Herein, we present an overview of the most recent achievements and innovations regarding the development of flexible visible transparent films for selective ultraviolet (UV) shielding, with focus on those based on hybrid inorganic-organic materials. The main synthetic paths used nowadays to ensure a high degree of protection are reviewed. Polymers containing organic UV absorbing molecules, hybrid mixtures of polymers and nanoparticles, and the recently introduced series of structures displaying structural color, are identified as the three main types of materials used for this purpose.The use of biocompatible and flexible films to achieve spectrally selective UV protection can find applications in a wide diversity of fields such as photo-treatment of skin diseases, food and beverage packing, and storage of cosmetics. V C 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: [945][946][947][948][949][950][951][952][953][954][955][956] 2012

A new type of nanostructured selective ultraviolet (UV) reflecting mirror is presented. Periodic porous multilayers with photonic crystal properties are built by spin‐coating‐assisted layer‐by‐layer deposition of colloidal suspensions of nanoparticles of ZrO2 and SiO2 (electronic band gap at λ < 220 nm). These optical filters are designed to block well‐defined wavelength ranges of the UVA, UVB, and UVC regions of the electromagnetic spectrum while preserving transparency in the visible. The shielding against those spectral regions arises exclusively from optical interference phenomena and depends only on the number of stacked layers and the refractive index contrast between them. In addition, it is shown that the accessible pore network of the as‐deposited multilayer allows preparing thin, flexible, self‐standing, transferable, and adaptable selective UV filters by polymer infiltration, without significantly losing reflectance intensity, i.e., preserving the dielectric contrast. These films offer a degree of protection comparable to that of traditional ones, without any foreseeable unwanted secondary effects, such as photodegradation, increase of local temperature or, as is the case for organic absorbers, generation of free radicals, all of which are caused by light absorption.

Insulated polythiophenes bearing conjugated backbones that are fully (IPT) or half (½IPT) encapsulated are investigated to determine the relationship between their structure, photophysics and light amplifying properties.

Antireflective transparent materials are essential for a myriad of applications to allow for clear vision and efficient light transmission. Despite the advances, efficient and low cost solutions to clean antireflective surfaces have remained elusive. Here, we present a practical approach that enables the production of antireflective polymer surfaces based on moth-eye inspired features incorporating photoinduced self-cleaning properties and enhanced mechanical resistance. The methodology involves the fabrication of sub-wavelength moth-eye nanofeatures onto transparent surface composite films in a combined processing step of nanoparticle coating and surface nanoimprinting. The resulting surfaces reduced the optical reflection losses from values of 9% of typical PMMA plastic films to an optimum value of 0.6% in the case of double-sided moth-eye nanoimprinted films. The composite moth-eye topography also showed an improved stiffness and scratch resistance. This technology represents a significant advancement not limited by scale, for the development of antireflective films for low cost application products.

Here we present the assembly of novel transparent all-polymer distributed feedback (DFB) lasers. Flexible and highly transparent cellulose diacetate (CdA) was employed as substrate on which gratings with different periods were engraved by thermal nanoimprinting with high fidelity. Highly luminescent conjugated polymers (CP), poly (9,9-dioctylfluorene) (PFO), poly(9,9dioctylfluorene-alt-benzothiadiazole) (F8BT), and a blend of F8BT and poly(3-hexylthiophene)-poly(9,9-dioctylfluorene-altbenzothiadiazole) (P3HT:F8BT) were deposited by spin coating onto the nanostructured plastic surfaces, giving rise to perpendicular single-mode lasing emission in the blue, green, and red wavelength ranges, respectively. These lasers show linewidths below 1 nm and low thresholds (≈6 μJcm −2 for blue and red lasing emission), comparable to other state-of-the-art lasers obtained from similar optical gain materials on rigid substrates. The followed strategy is scalable and versatile, enabling the development of large area nanoimprinted DFB lasers (>1cm 2 ) on plastic, which is highly relevant for applications in various markets.npj Flexible Electronics (2019) 3:17 ; https://doi.

The fabrication of all polymer optical waveguides, based on a highly fluorescent conjugated polymer (CP) poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) and a mechanically flexible and biodegradable polymer, cellulose acetate (CA), is reported. The replication by hot embossing of patterned surfaces in CA substrates, onto which high quality F8BT films can be easily processed by spin coating, is exploited to produce an entirely plastic device that exhibits low optical loss and low threshold for amplified spontaneous emission (ASE). As a result, highly transparent and flexible waveguides are obtained, with excellent optical properties that remain unaltered after bending, allowing them to be adapted in various flexible photonic devices.

a series of undesirable photoreactions promoted by the absorption of UV photons, which lead to the deterioration of their mechanical and optical properties. Polymers are usually transparent to part of the UV spectrum, so a commonly employed synthetic strategy to attain UV blocking fi lms is based on embedding inorganic [3][4][5][6][7] or organic [8][9][10] UV absorbers within a polymeric matrix. The main drawback of this approximation is the short term durability of the shielding effect as a result of the photodegradation of either host, guest, or both, caused by the absorption of the same radiation from which protection is sought after. [11][12][13] Approaches based on fl exible inorganic nano structured multilayers that effi ciently refl ect radiation in an arbitrary spectral range as a result of interference effects, rather than by absorption, present a promising alternative route worth to be explored. [14][15][16][17] Unfortunately, a similar approach based on the alternation of polymeric fi lms exclusively is not feasible since the refractive index contrast typically achieved is so small that a large number of layers is required to reach a signifi cant refl ectance, and only in a narrow spectral range. [ 18,19 ] The use of all-polymeric materials of high refractive index contrast to build multilayer back refl ectors or UV shields will also be an advantage in the fi eld of fl exible and polymeric solar cells, in which some approaches based on inorganic materials have already been developed. [ 20,21 ] Very recently, some of us proved that a porous stratifi ed structure displaying strong refl ection peaks in the UV range can be attained from a block copolymer (BCP) fi lm. [ 22 ] In particular, it was demonstrated that a fi lm made of a diblock copolymer containing polystyrene (PS) and polymethyl methacrylate (PMMA), in brief [poly(styreneblock -methyl methacrylate) PS-b -PMMA)], can be used as starting material to attain ordered porous multilayers through a process that involves collective osmotic shock (COS). The fi nal structure shows alternate dense and porous layers, with signifi cant refractive index contrast, which endow it with photonic crystal properties in the UV range. At that moment, the appearance of the layered structure was hypothetically attributed to dynamic effects during the COS process occurring over ordered arrangements of isolated PMMA spheres embedded in a cross-linked PS matrix in the starting slab, which had previously been subjected to thermal and UV annealing processes. Further studies, herein reported, have demonstrated that the mechanism of formation of the porous layered structure is different to that originally A synthetic route is demonstrated to build purely polymeric nanostructured multilayer coatings, adaptable to arbitrary surfaces, and capable of effi ciently blocking by refl ection a targeted and tunable ultraviolet (UV) range. Refl ection properties are determined by optical interference between UV light beams refl ected at the interfaces between polystyrene layers of diff...

We demonstrated a simple, directly-readable approach for high resolution pH sensing. The method was based on sharp changes in Amplified Spontaneous Emission (ASE) of a Stilbene 420 (ST) laser dye triggered by the pH-dependent absorption of Bromocresol Green (BG). The ASE threshold of BG:ST solution mixtures exhibited a strong dependence on BG absorption, which was drastically changed by the variations of the pH of BG solution. As a result, ASE on-off or off-on was observed with different pH levels achieved by ammonia doping. By changing the concentration of the BG solution and the BG:ST blend ratio, this approach allowed to detect pH changes with a sensitivity down to 0.05 in the 10–11 pH range.