Alternative UV Research Articles

A novel photochromic material based on halophosphate: Remote light-controlled reversible luminescence modulation and fluorescence lifetime regulation

Luminescent material Ca2Ba3(PO4)3F:Eu2+ displays green emitting in the range of 400–700 nm, which is ascribed to the 4f65d1 →4f7 transition of Eu2+ ions. Amazingly, the body color of the samples can be changed between colorless and green upon alternative UV and visible light irradiation/heating treatment with robust fatigue resistance due to photochromism. The photochromic effect strongly depends on the Eu2+ doping concentration. After remote-controlled short-UV irradiation, the overall Eu2+ emission intensity presents a significant decrease, and inversely, exhibits an increase to the initial level after illuminated by longer wavelength light or heat treatment. Moreover, the fluorescence lifetime also can be regulated reversibly, of which the regulation degree depends on the short-UV irradiation and longer wavelength illumination time/heating temperature. A schematic diagram based on energy levels is proposed to illustrate the photochromism mechanism.

Photo- and pH- Dual-Responsive β-Cyclodextrin-Based Supramolecular Prodrug Complex Self-Assemblies for Programmed Drug Delivery.

Despite the fact that progress has been made in the application of supramolecular prodrug self-assemblies to enhance the functionality of drug-delivery systems, corresponding research on multi-responsive supramolecular prodrug self-assemblies for programmed drug delivery is still limited. In this paper, the synthesis and self-assembly behavior of supramolecular prodrug complexes (SPCs) with β-cyclodextrin-acylhydrazone-doxorubicin (β-CD-hydrazone-DOX) and the targeting of azobenzene-terminated poly[2-(dimethylamino)ethyl methacrylate] (Azo-PDMA-FA) as a building block were investigated. The obtained SPCs could also form self-assemblies on the basis of their amphiphilic nature. Next, SPC-based multi-compartment vesicles and complex micelles, which were confirmed by transmission electron microscopy and dynamic/static light scattering, were obtained with good reversibility under alternative visible light or UV irradiation. Furthermore, three-stage programmed drug-delivery behavior was observed from dual-responsive SPC-based self-assemblies by utilizing UV and pH stimuli. Specifically, the SPCs first self-assembled into multicompartmental vesicles, which was accompanied by a slow release of DOX. Next, UV-light irradiation induced the dissociation of β-CD/Azo, which led to morphology transition and a slight increase in the rate of release of DOX. Upon transferring the self-assemblies to phosphate-buffer solution (pH 5.0), the release rates increased notably as a result of the broken acylhydrazone bond. Finally, basic cell experiments further demonstrated that the SPC-based self-assemblies could be internalized into cancer cells, which suggests their promise for applications in cancer therapy.

Investigation of reversible photoluminescence switching driven by colorless-purple photochromism in Sr5(PO4)3F:Eu2+ for optical storage applications

We report a novel photoresponsive powder material, haloapatite Sr5(PO4)3F:Eu2+, which exhibits good photochromic properties and undergoes reversible colorless-purple color changes after alternative UV and visible irradiation/heating. The effect of Eu2+ doping concentration on the photochromic behavior is investigated, and the optimum doping concentration of Eu2+ is found to be approximately 0.5 mol%. Further recycling coloring-bleaching measurements at room and high temperature confirm the high fatigue resistance of the material and the good thermal stability of its photochromic performance. Based on these findings, the photoluminescence performance of the present material can be effectively modulated through its photochromism. A luminescence switching efficiency of up to ∼40% is obtained for x = 0.005. The present results allow discussing the critical role of the charge carrier dynamics in the photochromism. Finally, we propose a tentative model illustrating the photochromism and luminescence modulation mechanisms.

Facile preparation and dual responsive behaviors of starch-based hydrogel containing azo and carboxylic groups

Starch-based hydrogel containing azo group (SHA) was prepared through radical cross-linking reaction among starch- and PVA-based macromonomers, acrylic acid (AA) and 4-acryloyoxyazobenzene (AHAB). AHAB was prepared through an acylation reaction between acryloyl chloride and 4-hydroxyazobenzene (p-HAB), which was obtained by the diazo coupling reaction between aniline and phenol. The structure of SHA was confirmed with Fourier transform infrared spectrometer, thermogravimetric analysis and UV–Visible spectroscopy. SHA displayed pH-sensitive swelling in buffer saline. SHA film also exhibited a reversible trans-cis-trans photoisomerization behavior when they were subjected to alternative UV and visible light irradiation or dark storage. The dual-responsive characteristic was easily to be tailored via varying the initial amount of AHAB or AA.

Ultraviolet Sensor Performance of Nanostructured LaCoO3 Prepared by the Solution-Polymerization Method

LaCoO3 is a p-type semiconductor material with bandgap of ~2.2 eV, which compared with those reported for TiO2 and ZnO (3.2 and 3.3 eV, respectively) make this material a potential candidate for detecting UV radiation. In this work nanostructured LaCoO3 was prepared by the solution-polymerization method, using polyvinyl alcohol as polymerizing agent. The morphology of the powder calcined at 700°C corresponds to nanostructured sheets having abundant porosity. Thick films were prepared by a simple deposition method using a suspension of the powder. The detection of UV (λ = 365 nm) showed a uniform response pattern. When the optical irradiance was varied the results revealed a quantitative detection. Analogous results were obtained using light of larger λ. In conclusion, LaCoO3 may be used as an alternative UV detector material to prevent skin cancer and as photoresistive material for solar photocells, among others.

Dual-responsive cellulose fabric based on reversible acidichromic and photoisomeric polymeric dye containing pendant azobenzene

An acid and UV dual-responsive cellulose fabric was developed via coating with a polymeric dye based on waterborne polyurethane and azobenzene chromophore to provide additional smart characteristics for textiles. The incorporation of azobenzene chromophore into polyurethane chain through chemical bonding enhanced the thermal stability. The maximum absorption peak of the polymeric dye and its coated fabric shifted from 410 nm to 520 nm upon pH decreasing from 6 to 1, accompanying with pronounced color change from yellow to amaranth due to structural transition from diazo to hydrazone form. The acidichromic property of the polymeric dye also presents an outstanding repetition stability. The trans-isomers in the polymeric dye transformed into cis-isomers rapidly (1 s) in response to UV irradiation, while its recovery was much slower (6 h) in dark due to the large molecular and volume of polyurethane chains. Upon trans-cis isomerism, the coated fabric presented slight color change between yellow and orange after alternative UV irradiation and dark. The stimuli-responsive cellulose fabric with reversible acidichromic and photoisomeric properties can be a promising candidate for developing a wearable and flexible sensor to monitor environmental changes.

The Usage of Crumb Rubber Filtration and UV Radiation for Ballast Water Treatment

This research is aimed to build ship’s ballast water treatment prototipe that used to inactivate microbial water patogen in ballast water to produce unpolluted ballast water that can be standardised by IMO Ballast Water Management Convention. A simple concept that used in the development of this prototype is by draining ballast water with capacity at 5 lpm, 10 lpm and 20 lpm into alternative filtration crumb rubber and UV reactor. In the filtration process using crumb rubber, ballast water will be filtered with the precision filtration up to 50 micron, while in the UV reactor ballast water will be illuminated by UV-C with maksimum dose 16,58 mW/cm2. Finally,the study shows the performance of alternative filtration of crumb rubber and UV-C irradiation on microbial water phatogen, and at what UV-C dose ballast water treatment prototipe can inactivate microbial water phatogens, which are complying with IMO Ballast Water Management Convention ANNEX D. This research is aimed to build ship’s ballast water treatment prototipe that used to inactivate microbial water patogen in ballast water to produce unpolluted ballast water that can be standardised by IMO Ballast Water Management Convention. A simple concept that used in the development of this prototype is by draining ballast water with capacity at 5 lpm, 10 lpm and 20 lpm into alternative filtration crumb rubber and UV reactor. In the filtration process using crumb rubber, ballast water will be filtered with the precision filtration up to 50 micron, while in the UV reactor ballast water will be illuminated by UV-C with maksimum dose 16,58 mW/cm2. Finally,the study shows the performance of alternative filtration of crumb rubber and UV-C irradiation on microbial water phatogen, and at what UV-C dose ballast water treatment prototipe can inactivate microbial water phatogens, which are complying with IMO Ballast Water Management Convention ANNEX D. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Times New Roman; mso-bidi-theme-font:minor-bidi; mso-ansi-language:IN;}

(Invited) Photo-Assisted ALD: Process Development and Application Perspectives

Photons can be utilized to create new ALD chemistry or enhance existing ALD processes. Photo-enhancement provides many potential advantages such as lower deposition temperature, novel growth chemistries, selective area deposition, and improvement of film properties. Despite these attractive advantages, there are not many reports available on the topic, materials deposited being mostly oxides, e.g. ZnO, Al2O3 and Ta2O5.[1-3] The main challenges are the reactor design and the complexity of photochemistry in the heterogeneous system. The reactor must ensure intensive light of appropriate wavelength on the substrate while avoiding film growth on the optical components. On the other hand, optical properties of the adsorbed precursor, the substrate, and the film can all contribute to the deposition photochemistry. We have been studying and developing photo-assisted ALD processes for oxide and metal thin films. A customized Picosun™ R-200 ALD reactor with two alternative UV sources has been employed. A single-source approach with metal alkoxides has proved itself an effective method for depositing Ti, Zr, Hf, Nb, and Ta oxides.[4] Area-selectivity of the photo-assisted Ta2O5 ALD was demonstrated by depositing a University of Helsinki emblem with two aluminum shadow masks (Fig.1). Resolution does not allow device level patterning but can be exploited to protect contact areas, for example. The photo-assisted ALD of metals is fundamentally different from the case of oxides in that the deposited material is optically absorbing and electrically conductive. Furthermore, the metal typically needs to be reduced during the ALD cycle. In this presentation, results on process development and the material properties of photo-assisted ALD of metal oxides, and Ru and Cu will be discussed, together with potential applications in sight. Focused ion beam patterning, wet etching and pre-patterned substrates can be used to demonstrate the capabilities of photo-ALD films. The Semiconductor Research Corporation (SRC) and Finnish Centre of Excellence in Atomic Layer Deposition (ALDCoE) are acknowledged for funding. Picosun provided the customized reactor for the project.

Protection of high‐density polyethylene–silicon composites from ultraviolet–visible photodegradation

ABSTRACTThe extent of the ultraviolet–visible (UV–vis) photoirradiation effect on high‐density polyethylene (HDPE) and HDPE–silicon (Si) composites is reported in terms of the addition of Si microparticles at contents of 0.1, 1, and 5 wt %. A standard accelerated UV–vis exposure was applied over 2750 h, corresponding to 22 months in Florida. Thermogravimetry, differential scanning calorimetry, and Fourier transform infrared spectroscopy were used as reliable techniques for monitoring the quality of the HDPE–Si composites. The increasing addition of Si microparticles delayed the photodegradation of the HDPE–Si composites. Because of their strong light‐scattering effects, Si microparticles blocked the degradation of tertiary carbons of the HDPE backbone and reduced the apparition of vinyl groups; this prevented the structural impoverishment of HDPE–Si composites. Consequently, variations in the crystallization temperature (Tc) and melting temperature (Tm), which were indicators of photodegradation, were not modified. In general, the HDPE–Si composite formulation with 5 wt % Si microparticles was useful for protecting the material from photodegradation and, thus, should be an environmentally friendly, reliable alternative UV–vis blocker. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45439.

Application of luminescence downshifting materials for enhanced stability of CH3NH3PbI3(1-x)Cl3x perovskite photovoltaic devices

The application of luminescent down shifting (LDS) layers as alternative UV filters for CH3NH3PbI3(1-x)Cl3x perovskite solar cell (PSC) devices is reported. A combination of photo-absorption measurements and of device decay measurements during light soaking are used to verify the stability. The application of a UV filter or LDS layer was able to significantly retard photo-induced degradation with ∼18% drop in device power conversion efficiency (PCE) observed over 30 h for non-encapsulated devices, which is compared to ∼97% for an un-filtered device, also without encapsulation. Whilst the PCE of the PSC device decreases with the application of the LDS layer, the drop is not as significant as when a commercial UV filter is used. Considering that UV filters will be essential for the commercialization of PSCs, the work provides evidence that the LDS layer can act as an alternative UV filter in PSCs and can limit the drop in PCE that can be expected from the inclusion of a UV filter, thus providing an added benefit over commercial UV filters.

Near-Infrared Promoted Wettability Recovery of Superhydrophilic ZnO

Superhydrophilic and superhydrophobic surfaces exhibit numerous industrial applications such as self-cleaning, antifogging, anti-icing, electrowetting, and photocatalysis. A surface with reversible wetting behaviors that can be controlled by external field is both scientifically and technologically of importance. Light is a major external trigger for many natural processes. We report here an intelligent remote technology based on alternative UV and near-infrared (NIR) irradiation that enables dynamical wettability tuning of ZnO wafers. Notably, NIR irradiation with a moderate power density of 500 ± 5 mW/cm2 can rapidly recover patterned ZnO from the UV-induced superhydrophilic state (<5°) to the original state (125 ± 3°) in just 2 h. We discover that the chemical environments of O 1s and Zn 2p electrons exhibit a back-and-forth shift upon UV and NIR irradiation, respectively. The NIR-promoted wettability recovery is attributed to selective actuation of vibrational overtone transitions of hydroxyl (OH) band and background absorption of water in the NIR region. Our results highlight that oxygen and water in air are two crucial factors in determining the wettability recovery process, which could be selectively activated or deactivated by remote optical sources. We expect that this discovery could help us to understand many natural processes and shed light on the design of novel devices.

Microwave-assisted synthesis and photochromic properties of new azo-imidazoles

A convenient, one-pot three-component synthesis of new photochromic azo-imidazoles (1a-1h) from the corresponding azo dyes (2a-2h), benzil and ammonium acetate under microwave irradiation were described and their photochromic properties were investigated. The structures of the new azo-imidazoles were confirmed by UV–Vis, FT-IR and NMR spectroscopies and elemental analysis. The properties and photochromic structural behavior relationship (PSBR) of these compounds have been analyzed. All the compounds exhibit good photochromic behavior upon irradiation with alternative UV and visible light.

Synthesis and properties of tetraphenylethylene derivatived diarylethene with photochromism and aggregation-induced emission

A series of new diarylethene compounds with both photochromism and aggregation-induced emission have been synthesized by connecting tetraphenylethene and triphenylethene to the bisthienylethene. All the four compounds exhibit good photochromism upon irradiation with alternative UV and visible light. And they are all provided with aggregation-induced emission properties in tetrahydrofuran solution with different fraction of water, non-emissive in the pure tetrahydrofuran solution but yellowish green fluorescence in the aggregate or solid state. Furthermore, the compounds connecting tetraphenylethene to the bisthienylethene were found to exhibit the stronger fluorescence emission in the aggregate or solid state than the ones connecting triphenylethene to the bisthienylethene.

Photo-responsive supramolecular polymer based on a CB[5] analogue

A supramolecular polymer was constructed in aqueous solution via the intermolecular recognition between a cucurbit[5]uril-like macrocycle (Me10TD[5]) and trans-4,4′-bis(aminomethyl)azobenzene dihydrochloride, whose binding behaviors were confirmed by proton nuclear magnetic resonance (1H NMR), isothermal titration calorimetry (ITC) and electrospray ionization mass spectrometry (ESI-MS) experiments. The resulting polymer exhibited bending/extending behaviors under alternative UV light irradiations due to the trans/cis isomerization of the azobenzene group. The photo-responsive performance of the polymer was investigated by UV–Vis, transmission electron microscopy (TEM), and dynamic light scattering (DLS) measurements.

Vector Dark Matter through a radiative Higgs Portal

We study a model of spin-1 dark matter which interacts with the Standard Model predominantly via exchange of Higgs bosons. We propose an alternative UV completion to the usual Vector Dark Matter Higgs Portal, in which vector-like fermions charged under SU(2)$_W \times$ U(1)$_Y$ and under the dark gauge group, U(1)$^\prime$, generate an effective interaction between the Higgs and the dark matter at one loop. We explore the resulting phenomenology and show that this dark matter candidate is a viable thermal relic and satisfies Higgs invisible width constraints as well as direct detection bounds.

Enabling Light Work in Helical Self-Assembly for Dynamic Amplification of Chirality with Photoreversibility.

Light-driven transcription and replication are always subordinate to a delicate chirality transfer. Enabling light work in construction of the helical self-assembly with reversible chiral transformation becomes attractive. Herein we demonstrate that a helical hydrogen-bonded self-assembly is reversibly photoswitched between photochromic open and closed forms upon irradiation with alternative UV and visible light, in which molecular chirality is amplified with the formation of helixes at supramolecular level. The characteristics in these superhelixes such as left-handed or right-handed twist and helical length, height, and pitch are revealed by SEM and AFM. The helical photoswitchable nanostructure provides an easily accessible route to an unprecedented photoreversible modulation in morphology, fluorescence, and helicity, with precise assembly/disassembly architectures similar to biological systems such as protein and DNA.

Ordered DNA-Surfactant Hybrid Nanospheres Triggered by Magnetic Cationic Surfactants for Photon- and Magneto-Manipulated Drug Delivery and Release.

Here we construct for the first time ordered surfactant-DNA hybrid nanospheres of double-strand (ds) DNA and cationic surfactants with magnetic counterion, [FeCl3Br](-). The specificity of the magnetic cationic surfactants that can compact DNA at high concentrations makes it possible for building ordered nanospheres through aggregation, fusion, and coagulation. Cationic surfactants with conventional Br(-) cannot produce spheres under the same condition because they lose the DNA compaction ability. When a light-responsive magnetic cationic surfactant is used to produce nanospheres, a dual-controllable drug-delivery platform can be built simply by the applications of external magnetic force and alternative UV and visible light. These nanospheres obtain high drug absorption efficiency, slow release property, and good biocompatibility. There is potential for effective magnetic-field-based targeted drug delivery, followed by photocontrollable drug release. We deduce that our results might be of great interest for making new functional nucleic-acid-based nanomachines and be envisioned to find applications in nanotechnology and biochemistry.

Photo-responsive chiral cyclic molecular switches based on stiff stilbene

Two novel photo-responsive chiral cyclic molecular switches constituted of stiff stilbene and binaphthyl moieties connected through alkyl chains of different length were fabricated. The cyclization synthetic strategy employed herein made it convenient to obtain the pure Z isomers rather than Z/E isomer mixtures. The detailed photo-switching behaviors of target compounds were studied by the UV–Vis absorption and circular dichroism spectra in dichloromethane. The twist angles of the binaphthyl of the switches were able to be reversibly modulated by Z/E isomerization of stiff stilbene unit under alternative UV light stimuli and influenced by the length of alkyl chain to some extent.

Comparative study for measurement of environmental natural radioactivity in the crude phosphoric acid using nuclear and non-nuclear techniques

The present work was attempts to develop rapid and accurate alternative analytical method for measuring naturally occurring radioactivity in the crude phosphoric acid (CPA). The measurements were achieved using nuclear method based on the non-destructive γ-ray measurements; and non-nuclear methods, including the ICP-OES and UV–vis colorimetric method. The results showed that, radionuclides of Th-234, Pa-234m (daughters of U-238) and U-235 were identified and quantified. The activity ratio of Th-234:U-235 was 21.0±0.86. This value is significant because it is close and agrees with the reference naturally occurring activity ratio of 21.7 between U-238 and U-235. Total U in four different brands of the CPA (I–IV) was quantified using γ-emissions of its progeny (Th-234) for the aged samples only, or its natural isotope (U-235) for both fresh and aged samples. It was found that, the total U concentration in different four brands CPA (I–IV) of CPA using γ-emissions of Th-234 was 100.2, 68.7, 67.9 and 87.6ppm for the brands I, II, III and IV, respectively with small coefficient of variance (CV,%) does not exceed 4%. For the same brands (I–IV) using γ-emissions of U-235 isotope, the total U concentration was 98.3, 75.5, 70.2 and 89.6ppm, respectively with CV(%) below 5.3%. By ICP-OES method, U determination is negatively interfered with the phosphorous in all brands of CPA(I-IV). Alternative UV–vis spectrophotometry analytical method has been developed to detect the total U concentration using 10% oxalic acid as an efficient masking agent for Fe. By UV–vis method, the total U concentration in CPA brands was 102.3, 58, 56 and 73ppm for I, II, III and IV brands, respectively with CV (%) less than 3.3%. Finally, it is concluded that the nondestructive γ-ray spectrometry may be the best choice for uranium measurement, especially in crude phosphoric acid (CPA) with relatively high P and Fe concentration.

Printable luminescent down shifter for enhancing efficiency and stability of organic photovoltaics

The proof of concept of using luminescent down shifting (LDS) layers as alternative UV filters for P3HT:PCBM OPVs is demonstrated using a lanthanide-based metal complex. The results are verified using a combination of indoor light soaking, with single cell devices, and outdoor performance monitoring, using a 16-cell monolithically connected OPV module. By applying the LDS layer, a ~5% relative enhancement in photocurrent is observed for both sets of devices. More significantly, indoor light soaking tests on single cell devices without encapsulation showed an 850% enhancement in the measured half-life (T50%). The OPV modules were encapsulated and tested for outdoor stability over a 70 day period in the Negev desert, Israel. The modules made with the LDS filter are shown to match the stability of those made with a commercial UV filter and outperform the modules with no filter applied, with a 51% enhancement in the measured stability (T75%). Significantly, the work provides clear experimental evidence that the LDS layer can act as a UV filter in OPVs without compromising the efficiency of the solar cell, thus providing an added benefit over commercial UV filters.