Influence of Laser‐Induced Topography Changes on the Activity of Catalyst Coatings as Examined by Infrared Thermography

A mixed metal oxide catalyst coating is subjected to laser irradiation by a Nd:YAG laser operating at 266 nm to induce local changes in surface topography. The coating is exposed to laser interference patterns as well as to direct laser irradiation without interference. Samples are characterized by means of White Light Interferometry and Scanning Electron Microscopy. Irradiation with interference patterns causes the formation of wave‐like surface patterns in micrometer scale whereas direct laser irradiation generates porosity with pore sizes in the range of 100nm. Emissivity‐corrected infrared thermography (ecIRT) is applied to analyze the effect of surface topography changes on the catalytic activity of coatings in parallel. The catalytic combustion of iso‐octane with different contents of oxygen in nitrogen is used as a test reaction for catalytic activity. Local temperature increase on the substrate is chosen as a measure for catalytic activity. For laser interference structured coating, the catalytic activity improves with increase in geometric surface area caused by the wave‐like pattern. For direct laser irradiation, the porosity created by the laser enhances catalytic activity with respect to the unstructured coating.     

Mussel Byssus‐Like Reversible Metal‐Chelated Supramolecular Complex Used for Dynamic Cellular Surface Engineering and Imaging

Inspired by the load‐bearing biostructures in nature, a multifunctional shell for encapsulating cell using the polyphenol–metal complexes is fabricated. The artificial shell is formed by cross‐linking of tannic acid and iron ion on cell surface. It can protect cells from unfriendly environments, including UV light irradiation and reactive oxygen damage. With the hybrid property of polyphenol and metal liands, the shell provides a versatile platform for cell surface engineering. The magnetic nanoparticles, DNA molecules, as well as the magnetic resonance imaging agents are easily incorporated into the shell. More interestingly, unlike the traditional passive coatings, here the shell can be controllably disassembled under external stimuli. The dynamic coating is used as a reversible element to regulate cell division and surface modification. The cell viability and protein expression experiments further confirm that the shell formation and degradation processes are biocompatible. This multifunctional coating strategy is applicable to multiple living cell types, including yeast cells, Escherichia coli bacteria, and mammalian cells. Therefore, this platform would be useful for living cell based fundamental research and biological applications.     

Photoinduced Tetrazole‐Based Functionalization of Off‐Stoichiometric Clickable Microparticles

We report the preparation of tetrazole‐containing step‐growth microparticles and the subsequent use of photoinduced nitrile imine‐mediated tetrazole‐ene cycloaddition (NITEC) reactions on the particles with spatiotemporal control. Microparticles with an average diameter of 4.1 µm and with inherent tetrazole‐ene dual functionality are prepared by a one‐pot off‐stoichiometric thiol‐Michael addition dispersion polymerization. The NITEC reaction is performed efficiently in the solid phase by UV irradiation, leading to the formation of fluorescent pyrozoline adducts, with an estimated quantum yield of 0.7. Particle concentration‐independent reaction kinetics are observed and full conversion is reached within 10 min of UV exposure at an intensity of 8 mW cm^?2. Temporal control is demonstrated with either UV or rooftop sunlight irradiation of variable duration. By using two‐photon writing with a laser centered around 700 nm wavelength, spatial control is demonstrated with micrometer‐scale resolution via surface patterning of the microparticles. Further, microparticles with exclusive tetrazole functionality are prepared by a one‐pot, two‐step thiol‐Michael addition dispersion polymerization. The NITEC reaction between tetrazole‐functional particles and acrylates in solution is examined at various tetrazole/alkene molar ratios, and a 10:1 excess of alkenes in solution is found necessary for efficient functionalization.     

380‐nm Ultraviolet Light‐Emitting Diodes with InGaN/AlGaN MQW Structure

In this paper, we demonstrate the capabilities of 380‐nm ultraviolet (UV) light‐emitting diodes (LEDs) using metal organic chemical vapor deposition. The epi‐structure of these LEDs consists of InGaN/AlGaN multiple quantum wells on a patterned sapphire substrate, and the devices are fabricated using a conventional LED process. The LEDs are packaged with a type of surface mount device with Al‐metal. A UV LED can emit light at 383.3 nm, and its maximum output power is 118.4 mW at 350 mA.     

Template‐Free Sol‐Gel Preparation of Superhydrophobic ORMOSIL Films for Double‐Wavelength Broadband Antireflective Coatings

A double‐layer double‐wavelength antireflective (AR) coating with 100% transmittance at both 1064 nm and 532 nm, which is very important in high power laser systems, is designed using thin film design software (TFCalc). The refractive indices for the bottom and top layers of the designed AR coating are about 1.30 and 1.14. A simple, template‐free sol‐gel route is proposed to prepare the superhydrophobic ORMOSIL (organically modified silicate) thin film, which has an ultralow refractive index, by silica particle surface modification using hexamethylisilazane (HMDS); this treatment decreases the refractive index of the silica thin film from 1.23 to 1.13. The formation mechanism of the ultralow refractive index thin film is proposed. The particle surface modification with HMDS significantly improves the hydrophobicity of the coated film; the water contact angle of the film increases from 23.4° to 160°. The bottom layer, which has a refractive index of 1.30, is prepared from acid‐catalyzed and base‐catalyzed mixed silica sol. A double‐layer silica AR coating is obtained with transmittances of 99.6% and 99.8% at 532 nm and 1064 nm, respectively.     

Near‐Infrared Light‐Driven,Highly Efficient Bilayer Actuators Based on Polydopamine‐Modified Reduced Graphene Oxide

Near‐infrared (NIR) light‐driven bilayer actuators capable of fast, highly efficient, and reversible bending/unbending motions toward periodic NIR light irradiation are fabricated by exploiting the photothermal conversion and humidity‐sensitive properties of polydopamine‐modified reduced graphene oxide (PDA‐RGO). The bilayer actuator comprises a PDA‐RGO layer prepared by a filtration method, and this layer is subsequently spin‐coated with a layer of UV‐cured Norland Optical Adhesive (NOA)‐63. Given the hydrophilicity of PDA, the PDA‐RGO layer can absorb water to swell and lose water to shrink. The intrinsic NIR absorbance of RGO sheets convertes NIR light into thermal energy, which transfers the humidity‐responsive PDA‐RGO layer to be NIR light‐responsive. Considering that the shape of the NOA‐63 layer remains unchanged under NIR light, periodic NIR light irradiation leads to asymmetric shrinkage/expansion of the bilayer, which enables fast and reversible bending/unbending motions of the bilayer actuator. We demonstrate that compared with a poly(ethylenimine)‐modified graphene oxide layer, the PDA‐RGO layer is unique in fabricating highly efficient bilayer actuators. A NIR light‐driven walking device capable of performing quick worm‐like motion on a ratchet substrate is built by connecting two polyethylene terephthalate plates as claws on opposite ends of the PDA‐RGO/NOA‐63 bilayer actuator.     

Defect‐Related Optical Behavior in Surface Modified TiO2 Nanostructures

The surface modification of TiO₂ nanostructures to incorporate nitrogen and form visible light absorbing titanium oxynitride centers is studied. Anatase TiO₂ structures in the 5–20 nm range, formed by a wet chemical technique, were surface modified and the nitridation of the highly reactive TiO₂ nanocolloid surface, as determined by X‐ray photoelectron spectroscopy (XPS) studies, is achieved by a quick and simple treatment in alkyl ammonium compounds. The nitriding process was also simultaneously accompanied by metal seeding resulting in a metal coating layer on the TiO₂ structures. The structure of the resultant titanium oxynitride nanostructures remains anatase. These freshly prepared samples exhibited a strong emission near 560 nm (2.21 eV), which red‐shifted to 660 nm (1.88 eV) and dropped in intensity with aging in the atmosphere. This behavior was also evident in some of the combined nitrogen doped and metal seeded TiO₂ nanocolloids. Electron spin resonance (ESR) performed on these samples identified a resonance at g = 2.0035, which increased significantly with nitridation. The resonance is attributed to an oxygen hole center created near the surface of the nanocolloid, which correlates well with the observed optical activity.     

Optimizing the Size of Micellar Nanoparticles for Efficient siRNA Delivery

Delivery of small interfering RNA (siRNA) by nanocarriers has shown promising therapeutic potential in cancer therapy. However, poor understanding of the correlation between the physicochemical properties of nanocarriers and their interactions with biological systems has significantly hindered its anticancer efficacy. Herein, in order to identify the optimal size of nanocarriers for siRNA delivery, different sized cationic micellar nanoparticles (MNPs) (40, 90, 130, and 180 nm) are developed that exhibit similar siRNA binding efficacies, shapes, surface charges, and surface chemistries (PEGylation) to ensure size is the only variable. Size‐dependent biological effects are carefully and comprehensively evaluated through both in vitro and in vivo experiments. Among these nanocarriers, the 90 nm MNPs show the optimal balance of prolonged circulation and cellular uptake by tumor cells, which result in the highest retention in tumor cells. In contrast, larger MNPs are rapidly cleared from the circulation and smaller MNPs are inefficiently taken up by tumor cells. Accordingly, 90 nm MNPs carrying polo‐like kinase 1 (Plk1)‐specific siRNA (siPlk1) show superior antitumor efficacy, indicating that 90 nm could either be the optimal size for systemic delivery of siRNA or close to it. Our findings provide valuable information for rationally designing nanocarriers for siRNA‐based cancer therapy in the future.     

Vapor‐Based Initiator Coatings for Atom Transfer Radical Polymerization

A novel polymeric initiator coating for surface modification via atom transfer radical polymerization (ATRP) is reported. The synthetic approach involves the chemical vapor deposition of [2.2]paracyclophane‐4‐methyl 2‐bromoisobutyrate and can be applied to a heterogeneous group of substrates including stainless steel, glass, silicon, poly(dimethylsiloxane), poly(methyl methacrylate), poly(tetrafluoroethylene), and polystyrene. Surface analysis using X‐ray photoelectron spectroscopy and Fourier‐transformed infrared spectroscopy confirmed the chemical structure of the reactive initiator coatings to be consistent with poly[(p‐xylylene‐4‐methyl‐2‐bromoisobutyrate)‐co‐(p‐xylylene)]. Appropriate reactivity of the bromoisobutyrate side groups was confirmed by surface initiated atom transfer radical polymerization of a oligo(ethylene glycol) methyl ether methacrylate. After solventless deposition of the CVD‐based initiator coating, hydrogel films as thick as 300 nm could be conveniently prepared within a 24 h timeframe via ATRP. Moreover, the polymerization showed ATRP‐specific reaction kinetics and catalyst concentration dependencies. In addition, spatially controlled deposition of the initiator coatings using vapor‐assisted microstructuring in replica structures resulted in fabrication of spatially confined hydrogel microstructures. Both protein adsorption and cell adhesion was significantly inhibited on areas that were modified by surface‐initiated ATRP, when compared with unmodified PMMA substrates. The herein described initiator coatings provide a convenient access route to controlled radical polymerization on a wide range of different materials. While demonstrated only for a representative group of substrate materials including polymers, metals, and semiconductors, this method can be expected to be generically applicable – thereby eliminating the need for cumbersome modification protocols, which so far had to be established for each substrate material independently.     

Skin Pigmentation‐Inspired Polydopamine Sunscreens

Commercial sunscreens usually rely on multiple component formulas against solar irradiation, including UV filters, antioxidants, and nanomaterial matrices. While many efforts are devoted, concern has arisen that the effectiveness and safety issues of most sunscreens are largely limited by their complex formulations, photostability, and toxicity. Inspired by skin pigmentation as primary photoprotective mechanism in human body, novel sunscreen products based on polydopamine (PDA) gels, with a bioinspired protection concept and improved photoprotective capacities, were rationally designed and facilely prepared. The diverse formula of those sunscreen gels can be achieved by the use of PDA nanoparticle, a kind of naturally melanin mimics, to complex/conjugate with different polymers. The resulting PDA sunscreens are bioadhesive, water resistant, and nonskin penetration, yet can be directly removed by towel wiping. They also perform many promising features including superior UV shielding properties, high in vitro and in vivo UV protection efficiencies, nonphototoxicity, and nonirritating nature. These PDA materials in an initial proof‐of‐concept study were described and it is proposed that this class of bioinspired gels will be useful for incident UV protection where simple, safe, and efficient sunscreens are still highly desirable.     

Patterning and Conductivity Modulation of Conductive Polymers by UV Light Exposure

A novel patterning technique of conductive polymers produced by vapor phase polymerization is demonstrated. The method involves exposing an oxidant film to UV light which changes the local chemical environment of the oxidant and subsequently the polymerization kinetics. This procedure is used to control the conductivity in the conjugated polymer poly(3,4‐ethylenedioxythiophene):tosylate by more than six orders of magnitude in addition to producing high‐resolution patterns and optical gradients. The mechanism behind the modulation in the polymerization kinetics by UV light irradiation as well as the properties of the resulting polymer are investigated.     

Patterned Color and Fluorescent Images with Polydiacetylene Supramolecules Embedded in Poly(vinyl alcohol) Films

Poly(vinyl alcohol) (PVA) films embedded with functional polydiacetylene (PDA) are efficiently prepared for color and fluorescence imaging. Intensely blue films are obtained by mixing and drying solutions containing PDA vesicles and PVA. A blue‐to‐red color transition is observed upon heating the polymer films. In addition, selective UV irradiation (through a photomask) of PVA films containing diacetylene monomer results in the generation of micropatterned color (without heating) and both color and fluorescent images (after heating the films at 120 °C for 10 s). Patterned two‐color (blue and red) images in the polymer film are readily obtained by a sequential process of photomasked irradiation, heating, and unmasked irradiation.     

Spray‐Coating Magnetic Thin Hybrid Films of PS‐b‐PNIPAM and Magnetite Nanoparticles

Spray coating is employed to fabricate magnetic thin films composed of the diblock copolymer polystyrene‐block‐poly(N‐isopropylacrylamide) and Fe₃O₄ magnetic nanoparticles (MNPs) functionalized with hydrophobic coatings. The kinetics of structure formation of the hybrid films is followed in situ with grazing incidence small angle X‐ray scattering during the spray deposition. To gain a better understanding of the influence of MNPs on the overall structure formation, the pure polymer film is also deposited as a reference via an identical spray protocol. At the initial spraying stage, the hybrid film (containing 2 wt% of MNPs) exhibits a faster formation process of a complete film as compared to the reference. The existence of MNPs depresses the dewetting behavior of polymer films on the substrate at macroscale and simultaneously alters the polymer microphase separation structure orientation from parallel to vertical. As spraying proceeds, MNPs aggregate into agglomerates with increasing sizes. After the spray deposition is finished, both samples gradually reach an equilibrium state and magnetic films with stable structures are achieved in the end. Superconducting quantum interference device investigation reveals the superparamagnetic property of the sprayed hybrid film. Consequently, potential application of sprayed films in fields such as magnetic sensors or data storage appears highly promising.     

Broadband Photoresponse Enhancement of a High‐Performance t‐Se Microtube Photodetector by Plasmonic Metallic Nanoparticles

Broadband responsivity enhancement of single Se microtube (Se‐MT) photodetectors in the UV–visible region is presented in this research. The pristine Se‐MT photodetector demonstrates broadband photoresponse from 300 to 700 nm with peak responsivity of ≈19 mA W^?1 at 610 nm and fast speed (rise time 0.32 ms and fall time 23.02 ms). To further enhance the responsivity of the single Se‐MT photodetector, Au and Pt nanoparticles (NPs) are sputtered on these devices. In contrast to only enhancement of responsivity in UV region by Pt NPs, broadband responsivity enhancement (≈600% to ≈800%) of the Se‐MT photodetector is realized from 300 to 700 nm by tuning the size and density of Au NPs. The broadband responsivity enhancement phenomena are interpreted by both the surface modification and surface plasmon coupling. The experimental results of this work provide an additional opportunity for fabricating high‐performance UV–visible broadband photodetectors.     

Inkjet‐Printable Amphiphilic Polydiacetylene Precursor for Hydrochromic Imaging on Paper

Hydrochromic materials find great utility in a wide range of applications including humidity sensing and measuring the water contents of organic solvents, as well as substrates for rewritable paper and human sweat pore mapping. Herein, an inkjet printable diacetylene (DA) is described that can be transformed by UV irradiation to a hydrochromic‐conjugated polymer on conventional paper. Specifically, an amphiphilic DA that contains an ­imidazolium ion head‐group is found to be compatible with a common office inkjet printer. Various computer‐designed images are printed on paper using this substance. UV irradiation of the printed images results in the generation of blue‐colored images associated with formation of a polydiacetylene (PDA). The resolutions of the images are almost identical to those generated using a conventional black ink. Importantly, the printed images undergo a blue‐to‐red color change upon exposure to water and the hydrochromism is found to be temperature dependent. The facile color change that occurs near body ­temperatures enables use of the hydrochromic PDA‐coated paper for rapid and precise mapping of human sweat pores from fingers, palms, and feet.     

Metal–Insulator–Semiconductor Coaxial Microfibers Based on Self‐Organization of Organic Semiconductor:Polymer Blend for Weavable,Fibriform Organic Field‐Effect Transistors

With the increasing importance of electronic textiles as an ideal platform for wearable electronic devices, requirements for the development of functional electronic fibers with multilayered structures are increasing. In this paper, metal–polymer insulator–organic semiconductor (MIS) coaxial microfibers using the self‐organization of organic semiconductor:insulating polymer blends for weavable, fibriform organic field‐effect transistors (FETs) are demonstrated. A holistic process for MIS coaxial microfiber fabrication, including surface modification of gold microfiber thin‐film coating on the microfiber using a die‐coating system, and the self‐organization of organic semiconductor–insulator polymer blend is presented. Vertical phase‐separation of the organic semiconductor:insulating polymer blend film wrapping the metal microfibers provides a coaxial bilayer structure of gate dielectric (inside) and organic semiconductor (outside) with intimate interfacial contact. It is determined that the fibriform FETs based on MIS coaxial microfiber exhibit good charge carrier mobilities that approach the values of typical devices with planar substrate. It additionally exhibits electrical property uniformity over the entire fiber surface and improved bending durability. Fibriform organic FET embedded in a textile is demonstrated by weaving MIS coaxial microfibers with cotton and conducting threads, which verifies the feasibility of MIS coaxial microfiber for use in electronic textile applications.     

A Simple and Versatile Pathway for the Synthesis of Visible Light Photoreactive Nanoparticles

This work pioneers the design of visible (415 nm) and UV‐B light (300 nm) reactive nanoparticles via radical polymerization in aqueous heterogeneous media based on methyl methacrylate (MMA) and unique acrylates bearing tetrazole functionalities in a simple and straightforward two step reaction. Stable colloidal nanoparticles with an average diameter of 150 nm and inherent tetrazole functionality (varying from 2.5 to 10 wt% relative to MMA) are prepared via one‐pot miniemulsion polymerization. In a subsequent step, fluorescent pyrazoline moieties serving as linkage points are generated on the nanoparticles by either photoinduced nitrile imine‐mediated tetrazole‐ene cycloaddition (NITEC) or nitrile imine carboxylic acid ligation (NICAL) in water, thus enabling the particles as fluorescent tracers. Through in‐depth molecular surface analysis, it is demonstrated that the photoreactive nanoparticles undergo ligation to a variety of substrates bearing functionalities including maleimides, acrylates, or carboxylic acids, illustrating the versatility of the particle modification process. Critically, the unique ability of the photoreactive nanoparticles to be activated with visible light allows for their decoration with UV light–sensitive molecules. Herein, the ligation of folic acid—a vitamin prone to degradation under UV light—to the photoreactive nanoparticles using visible light is exemplified, demonstrating the synthetic power of our photoreactive fluorescent nanoparticle platform technology.     

Charge Modified Cowpea Mosaic Virus Particles for Templated Mineralization

Surface charge modification of wild‐type Cowpea mosaic virus, a plant virus, is sufficient to promote the templated mineralization of metal and metal oxide. Surface negative charge is increased by the chemical introduction of succinamate on surface lysine groups. The cobalt and iron oxide templated nanoparticles subsequently obtained are monodisperse with a diameter of ca. 32 nm. Further, the iron oxide‐CPMV nanoparticles can be readily decorated with thiol‐containing molecules.     

Open Air Plasma Deposition of Superhydrophilic Titania Coatings

A method for the deposition and functionalization of a nanostructured organotitanate thin film, which imparts superhydrophilicity to a surface with a one‐step, open‐air process, is described. Extreme wetting (Θ < 5°) is achieved through synergistic contributions from both nanoscale roughness, visible light absorption caused by nonmetal dopants, and oxygen vacancies and surface activation by reactive plasma species. To test the efficacy of this material as an antifog coating, glass is coated and subjected to aggressive changes in humidity. Under both fogging and defrosting conditions, the superhydrophilic coating achieves a high degree of transparency, showing nearly two orders of magnitude improvement over the bare glass. The measured adhesion of the superhydrophilic coating is 5.9 J m^?2, nearly double that of the solution‐processed control. The reliability of the coating is further validated by demonstrating scratch‐resistance. Additionally, the incorporation of organic matter into the molecular structure of the coating disrupts long‐range crystallinity from developing. This structural and subsequent chemical analysis of the coating reveals that inorganic and organic species are intimately connected at the nanoscale via alkyl and alkoxy bridges. The amorphous organotitanate material is distinct from conventional TiO₂, which requires high temperature crystallization and extensive UV irradiation to display similar superhydrophilic qualities.     

Network Polydiacetylene Films: Preparation,Patterning, and Sensor Applications

The synthesis, characterization, and functionalization of polydiacetylene (PDA) networks on solid substrates is presented. A highly transparent and cross‐linked diacetylene film of DCDDA‐bis‐BA on a solid substrate is prepared first by tailoring the monomers with organoboronic acid moieties as pendant side groups and consequent drop‐casting and dehydration steps. Precisely controlled thermal curing plays a key role to obtain properly aligned diacetylene monomers that are closely packed between the boronic acid derived anhydride structures. A second cross‐linking, which occurs by polymerization of the diacetylene monomers with UV irradiation, induces a transparent to blue color shift. Accordingly, colored image patterns are readily available by polymerization through a photomask. The color change that takes place as a response to various organic solvents can be simply detected by naked eyes. The thermofluorescence change of PDA networks is demonstrated to be an effective method by which to obtain the microscale temperature distribution of thermal systems. The ease of film formation and stress‐induced blue‐to‐red color change with a simultaneous fluorescence generation features of the network structure should find a great utility in a wide range of chemical and thermal sensing platforms.