Localized UV Research Articles

Reconfigurable Droplet-Droplet Communication Mediated by Photochemical Marangoni Flows.

Droplets are attractive building blocks for dynamic matter that organizes into adaptive structures. Communication among collectively operating droplets opens untapped potential in settings that vary from sensing, optics, protocells, computing, or adaptive matter. Inspired by the transmission of signals among decentralized units in slime mold Physarum polycephalum, we introduce a combination of surfactants, self-assembly, and photochemistry to establish chemical signal transfer among droplets. To connect droplets that float at an air-water interface, surfactant triethylene glycol monododecylether (C12E3) is used for its ability to self-assemble into wires called myelins. We show how the trajectory of these myelins can be directed toward selected photoactive droplets upon UV exposure. To this end, we developed a strategy for photocontrolled Marangoni flow, which comprises (1) the liquid crystalline coating formed at the surface of an oleic acid/sodium oleate (OA/NaO) droplet when in contact with water, (2) a photoacid generator that protonates sodium oleate upon UV exposure and therefore disintegrates the coating, and (3) the surface tension gradient that is generated upon depletion of the surfactant from the air-water interface by the uncoated droplet. Therefore, localized UV exposure of selected OA/NaO droplets results in attraction of the myelins such that they establish reconfigurable connections that self-organize among the C12E3 and OA/NaO droplets. As an example of communication, we demonstrate how the myelins transfer fluorescent dyes, which are selectively delivered in the droplet interior upon photochemical regulation of the liquid crystalline coating.

Light‐Driven Folding Liquid Crystal Elastomer Catapult with Improved Morphing Velocity

As a typical behavior of releasing energy in a short time, catapulting is a way for organisms to adapt to complex and changeable environments, such as crossing terrain obstacles and spreading seeds. The essence of catapulting behavior is that plants and animals use their structural characteristics to control elastic strain energy locking, triggering, and releasing under external stimulation. At present, bistable or multistable structures are attractive for optimizing the system energy and improving the performance of liquid crystal elastomer (LCE) soft actuators. However, the overelaborate designation of such structures makes it a great challenge to achieve fast morphing LCE soft actuators. Here, a light‐driven azobenzene liquid crystal elastomer (azo‐LCE) soft actuator mimicking the catapulting behavior of fern sporangia is reported. 2D azo‐LCE monoliths are simply folded to construct V‐shaped structures as 3D catapults, which exhibit higher morphing velocity upon UV light, and the morphing velocity is related to the aspect ratio of films. Furthermore, asymmetric morphing behavior occurs by constructing localized UV irradiation conditions, which greatly improves the morphing velocity. It is envisioned that the origami‐inspired azo‐LCE catapults can be further designed as the throwing component in fast‐morphing soft robots for the remote delivery of microcargoes.

A Localized Kinematic Structure Detected in Atomic Carbon Emission Spatially Coincident with a Proposed Protoplanet in the HD 163296 Disk

Over the past 5 yr, studies of the kinematics in protoplanetary disks have led to the discovery of new protoplanet candidates and several structures linked to possible planet−disk interactions. We detect a localized kinematic bipolar structure in the HD 163296 disk present inside the deepest dust gap at 48 au from atomic carbon line emission. HD 163296's stellar jet and molecular winds have been described in detail in the literature; however, the kinematic anomaly in C i emission is not associated with either of them. Further, the velocity of the kinematic structure points indicates a component fast enough to differentiate it from the Keplerian profile of the disk, and its atomic nature hints at a localized UV source strong enough to dissociate CO and launch a C i outflow or a strong polar flow from the upper layers of the disk. By discarding the stellar jet and previously observed molecular winds, we explore different sources for this kinematic feature in C i emission that could be associated with a protoplanet inflow/outflow or disk winds.

Potent Inactivation of Human Respiratory Viruses Including SARS-CoV-2 by a Photoactivated Self-Cleaning Regenerative Antiviral Coating.

The COVID-19 pandemic marks an inflection point in the perception and treatment of human health. Substantial resources have been reallocated to address the direct medical effects of COVID-19 and to curtail the spread of the virus. Thereby, shortcomings of traditional disinfectants, especially their requirement for regular reapplication and the related complications (e.g., dedicated personnel and short-term activity), have become issues at the forefront of public health concerns. This issue became especially pressing when infection-mitigating supplies dwindled early in the progression of the pandemic. In consideration of the constant threat posed by emerging novel viruses, we report a platform technology for persistent surface disinfection to combat virus transmission through nanomaterial-mediated, localized UV radiation emission. In this work, two formulations of Y2SiO5-based visible-to-UV upconversion nanomaterials were developed using a facile sol–gel-based synthesis. Our formulations have shown substantial antiviral activities (4 × 104 to 0 TCID50 units in 30 min) toward an enveloped, circulating human coronavirus strain (OC43) under simple white light exposure as an analogue to natural light or common indoor lighting. Additionally, we have shown that our two formulations greatly reduce OC43 RNA recovery from surfaces. Antiviral activities were further demonstrated toward a panel of structurally diverse viruses including enveloped viruses, SARS-CoV-2, vaccinia virus, vesicular stomatitis virus, parainfluenza virus, and Zika virus, as well as nonenveloped viruses, rhinovirus, and calicivirus, as evidence of the technology’s broad antiviral activity. Remarkably, one formulation completely inactivated 105 infectious units of SARS-CoV-2 in only 45 min. The detailed technology has implications for the design of more potent, long-lived disinfectants and modified/surface-treated personal protective equipment targeting a wide range of viruses.

Thermal Instability–Induced Fundamental Magnetic Field Strands in the Solar Corona

Abstract Thermal instability is a fundamental process of astrophysical plasmas. It is expected to occur whenever the cooling is dominated by radiation and cannot be compensated for by heating. In this work, we conduct 2.5D radiation MHD simulations with the Bifrost code of an enhanced activity network in the solar atmosphere. Coronal loops are produced self-consistently, mainly through Joule heating, which is sufficiently stratified and symmetric to produce thermal nonequilibrium. During the cooling and driven by thermal instability, coronal rain is produced along the loops. Due to flux freezing, the catastrophic cooling process leading to a rain clump produces a local enhancement of the magnetic field, thereby generating a distinct magnetic strand within the loop up to a few Gauss stronger than the surrounding coronal field. These strands, which can be considered fundamental, are a few hundred kilometers in width, span most of the loop leg, and emit strongly in the UV and extreme UV (EUV), thereby establishing a link between the commonly seen rain strands in the visible spectrum with the observed EUV coronal strands at high resolution. The compression downstream leads to an increase in temperature that generates a plume-like structure, a strongly emitting spicule-like feature, and short-lived brightening in the UV during the rain impact, providing an explanation for similar phenomena seen with IRIS. Thermal instability and nonequilibrium can therefore be associated with localized and intermittent UV brightening in the transition region and chromosphere, as well as contribute to the characteristic filamentary morphology of the solar corona in the EUV.

Viral Inactivation Using Visible to UV Upconversion Nanomaterials and Application in Self-Cleaning Anti-Viral Nanofilms on Personal Protective Equipment (PPE) to Mitigate Coronavirus Spread

COVID-19 has become one of the deadliest pandemics in human history and has taken a tremendous toll on human life in large part due to its ability to transmit through the air and from surface to surface. We developed a novel conformal nano-coating on PPE surfaces intended to capture and kill (inactivate) COVID-19 viruses on PPE surfaces. Disinfection and Sterilization has long been done using UV radiation. Taking inspiration from this conventional method, we came up with a product that can produce UV radiation locally and regeneratively, a visible to UV Upconversion Nanomaterial (UCNP). The idea here is to expose viruses to localized UV radiation (within the mutagenic range) to kill or deactivate them. In our work, we developed a Yttrium Orthosilicate-based UCNP. These nanoparticles were coated on PPE surfaces and cationic and anionic polymers using the layer by layer (LBL) coating method. An oligosaccharide species, chosen to possess strong bond affinity/complementarity to novel coronavirus S glycoprotein, was grafted to the polymer using functional groups/sites via click chemistry to add one more mechanism of virus inactivation. In our testing, two formulations, Y2SiO5(1% Pr, 1% Gd) and Y2SiO5 (1.2% Pr, 1.2% Gd, 7.2% Li) have reduced active coronavirus viral load 4*104 to 0 in an hour of exposure to white light.

A data-driven statistical description for the hydrodynamics of active matter

Modeling living systems at the collective scale can be very challenging because the individual constituents can themselves be complex and the respective interactions between the constituents may not be fully understood. With the advent of high throughput experiments and in the age of big data, data-driven methods are on the rise to overcome these challenges. Although machine-learning approaches can help quantify correlations between the various players, they do not directly shed light on the underlying physical principles of such systems. Here, we present a data-driven method for obtaining the phase-space density of active matter systems such that the solution to the stochastic dynamic equation for active matter readily emerges, from which time and space dependence of physical order parameters can be readily extracted. If the system is near a steady state, we illuminate how to construct a field theory to subsequently make physical predictions about the system. The method is first developed analytically and subsequently calibrated using simulated data. The method is then applied to an experimental system of particles actively driven by a Serratia marcescens bacterial swarm and in the presence of localized UV light. The analysis demonstrates that the particles are in the steady-state before and sometime after the UV light and obey a Gaussian field theory with a spatially-varying ‘mass’ in those regimes. This novel yet simple finding is surprising given the complex dynamics of the bacterial swarm. In response to the UV light, we demonstrate that there is a net flow of the particles away from the UV light and that the entropy of the particles increases away from the light. We conclude with a discussion of additional potential applications of our data-driven method such as when the internal structure of the individual constituents dynamically changes to result in a modified stochastic dynamic equation governing the system.

Application of lanthanide-doped upconversion nanoparticles for cancer treatment: a review.

With the excellent ability to transform near-infrared light to localized visible or UV light, thereby achieving deep tissue penetration, lanthanide ion-doped upconversion nanoparticles (UCNP) have emerged as one of the most striking nanoscale materials for more effective and safer cancer treatment. Up to now, UCNPs combined with photosensitive components have been widely used in the delivery of chemotherapy drugs, photodynamic therapy and photothermal therapy. Applications in these directions are reviewed in this article. We also highlight microenvironmental tumor monitoring and precise targeted therapies. Thenwe briefly summarize some new trends and the existing challenges for UCNPs. We hope this review can provide new ideas for future cancer treatment based on UCNPs.

Extended UV detection bandwidth: h-BN/Al powder nanocomposites photodetectors sensitive in a middle UV region due to localized surface plasmon resonance effect

The development of high-effective photodetectors operating in a wide spectral range is an important technological task. In this work we have demonstrated that the detection bandwidth of h-BN photodetectors in the UV range can be extended due to the surface plasmon resonance (SPR) effect. Theoretical calculations showed that, among Al, Au, Ag, and Cu, Al is the most suitable metal for the h-BN UV sensible detectors due to the SPR effect in the middle UV range. Based on the theoretical predictions, a simple and highly efficient method for obtaining h-BN/Al nanocomposites for localized SPR-based UV detectors was developed. It was demonstrated that the h-BN/Al material is sensitive to UV radiation with a wavelength of 266 nm that is far away of the detection limit of 240 nm inherent for pure h-BN.

Tumor-targeted upconverting nanoplatform constructed by host-guest interaction for near-infrared-light-actuated synergistic photodynamic-/chemotherapy

The strategic combination of photodynamic therapy and chemotherapy has emerged as a promising treatment option for various tumor indications, which not only expands our understanding of each individual modality but also reveals new opportunities to achieve superadditive benefit via exploring their internal synergy rather than simple mixing. In this study, dual-emissive upconverting nanoparticle (UCNP) was employed to bridge the two treatment regimens to synergistically reinforce the therapeutic efficacy. The UCNP-based drug delivery nanoplatform was first co-loaded with 1,8-dihydroxy-3-methylanthraquinone (DHMA) photosensitizers and UV-activatable camptothecin prodrug (NBCCPT) and then complexed with biofunctional β-cyclodextrin species (β-CD-PEG-LA) via highly specific host-guest interactions to cap the camptothecin prodrug conjugated on the nanoparticle surface. The supramolecularly attached β-CD-PEG-LA could not only enhance the aqueous dispersity of the nanocarriers and prevent DHMA leakage, but also imbues targeting effect against asialoglycoprotein receptor-overexpressing tumor cells. The UCNP core would convert the NIR excitation (980 nm) into localized UV (360 nm) and visible (480 nm) emissions, of which the former would cleave the nitrobenzene linker to restore the cytotoxicity of CPT while the latter could excite the photosensitizer to generate reactive oxygen species (ROS). In addition to the photodynamic damage, the light-generated ROS could also facilitate the endo/lysosomal escape of the endocytosed nanoparticles and improve the overall antitumor potency in a synergistic manner.

Effect of localized UV irradiation on the crystallinity and electrical properties of dip-coated polythiophene thin films.

Ensuring high performance in polymer devices requires conjugated polymers with interchain π–π stacking interactions via van der Waals forces, which can induce structural changes in the polymer thin film. Here, we present a systematic study of using simple localized UV irradiation to overcome the low crystallinity and poor charge carrier transport in dip-coated poly(3-hexylthiophene) (P3HT) thin films, which are consequences of the limited selection of solvents compatible with the dip-coating process. UV irradiation for only a few minutes effectively promoted P3HT chain self-assembly and association in the solution state. Brief UV irradiation of a P3HT solution led to well-ordered molecular structures in the resultant P3HT films dip-coated using a low boiling point solvent with rapid solvent evaporation. In addition, the position at which UV light was irradiated on the dip-coating solutions was varied, and the effects of the irradiation position and time on the crystallinity and electrical properties of the resultant P3HT thin films were investigated.

Iridium size effects in localized surface plasmon-enhanced diamond UV photodetectors

Localized surface plasmon-enhanced diamond UV photodetectors with different Ir nanoisland arrays had been successfully fabricated. Three different Ir nanoisland arrays with the diameters of 20(D20), 30(D30) and 40(D40) nm were deposited on the diamond surface, respectively, and their height was 10 nm. Ti/Au metal electrodes were patterned on Ir nanoisland arrays area and bare diamond surface to form UV photodetectors. According to photoelectric performance test results, the responsivities of diamond photodetectors with Ir nanoislands were far greater than that of diamond photodetector, and the D40 showed the highest photocurrent and responsivity at 210 nm, and the D20 indicated the highest UV/vis rejection ratio. The results of simulated extinction spectra exhibited three resonance peaks at UV and visible region for each sample, indicating that D20 had the highest ratio of UV/vis, which was coincide with experiment results.

Effect of microstructural arrangement of MDI‐based polyurethanes on their photoproperties

ABSTRACTAmong the vast variety of polyurethane applications, several applications use the fluorescing nature of some of the polyurethanes. Even though 4,4′‐methylenebis(phenylisocyanate) (MDI)‐based polyurethanes fluoresce, their applications are rare because of the lack of knowledge about the fluorescence behavior of these polymers. In this study, the fluorophores responsible for the emission spectra of MDI‐based polyurethanes were identified, and their emission behavior was investigated. When excited, these polymers produce two prominent emission peaks located at 356 nm and 423 nm, which are assigned to the radiative relaxation of excited isolated hard segments and excited crystalline hard segment bundles of the MDI‐based polyurethanes, respectively. It was found that both chromophores can be excited by 293 nm UV radiation. The observed intensity variations of the two peaks with exposure time were attributed to the localized UV melting‐assisted migration of isolated hard segments. This migration facilitates the formation of crystalline hard segments. As the two chromophore populations are inversely propositional to each other, the relative intensity of the two emission peaks varies with UV exposure in a similar manner. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47431.

A pilot study on the disinfection efficacy of localized UV on the flushing-generated spread of pathogens

The process of toilet-flushing can generate flushing-associated water droplets which can potentially expose humans to pathogen-laden aerosols. Very little is known about such aerosol dissemination or the means for minimizing exposure to these aerosols. This study has evaluated the efficacy of ultraviolet waveband C (UV-C) for disinfection of flushing-generated pathogen-laden aerosols through tests with localized disinfection systems for airborne and surface contaminations. Three types of bacteria were chosen for investigation: Staphylococcus epidermidis, Escherichia coli, and Salmonella typhimurium. Tests were conducted with UV-C tubes of 5 W and 10 W. High levels of disinfection efficacies were observed, ranging from 76% to 97% for bacteria-laden aerosols at sources of emission, and efficiencies of 53% to 79% for surface samples in localized systems. The results from the localized systems were further compared with those obtained with an upper-room ultraviolet germicidal irradiation (UVGI) system. As it is important to note, the UV-C doses and ozone emissions for the localized systems were found well below the limits recommended in current guidelines. This research has shown that the disinfection of flushing-generated pathogen-laden aerosols in proximity to the source of emission was more effective than at the more distant sites where aerosols may be dispersed to the environment.

Surface Processing for Area Selective Mist Deposition of Nanocrystalline Quantum Dot Films

This study explores surface engineering for the purpose of selective deposition of cadmium selenide (CdSe) nanocrystalline quantum dot (NQD) thin films using the process of mist deposition. Surfaces of silicon and/or glass substrates were made uniformly hydrophobic by exposure to trichloro (1H,1H,2H,2H-perfluorooctyl) silane (FOTS) anhydrous hexane solution. Subsequent localized UV exposure increased surface energy making it locally hydrophilic, and thus, allowing area selective deposition of NQD film. Electric field involved in the mist deposition process was shown to reverse process selectivity through the electrowetting effect. The role of IR rapid optical surface treatment (ROST) in controlling surface energy of FOTS material was explored. Findings of this study will allow area selective deposition of the variety of NQD precursors in the form of colloidal solution.

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation

Single ZnO nanotetrapod-based sensors for monitoring localized UV irradiation were constructed with ohmic and Schottky contact characteristics. Localized UV irradiation at the third leg of the tetrapod was monitored by measuring the sensor's current response. Measurements of I-V performances and time-resolved current were conducted. The results demonstrate that localized UV irradiation can be detected in real time as electrical transport properties can be modulated by localized UV irradiation, and the higher the UV light power density gets, the larger the current response becomes, which is observed to be completely repeatable and reversible. Additionally, Schottky-contact type sensors clearly show a greater current response than ohmic-contact-type sensors, which further proved that Schottky-contact-type sensors are a better choice for detection in an irradiation environment. Two possible explanations are given for the phenomenon, including an electron transfer effect and a surface/interface effect on the band structure. The as-constructed sensors exhibit different sensitivities towards irradiation with various power densities, indicating that ZnO nanotetrapod-based sensors can be a promising candidate for detection in many areas including electron irradiation detection, ultraviolet irradiation monitoring, strain sensing, and complicated microenvironment observations such as biological cell inspection.

Spatiotemporal control of microRNA function using light-activated antagomirs

MicroRNAs (miRNAs) are small non-coding RNAs that act as post-transcriptional gene regulators and have been shown to regulate many biological processes including embryonal development, cell differentiation, apoptosis, and proliferation. Variations in the expression of certain miRNAs have been linked to a wide range of human diseases - especially cancer - and the diversity of miRNA targets suggests that they are involved in various cellular networks. Several tools have been developed to control the function of individual miRNAs and have been applied to study their biogenesis, biological role, and therapeutic potential; however, common methods lack a precise level of control that allows for the study of miRNA function with high spatial and temporal resolution. Light-activated miRNA antagomirs for mature miR-122 and miR-21 were developed through the site-specific installation of caging groups on the bases of selected nucleotides. Installation of caged nucleotides led to complete inhibition of the antagomir-miRNA hybridization and thus inactivation of antagomir function. The miRNA-inhibitory activity of the caged antagomirs was fully restored upon decaging through a brief UV irradiation. The synthesized antagomirs were applied to the photochemical regulation of miRNA function in mammalian cells. Moreover, spatial control over antagomir activity was obtained in mammalian cells through localized UV exposure. The presented approach enables the precise regulation of miRNA function and miRNA networks with unprecedented spatial and temporal resolution using UV irradiation and can be extended to any miRNA of interest.

Nucleotide Excision Repair Proteins Rapidly Accumulate but Fail to Persist in Human XP‐E (DDB2 Mutant) Cells

The xeroderma pigmentosum (XP-E) DNA damage binding protein (DDB2) is involved in early recognition of global genome DNA damage during DNA nucleotide excision repair (NER). We found that skin fibroblasts from four newly reported XP-E patients with numerous skin cancers and DDB2 mutations had slow repair of 6-4 photoproducts (6-4PP) and markedly reduced repair of cyclobutane pyrimidine dimers (CPD). NER proteins (XPC, XPB, XPG, XPA and XPF) colocalized to CPD and 6-4PP positive regions immediately (<0.1 h) after localized UV irradiation in cells from the XP-E patients and normal controls. While these proteins persist in normal cells, surprisingly, within 0.5 h these repair proteins were no longer detectable at the sites of DNA damage in XP-E cells. Our results indicate that DDB2 is not required for the rapid recruitment of NER proteins to sites of UV photoproducts or for partial repair of 6-4PP but is essential for normal persistence of these proteins for CPD photoproduct removal.

Photons bring light into DNA repair: The comet assay and laser microbeams for studying photogenotoxicity of drugs and ageing

This contribution reviews recent applications of micromanipulation, by UV photons, in DNA repair and ageing research as well as in the evaluation of the phototoxicity of drugs. In some cases, micromanipulation is combined with the comet assay, a technique, which allows a direct view on DNA damages. It is shown that, in humans, the sensitivity of DNA to UV induced damage and its subsequent repair is surprisingly stable up to high age and that drugs which are usually non-toxic induce DNA damage when irradiated in parallel by UV irradiation. Using the immune fluorescent comet assay, IFCA, a variant of the comet assay, direct comparison of the effects of ionizing (137) Cs radiation with those of localized UV radiation is possible. When a laser microbeam is used to damage DNA in a cell nucleus with high temporal and spatial resolution, it can be observed directly how repair molecules accumulate (are recruited) at the site of damage. Comparison of the recruitment speed allows establishing an order of DNA repair events.

UV-induced histone H2AX phosphorylation and DNA damage related proteins accumulate and persist in nucleotide excision repair-deficient XP-B cells

DNA double strand breaks (DSB) may be caused by ionizing radiation. In contrast, UV exposure forms dipyrimidine photoproducts and is not considered an inducer of DSB. We found that uniform or localized UV treatment induced phosphorylation of the DNA damage related (DDR) proteins H2AX, ATM and NBS1 and co-localization of γ-H2AX with the DDR proteins p-ATM, p-NBS1, Rad51 and FANCD2 that persisted for about 6 h in normal human fibroblasts. This post-UV phosphorylation was observed in the absence of nucleotide excision repair (NER), since NER deficient XP-B cells (lacking functional XPB DNA repair helicase) and global genome repair-deficient rodent cells also showed phosphorylation and localization of these DDR proteins. Resolution of the DDR proteins was dependent on NER, since they persisted for 24 h in the XP-B cells. In the normal and XP-B cells p53 and p21 was detected at 6 h and 24 h but Mdm2 was not induced in the XP-B cells. Post-UV induction of Wip1 phosphatase was detected in the normal cells but not in the XP-B cells. DNA DSB were detected with a neutral comet assay at 6 h and 24 h post-UV in the normal and XP-B cells. These results indicate that UV damage can activate the DDR pathway in the absence of NER. However, a later step in DNA damage processing involving induction of Wip1 and resolution of DDR proteins was not observed in the absence of NER.