Highly enhanced UV absorption and light emission of monolayer WS_(2)through hybridization with Ti_(2)N MXene quantum dots and g-C_(3)N_(4)quantum dots

Two-dimensional(2D)transition metal dichalcogenides(TMD)are atomically thin semiconductors with promising optoelectronic applications across the visible spectrum.However,their intrinsically weak light absorption and the low photoluminescence quantum yield(PLQY)restrict their performance and potential use,especially in ultraviolet(UV)wavelength light ranges.Quantum dots(QD)derived from 2D materials(2D/QD)provide efficient light absorption and emission of which energy can be tuned for desirable light wavelength.In this study,we greatly enhanced the photon absorption and PLQY of monolayer(1L)tungsten disulfide(WS_(2))in the UV range via hybridization with 2D/QD,particularly titanium nitride MXene QD(Ti_(2)N MQD)and graphitic carbon nitride QD(GCNQD).With the hybridization of MQD or GCNQD,1LWS_(2)showed a maximum PL enhancement by 15 times with 300 nm wavelength excitation,while no noticeable enhancement was observed when the excitation photon energy was less than the bandgap of the QD,indicating that UV absorption by the QD played a crucial role in enhancing the light emission of 1L-WS_(2)in our 0D/2D hybrid system.Our findings present a convenient method for enhancing the photo-response of 1L-WS_(2)to UV light and offer exciting possibilities for harvesting UV energy using 1L-TMD.

Effect of Heat-treatment on Crystalline Phase and UV Absorption of 60CeO_2-40TiO_2 Thin Films by Magnetron Sputtering

60CeO2-40TiO2 thin films were deposited on soda-lime silicate glass substrates by R.F. magnetron sputtering. The effects of heat-treatment on the UV-absorption of the thin films were studied on the 60CeO2-40TiO2 thin film with the largest UV cut-off wavelength. The sample films with CeO2：TiO2=60：40 were heated at 773 K, 873 K, 973 K for 30 min. These films are characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, and X-ray photoelectron spectroscopy and spectrometer （XPS）. XRD analysis proves that the addition of TiO2 to CeO2 changed the crystalline state of CeO2. But the UV absorption effect of CeO2-TiO2 films with CeO2 crystallite phase is inferior to that of the amorphous phase CeO2-TiO2 films. XPS analysis also indicates that the amorphous phase CeO2-TiO2 films have the most Ce3＋ content in these films. Amorphous phase and crystalline phase of the CeO2-TiO2 films have different effects on UV absorption of the thin films.

Preparation of nanometer yellow iron and its UV absorption capacity

The nanometer yellow iron oxide was prepared by oxidizing Fe（OH）2 with air, which was verified with XRD and TEM. The result shows that nanometer yellow iron oxide is spindle-shaped and well-distributed with a long axis of 150-200 nm and short axis of 40-50 nm. Ultraviolet （UV） transmittance of the iron oxide shows the great effect of concentration on both transparency and UV ab- sorption, and it has been proven that iron oxide with a concentration of 0.025wt% is preferred. The spectrum of XRD indicates that it is goethite. When the yellow iron is dispersed in sol, given that the wavelength of UV is less than 300 nm, its UV absorption capacity is superior to those of ZnO and TiO2. The absorption capacity of the yellow iron is less than TiO2 and more than ZnO as the wavelength of UV is 300-400 nm.

Cell-cycle-dependent variation in UV absorption spectrum of Hela cells treated with Trichostatin A

Objective： The aim of our study was to discovery the different cell cycle arrest effect after different densities HeLa cells treated with Trichostatin A （TSA）. In addition, this study would find some important relationship between cycle arrest effect and UV absorption spectrum of cell. Methods： 0.2 IJM TSA was applied to act on HeLa cells of different density. Then, the cycle arrest effect and UV absorption spectrum of cells were investigated, which provide support to analyze the effect of TSA on cancer cells. Results： Cell cycle arrest effect in G0/G1 of the lower density cells was more obvious than that in other groups. The other discovery in this work was that the cellular UV absorption value was higher when the density of cultured cell was lower. Conclusion： This experiment would guide the clinical study on early or late stage cancer patients in the future. On the other hand, this work indicates when cells were arrested in G0/G1 phase, the cellular absorption value increased at the same time, so UV absorption spectrum could characterize the change of cell cycle.

Comparison of Nitric Oxide Concentrations in μs-and ns-Atmospheric Pressure Plasmas by UV Absorption Spectroscopy

In this paper,an absorption spectroscopy measurement method was applied on two atmospheric pressure plasma sources to determine their production of nitric oxide.The concentrations are essential for evaluating the plasma sources based on the principle of the Dielectric Barrier Discharge（DBD）for applications in plasma medicine.The described method is based on a setup with an electrodeless discharge lamp filled with a mixture of oxygen and nitrogen.One of the emitted wavelengths is an important resonance wavelength of nitric oxide（λ = 226.2 nm）.By comparing the absorption behaviour at the minimum and maximum of the spectral absorption cross section of nitric oxide around that wavelength,and measuring the change in intensity by the absorbing plasma,the concentration of nitric oxide inside the plasma can be calculated.The produced nitric oxide concentrations depend on the pulse duration and are in the range of 180 ppm to 1400 ppm,so that a distance of about 10 cm to the respiratory tract is enough to conform to the VDI Guideline 2310.

A Bioinspired Strategy Toward UV Absorption Enhancement of Melaninlike Polymers for Sun Protection

Due to the complexity of the structure within melanin and synthetic polymers(i.e.,polydopamine,PDA),it is a challenge to regulate the ultraviolet(UV)absorption.In nature,melanocytes can biosynthesize more pheomelanins than eumelanins via protein and gene overexpression for photoprotection when the UV irradiation is enhanced.During this biosynthetic pathway,L-cystine,transported by xCT gene,can be involved to form a new monomer structure incorporating a benzothiazole group,finally resulting in the formation of UV absorption-enhanced pheomelanin.Inspired by this,we have proposed a facile strategy to regulate the UV absorption of PDA by introducing the benzimidazole(BI)unit through the thiol-Michael addition reaction during the polymerization process.It was further found that the introduction of BI units not only significantly increased the content of chromophores and auxochromes,but also effectively restricted the red-shift of the absorption spectrum via interrupting the conjugated microstructure within PDA,both of which contribute to UV absorption enhancement.These UV absorption-enhanced PDA nanoparticles could be used to fabricate bio-inspired sunscreens for efficient sun protection.This work will provide a facile strategy to regulate UV absorption of melanin-like materials and open new horizons for the design and construction of bioinspired sunscreens.

Effects of substituent and solvent on the UV absorption energy of 4,4'-disubstituted stilbenes

Twenty five samples of 4,4'-disubstituted stilbene derivatives were synthesized, and their UV absorption max wavelengths were determined in over 10 kinds of solvents including cyclohexane, ether, chloroform, acetonitrile and ethanol, in which 242 experimental data were recorded. The effects of substituents and solvents on the energy of their UV absorption max wavelengths were discussed. The research results showed: the energy of UV absorption max wavelengths of 4,4'-disubstituted stilbenes was mainly affected by their intramolecular structure (substituent effect) in a given solvent, that is, the energy is dominated by both of excited-state substituent parameter o-~c and polar substituent constant crp. While their energy was dominated by the substituent effect and solvent effect in different kinds of solvents. An equation quantifying the energy of UV absorption max wavelengths of 4,4'-disubstituted stilbenes was developed. In addition, it is found that the n-octanol/water partition coefficient (logP) is more effective than the solvatochromic dye (ET(30)) in scaling the solvent effect. The equation employed the parameter logP has a better correlation and more specific physical meaning. Further, the energies of UV absorption max wavelengths of some reported compounds were predicted by the obtained equation, which are in agreement with their experimental values.

Effect of Excited-state Substituent Constant on the UV Spectra of 1,4-disubstituted Benzenes

A correlation equation between the UV absorption wavenumbers of 1,4-disubstituted benzenes and the excited-state substituent constant was obtained. For 80 sorts of 1,4- disubstituted benzenes, the correlation coefficient was 0.9805, and the standard deviation was only 672.27 cm^-1. The results imply that the excited-state substituent constant can be used productively for research on UV energy of 1,4-disubstituted benzenes. The present method provides a new avenue to study the UV absorption spectra of aromatic systems with the excited-state substituent constant, and it is helpful to understand the effect of substituent electrostatic effects on the chemical and physical properties of conjugated compounds with multiple substituents in excited state.

Study on UV Shielding TiO_2 Thin Film Prepared by Sol-Gel Method

Titanium dioxide (TiO_2) thin films were prepared on microscopes slides by sol-gel and dip-coating processes from specially formulated sols.The results show that there exists anatase and rutile structure of TiO_2 when heat treatment temperature is 450℃,and at 800℃,TiO_2 particle size is of below 100 nm and rutile structure is presented.In the range of 360 nm～400 nm the transmittance of TiO_2 sol increases with the increasing of the concentration of Ti(OC_4H_9)_4 in ethanol solution. The transmittance of TiO_2 films with various number of the layer is measured to be 0% below 320 nm,and the three-layer TiO_2 film is of the best UV resistance in the range of 320 nm～400 nm.

UV-Polarizing Linear Polyyne Molecules Aligned in PVA

Electronic absorption bands of conjugated linear carbon chain molecules, namely polyynes H(C≡C)nH (n=5-7), are exploited to devise light-polarizing films applicable to the UV. Laser ablated polyynes are separated in size and dispersed in a film of polyvinyl alcohol (PVA), which is stretched to align the trapped linear polyyne molecules inside. As a nature of the structural anisotropy, transition dipole of the UV absorption for polyyne molecules is in parallel with the molecular axis and the absorption occurs only for the electromagnetic wave having the amplitude of its electric vector along the molecular axis. Aligned and fixed orientationally in the solid PVA film, polyyne molecules act as selective absorbers of one of the polarization components of incident light at particular wavelength. Using a light source of linearly polarized UV light, whose direction of polarization is rotatable, angular dependence of the absorption intensity is investigated for the stretched PVA film containing aligned polyyne molecules and analyzed in terms of an order parameter in the theory of linear dichroism.

ASb(SO_(4))_(2)(A=Rb,Cs):Two short-wave UV antimony sulfates exhibiting large birefringence

Herein,two antimony sulfates,named RbSb(SO_(4))_(2)(1)and CsSb(SO_(4))_(2)(2),have been successfully synthesized with the introduction of Sb^(3+)cation with stereochemically active lone pairs(SCALP)into sulfates by the conventional hydrothermal method.Both two compounds endow short ultraviolet(UV)absorption edges(281 nm and 278 nm,respectively)and large birefringence(0.171@546 nm and 0.174@546 nm,respectively),which means that they are promising short-wave UV optical materials.Interestingly,though both of the two compounds exhibit similar 1D chained structures,and possess the same functional moieties including SbO4 seesaws and SO4 tetrahedral groups,they exhibit significantly opposite macroscopic symmetries,i.e.,compound 1 crystallizes in a centrosymmetric(CS)manner(P2_(1)/n)and compound 2 in a noncentrosymmetric(NCS)manner(P2_(1)2_(1)2_(1)),due to the size of cations[r(Rb+)=1.56 A˚,r(Cs+)=1.67 A˚]affects the orientation of SCALP of the adjacent Sb^(3+).

Synthesis and Characterization of 9,9-diethyl-1-phenyl-1,9-dihydrofluoreno[2,3-d]imidazole-ended Fluorophores

A series ofπ-conjugated compounds ending with 9,9-diethyl-1-phenyl-1,9-dihydrofluoreno[2,3-d]imidazole were conveniently synthesized by condensation of the key intermediate9,9-diethyl-N^(2)-phenyl-9H-fluorene-2,3-diamine with the corresponding symmetric aryl phthalaldehydes under very mild conditions.The structures of these compounds were confirmed by^(1)H NMR,^(13)C NMR,and HRMS.Their UV-Vis spectroscopy data,fluorescent spectroscopy data,and further details of the electronic properties from cyclic voltammetry measurements and theoretical calculations were studied.Most compounds possess good fluorescence-emitting ability with quantum yield of fluorescence values in the region of 0.36-0.92 and display emission within 449-513 nm depending on the molecular nature.

Structural disruption of melanin-like polymers with boosted UV protection

Manipulating the energy structure of materials represents an efficient way to regulate their light absorption behaviors. For example, constructing donor-acceptor(D-A) structures to increase the polarizability and reduce the energy bandgap of local molecules has been widely used in the field of organic photovoltaics with ordered structures. Remarkably, even in disordered and chaotic systems such as melanin-like polydopamine(PDA), visible and near-infrared light absorption can be significantly improved using this strategy. However, there has been a noticeable dearth of research on the ultraviolet(UV) light absorption regulation of bioinspired polymers with disordered and chaotic architectures by tailoring the D-A microstructures. In this study, a series of benzoheterocyclic molecules with strong electron-donating features screened by molecular simulation calculations were involved in disrupting the D-A structures within PDA. The destruction of D-A structures promoted the increase of the energy band gap and finally boosted the UV absorption of PDA. The resulting PDA nanoparticles with enhanced UV absorption were further employed to fabricate UV shielding composite films to protect the growth of plants from harmful UV radiation. This research may open up new avenues for structural disruption of bioinspired polymers for enhanced photoprotection applications.

Synthetic fungal melanin UV absorbers

Agents with robust ultraviolet(UV)absorption capabilities play a vital role in safeguarding organisms and inorganic materials from UV damage.Nonetheless,the synthetic procedures towards these UV absorbers are usually lengthy and complicated,accompanied by undesirable side reactions and the generation of toxic substances.In nature,allomelanin,a class of melanins variant found in melanized fungi near the Chernobyl nuclear power plant,plays crucial roles in the cell wall of melanized fungi,offering resistance to harsh external environments and promising UV resistance capabilities.Notably,allomelanin can be rapidly biosynthesized via the polymerization of 1,8-dihydroxynaphthalene in presence of enzymes in fungi.Inspired by this,we report here a green enzymatic polymerization strategy to efficiently and eco-friendly synthesize polydihydroxynaphthalene(PDHN)-based artificial allomelanin nanoparticles(NPs)with interesting features.Theoretical calculations and experimental results demonstrated that the PDHN NPs exhibited excellent UVabsorption capacity,surpassing another widely used artificial melanin,polydopamine(PDA).Moreover,the light absorption mechanism of PDHN NPs was systematically elucidated for the first time.Then,the PDHN NPs were incorporated with polyvinyl alcohol(PVA)to create an anti-aging composite film with significantly enhanced UV shielding ability.The potential of these composite films in safeguarding plants from UV damage was meticulously verified.Remarkably,these PDHN NPs were first found to produce hydroxyl radicals(·OH)under UV irradiation,offering antibacterial properties that expand their potential applications.

Two UV organic-inorganic hybrid antimony-based materials with superior optical performance derived from cation-anion synergetic interactions

Finding suitable strategies to effectively enhance the optical properties of materials are the goal being pursued by researchers.Herein,cation-anion synergetic interactions strategy was proposed to develop two novel organic-inorganic hybrid antimony-based optical materials,(C_(3)H_(5)N_(2))Sb F_(2)SO_(4)(I)and(C_(5)H_(6)N)Sb F_(2)SO_(4)(Ⅱ),which were obtained by introducing Sb^(3+)cation containing stereochemically active lone-pair(SCALP)and organicπ-conjugated cations into sulphate system.The synergistic interactions of the organicπ-conjugated cations,the inorganic[SbO_(2)F_(2)]^(3-)seesaw anions and the[SO_(4)]^(2-)distorted tetrahedra anions make their ultraviolet(UV)absorption edges approach 297 and 283 nm,respectively,and raise their birefringence up to 0.193@546 nm and 0.179@546 nm,respectively.Interestingly,although the two compounds have the same stoichiometric ratio and similar one-dimensional(1D)chain structure,they show opposite macroscopic symmetry,where the NCS compound(Ⅱ)exhibits a large secondharmonic generation(SHG)response(1.6 times that of KH_(2)PO_(4)).The two reported compounds are found to be promising UV optical materials in the experimental tests.

Interaction of Nicotine and Bovine Serum Albumin

The binding of nicotine to bovine serum albumin (BSA) was studied by UV absorption. fluorescence, and H-1 NMR methods. With the addition of nicotine, the absorption band of BSA at about 210 nm decreased gradually, moved to longer wavelengths, and narrowed. BSA fluorescence of tryptophan residue was quenched by nicotine. The H-1 NMR peaks of nicotine moved to downfield by the addition of BSA. The experimental results showed that nicotine was capable of binding with BSA to form a 1:1 complex. BSA's high selectivity for nicotine binding suggests a unique role for this protein in the detoxification and/or transport of nicotine.

Crystal Structures and Spectroscopy of Anti-2,4-bis(3-R-phenyl)pentane-2,4-diols (R = Me, SMe)

Two anti-2,4-bis（3-R-phenyl）pentane-2,4-diols （1, R = Me; 2, R = SMe） have been synthesized and were characterized by X-ray diffraction, IR and UV spectra. X-ray diffractions indicate that intra- and intermolecular hydrogen bonding interactions form one-dimensional （ID） ribbons. The adjacent infinite I D ribbons result in 3D supramolecular structures. The dihedral angles between every two benzene rings in the two diols are 31.61（12） and 31.80（7）°, respectively. UV absorption spectra of the title compounds were recorded in MeOH, C2H5OH, CH3CN, n-BuOH and cyclohexane solvents with different dielectric constants.

Synthesis,Crystal Structure and Properties of a Coordination Compound:Ni(C_6H_(12)N_4)_2SO_4·4H_2O

A new coordination compound, Ni（C6H12N4）2SO4.4H20（NSH-HMTA） （HMTA, hexamethylenetetramine, C6H12N4）, has been synthesized and its single crystals were obtained. NSH-HMTA belongs to the triclinic system, space group Pi with a = 9.2534（6）, b = 13.3131（2）, c = 16.0373（2） A, α = 65.981（6）, β = 89.792（3）, γ = 89.677（4）°, Mr= 880.2, Z = 2, V= 1804.6（3） A3, μ = 1.254 mm-1, F（000） = 932, R = 0.0555 （1 〉 2σ（I）） and wR = 0.1908 for 19343 observed reflections. HMTA substitutes for water molecules are located at the para-positions, forming a stretching octahedral nickel ion unit. Thermo-gravimetric analysis shows that the dehydration temperature of NSH-HMTA is about 92℃. The characteristic UV peaks are approximately 10 nm red-shifted by the absorption of octahedral HMTA complex ion units.

UV-resistant salicylic acid as interface modifier for efficient and stable perovskite solar cells

Interfacial defect is one of the main hurdles to impede the improvement of efficiency and stability of perovskite solar cells(PSCs).Additionally,the ultraviolet(UV)irradiate induces the generation of deep defects,and further accelerate the decomposition of perovskite films.Thus,the interfacial modification is crucial to improve the ef-ficiency and stability of PSCs.Here,the salicylic acid(SA)as a multifunctional interface material is employed to modify the interface of mesoporous cerium oxide(m-CeO_(x))and perovskite.The introduced SA molecules can interact with Ce in m-CeO_(x)and Pb in perovskite through carboxylic acid functional groups to passivate interfacial defects and promote interfacial electron extraction and transport.The PSC with SA modification exhibits an improved power conversion efficiency(PCE)of 23.33%.More importantly,the SA can absorb UV light and reduce the damage of UV light to perovskite film,then improving the UV stability and overall stability of devices.This work provides a novel insight to design the interfacial modification materials for preparing efficient and stable PSCs.

Ultraviolet Spectrum of Nanometer Zinc Oxide Prepared by Sol-Gel Process

Zinc oxide nanometer powders were prepared by the sol-gel process.The sol and the powders characteristic of absorbing ultraviolet light is detected by the ultraviolet spectrometer.The results indicate the concentration of zinc acetate dihydrate in isopropyl alcohol solution and the final pH value of the aqueous sol have effect on the UV absorption of the sol. The nanometer zinc oxide has strong absorption at 200 nm～360 nm,and over 90% ultraviolet in the range of 200 nm～360 nm wavelength are absorbed.The characteristic of absorbing ultraviolet light of zinc oxide increases as the particle size of zinc oxide decreases.