near-UV Emission Research Articles

Ultraviolet Photometry and Habitable Zones of over 2700 Planet-hosting Stars

The ongoing discovery of exoplanets has sparked significant interest in finding suitable worlds that could potentially support life. Stellar ultraviolet (UV; 100–3000 Å) radiation may play a crucial role in determining the habitability of their planets. In this paper, we conducted a detailed analysis of the UV photometry of over 2700 host stars with confirmed planets, using observational data from the Galaxy Evolution Explorer and Swift Ultraviolet/Optical Telescope missions. We performed aperture photometry on single-exposure images and provided photometric catalogs that can be used to explore a wide range of scientific questions, such as stellar UV activity and planet habitability. By calculating the circumstellar habitable zone and UV habitable zone, we found that fewer than 100 exoplanets fall within both of these zones, with the majority being gas giants. We also examined stellar activity based on their far-UV (FUV) and near-UV (NUV) emissions. We found the FUV−NUV color more effectively represents stellar activity compared to the RFUV′ and RNUV′ indices. The Sun’s low FUV emission and moderate NUV emission highlight its uniqueness among (solar-like) stars.

Optical Centers in Cr-, Mn-, and O-Doped AlN and Their Thermodynamic Stability Designed by a Multiscale Computational Approach.

The optical centers in AlN can frequently exist in various charge states and can be accompanied by many coexisting defect species, creating a complex environment where mutual interactions are inevitable. Therefore, it is an immediate quest to design AlN crystal growth protocols that can target a specific optical center of interest and tune its concentration while preventing the formation of other unwanted point defects. Here, we provide a powerful workflow for point defect engineering in wide band gap, binary semiconductors that can be readily used to design optimal crystal growth protocols through combining CALPHAD-based phase analysis, and ab initio defect calculations. We investigate technologically relevant chromium- and manganese-induced optical centers in AlN, followed by studying the impact of oxygen that can be unintentionally incorporated during crystal growth. We present the dominant defects in all three cases as a function of process parameters along with the optical signatures. In the case of both Cr and Mn doping, the CrAl and MnAl defects are most likely, and increasing nitrogen partial pressure tends to enhance their concentration. We show that it is possible to use nitrogen fugacity as a tool for tuning the intensity of optical signatures. We calculate the CrAl charge transition levels with respect to the valence-band maximum at 2.60 eV (E+/-), 3.83 eV (E0/-), and 5.41 eV (E-/2-) and electron and hole capture transitions with luminescence bands centered at 2.82, 1.91, and 3.15 eV. Unlike the Cr doping, Mn aggregation is unlikely, and the MnAl-VN is the most abundant defect after MnAl under most synthesis conditions. Oxygen tends to form complexes with VAl, and ON-VAl is a prominent defect following ON, with near-UV emission bands at 3.17, 3.26, and 3.81 eV. Our results agree with the available experimental optical signatures of Cr-, Mn-, and O-related centers and provide pathways on how to tune the luminous intensity of these centers through changes in growth conditions.

Predicting Photospheric Ultraviolet Emission from Stellar Evolutionary Models

Stellar ultraviolet (UV) emission serves as a crucial indicator for estimating magnetic activity and evaluating the habitability of exoplanets orbiting stars. In this paper, we present a straightforward method to derive stellar photospheric UV emission for F to M main-sequence stars. By using PARSEC models, we establish relations between near-UV (NUV) and far-UV (FUV) magnitudes from the Galaxy Evolution Explorer, NUV magnitudes from the China Space Station Telescope, and stellar effective temperatures and Gaia blue photometer–red photometer colors for different metallicities. Together with the observed sample, we find that for NUV emission, the photospheric contribution to the observed flux is less than 20% for M stars, around 10%–70% for K stars, and in a range from 30% to 85% for G and F stars. For FUV emission, the photospheric contribution is less than 10−6 for M stars, below 10−4 for K stars, around 10−4–10% for G stars, and between 6% and 50% for F stars. Our work enables the simple and effective determination of stellar excess UV emission and the exploration of magnetic activity.

Registration of the auroral near-UV emission by the orbital detector TUS

The TUS detector is a highly sensitive orbital telescope. Due to the polar orbit of the spacecraft, the detector made observations of the UV luminosity of the atmosphere above the aurora oval. Events with intensity variations characteristic of pulsating auroras have been registered. The events are located along the equatorial boundary of the auroral oval and occur during long-term geomagnetic disturbances. Comparison with data from charged particle detectors shows the presence of an increased flux of precipitating high-energy electrons (with energies above 100 keV) simultaneously with UV pulsations.

Elucidating the Role of Electron Transfer in the Photoluminescence of MoS2 Quantum Dots Synthesized by fs-Pulse Ablation.

Herein, MoS2 quantum dots (QDs) with controlled optical, structural, and electronic properties are synthesized using the femtosecond pulsed laser ablation in liquid (fs-PLAL) technique by varying the pulse width, ablation power, and ablation time to harness the potential for next-generation optoelectronics and quantum technology. Furthermore, this work elucidates key aspects of the mechanisms underlying the near-UV and blue emissions the accompanying large Stokes shift, and the consequent change in sample color with laser exposure parameters pertaining to MoS2 QDs. Through spectroscopic analysis, including UV-visible absorption, photoluminescence, and Raman spectroscopy, we successfully unraveled the mechanisms for the change in optoelectronic properties of MoS2 QDs with laser parameters. We realize that the occurrence of a secondary phase, specifically MoO3-x, is responsible for the significant Stokes shift and blue emission observed in this QD system. The primary factor influencing these activities is the electron transfer observed between these two phases, as validated by excitation-dependent photoluminescence and XPS and Raman spectroscopies.

Evidence of extended [CII] and dust emission in local dwarf galaxies

Aims. The evolution of dwarf galaxies is dramatically affected by gaseous and dusty outflows, which can easily deprive their interstellar medium of the material needed for the formation of new stars, simultaneously enriching their surrounding circumgalactic medium (CGM). In this Letter, we present the first evidence of extended [CII] 158 μm line and dust continuum emission in local dwarf galaxies hosting star-formation-driven outflows. Methods. By stacking the [CII], far-infrared, and near-UV (NUV) emission obtained from Herschel and GALEX data, we derived the average radial profiles, and compared the spatial extension of gas, dust, and stellar activity in dwarf galaxies. Results. We find that [CII] and dust emissions are comparable to each other, and more extended than the NUV continuum. The [CII] size is in agreement with that measured for z > 4 star-forming galaxies, suggesting that similar mechanisms could be at the origin of the observed atomic carbon reservoir around local and high-z sources. The cold dust follows the [CII] emission, going beyond the stellar continuum as opposed to what is typically observed in the early Universe where measurements can be affected by the poor sensitivity and faintness of dust emission in the CGM of high-z galaxies. Conclusions. We attribute the extended [CII] and dust continuum emission to the presence of galactic outflows. As local dwarf galaxies are considered analogs of primordial sources, we expect that comparable feedback processes can be at the origin of the observed [CII] halos at z > 4, dominating over other possible formation mechanisms.

The Growth Mechanism, Luminescence, and Lasing of Polyhedral ZnO Microcrystals with Whispering-Gallery Modes

This work studies the features of the formation of isometric polyhedral ZnO microcrystals that provide stimulated emission and whispering-gallery-mode (WGM) lasing in the near-UV range. For this purpose, the growth stages of such crystals in the process of gas-transport synthesis and the luminescent properties of the structures obtained at each stage were investigated. It was shown that the growth of laser microcrystals begins with the formation of microspheroids with thin ZnO shells. Such spheroids exhibit mainly white luminescence with a small contribution of near-UV emission. Increasing the synthesis duration results in thickening and faceting of the spheroid shells, as well as a decrease in the contribution of the yellow–red component to the luminescence spectrum. At the same time, ZnO microcrystallites nucleate and grow inside the spheroids, using as a material the remains of a liquid zinc drop and oxygen entering the spheroids through their shells. Such growth conditions allow them to take on an equilibrium polyhedral shape. Eventually, upon destruction of the spheroid shell, a polyhedral ZnO microcrystal supporting WGMs is observed.

First Results from the JWST Early Release Science Program Q3D: The Warm Ionized Gas Outflow in z ∼ 1.6 Quasar XID 2028 and Its Impact on the Host Galaxy

Quasar feedback may regulate the growth of supermassive black holes, quench coeval star formation, and impact galaxy morphology and the circumgalactic medium. However, direct evidence for quasar feedback in action at the epoch of peak black hole accretion at z ≈ 2 remains elusive. A good case in point is the z = 1.6 quasar WISEA J100211.29+013706.7 (XID 2028), where past analyses of the same ground-based data have come to different conclusions. Here, we revisit this object with the integral-field unit of the Near Infrared Spectrograph on board the JWST as part of Early Release Science program Q3D. The excellent angular resolution and sensitivity of the JWST data reveal new morphological and kinematic substructures in the outflowing gas plume. An analysis of the emission-line ratios indicates that photoionization by the central quasar dominates the ionization state of the gas with no obvious sign for a major contribution from hot young stars anywhere in the host galaxy. The rest-frame near-UV emission aligned along the wide-angle cone of outflowing gas is interpreted as a scattering cone. The outflow has cleared a channel in the dusty host galaxy, through which some of the quasar ionizing radiation is able to escape and heat the surrounding interstellar and circumgalactic media. Although the warm ionized outflow is not powerful enough to impact the host galaxy via mechanical feedback, radiative feedback by the active galactic nucleus, aided by the outflow, may help to explain the unusually small molecular gas mass fraction in the galaxy host.

Judicious Heteroatom Doping Produces High Performance Deep Blue/Near UV Multiresonant Thermally Activated Delayed Fluorescence OLEDs.

We present two multi-resonant thermally activated delayed fluorescence (MR-TADF) emitters and show how further borylation of a deep blue MR-TADF emitter, DIDOBNA-N, both blue shifts and narrows the emission producing a new near-UV MR-TADF emitter, MesB-DIDOBNA-N. DIDOBNA-N emits bright blue light (lPL = 444nm, FWHM = 64nm, FPL = 81%, td = 23 ms, 1.5 wt% in TSPO1). The deep blue organic light-emitting diode (OLED) based on this twisted MR-TADF compound shows a very high maximum external quantum efficiency (EQEmax) of 15.3% for a device with CIEy of 0.073. The fused planar MR-TADF emitter, MesB-DIDOBNA-N shows efficient and narrowband near UV emission (lPL = 402nm, FWHM = 19nm, FPL = 74.7%, td = 133 ms, 1.5 wt% in TSPO1). The best OLED with MesB-DIDOBNA-N, doped in a co-host, shows the highest efficiency reported for a near UV OLED at 16.2%. With a CIEy coordinate of 0.049, this device also shows the bluest EL reported for a MR-TADF OLED to date. This article is protected by copyright. All rights reserved.

Realization of ZnO microrods and Ag nanoparticles on glass and Si substrates by magnetron sputtering and near band edge photoluminescence enhancement from the exciton-plasmon system

• A dry method of fabrication of Ag nanoparticles and ZnO microrods heterostructure. • Preferential nucleation of Ag nanoparticles in proximities of ZnO microrods. • Seed assisted growth of ZnO microrods at higher gas pressure and shorter duration. • Near-UV (380 nm) emission enhancement possibly due to exciton-plasmon interaction. • Nearly 3-fold enhancement of near band edge photoluminescence from ZnO microrods. This work presents a physical vapour-based fabrication of an exciton-plasmon system via depositions of ZnO microrods (ZnOµRs) and Ag nanoparticles (AgNPs) on glass and p-type Si substrates. Pulsed DC sputtering of ZnO at a relatively higher Ar pressure and varying applied power enables deposition of ZnOµRs on ZnO seed layers. Sputtering of Ag ensures fabrication of AgNP/ZnOμR heterostructure with good adhesion suitable for device realization. Microstructural analyses confirm formations of wurtzite ZnOμRs and f.c.c. AgNPs. AgNPs are observed as isolated clusters due to preferential nucleation in the proximities of ZnOµRs. UV-Vis absorption spectroscopy reveals broad surface plasmon resonance (SPR) of Ag NPs around 538 nm, which experiences a bathochromic shift in AgNP/ZnOμR heterostructure. The photoluminescence (PL) spectra of AgNP/ZnOμR heterostructure suggest a 3-fold enhancement of narrow near band edge (NBE) emission attributed to the exciton-plasmon interaction.

SDSS J1058+5443: A Blue Quasar without Optical/NUV Broad Emission Lines

In this paper, the blue quasar SDSS J105816.19+544310.2 (=SDSS J1058+5443) at redshift 0.479 has been reported as the best true type 2 quasar candidate with the disappearance of central broad-line regions. There are no definite conclusions on the very existence of true type 2 active galactic nuclei (AGN), mainly due to detected optical broad emission lines in high-quality spectra of some previously classified true type 2 AGN candidates. Here, unlike previously reported true type 2 AGN candidates among narrow emission-line galaxies with weak AGN activities but strong stellar lights, the definitely blue quasar SDSS J1058+5443 can be well confirmed as a true type 2 quasar due to apparent quasar-shape blue continuum emissions but an apparent loss of both the optical broad Balmer emission lines and the near-UV (NUV) broad Mg ii emission line. Based on different model functions and the F-test statistical technique, after considering blueshifted optical and UV Fe ii emissions, there are no apparent broad optical Balmer emission lines and/or broad NUV Mg ii lines, and the confidence level is smaller than 1σ in support of broad optical and NUV emission lines. Moreover, assuming the virialization assumption to broad-line emission clouds, the reconstructed broad emission lines strongly indicate that the probable intrinsic broad emission lines, if they exist, cannot be hidden or overwhelmed in the noise of the Sloan Digital Sky Survey spectrum of SDSS J1058+5443. Therefore, SDSS J1058+5443 is so far the best and most robust true type 2 quasar candidate, leading to the clear conclusion of the very existence of true type 2 AGN.

Balmer continuum enhancement detected in a mini flare observed with IRIS

Context. Optical and near-UV continuum emissions in flares contribute substantially to the flare energy budget. Two mechanisms play an important role for continuum emission in flares: hydrogen recombination after sudden ionization at chromospheric layers, and transportation of the energy radiatively from the chromosphere to lower layers in the atmosphere, the so-called back-warming. Aims. The aim of the paper is to distinguish between these two mechanisms for the excess of the Balmer continuum observed in a flare. Methods. We combined the observations of the Balmer continuum obtained with the Interface Region Imaging Spectrograph (IRIS) (spectra and slit-jaw images (SJIs) 2832 Å) and hard X-ray (HXR) emission detected by the Fermi/Gamma Burst Monitor (GBM) during a mini flare. The calibrated Balmer continuum was compared to non-local thermodynamic equilibrium (LTE) radiative transfer flare models, and the radiated energy was estimated. Assuming thick target HXR emission, we calculated the energy of the nonthermal electrons detected by the Fermi/GBM and compared it to the radiated energy. Results. The favorable argument of a relation between the Balmer continuum excess and the HXR emission is that there is a good time coincidence between them. In addition, the shape of the maximum brightness in the 2832 SJIs, which is mainly due to this Balmer continuum excess, is similar to that of the Fermi/GBM light curve. The electron-beam flux estimated from Fermi/GBM between 109 and 1010 erg s−1 cm−2 is consistent with the beam flux required in non-LTE radiative transfer models to obtain the excess of Balmer continuum emission observed in this IRIS spectra. Conclusions. The low-energy input by nonthermal electrons above 20 keV is sufficient to produce the enhancement in the Balmer continuum emission. This could be explained by the topology of the reconnection site. The reconnection starts in a tiny bald-patch region, which is transformed dynamically into an X-point current sheet. The size of the interacting region would be below the spatial resolution of the instrument.

Facilely Solution‐Processed Lithium Carbonate for Tailoring Electron Injection in High‐Performance Inverted Near‐UV Organic Light‐Emitting Diodes

Electron injection plays a key role in electron–photon conversion properties of inverted UV–visible organic light‐emitting diodes (OLEDs). Herein, facilely prepared solution‐processed lithium carbonate (Li2CO3) formic acid and boric acid solutions for tailoring electron injection in inverted near‐UV (NUV) OLEDs are studied. Superior film morphology and exceptional electronic properties of spin‐coated Li2CO3 films are examined by atomic force microscopy, X‐ray/ultraviolet photoelectron spectroscopy, current–voltage curves, and impedance spectroscopy. Efficient inverted NUV OLEDs are assembled using wide‐bandgap molecule of 2‐(4‐biphenyl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole as emissive layer, showing maximum radiance of 5.24 mW cm−2 (2.28 mW cm−2) and external quantum efficiency of 2.47% (2.17%) with an optimal Li2CO3 formic acid of 3 mg ml−1 (Li2CO3 boric acid of 7 mg ml−1) as electron injection tailoring. The NUV emission shows electroluminescence peaks of 404–406 nm and full width at half maximum of 52–56 nm. The results provide some feasible approaches for enhancing the performance of organic electronic devices, which require strong electron injection/extraction and accelerate industrialization.

Revisiting Attenuation Curves: The Case of NGC 3351*

Abstract Multiwavelength images from the far-UV (∼0.15 μm) to the submillimeter of the central region of the galaxy NGC 3351 are analyzed to constrain its stellar populations and dust attenuation. Despite hosting a ∼1 kpc circumnuclear starburst ring, NGC 3351 deviates from the IRX–β relation, the relation between the infrared-to-UV luminosity ratio and the UV continuum slope β that other starburst galaxies follow. To understand the reason for the deviation, we leverage the high angular resolution of archival near-UV-to-near-IR Hubble Space Telescope images to divide the ring into ∼60–180 pc size regions and model each individually. We find that the UV slope of the combined intrinsic (dust-free) stellar populations in the central region is redder than what is expected for a young model population. This is due to the region’s complex star formation history, which boosts the near-UV emission relative to the far-UV. The resulting net attenuation curve has a UV slope that lies between those of the starburst attenuation curve (Calzetti et al. 2000) and the Small Magellanic Cloud extinction curve; the total-to-selective attenuation value, R ′ (V) = 4.93, is larger than both. As found for other star-forming galaxies, the stellar continuum of NGC 3351 is less attenuated than the ionized gas, with E(B − V)star = 0.40 E(B − V)gas. The combination of the “red” intrinsic stellar population and the new attenuation curve fully accounts for the location of the central region of NGC 3351 on the IRX–β diagram. Thus, the observed characteristics result from the complex mixture of stellar populations and dust column densities in the circumnuclear region. Despite being a sample of one, these findings highlight the difficulty of defining attenuation curves of general applicability outside the regime of centrally concentrated starbursts.

Novel imidazole-alkyl spacer-carbazole based fluorophores for deep-blue organic light emitting diodes: Experimental and theoretical investigation

A series of fluorescent emitters based on Imidazole-Alkyl spacer-Carbazole were designed and synthesized by connecting donor and acceptor moieties through alkyl spacer. In these design strategy we have chosen carbazole as electron rich and imidazole as electron deficient with deferent functional black (phenyl and phenyl substituted) at the N1 position of imidazole moiety. All the fluorophores were structurally confirmed by spectroscopic methods (NMR, MASS, and FTIR). The photophysical, electrochemical and electroluminescence properties were thoroughlyexamined. All the fluorophores showed good thermal stability and near-UV emission with high photoluminescence quantum yield (PLQY)of ~59% in the solid state. All the synthesized compounds feature Commission International de L'Eclairage (CIE) coordinates of y < 0.08 for a particular doping concentration, which is very close to the National Television Standards Committee (NTSC) standard blue (0.14, 0.08). Solution-processed organic light emitting diode (OLED) device consisting of molecule BIPOCz displays a maximum external quantum efficiency EQE of 1.9% with CIE coordinates of (0.17, 0.07). All these results reveal that this work provides novel approaches for realizing ultra-deep-blue emission with high performance.

Rotationally Driven Ultraviolet Emission of Red Giant Stars

Abstract Main-sequence stars exhibit a clear rotation-activity relationship, in which rapidly rotating stars drive strong chromospheric/coronal ultraviolet and X-ray emission. While the vast majority of red giant stars are inactive, a few percent exhibit strong ultraviolet emission. Here we use a sample of 133 red giant stars observed by Sloan Digital Sky Survey APOGEE and Galaxy Evolution Explorer to demonstrate an empirical relationship between near-UV (NUV) excess and rotational velocity ( ). Beyond this simple relationship, we find that NUV excess also correlates with rotation period and with Rossby number in a manner that shares broadly similar trends to those found in M dwarfs, including activity saturation among rapid rotators. Our data also suggest that the most extremely rapidly rotating giants may exhibit so-called supersaturation, which could be caused by centrifugal stripping of these stars rotating at a high fraction of breakup speed. As an example application of our empirical rotation-activity relation, we demonstrate that the NUV emission observed from a recently reported system comprising a red giant with a black hole companion is fully consistent with arising from the rapidly rotating red giant in that system. Most fundamentally, our findings suggest a common origin of chromospheric activity in rotation and convection for cool stars from main sequence to red giant stages of evolution.

HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Stars

Abstract Quantifying the evolution of stellar extreme ultraviolet (EUV, 100–1000 Å) emission is critical for assessing the evolution of planetary atmospheres and the habitability of M dwarf systems. Previous studies from the HAbitable Zones and M dwarf Activity across Time (HAZMAT) program showed the far- and near-UV (FUV, NUV) emission from M stars at various stages of a stellar lifetime through photometric measurements from the Galaxy Evolution Explorer (GALEX). The results revealed increased levels of short-wavelength emission that remain elevated for hundreds of millions of years. The trend for EUV flux as a function of age could not be determined empirically because absorption by the interstellar medium prevents access to the EUV wavelengths for the vast majority of stars. In this paper, we model the evolution of EUV flux from early M stars to address this observational gap. We present synthetic spectra spanning EUV to infrared wavelengths of 0.4 ± 0.05 M ☉ stars at five distinct ages between 10 and 5000 Myr, computed with the PHOENIX atmosphere code and guided by the GALEX photometry. We model a range of EUV fluxes spanning two orders of magnitude, consistent with the observed spread in X-ray, FUV, and NUV flux at each epoch. Our results show that the stellar EUV emission from young M stars is 100 times stronger than field age M stars, and decreases as t −1 after remaining constant for a few hundred million years. This decline stems from changes in the chromospheric temperature structure, which steadily shifts outward with time. Our models reconstruct the full spectrally and temporally resolved history of an M star’s UV radiation, including the unobservable EUV radiation, which drives planetary atmospheric escape, directly impacting a planet’s potential for habitability.

Achieving efficient deep-blue TADF in carbazole-pyrimidine compounds

An approach for achieving deep blue thermally activated delayed fluorescence (TADF) is presented. A simple carbazole-pyrimidine compound Cbz-PYR with near-UV emission and simultaneous room-temperature phosphorescence (RTP) was selectively modified by lowering the singlet state energy, simultaneously preserving high triplet energy. The modified compound tCbz-mPYRs was shown to be efficient TADF emitter with 0.5 solid-state emission yield and peak wavelength of 428 nm. When used in OLED device, tCbz-mPYRs based OLED showed electroluminescence with 8.7% external quantum efficiency (EQE) and Commission Internationale de l’Eclairage (CIE) coordinates of (0.16; 0.12). • Deep-blue TADF was achieved in carbazole-pyrimidine compounds. • The bandgap was controlled by the expedient manipulation of molecular structure. • EQE of OLED device peaked at 8.7% with CIE colour coordinates of (0.16; 0.12).

Current Population Statistics Do Not Favor Photoevaporation over Core-powered Mass Loss as the Dominant Cause of the Exoplanet Radius Gap

Abstract We search for evidence of the cause of the exoplanet radius gap, i.e., the dearth of planets with radii near 1.8 R ⊕. If the cause were photoevaporation, the radius gap should trend with proxies for the early-life high-energy emission of the planet-hosting stars. If, alternatively, the cause were core-powered mass loss, no such trends should exist. Critically, spurious trends between the radius gap and stellar properties arise from an underlying correlation with instellation. After accounting for this underlying correlation, we find that no trends remain between the radius gap and stellar mass or present-day stellar activity as measured by near-UV emission. We dismiss the nondetection of a radius gap trend with near-UV emission because present-day near-UV emission is unlikely to trace early-life high-energy emission, but we provide a catalog of Galaxy Evolution Explorer near-UV and far-UV emission measurements for general use. We interpret the nondetection of a radius gap trend with stellar mass by simulating photoevaporation with mass-dependent evolution of stellar high-energy emission. The simulation produces an undetectable trend between the radius gap and stellar mass under realistic sources of error. We conclude that no evidence, from this analysis or others in the literature, currently exists that clearly favors either photoevaporation or core-powered mass loss as the primary cause of the exoplanet radius gap. However, repeating this analysis once the body of well-characterized &lt;4 R ⊕ planets has roughly doubled could confirm or rule out photoevaporation.

Soft fluorescent organic nanodots as nanocarriers for porphyrins

Novel fluorescent organic nanoparticles made from citric acid and diethylenetriamine were used as biocompatible and highly water-soluble nanocarriers for hydrophobic tetraphenylporphyrin (TPP). The tetraphenylporphyrin units were covalently attached to the nanoparticles, generating conjugated nanoparticles which retain water solubility and preserve the photophysical properties of monomeric TPP. The conjugated nanoparticles show two distinct fluorescence features: blue emission from the nanoparticle when excited in the near-UV (360 nm) and characteristic far-red emission of the TPP when excited in the visible (Soret band or Q bands). The uptake of the conjugated nanoparticles in live human neuroblastoma cancer cells was evidenced using two-photon microscopy. These experiments demonstrate that the fluorescent organic nanoparticles do act as efficient nanocarriers, allowing cell internalization of hydrophobic porphyrins. These conjugated nanoparticles appear as promising nanotools for theranostic (based on the combination of imaging and monitoring of the nanoparticle fluorescence) and therapeutic (photodynamic therapy by selectively exciting the grafted porphyrin units) modalities.