Unconventional method for morphology-controlled carbonaceous nanoarrays based on electron irradiation of a polystyrene colloidal monolayer

Au/SiNCA-based SERS analysis coupled with machine learning for the early-stage diagnosis of cisplatin-induced liver injury

Cisplatin has been widely applied in the clinical treatment of various cancers, whereas liver injury induced by its hepatotoxicity is still a severe issue. Reliable identification of early-stage cisplatin-induced liver injury (CILI) can improve clinical care and help to streamline drug development. Traditional methods, however, cannot achieve enough information at the subcellular level due to the requirement of the labeling process and low sensitivity. To overcome these, we designed an Au-coated Si nanocone array (Au/SiNCA) to fabricate the microporous chip as the surface-enhanced Raman scattering (SERS) analysis platform for the early diagnosis of CILI. A CILI rat model was established, and the exosome spectra were obtained. The principal component analysis (PCA)-representation coefficient-based k-nearest centroid neighbor (RCKNCN) classification algorithm was proposed as the multivariate analysis method to build the diagnosis and staging model. The PCA-RCKNCN model has been validated to achieve a satisfactory result, with accuracy and AUC of over 97.5%, and sensitivity and specificity of over 95%, indicating that SERS combined with the PCA-RCKNCN analysis platform can be a promising tool for clinical applications.

Rapid and sensitive SERS detection of opioids in solutions based on the solid chip Au-coated Si nano-cone array

Rapid and flexible detection or accurate recognition of trace drugs is of great importance in cracking down on drug crimes, but it remains to be expected. Here, a solid chip is presented for the efficient detection and recognition of trace opioids (typically morphine) in aqueous solutions based on surface-enhanced Raman spectroscopy (SERS). Firstly, a Au-coated Si nano-cone array (Au-SNCA) is designed and fabricated via Si-based organic colloidal template etching and Au deposition. This Au-SNCA shows three-dimensional nanostructure with high densities of nanotips and deep nanogaps as well as high structural consistency, which exhibits strong SERS activity to morphine and outstanding stability. Then, such Au-SNCA is used as solid SERS chip to detect morphine in aqueous solutions. It has been demonstrated that using such solid chip, trace morphine in solutions could be recognized and detected within 1 min, and the detection limit is 10^-5 mg/mL (∼10 ppb), showing rapid and sensitive detection, which is much better than the previous reports. Meanwhile, the Au-SNCA chip also can be utilized to detect trace morphine in tap water and reservoir water, the recoveries range from 90.4% to 102.4%. Such excellent SERS performance of this Au-SNCA chip is attributed to its special structure which enhances not only local electromagnetic field but also molecular adsorption. The experimental results about the effects of immersion time and concentration show that the adsorption behavior of morphine molecules on such Au-SNCA chip can be explained by the pseudo-second-order kinetic model and Freundlich adsorption mode. Moreover, the Au-SNCA chip is also suitable for the identification of morphine homologues and the broad-spectrum detection of various common drugs. This study presents a practical solid chip and a simple approach for the efficient SERS detection and recognition of trace drugs in solutions. This is of significance to on-site detect drugs in forensic science.

Nanosphere Lithography: A Versatile Approach to Develop Transparent Conductive Films for Optoelectronic Applications

Transparent conductive films (TCFs) are irreplaceable components in most optoelectronic applications such as solar cells, organic light-emitting diodes, sensors, smart windows, and bioelectronics. The shortcomings of existing traditional transparent conductors demand the development of new material systems that are both transparent and electrically conductive, with variable functionality to meet the requirements of new generation optoelectronic devices. In this respect, TCFs with periodic or irregular nanomesh structures have recently emerged as promising candidates, which possess superior mechanical properties in comparison with conventional metal oxide TCFs. Among the methods for nanomesh TCFs fabrication, nanosphere lithography (NSL) has proven to be a versatile platform, with which a wide range of morphologically distinct nanomesh TCFs have been demonstrated. These materials are not only functionally diverse, but also have advantages in terms of device compatibility. This review provides a comprehensive description of the NSL process and its most relevant derivatives to fabricate nanomesh TCFs. The structure-property relationships of these materials are elaborated and an overview of their application in different technologies across disciplines related to optoelectronics is given. It is concluded with a perspective on current shortcomings and future directions to further advance the field.

Quantitative Surface-Enhanced Raman Spectroscopy for Field Detections Based on Structurally Homogeneous Silver-Coated Silicon Nanocone Arrays

Practical application of surface-enhanced Raman spectroscopy (SERS) is greatly limited by the inaccurate quantitative analyses due to the measuring parameter's fluctuations induced by different operators, different Raman spectrometers, and different test sites and moments, especially during the field tests. Herein, we develop a strategy of quantitative SERS for field detection via designing structurally homogeneous and ordered Ag-coated Si nanocone arrays. Such an array is fabricated as SERS chips by depositing Ag on the template etching-induced Si nanocone array. Taking 4-aminothiophenol as the typical analyte, the influences of fluctuations in measuring parameters (such as defocusing depth and laser powers) on Raman signals are systematically studied, which significantly change SERS measurements. It has been shown that the silicon underneath the Ag coating in the chip can respond to the measuring parameters' fluctuations synchronously with and similar to the analyte adsorbed on the chip surface, and the normalization with Si Raman signals can well eliminate the big fluctuations (up to 1 or 2 orders of magnitude) in measurements, achieving highly reproducible measurements (mostly, <5% in signal fluctuations) and accurate quantitative SERS analyses. Finally, the simulated field tests demonstrate that the developed strategy enables quantitatively analyzing the highly scattered SERS measurements well with 1 order of magnitude in signal fluctuation, exhibiting good practicability. This study provides a new practical chip and reliable quantitative SERS for the field detection of real samples.

Non-Close-Packed Particle Arrays Based on Anisotropic Red Blood Cell (RBC) like Particles via Stretching Deformation Method

Non-close-packed (NCP) particle arrays have potential applications in many fields such as photonics and sensors. However, due to thermodynamic stability, it is still a challenge to produce NCP arrays by the traditional approach. Here, we demonstrated a facile method to fabricate hexagonal close-packed (HCP) arrays with different orientations from that of the Janus particles. After that, the HCP arrays can be easily tuned by stretching deformation of polyethylene film. By tuning the stretching elongations, NCP arrays with five Bravais lattice structures were obtained. Besides, to fabricate the complex structure, these arrays were used as templates to assemble binary particle arrays. Such tunable crystal lattice and binary self-assembly crystal can be useful for fabricating more flexible structures and more open systems.

Current status and future developments in preparation and application of nonspherical polymer particles

Nonspherical polymer particles (NPPs) are nano/micro-particulates of macromolecules that are anisotropic in shape, and can be designed anisotropic in chemistry. Due to shape and surface anisotropies, NPPs bear many unique structures and fascinating properties which are distinctly different from those of spherical polymer particles (SPPs). In recent years, the research on NPPs has surprisingly blossomed in recent years, and many practical materials based on NPPs with potential applications in photonic device, material science and biomedical engineering have been generated. In this review, we give a systematic, balanced and comprehensive summary of the main aspects of NPPs related to their preparation and application, and propose perspectives for the future developments of NPPs.

A Nanoporous Cytochrome c Film with Highly Ordered Porous Structure for Sensing of Toxic Vapors

Creating well-ordered nanoporosity in biomolecules promises stability and activity, offering access to an even wider range of application possibilities. Here, the preparation of nanoporous protein films containing cytochrome c protein molecules is reported through a soft-templating strategy using polystyrene (PS) spheres of different sizes as templates. The stability of the cytochrome c film is demonstrated through electrochemistry studies to show a reusable nature of these films over a long period of time. The size of the PS spheres is varied to tune the pore diameter and the thickness of the cytochrome c films, which are quite stable and highly selective for sensing toxic acidic vapors. The fusion of the templating strategy and the self-assembly of biomolecules may offer various possibilities by generating a new series of porous biomolecules including enzymes with different molecular weights and diameters, peptides, antibodies, and DNA with interesting catalytic, adsorption, sensing, and electronic properties.

Distorted colloidal arrays as designed template

In this paper, a novel type of colloidal template with broken symmetry was generated using commercial, inductively coupled plasma reactive ion etching (ICP-RIE). With proper but simple treatment, the traditional symmetric non-close-packed colloidal template evolves into an elliptical profile with high uniformity. This unique feature can add flexibility to colloidal lithography and/or other lithography techniques using colloidal particles as building blocks to fabricate nano-/micro-structures with broken symmetry. Beyond that the novel colloidal template we developed possesses on-site tunability, i.e. the transformability from a symmetric into an asymmetric template. Sandwich-type particles with eccentric features were fabricated utilizing this tunable template. This distinguishing feature will provide the possibility to fabricate structures with unique asymmetric features using one set of colloidal template, providing flexibility and broad tunability to enable nano-/micro-structure fabrication with colloidal templates.

Catalyst-free synthesis of carbon nanospheres for potential biomedical applications: waste to wealth approach

A single step and simple pyrolysis technique is used to prepare carbon nanospheres (CNSs) from natural biowaste sago hampas in a nitrogen atmosphere without any catalyst.

Synthesis of photoluminescent carbon dots for the detection of cobalt ions

Photoluminescent carbon dots (C-dots) were prepared from l-cysteine through a simple hydrothermal process and used for selective detection of cobalt ions (Co²⁺), based on analyte induced aggregation and photoluminescence quenching of C-dots.

Fabrication and functionalization of periodically aligned metallic nanocup arrays using colloidal lithography with a sinusoidally wrinkled substrate

We propose a general strategy for fabricating ultrasmall attoliter-sized (10(-18) L) one-dimensional (1D) aligned nanocup arrays embedded in poly(dimethylsiloxane) (PDMS) films based on a combination of colloidal soft-lithography and wrinkle processing. The nanocup consists of a metallic shell (silver-single or double-layer silver/gold type) with a thickness of several tens of nanometers and whose diameter was ca. 500 nm and cavity depth was ca. 250 nm. First, monodisperse polystyrene (PS) colloids (d = 500 nm) were arranged onto a sinusoidally wrinkled PDMS substrate. Then, the colloid particle arrays were transferred onto another flat PDMS substrate, and a metal film was vacuum deposited over the array to form a nanostructured surface consisting of half-shell metal-coated colloid particle arrays. After the metal-coated PS array was gently transferred onto another soft PDMS substrate prepared by nonthermal curing, the attached films were thermally cured. After that, both films were carefully separated to selectively transfer the metal-coated PS particle arrays, since the metallic shell on the PS surface can adhere to the soft PDMS. Finally, the PS colloids were removed by plasma etching, leaving behind the 1D hemispherical metallic shells, called here the "metallic nanocup array structure". This structure was evaluated by performing atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy measurements. We further demonstrate chemical modification of the inner nanocup surface through construction of a self-assembled monolayer, and we also fill them with nanomaterials (silica nanoparticles) to demonstrate their application to size-selecting devices. The obtained metallic nanocup arrays could be components in a new class of chemical and/or biological nanoreactors with small reaction vessels, surface-enhanced Raman scattering (SERS)-based sensors, and size separators for nanoparticles.

Easy synthesis of hierarchical carbon spheres with superior capacitive performance in supercapacitors

An easy template-free approach to the fabrication of pure carbon microspheres has been achieved via direct pyrolysis of as-prepared polyaromatic hydrocarbons including polynaphthalene and polypyrene. The polyaromatics were synthesized from aromatic hydrocarbons (AHCs) using anhydrous zinc chloride as the Friedel-Crafts catalyst and chloromethyl methyl ether as a cross-linker. The experimental results show that the methylene bridges between phenyl rings generate a hierarchical porous polyaromatic precursor to form three-dimensionally (3D) interconnected micro-, meso-, and macroporous networks during carbonization. These hierarchical porous carbon aggregates of spherical carbon spheres exhibit faster ion transport/diffusion behavior and increased surface area usage in electric double-layer capacitors. Furthermore, micropores are present in the 3D interconnected network inside the cross-linked AHC-based carbon microspheres, thus imparting an exceptionally large, electrochemically accessible surface area for charge accumulation.

Generalized fabrication of monolayer nonclose-packed colloidal crystals with tunable lattice spacing

Here, we report a simple colloidal transfer technology that enables scalable fabrication of monolayer nonclose-packed silica colloidal crystals on a large variety of substrates. Two-dimensional colloidal crystals with an unusual nonclose-packed structure are first assembled on silicon wafers by a spin-coating technique. A poly(vinyl alcohol) (PVA) film cast upon the spin-coated colloidal crystal is used to transfer the nonclose-packed particle arrays onto various substrates. The lattice spacing of the transferred monolayer colloidal crystal can easily be adjusted by thermally treating the PVA-silica spheres composite film for varied durations. We also have demonstrated the templating fabrication of periodic arrays of gold nanodots using a transferred monolayer nonclose-packed colloidal crystal as a structural template. The resultant plasmonic array exhibits high surface-enhanced Raman scattering enhancement factor (~3.8 × 10(7)) for adsorbed benzenethiol molecules.

Fundamental research on the label-free detection of protein adsorption using near-infrared light-responsive plasmonic metal nanoshell arrays with controlled nanogap

In this work, we focused on the label-free detection of simple protein binding using near-infrared light-responsive plasmonic nanoshell arrays with a controlled interparticle distance. The nanoshell arrays were fabricated by a combination of colloidal self-assembly and subsequent isotropic helium plasma etching under atmospheric pressure. The diameter, interparticle distance, and shape of nanoshells can be tuned with nanometric accuracy by changing the experimental conditions. The Au, Ag, and Cu nanoshell arrays, having a 240-nm diameter (inner, 200-nm polystyrene (PS) core; outer, 20-nm metal shell) and an 80-nm gap distance, exhibited a well-defined localized surface plasmon resonance (LSPR) peak at the near-infrared region. PS@Au nanoshell arrays showed a 55-nm red shift of the maximum LSPR wavelength of 885 nm after being exposed to a solution of bovine serum albumin (BSA) proteins for 18 h. On the other hand, in the case of Cu nanoshell arrays before/after incubation to the BSA solution, we found a 30-nm peak shifting. We could evaluate the difference in LSPR sensing performance by changing the metal materials.

Layer-controlled synthesis of WO₃ ordered nanoporous films for optimum electrochromic application

We report on a layer-controlled fabrication of two-dimensional (2D) WO3 ordered nanoporous films via a step-by-step template-assisted strategy. For this purpose, a polystyrene sphere monolayer colloidal crystal (MCC), capable of intact transfer, is adopted as the fabrication template. WO3 nanoporous films with a monolayer (L1), bilayer (L2) and trilayer (L3) were typically constructed and technical analysis illustrates that each layer is composed of fully crystalline monoclinic WO3 nanoparticles and aggregated skeletons possessing hexagonally ordered arrangements at long range. Electrochromic characterization reveals that the ITO-based WO3 nanoporous films have long cycling stability over time and improved cation insertion/extraction capacities with increasing film layer. The inserted/extracted cations of the L2 film are nearly twice that of L1, while slightly inferior to that of L3. For the L3 film, the excessive layer thickness results in longer cation diffusion path lengths, leading to relatively poor charge reversibility. Therefore, the WO3 nanoporous bilayer films prepared in our work show optimum electrochromic properties after comprehensive characterization. Additionally, the uniform nanoporous film prepared by the proposed strategy can be successfully constructed onto a curved ceramic substrate with rough surfaces, which is still a challenge for traditional spin- or dip-coating methods. This substrate-compatible feature will facilitate construction of specific functional devices and layer-controlled fabrication by a low-cost strategy could find promising applications in chemical sensors, electrochromic windows, and so on.

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).

Improvement in the photoelectrochemical responses of PCBM/TiO2 electrode by electron irradiation

The photoelectrochemical (PEC) responses of electron-irradiated 66-phenyl-C61-butyric acid methyl ester (PCBM)/TiO2 electrodes were evaluated in a PEC cell. By coating PCBM on TiO2 nanoparticle film, the light absorption of PCBM/TiO2 electrode has expanded to the visible light region and improved the PEC responses compared to bare TiO2 electrode. The PEC responses were further improved by irradiating an electron beam on PCBM/TiO2 electrodes. Compared to non-irradiated PCBM/TiO2 electrodes, electron irradiation increased the photocurrent density and the open-circuit potential of PEC cells by approximately 90% and approximately 36%, respectively at an optimum electron irradiation condition. The PEC responses are carefully evaluated correlating with the optical and electronic properties of electron-irradiated PCBM/TiO2 electrodes.

Untraditional approach to complex hierarchical periodic arrays with trinary stepwise architectures of micro-, submicro-, and nanosized structures based on binary colloidal crystals and their fine structure enhanced properties

A unique approach for fabricating complex hierarchical periodic arrays with trinary stepwise architectures of micro- and submicro- as well as nanosized structures by combining a novel double-layered binary colloidal crystal with pulsed laser deposition techniques is developed. The present strategy is universal and nanostructures with different materials can be easily prepared in the complex hierarchical periodic arrays. This approach offers the advantage of low costs compared to conventional lithographic techniques. These as-prepared unique structures cannot be directly fabricated by conventional lithography. These special hierarchically structured arrays demonstrate fine structure-enhanced performances, including superhydrophilicity without UV irradiation and surface enhanced Raman scattering (SERS), which is highly valuable for designing micro/nanodevices, such as biosensors or microfluidic devices.

Tuning the electronic band structure of PCBM by electron irradiation

Tuning the electronic band structures such as band-edge position and bandgap of organic semiconductors is crucial to maximize the performance of organic photovoltaic devices. We present a simple yet effective electron irradiation approach to tune the band structure of [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM) that is the most widely used organic acceptor material. We have found that the lowest unoccupied molecular orbital (LUMO) level of PCBM up-shifts toward the vacuum energy level, while the highest occupied molecular orbital (HOMO) level down-shifts when PCBM is electron-irradiated. The shift of the HOMO and the LUMO levels increases as the irradiated electron fluence increases. Accordingly, the band-edge position and the bandgap of PCBM can be controlled by adjusting the electron fluence. Characterization of electron-irradiated PCBM reveals that the variation of the band structure is attributed to the molecular structural change of PCBM by electron irradiation.

Fabrication of size-controllable Fe2O3 nanoring array via colloidal lithography

Tailed-Fe(2)O(3) ring arrays are fabricated by solution-dipping on a colloidal monolayer template. The influence of synthesis parameters on the quality of nanostructures has been investigated. The ring size can be controlled by changing the precursor concentration and varying the annealing time of the polystyrene sphere colloidal monolayer. In addition, the edge of the rings is sensitive to the surface tension of precursor solution, and high quality ordered ring arrays can be obtained by tuning the surface tension. This strategy allows the fabrication of specific metal oxides ring arrays with high quality and uniform morphology.

Fabrication of size-controllable hexagonal non-close-packed colloidal crystals and binary colloidal crystals by pyrolysis combined with plasma-electron coirradiation of polystyrene colloidal monolayer

We present an unprecedented and systematic route to controllably fabricate hexagonal non-close-packed (hncp) monolayer colloidal crystals and binary colloidal crystals (BCCs) based on plasma-electron coirradiation of polystyrene colloidal monolayers followed by thermal decomposition. Hncp colloidal crystals with tunable particle sizes and periods could be fabricated by changing the pristine colloidal particle size and the thermal decomposition time. In addition, BCCs and trimodal colloidal crystals that are composed of different-sized colloidal particles can also be fabricated by adding small particles on the prepared hncp colloidal crystals. Both the particle size ratio and the volume fraction of the BCCs can be widely tuned. These hncp colloidal crystals and BCCs have various potential applications as optical and photonic materials as well as in catalysis and sensors.

Colloidal self-assembly meets nanofabrication: from two-dimensional colloidal crystals to nanostructure arrays

Self-assembly of colloidal microspheres or nanospheres is an effective strategy for fabrication of ordered nanostructures. By combination of colloidal self-assembly with nanofabrication techniques, two-dimensional (2D) colloidal crystals have been employed as masks or templates for evaporation, deposition, etching, and imprinting, etc. These methods are defined as "colloidal lithography", which is now recognized as a facile, inexpensive, and repeatable nanofabrication technique. This paper presents an overview of 2D colloidal crystals and nanostructure arrays fabricated by colloidal lithography. First, different methods for fabricating self-assembled 2D colloidal crystals and complex 2D colloidal crystal structures are summarized. After that, according to the nanofabrication strategy employed in colloidal lithography, related works are reviewed as colloidal-crystal-assisted evaporation, deposition, etching, imprinting, and dewetting, respectively.

Fabrication of porous hierarchical polymer/ceramic composites by electron irradiation of organic/inorganic polymers: route to a highly durable, large-area superhydrophobic coating

Polymer/ceramic composite films with micro- and nanocombined hierarchical structures are fabricated by electron irradiation of poly(methyl methacrylate) (PMMA) microspheres/silicone grease. Electron irradiation induces volume contraction of PMMA microspheres and simultaneously transforms silicone grease into a ceramic material of silicon oxycarbide with many nanobumps. As a result, highly porous structures that consist of micrometer-sized pores and microparticles decorated with nanobumps are created. The fabricated films with the porous hierarchical structure exhibit good superhydrophobicity with excellent self-cleaning and antiadhesion properties after surface treatment with fluorosilane. In addition, the porous hierarchical structures are covered with silicon oxycarbide, and thus the superhydrophobic coatings have high hardness and strong adhesion to the substrate. The presented technique provides a straightforward route to producing large-area, mechanically robust superhydrophobic films on various substrate materials.

Unconventional lithography for hierarchical micro-/nanostructure arrays with well-aligned 1D crystalline nanostructures: design and creation based on the colloidal monolayer

We have developed a strategy for designing and fabricating hierarchical micro-/nanostructured arrays based on the combination of a colloidal monolayer substrate and the pulsed laser deposition (PLD) process. In this approach, microstructures are provided by the colloidal monolayer and can be tuned by changing colloidal monolayer periodicities, while crystalline nanostructures are supplied by PLD and can be controlled by PLD experiment parameters (e.g., ambient gas pressure). In comparison with the traditional lithography techniques, the proposed method has the obvious advantage of low cost. More importantly, the complicated hierarchical micro-/nanostructure arrays obtained by the present strategy cannot easily be designed and synthesized by traditional lithography techniques. This fact suggests that the proposed method can be a quite powerful alternative to fabricate complicated hierarchical arrays by complementing the weakness of traditional lithographic routes. In addition to these, the strategy also features uniform surface morphology, room-temperature reaction, and pure sample surfaces that are highly valuable to build a new generation of microdevices or nanodevices in nanophotonics, energy storage, etc. on the basis of these special hierarchical micro-/nanostructured arrays.

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.

Preparing patterned carbonaceous nanostructures directly by overexposure of PMMA using electron-beam lithography

The overexposure process of poly(methyl methacrylate) (PMMA) was studied in detail using electron-beam lithography. It was found that PMMA films could be directly patterned without development due to the electron-beam-induced collapse of PMMA macromolecular chains. By analyzing the evolution of surface morphologies and compositions of the overexposed PMMA films, it was also found that the transformation of PMMA from positive to negative resist was a carbonization process, so patterned carbonaceous nanostructures could be prepared directly by overexposure of PMMA using electron-beam lithography. This simple one-step process for directly obtaining patterned carbonaceous nanostructures has promising potential application as a tool to make masks and templates, nanoelectrodes, and building blocks for MEMS and nanophotonic devices.

Non-adhesive PEG hydrogel nanostructures for self-assembly of highly ordered colloids

In this paper, we report on the effect of patterned non-adhesive hydrogel nanosurfaces on the self-assembly of highly ordered colloids. Polyethylene glycol (PEG) hydrogel is employed as the substrate material in the study, for its desired non-adhesive property, and biocompatibility as well as photopatternability. Ultrafine PEG features are photopatterned onto glass substrates with minimal feature resolution of 500 nm using ultraviolet or deep ultraviolet exposure. By simply controlling the colloidal concentration of the nanoassembly solutions and the dimensions of the wells, a range of highly organized nanocolloidal patterns are formed inside the PEG wells. Unlike the traditional surface modification techniques, ours takes advantage of the unique non-adhesive property of PEG hydrogels to achieve extremely high selectivity in the pattern-assisted nanoassembly. Our experiments show that with oxygen plasma treatment, the non-adhesive property of the PEG surface deteriorates significantly, leading to non-selective assembly with complete surface coverage of nanocolloidal beads under the same processing condition. Therefore, benefiting from the unique non-adhesive surface property, the pattern-assisted nanoassembly method enables a highly predictable and robust process for colloidal nanofabrication, and the obtained nanocolloidal arrays with well organized patterns could potentially find applications in photonic crystal fabrication, biological sensing and analytical detection.

High-quality ZnO nanowire arrays directly fabricated from photoresists

We report a simple and effective method for fabricating and patterning high-quality ZnO nanowire arrays using carbonized photoresists to control the nucleation site, density, and growth direction of the nanowires. The ZnO nanowires fabricated using this method show excellent alignment, crystal quality, and optical properties that are independent of the substrates. The carbonized photoresists provide perfect nucleation sites for the growth of aligned ZnO nanowires and they also perfectly connect to the nanowires to form ideal electrodes that can be used in many applications of ZnO nanomaterials.