A New Method of Photopatterning with LB Films Based on a Chemically Amplified Mechanism

A new approach to introducing a photoacid generator（PAG） into Langmuir-Blodgett （LB） films to draw photopatterns as a lithographic process is described here. The chemically amplified positive-tone resist system used here consists of two components ： a copolymer, poly （ dodecrylacrylamide-co-4-t-butyloxylvinyl-phenylcarbonate ） [ P （ DDA-t- BVPC53 ） ] and a PAG, tri （2,3-dibromopropyl） isocyanurate （ TDBPIC ）. In the two-component system, the acid generated by the PAG catalyzes the deprotection reaction of P（ DDA-t-BVPC53）, to remove the tert-butoxycarbonyl group（t-BOC） in the exposed region during the postexposure baking process, thus rendering the exposed region soluble to alkaline aqueous solvents to form a positive tone. Photolithographic properties of the LB films have been evaluated. The patterns can be resolved with a resolution of 1 μm line width by UV irradiation, followed by development with an alkaline solution. The LB films can be used to generate etched gold relief images on a glass substrate via an aqueous iodide, like ammonium iodide, in alcohol/water as the etchant. The etch resistance of such LB films is sufficiently good, allowing patterning of a gold film suitable for photomask fabrication.

Photopatterning via photofluidization of azobenzene polymers

In current photo-based patterning techniques,an image is projected onto a photosensitive material to generate a pattern in the area where the light is focused.Thus,the size,shape,and periodicity of the pattern are determined by the features on the photomask or projected images,and the materials themselves generally do not play an active role in changing the features.In contrast,azobenzene polymers offer a unique type of photopatterning platform,where photoisomerization of the azobenzene groups can induce substantial material movements at the molecular,micro-,and macroscales.Stable surface relief patterns can be generated by exposure to interference light beams.Thus,periodic nano-and microstructures can be fabricated with both two-and three-dimensional spatial control over a large area in a remarkably simple way.Polarized light can be used to guide the flow of solid azobenzene polymers along the direction of light polarization via an unusual solid-to-liquid transition,allowing for the fabrication of complex structures using light.This review summarizes the recent progress in advanced manufacturing using azobenzene polymers.This includes a brief introduction of the intriguing optical behaviors of azobenzene polymers,followed by discussions of the recent developments and successful applications of azobenzene polymers,especially in micro-and nanofabrication.

In Situ Generation of N-Heteroaromatic Polymers:Metal-Free Multicomponent Polymerization for Photopatterning,Morphological Imaging,and Cr(Ⅵ)Sensing

Electron-deficient N-heteroaromatic polymers are crucial for the high-tech applications of organicmaterials,especially in the electronic and optoelectronic fields.Thus,the development of new polymerizations to afford adaptable electron-donating-accepting scaffolds in N-heteroaromatic polymers is in high demand.Herein,we have developed metal-free multicomponent polymerizations of diynes,diamines,and glyoxylates successfully for in situ generation of poly(quinoline)s with high molecular weights(Mw up to 16,900)in nearly quantitative yields.By tuning the electron distributions of the polymer backbones,the resulting poly(quinoline)s showed various aggregation-induced behaviors and photoresponsive abilities:The thin films of the poly(quinoline)s could be fabricated readily intowell-resolved photopatterns by photolithography techniques.They could be utilized as fluorescent probes to visualize themorphologies of polymer materials directly;these include spherulites and microphase separation of polymer blends.Their nanoparticles demonstrated sensitive and highly selective fluorescence quenching to hexavalent chromium ion Cr(Ⅵ),thereby providing access for biological imaging of Cr(Ⅵ)in unicellular algae.

Photopatterned liquid crystal mediated terahertz Bessel vortex beam generator [Invited]

In this Letter, we propose that the photopatterned liquid crystal(LC) can act as a broadband and efficient terahertz(THz) Bessel vortex beam(BVB) generator. The mechanism lies in the frequency-independent geometric phase modulation induced by the spatially variant LC directors. By adopting large birefringence LCs and optimizing the cell gap, the maximized mode conversion efficiency can be continuously adjusted in broadband.Furthermore, the LC patterns can be designed and fabricated at will, which enables the THz BVBs to carry various topological charges. Such a THz LC BVB generator may facilitate the advanced THz imaging and communication apparatus.

Photopatternable PEDOT:PSS/PEG hybrid thin film with moisture stability and sensitivity

Degradation and delamination resulting from environmental humidity have been technically challenging for poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)thin-film processing.To overcome this problem,we introduced a one-step photolithographic method to both pattern and link a PEDOT:PSS film onto a poly(ethylene glycol)(PEG)layer as a hybrid thin film structure on a flexible substrate.This film exhibited excellent long-term moisture stability(more than 10 days)and lithographic resolution(as low as 2μm).Mechanical characterizations were performed,including both stretching and bending tests,which illustrated the strong adhesion present between the PEDOT:PSS and PEG layers as well as between the hybrid thin film and substrate.Moreover,the hybrid moisture-absorbable film showed a quick response of its permittivity to environmental humidity variations,in which the patterned PEDOT:PSS layer served as an electrode and the PEG layer as a moisture-sensing element.Perspiration tracking over various parts of the body surface as well as breath rate measurement under the nose were successfully carried out as demonstrations,which illustrated the potential utility of this stable hybrid thin film for emerging flexible and wearable electronic applications.

A Luminescent Dicyanodistyrylbenzene-based Liquid Crystal Polymer Network for Photochemically Patterned Photonic Composite Film

A novel photonic composite film based on a luminescent dicyanodistyrylbenzene-based liquid crystal polymer network（LCN） was fabricated by using a silica colloidal crystal as a template. The upper part of inverse opal structure and the luminescence characteristics of dicyanodistyrylbenzene-based moiety endowed the resulting bilayer photonic film with structural color arising from coherent Bragg reflection and fluorescence properties, respectively. A fluorescence enhancement phenomenon was observed in the photonic film due to the overlap between the reflection band and emission band of the fluorescent LCN. More importantly, the photo-induced irreversible Z/E photoisomerization of dicyanodistyrylbenzene-based moiety in the photonic film led to both a reflection spectral shift and an observable fluorescence variation. On the basis of this effective phototuning process, microscopic patterning of photonic film was developed under both fluorescence mode and reflection mode. The work demonstrated here provides a new route to construct photo-responsive photonic film.

A photopatterned SERS substrate with a sandwich structure for multiplex detection

Substrate photopatterning has provided versatile applications in biomedical fields. Herein, an universal and efficient photoligation reaction has been used to prepare a patterned capture substrate for a sandwich SERS immunoassay. Photoirradiation induces mild and efficient immobilization of antibodies at the desired region of a gold surface, and the antibody-antigen interaction helps the substrate to capture the antigens in solution specifically. After exposing to SERS probes, i.e., the gold nanoparticles labelled with both antibodies and intrinsically strong Raman reporters, multiple quantitative SERS determination of antigens can be achieved with high sensitivity and specificity. The limit of detection can be as low as 10^(-12) mol/L for four kinds of cancer biomarkers, which provides a promising method for the construction of highly sensitive and high-throughput SERS detection chip and the application of in vitro diagnosis.

Synthesis of Functional Hyperbranched Poly(methyltriazolylcarboxylate)s by Catalyst-free Click Polymerization of Butynoates and Azides

Azide-alkyne click polymerization has become a powerful tool for polymer synthesis.However,the click polymerization between internal alkynes and azides is rarely utilized to prepare functional polymers.In this work,the polymerization reactions of activated internal alkyne monomers of tris(2-butynoate)s(1)with tetraphenylethene-containing diazides(2)were performed in dimethylformamide(DMF)under simple heating,affording four hyperbranched poly(methyltriazolylcarboxylate)s(hb-PMTCs)with high molecular weights(A4W up to 2.4 x 104)and regioregularities(up to 83.9%)in good yields.The hb-PMTCs are soluble in common organic solvents,and thermally stable with 5%weight loss temperatures up to 400℃.They are non-emissive in dilute solution,but become highly emissive in aggregated state,exhibiting aggregationinduced emission characteristics.The polymers can generate fluorescent photopatterns with high resolution,and can work as fluorescent sensors to detect nitroaromatic explosive with high sensitivity.

Facile Synthesis of Functional Poly(methyltriazolylcarboxylate)s by Solvent-and Catalyst-free Butynoate-Azide Polycycloaddition

The copper-catalyzed and metal-free azide-alkyne click polymerizations have become efficient tools for polymer synthesis. However,the 1,3-dipolar polycycloadditions between internal alkynes and azides are rarely employed to construct functional polymers. Herein, the polycycloadditions of dibutynoate(1) and tetraphenylethene-containing diazides(2) were carried out at 100 °C for 12 h under solvent-and catalyst-free conditions, producing soluble poly(methyltriazolylcarboxylate)s(PMTCs) with high molecular weights in high yields. The resultant polymers were thermally stable with 5% weight loss temperatures up to 377 °C. The PMTCs showed aggregation-induced emission(AIE)properties. They could work as fluorescent sensors for detecting explosive with high sensitivity, and generate two-dimensional fluorescent photopatterns with high resolution. Furthermore, their triazolium salts could be utilized for cell-imaging applications.

Photosensitizer-assisted direct 2D patterning and 3D printing of colloidal quantum dots

Direct photopatterning is a powerful strategy for patterning colloidal quantum dots(QDs)for their integration in various electronic and optoelectronic devices.However,ultraviolet(UV)exposure required for QD patterning,especially those with short wavelength(e.g.,deep UV light),can degrade the photo-,and electroluminescence,and other properties of patterned QDs.Here we develop a photosensitizer-assisted approach for direct photopatterning of QDs with h-line(centered at 405 nm)UV light and better preservation of their luminescent properties.This approach uses a photosensitizer that can absorb the h-line UV light and transfer the energy to activate bisazide-based crosslinkers via Dexter energy transfer.Uniform,high-resolution(smallest feature size,2μm),and full-color patterns of red,green,and blue QD layers can be achieved.The patterned QD layers maintain up to~90%of their original photoluminescent quantum yields,comparing favorably with those(<60%)of QDs patterned without photosensitizers.We further extended the strategy to the direct three-dimensional(3D)printing of QDs.This photosensitizerassisted approach offers a new way for direct two-dimensional(2D)photopatterning and 3D printing of colloidal QDs,with implications in building high-performance QD optoelectronic devices.