Lichao Jia

Two-dimensional hierarchical porous silica film and its tunable superhydrophobicity

Base do na monolayer polystyrene (PS) colloidal crystal, large-scale two-dimensional (2D) hierarchical porous silica (orderly arranged macropores and disordered mesopores in its skeleton) with a high specific surface area was fabricated by the sol–gel technique. Such material has demonstrated superhydrophilicity with a water contact angle (CA) of 5 ◦ and superhydrophobicity with a water CA of 154 ◦ after surface modification with fluoroalkylsilane. More interestingly, the water CA can be increased to 165 ◦ using a heat-deformed PS template, which suggests that the superhydrophobicity can be controlled by the template with different heat-deformed extents. Such silica films have applications in fields of adsorbent, catalytic, chromatographic support, microseparator and microfluid devices. (Some figures in this article are in colour only in the electronic version)

Fabrication of self-standing silver nanoplate arrays by seed-decorated electrochemical route and their structure-induced properties

We present an electrochemical route to synthesize silver nanoplates on seed-decorated Indium tin oxide (ITO) glass substrate. The nanoplates are several tens of to several hundred nanometers in dimension. The density of nanoplates covered on the substrate can be controlled well by adjusting the amounts of seed. All the nanoplates are standing on the substrate uniformly even at very high density. Silver nanoplate arrays displayed an extraordinary superhydrophobicity after chemical modification and can serve as highly active surface-enhanced Raman scattering (SERS) substrates for microdetection. The arrays can also be used as electrodes for electrochemical capacitor with high power density.

Phase Diagram, Design of Monolayer Binary Colloidal Crystals, and Their Fabrication Based on Ethanol-Assisted Self-Assembly at the Air/Water Interface

Flexible structural design and accurate controlled fabrication with structural tunability according to need for binary or multicomponent colloidal crystals have been expected. However, it is still a challenge. In this work, the phase diagram of monolayer binary colloidal crystals (bCCs) is established on the assumption that both large and small polystyrene (PS) colloidal spheres can stay at the air/water interface, and the range diagram for the size ratio and number ratio of small to large colloidal spheres is presented. From this phase diagram, combining the range diagram, we can design and relatively accurately control fabrication of the bCCs with specific structures (or patterns) according to need, including single or mixed patterns with the given relative content. Further, a simple and facile approach is presented to fabricate large-area (more than 10 cm(2)) monolayer bCCs without any surfactants, using differently sized PS spheres, based on ethanol-assisted self-assembly at the air/water interface. bCCs with different patterns and stoichiometries are thus designed from the established phase diagram and then successfully fabricated based on the volume ratios (V(S/L)) of the small to large PS suspensions using the presented colloidal self-assembling method. Interestingly, these monolayer bCCs can be transferred to any desired substrates using water as the medium. This study allows us to design desired patterns of monolayer bCCs and to more accurately control their structures with the used V(S/L).

Size‐Tailored ZnO Submicrometer Spheres: Bottom‐Up Construction, Size‐Related Optical Extinction, and Selective Aniline Trapping

Fabrication of size-tailored semiconductor/metal submicrometer spherical particles has recently attracted signifi cant interest due to their unique physicochemical properties and emerging applications in many strategically important fi elds such as photonic crystals, pharmaceuticals, electronics, catalysis, energy, and environmental protection. [ 1 ] ZnO, with a wide bandgap of 3.37 eV and a large exciton binding energy of 60 meV, is one of the key semiconductors, widely utilized in piezoelectric transducers, varistors, phosphors, sensors, solar cells, and transparent conducting fi lms. [ 2 ] Due to the intrinsic nature of polar hexagonal-phase ZnO with an a : c axial ratio of 1:1.6, diverse well-defi ned 1D nanostructures have been synthesized [ 3 ] and utilized in a variety of functional device applications, such as light-emitting diodes, nanolasers, photodetectors, fi eld-effect transistors, photovoltaic devices, nanogenerators, and chemical sensors. [ 4 ] Comparatively, the creation of spherical crystals of ZnO, which are thought to be an attractive material for photonic crystals, sensors, solar cells, and photocatalysts, has seldom been reported. [ 5 ] Furthermore, even within those few existing reports, the resultant submicrometer ZnO spherical particles have usually been built up by secondary structures, such as nanoparticles and nanoplates, [ 5 ] where the lack of close contact between nanostructures will inevitably infl uence and possibly reduce the performance of ZnO submicrometer spheres in electric, magnetic, optoelectric, and thermoelectric applications. Consequently, it remains a challenge to acquire ZnO submicrometer spheres constructed without subunits. However, the synthesis of such spherical semiconductor/metal particles has been rarely reported. One effective approach has

Hetero-apertured micro/nanostructured ordered porous array: layer-by-layered construction and structure-induced sensing parameter controllability.

The double-layer hetero-apertured porous films with hierarchical micro/nanoarchitectures were fabricated on a desired substrate, based on a simple and flexible strategy alternately using the monolayer colloidal crystal with different sizes of colloidal spheres as templates. Such films are of biperiodic ordered structures and can be fully lifted off from the substrate and present a freestanding property. The structures and morphologies of the films can be controlled by combination of the colloidal monolayers with different sphere sizes. The corresponding gas sensing devices were also built. Representatively, the In(2)O(3) hierarchically micro/nanostructured porous film-based sensors have shown both higher sensitivity and much faster response to NH(3) atmosphere than the corresponding conventional nanostructured ones. Importantly, the gas-sensing parameters (i.e., response time and the sensitivity) can be well-controlled separately in a large range simply by changing the pore sizes in different layers of the porous film. Further, for the application, a diagram of gas-sensing parameters (t(R)-S diagram) was presented, which can not only give a measurement of sensing performances but also well guide design and fabrication of the hierarchically structure-based sensors with desired sensing performances. This work is an important step toward the practical application of the nanostructured porous film sensors.

Metal ion-doped SnO2 ordered porous films and their strong gas sensing selectivity

Based on a sol-gel technique and the colloidal monolayer template, ion-doped SnO2 ordered porous films were fabricated, and the corresponding gas-sensing properties were studied. The sensitivity to the given test gases strongly depends on the doping species and doping amount. Importantly, when the doping amount is 1% M, the Cr+3 and Pd+2 doped porous films demonstrate a greatly enhanced sensitivity and strong selectivity to ethanol and ammonia, respectively. The improved sensing properties are attributed to the doping-induced surface modification of the films. Such ion-doped porous films are expected to bring new opportunities for application of future porous film-based gas sensors.

Crack-Free Periodic Porous Thin Films Assisted by Plasma Irradiation at Low Temperature and Their Enhanced Gas-Sensing Performance

Homogenous thin films are preferable for high-performance gas sensors because of their remarkable reproducibility and long-term stability. In this work, a low-temperature fabrication route is presented to prepare crack-free and homogenous metal oxide periodic porous thin films by oxygen plasma irradiation instead of high temperature annealing by using a sacrificial colloidal template. Rutile SnO2 is taken as an example to demonstrate the validity of this route. The crack-free and homogenous porous thin films are successfully synthesized on the substrates in situ with electrodes. The SnO2 porous thin film obtained by plasma irradiation is rich in surface OH groups and hence superhydrophilic. It exhibits a more homogenous structure and lower resistance than porous films generated by annealing. More importantly, such thin films display higher sensitivity, a lower detection threshold (100 ppb to acetone) and better durability than those that have been directly annealed, resulting in enhanced gas-sensing performance. The presented method could be applied to synthesize other metal oxide homogenous thin films and to fabricate gas-sensing devices with high performances.

Layer-by-layer strategy for the general synthesis of 2D ordered micro/nanostructured porous arrays: structural, morphological and compositional controllability

In this paper, the general synthesis of two-dimensional (2D) ordered porous micro/nanostructured arrays by a layer-by-layer strategy based on the 2D colloidal template transfer are systematically studied. Using such a strategy, various 2D ordered porous films including hetero-pore sized, heterostructured and ion-doped porous films can be fabricated on any desired substrates. Moreover, the film thickness, chemical composition and packing geometry of the porous film also demonstrate a good manner of controllability. The formation mechanisms of these structures are briefly discussed. This synthetic route is highly expected to advance the synthesis of functional patterned 2D ordered porous nanostructures, which will find potential applications in sensors, optoelectronic devices, separation science and smart filters/flowmeters.

Photomediated assembly of single crystalline silver spherical particles with enhanced electrochemical performance

A bottom-up based photomediated strategy is presented to create single crystalline silver spherical particles by pulsed laser irradiation of silver nanoparticles in liquid, where the unique selective laser heating is responsible for the formation of spherical particles. The present approach is facile and flexible for the design of silver spherical particles with tunable sizes. Systematical studies reveal that the experimental parameters including laser fluence, laser irradiation time, dispersing liquid, and concentration of starting material are important factors that influence the formation of silver spherical particles. As a demonstration of the as-synthesized silver spheres for electrochemical applications, the performance of silver spherical particles as potential supercapacitors was investigated by cyclic voltammetry, and the results indicated a higher capacity of silver spherical particles compared to that of silver raw nanoparticles, which is considered to originate from the enhanced electronic conductivity due to the single crystalline feature of silver spherical particles. We believe that the photomediated method presented in this work can be set as a new alternative in creating a variety of noble metallic spherical particles.

Mono-, multi-layer nanostructured porous films and gas sensors

A simple and flexible strategy is presented for synthesis of mono or multi-layer nanostructured ordered porous films on any desired substrates with flat or even curved surface, based on the fact that polystyrene sphere colloidal monolayer on glass substrate can lift off and floated on some precursor solutions, which can, in turn, be transferred onto any substrates by picking it up. SnO/sub 2/ ordered nanostructured porous films are thus successfully synthesized on the cylindrical surface, the concave surface and the spherical surface, respectively, just by taking the easily acquired SnCl/sub 4/ solution as precursor. More importantly, the mono and multi-layer porous films are also directly synthesized on commercially supplied ceramic or porcelain tubes which are used for the substrate of gas sensors. And hence, the SnO2 ordered nanostructured porous gas-sensor is constructed. Sensitivity of the sensor can be easily controlled by changing the sizes of polystyrene spheres. Such method is universal and suitable for synthesis of many other oxides or doped porous films, mesoporous/macroporous gas sensor films and even the hetero-multi-layer porous films on the curved surfaces just by changing the compositions of the precursors or alternatively repeating this strategy. This strategy provides a good way to construct nanostructured gas-sensors and practical possibility of the nanostructured devices in the near future.