-crystal microrods of DBTTF-TCNQ were potentially useful for miniaturized devices.

All solution-processed large-area patterned flexible photodetectors were successfully fabricated by utilizing small-molecule organic semiconductor/polymer hybrid film as an active layer and patterned printed Ag electrodes. The large-area hybrid film could be fabricated by a direct solution-process self-assembly method and had a wide absorption spectrum and improved charge transport ability, resulting in high photoresponsivity. Moreover, the device displayed fast response time, high stability and broadband spectral response. Importantly, the device exhibited high flexibility, good folding strength and electrical stability on shafts with different curvature radiuses and after bending. Even after 500 bending cycles, the device still showed good photodetector and photoswitching properties. The facile low-cost large-area fabrication process and excellent performance gives potential applications in large-scale flexible electronic devices.

A facile and rapid microwave-assisted method was developed to synthesize uniform single-crystalline Sb2Se3 nanowires in high yields. The as-prepared Sb2Se3 nanowires were directly used for fabricating prototype photodetectors. The device displayed a remarkable response to light intensity with an on/off ratio larger than 150, short response/recovery times (0.2/1.2 s), and long-term durability. The high sensitivity and robust environmental stability of the devices demonstrate the bright prospects for Sb2Se3 nanowires in highly efficient photodetectors for practical use.

Well-defined single-crystalline nanobelts of butoxy-substituted copper phthalocyanine (CuPcOC4) have been rapidly prepared by a facile and reliable non-solvent nucleation method without any template. Remarkably, the nanobelt film exhibited an excellent electrical conductivity of up to 5.2 S m−1, which is one of the highest values reported for organic semiconducting materials.

Nanowire networks of zinc octaethylporphyrin (ZnOEP) were printed using an aerosol-jet printer on a poly(ethylene terephthalate) (PET) flexible substrate. The prototype photodetector based on the as-printed network exhibited high photosensitivity, fast photoresponse, and excellent mechanical stability.