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Luminescent metal–organic frameworks (MOFs) are of interest for sensing, theranostics, dosimetry, and other applications. The use of lanthanoids in MOF metal nodes allows for intrinsic met-al-based luminescence. In this work, a facile route for modulat-ing the photoluminescent and radioluminescent properties of Tb(III)-based MOFs is reported. By using Tb(III)-cluster nodes as X-ray attenuators, and organic linkers with varying excited state energies as sensitizers, MOFs with metal-based, linker-based, and metal+linker-based photo- and radioluminescence are reported.

Preliminary explorations of the annihilation electrogenerated chemiluminescence (ECL) of mixed metal complexes have revealed opportunities to enhance emission intensities and control the relative intensities from multiple luminophores through the applied potentials. However, the mechanisms of these systems are only poorly understood. Herein, we present a comprehensive characterisation of the annihilation ECL of mixtures of tris(2,2'-bipyridine) ruthenium(II) hexafluorophosphate ([Ru(bpy)(3)](PF6)(2)) and fac-tris(2-phenylpyridine)iridium(III) ([Ir(ppy)(3)]). This includes a detailed investigation of the change in emission intensity from each luminophore as a function of both the applied electrochemical potentials and the relative concentrations of the two complexes, and a direct comparison with two mixed (Ru/Ir) ECL systems for which emission from only the ruthenium-complex was previously reported. Concomitant emission from both luminophores was observed in all three systems, but only when: (1) the applied potentials were sufficient to generate the intermediates required to form the electronically excited state of both complexes; and (2) the concentration of the iridium complex (relative to the ruthenium complex) was sufficient to overcome quenching processes. Both enhancement and quenching of the ECL of the ruthenium complex was observed, depending on the experimental conditions. The observations were rationalised through several complementary mechanisms, including resonance energy transfer and various energetically favourable electron-transfer pathways. Refereed/Peer-reviewed

We investigate the long-range, two-body interactions between rubidium and potassium atoms in highly excited ($n=70$) Rydberg states. After establishing properly symmetrized asymptotic basis states, we diagonalize an interaction Hamiltonian consisting of the standard Coulombic potential expansion and atomic fine structure to calculate electronic potential energy curves. We find that when both atoms are excited to either the $70s$ state or the $70p$ state, both the $\Omega=0+$ symmetry interactions and the $\Omega=0-$ symmetry interactions demonstrate a deep potential well capable of supporting many bound levels; the size of the corresponding dimer states are on the order of 2.25 $\mu$m. We estabish $n$-scaling relations for the equilibrium separation $R_e$ and the dissociation energy $D_e$ and find these relations to be consistent with similar calculations involving the homonuclear interactions between rubidium and cesium. We discuss the specific effects of $\ell$-mixing and the exact composition of the calculated potential well \textit{via} the expansion coefficients of the asymptotic basis states. Finally, we apply a Landau-Zener treatment to show that the dimer states are stable with respect to predissociation., Comment: 8 pages, 4 figures, 4 tables

Two series of cyclometalated PtII and IrIII complexes with general formula [Pt(pbt){PPh2(R)-P,O)}] (2a-2c) and [Ir(pbt)2{PPh2(R)-P,O)}] (3a-3c), where Hpbt is 2-phenylbenzothiazol and PPh2(R) is a diphenylphosphino donor functionalized deprotonated based acid (R = o-C6H4CO2 a, o-C6H4SO3 b, CH2CH2CO2 c) are presented. The structures of 1, 2a-2c, 3a and 3b were confirmed by single X-ray diffraction analyses, and the intermolecular interactions in 2a were studied using Hirshfeld surface analysis and Non Covalent Interaction (NCI) methods on its X-ray structure. Their photophysical properties were investigated by absorption and emission [CH2Cl2, solid (298, 77 K) and doped polystyrene (PS) films], supported by TD-DFT calculations on 1, 2a-2c and 3a. The PtII complexes exhibit bright phosphorescence in the region 525-543 nm, adscribed to a mixed 3IL/3MLCT excited state with predominant 3IL contribution. The IrIII derivatives (3a-3c) show orange photoluminescence (534-584 nm, 298 K), blue shifted at 77 K (527-560 nm), originated from admixture of 3IL/3MLCT/3LLCT excited states. Interestingly, the photoluminescence quantum yields of the Pt complexes 2a-2c ( = 46.5-66.5%) in PS films are remarkably higher than those of the iridium corresponding complexes ( = 17.3-32%) and the precursor 1 ( = 17%). The calculated 3MC-3IL/3MLCT energy gap for 2a and 3a accounts for the higher quantum yield of the Pt in relation to the Ir complexes.

In this study, a new series of zinc oxide (ZnO) with high specific surface area and narrow energy band gap are prepared using a facile microwave-induced method. The corresponding formation mechanism is also discussed for the first time. Due to the introduction of C, these ZnO can be excited by long wave temperature light without harmful short wave radiation, and play an efficient photocatalytic activity. This valuable property fundamentally improves the biological safety of its photocatalytic application. Herein, taking teeth whitening as an example, the photocatalytic performance of ZnO is evaluated. The “pure” yellow light-emitting diode (PYLED) with high biological safety is used as the excitation source. It is found that this method could effectively remove pigment on the tooth surface through physical adsorption. In addition, these ZnO could generate active oxygen to degrade the pigment on the tooth surface under the irradiation of yellow light. Some further optimization of these “warm light” responsive ZnO is also discussed in this systematical study, which could open up new opportunities in biomedical field., Graphical abstract Image 1, Highlights • A series of ZnO (PZCs, ZnO-BC) with high specific surface area and low band gap were synthesized by simple microwave-induced synthesis. • The introduction of C or BC can effectively reduce the band gap of ZnO. • Long wavelength warm light can effectively stimulate the photocatalytic activity of PZCs and ZnO-BC. • Under the yellow light, ZnO can effectively decompose the pigment on the tooth surface. • Warm light whitening, from the light source and material two levels to reduce the stimulation of teeth, and no obvious damage to enamel.

The nitric oxide vibrationally excited levels in the daytime are studied, at altitudes between 80 and 200 km. For that, we use a coupled 1D Boltzmann kinetic-fluid model to find density profiles of the major ions: O 2 + ; N 2 + ; NO + ; N + ; O + , nitrogen atoms: N ( 4 S ) ; N ( 2 D ) and vibrationally excited levels: NO ( v ⩽ 7 ) . A variety of processes are included in the model calculations that are neutrals chemistry, ions chemistry, photoabsorption, energetic electrons acting on the neutral atmosphere, molecular diffusion, and turbulent diffusion transport. The vibrational excitation of the nitric oxide is under strong solar control, reaching its maximum value near noon, when the solar zenith angle has the smallest value and then decreases away from noon. Data measurements of NO 5.3 μ m volume emission rate (VER) provided by SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) satellite instrument corroborate our numerical results.

The synthesis, structural characterization and photophysical properties of a series of platinum(II) complexes of benzannulated pincer-type diarylamido ligands are described. The ligands all contain tricyclic phenanthridine (3,4-benzoquinoline) rings as donor arms, which were elaborated into N∧N−∧O-coordinating β-enaminoketonato chelates via partial condensation with acetylacetone. The proligands are easily deprotonated, and metallation can be achieved under mild conditions using simple Pt(II) salts and Ag2O as a base. The resulting Pt(II) complexes exhibit strong metal-to-ligand charge-transfer absorptions in the region of ∼450–575 nm and are phosphorescent in solution at room temperature, emitting bright orange light (λmax ∼ 600 nm) with quantum yields of up to 16% and excited-state lifetimes on the order of ∼20 μs, representing significant improvements to these photophysical properties compared with many previously reported N∧N∧O or N∧N∧N-ligated systems. Computational modelling reveals that the lowest-lying triplet state is populated efficiently thanks to strong coupling between singlet and triplet excited state manifolds, as in cyclometallated compounds of Pt(II). Substituents (CH3, tBu, or CF3) in the 2-position of the phenanthridinyl unit are found to have little influence on the optical properties, but the emission is severely quenched when a methyl substituent is introduced ortho to the coordinating nitrogen. Molecular distortions in the excited state are shown to be primarily responsible for the quenching in this complex.

Organic light-emitting device (OLED) is an attractive technology for display application in high-end electronics. Tetradentate Pt(II) complexes are phosphorescent emitters of great importance for OLED fabrications. A novel series of N-Heterocyclic carbene (NHC), benzocarbene (Ph/NHC) and pyridinocarbene (Py/NHC)-based tetradentate Pt(II) complexes with fused 5/6/6 metallocycles was designed and developed. Their electrochemical and photophysical properties were systematically studied through experimental and theoretical investigations, which greatly affected by the NHC, Ph/NHC and Py/NHC. Pt(NHC-1) shows dominant emission peak at 509 nm with a quantum efficiency of 40% and excited lifetime of 1.8 µs in 5 wt% doped PMMA film at room temperature. Pt(NHC-1)-doped green OLED using 26mCPy as host material demonstrated a very high Lmax of 64416 cd/m2, which was a record-high value for the reported Pt(II) complexes-based phosphorescent OLEDs. The OLED also achieved a peak EQE of 13.1% with small efficiency roll-off, which yet maintained EQEs of 12.8%, 11.6% and 8.6% at a high brightness of 100, 1000 and 10000 cd/m2.

Copper hexadecafluorophthalocyanine (CuFPc) has excellent environmental and thermal stability and stable n-type semiconducting properties under ambient conditions. We investigated the exciton diffu...

Substitutional metal doping is a powerful strategy for manipulating the emission spectra and excited state dynamics of semiconductor nanomaterials. Here, we demonstrate the synthesis of colloidal manganese (Mn

In electron-transfer initiated photosensitization processes, molecular oxygen (O2 ) is not involved in the first bimolecular event, but almost always participates in subsequent steps giving rise to oxygenated products. An exception to this general behavior is the photosensitized dimerization of tyrosine (Tyr), where O2 does not participate as a reactant in any step of the pathway yielding Tyr dimers (Tyr2 ). In the pterin (Ptr) photosensitized oxidation of Tyr, O2 does not directly participate in the formation of Tyr2 and quenches the triplet excited state of Ptr, the reactive species that initiates the process. However, O2 is necessary for the dimerization, phenomenon that we have named as the oxygen paradox. Here, we review the literature on the photosensitized formation of Tyr2 and present results of steady-state and time resolved experiments, in search of a mechanistic model to explain the contradictory role of O2 in this photochemical reaction system.

Proton transfer reactions are ubiquitous in chemistry, especially in aqueous solutions. We investigate photoinduced proton transfer between the photoacid 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) and water using fast fluorescence spectroscopy and ab initio molecular dynamics simulations. Photoexcitation causes rapid proton release from the HPTS hydroxyl. Previous experiments on HPTS/water described the progress from photoexcitation to proton diffusion using kinetic equations with two time constants. The shortest time constant has been interpreted as protonated and photoexcited HPTS evolving into an "associated" state, where the proton is "shared" between the HPTS hydroxyl and an originally hydrogen bonded water. The longer time constant has been interpreted as indicating evolution to a "solvent separated" state where the shared proton undergoes long distance diffusion. In this work, we refine the previous experimental results using very pure HPTS. We then use excited state ab initio molecular dynamics to elucidate the detailed molecular mechanism of aqueous excited state proton transfer in HPTS. We find that the initial excitation results in rapid rearrangement of water, forming a strong hydrogen bonded network (a "water wire") around HPTS. HPTS then deprotonates in ≤3 ps, resulting in a proton that migrates back and forth along the wire before localizing on a single water molecule. We find a near linear relationship between the emission wavelength and proton-HPTS distance over the simulated time scale, suggesting that the emission wavelength can be used as a ruler for the proton distance. Our simulations reveal that the "associated" state corresponds to a water wire with a mobile proton and that the diffusion of the proton away from this water wire (to a generalized "solvent-separated" state) corresponds to the longest experimental time constant.

Newly designed push-pull ligands (L1 and L2) with bithiophene (bth) as a donor and phenazine (phz) or quinoxalino[2,3-b]quinoxaline (qxq) as acceptors were synthesized and also incorporated with a bipyridyl Ru(II) complex to give Ru1 and Ru2, respectively. The ultrafast photophysical dynamics of the ligand and their respective Ru(II) complexes were well-characterized using time-resolved spectroscopies and quantum chemical calculations. Photoinduced charger transfer (CT) and intersystem crossing (ISC) processes were directly observed for L1 and L2. In addition, the interplay of three different triplet excited states was directly observed in the related Ru(II) complexes. The lowest-lying triplet excited states of the ligands and their respective Ru(II) complexes were both attributed to the CT transitions from donor (bth) to acceptor (phz or qxq) and result in 3ICT (intramolecular charge transfer) and 3ILCT (intraligand charge transfer) excited states, respectively. The lifetimes of the lowest-lying triplet excited states of L1, L2, Ru1, and Ru2 were measured to be 21.3, 50.4, 2.75, and 4.16 μs, respectively.

In the search for new multifunctional materials, particularly for application in solid-state lighting, a set of terbium salicylato (Sal) complexes of general composition [Cat][Tb(Sal)4] with the commonly ionic liquid-forming (IL) cations [Cat] = (2-hydroxyethyl)trimethylammonium (choline) (Chol+), diallyldimethylammonium (DADMA+), 1-ethyl-3-methylimidazolium (C2C1Im+), 1-butyl-3-methylimidazolium (C4C1Im+), 1-ethyl-3-vinylimidazolium (C2Vim+), and tetrabutylphosphonium (P4444+) were synthesized. All Tb compounds exhibit strong green photoluminescence of high color purity by energy transfer from the ligand in comparison with what the analogous La compounds show, and quantum yields can reach up to 63% upon ligand excitation. When excited with an HF generator, the compounds show strong green electroluminescence with the same features of mission. The findings promise a high potential of application as emitter materials in solid-state lighting. As an additional feature, the Tb compounds show a strong response to applied external fields, rendering them multifunctional materials., Terbium-containing organic-inorganic hybrid materials such as ionic complexes allow for unique property combinations that can open up new applications

This paper presents a new approach for material removal on silicon at atomic and close-to-atomic scale assisted by photons. The corresponding mechanisms are also investigated. The proposed approach consists of two sequential steps: surface modification and photon irradiation. The back bonds of silicon atoms are first weakened by the chemisorption of chlorine and then broken by photon energy, leading to the desorption of chlorinated silicon. The mechanisms of photon-induced desorption of chlorinated silicon, i.e., SiCl2 and SiCl, are explained by two models: the Menzel–Gomer–Redhead (MGR) and Antoniewicz models. The desorption probability associated with the two models is numerically calculated by solving the Liouville–von Neumann equations for open quantum systems. The calculation accuracy is verified by comparison with the results in literatures in the case of the NO/Pt (111) system. The calculation method is then applied to the cases of SiCl2/Si and SiCl/Si systems. The results show that the value of desorption probability first increases dramatically and then saturates to a stable value within hundreds of femtoseconds after excitation. The desorption probability shows a super-linear dependence on the lifetime of excited states.

A series of platinum(II) bimetallic complexes were studied to investigate the effects of ligands on both the geometric and electronic structure. Modulating the Pt-Pt distance through the bridging ligand architecture was found to dictate the nature of the lowest energy electronic transitions, localized in one-half of the molecule or delocalized across the entire molecule. By reducing the separation between the platinum atoms, the lowest energy electronic transitions will be dominated by the metal-metal-to-ligand charge transfer transition. Conversely, by increasing the distance between the platinum atoms, the lowest electronic transition will be largely localized metal-to-ligand charge transfer or ligand centered in nature. Additionally, the cyclometalating ligands were observed to have a noticeable stabilizing effect on the triplet excited states as the conjugation increased, arising from geometric reorientation and increased electron delocalization of the ligands. Such stabilization of the triplet state energy has been shown to alter the excited state potential energy landscape as well as the excited state trajectory.

A series of photochromic complexes with general formulas of [Ru(bpy)2(NHC-SR)]2+ and [Ru(bpy)2(NHC-S(O)R)]2+ were prepared and investigated by X-ray crystallography, electrochemistry, and ultrafast transient absorption spectroscopy {where bpy is 2,2'-bipyridine and NHC-SR and NHC-S(O)R are chelating thioether (-SR) and chelating sulfoxide [-S(O)R] N-heterocyclic carbene (NHC) ligands}. The only differences between these complexes are the nature of the R group on the sulfur (Me vs Ph), the identity of the carbene (imidazole vs benzimidazole), and the number of linker atoms in the chelate (CH2 vs C2H4). A total of 13 structures are presented {four [Ru(bpy)2(NHC-SR)]2+ complexes, four [Ru(bpy)2(NHC-S(O)R)]2+ complexes, and five uncomplexed ligands}, and these reveal the expected coordination geometry as predicted from other spectroscopy data. The data do not provide insight into the photochemical reactivity of these compounds. These carbene ligands do impart stability with respect to ground state and excited state ligand substitution reactions. Bulk photolysis reveals that these complexes undergo efficient S → O isomerization, with quantum yields ranging from 0.24 to 0.87. The excited state reaction occurs with a time constant ranging from 570 ps to 1.9 ns. Electrochemical studies reveal an electron transfer-triggered isomerization, and voltammograms are consistent with an ECEC (electrochemical-chemical electrochemical-chemical) reaction mechanism. The carbene facilitates an unusually slow S → O isomerization and an unusally fast O → S isomerization. Temperature studies reveal a small and negative entropy of activation for the O → S isomerization, suggesting an associative transition state in which the sulfoxide simply slides along the S-O bond during isomerization. Ultrafast studies provide evidence of an active role of the carbene in the excited state dynamics of these complexes.

Photosensitizing assemblies of pyrazine derivative PDA have been developed which exhibit a high photostability, 'lighted' excited state, balanced redox potential, high transportation potential and activate oxygen via type-I pathway only. These PDA assemblies in combination with Cu(II) ions catalyze the CuAAC reaction via in situ reduction of Cu(II) ions without any reducing or stabilizing agent. The present protocol has wide substrate scope with recyclability of the catalytic system up to six catalytic cycles and is applicable to gram-scale synthesis.

The photophysical mechanisms of tellurium-substituted uracils were studied at the multistate complete-active-space second-order perturbation level with a particular focus on how the position and number of tellurium substitutions affect their nonadiabatic relaxation processes. Electronic structure analysis reveals that the lowest several excited states are closely concerned with the n and π orbitals at the Te7-C2 [Te8-C4] moiety of 2-tellurouracil (2TeU) [4TeU and 24TeU]. Both planar and twisted minima were optimized for 2TeU, whereas only planar ones were obtained for 4TeU and 24TeU, except for a twisted T1 minimum of 4TeU. Based on intersection structures and linearly interpolated internal coordinate paths, we proposed several feasible excited-state deactivation paths. It is found that the relaxation channels for 2TeU are more complicated than those of 4TeU and 24TeU. The electronic population transfer to the T1 state for 2TeU is easier than that for 4TeU and 24TeU in consideration of the barrier heights from the S2 Franck-Condon point to the S2/S1 or S2/T2 intersections. In addition, the recovery of the ground state from the T1 state for 2TeU will be more efficient than that for the other two systems as well.

Effects of the hot and dense plasma on the doubly excited states (DES) of the four-electron beryllium-like ions (BLI) with Z varying from 4 to 10 have been investigated by applying the stabilization method. The Debye–Huckel model has been used to describe the effective potential in the plasma. The four-electron ions are treated as an effective three-body problem by means of the method of model potential. One, four and five DESs lying above the 1s 2 2p threshold are found to exist in the ions having Z = 4 , Z = 5 and Z = 6 − 10 respectively. For the plasma-free case our results for the energy and width of the DESs are in agreement with the available results in the literature. A detailed study is made on the changes of energy and width of the DESs of the ions with varying plasma screening strength. Particular emphasis is given to explore the effects of the plasma on the whole sequence of ions.

Composites have been prepared via thermal decomposition of gel-like mixtures containing yttrium, aluminum, and europium(III) salts and ethyl acetate as a basic component. Luminescence of the composites is due to Eu3+ 5D0,1 → 7Fj electronic transitions. The luminescence is excited in intrinsic absorption bands of the Eu3+ ions and as a result of resonance vibrational energy transfer from the host to their excited state levels and transitions of O2– 2p electrons to the europium 4f orbital. The luminescence and luminescence excitation spectra demonstrate changes in the peak position of individual bands, redistribution of their intensity, and changes in their Stark structure. The observed changes are related to the different fractions of fluorine atoms in the composition of activator centers, their concentration, and the Y3+ : Al3+ atomic ratio in the synthesis products, obtained at a temperature of 800°C and synthesis times from 4 to 12 h and differing in phase composition and structure.

A large-bore Sr vapor laser excited in a nanosecond pulsed longitudinal discharge is reported. The optimal discharge conditions for achieving a maximal average output power at several Sr atom and ion lines in the mid-IR spectral range are determined. High average output power of 29 W (at 25 kHz pulse repetition frequency) and laser pulse energy of 2.9 mJ (at 5 kHz pulse repetition frequency) are obtained at the multiline operation. These values are more than two times better than the ones achieved so far with a single-tube strontium or strontium halide vapor lasers.

This paper presents the reaction mechanism, cross sections, and product energy partitioning for the O + CO2 reaction, calculated using Born-Oppenheimer molecular dynamics simulations with the quasiclassical trajectory (BOMD-QCT) method. At collision energies up to 9.5 eV, three reactions, oxygen exchange (above ∼1.5 eV), abstraction (above ∼5.5 eV), and dissociation (above ∼7.5 eV) occur, with abstraction and dissociation involving either an insertion-elimination mechanism or a stripping mechanism. The insertion-elimination mechanism involves the formation of a planar CO3 intermediate which lies 0.52 eV above the ground-state CO2; the energetic barrier for oxygen abstraction via this mechanism is 3.52 eV. Interestingly, the insertion-elimination mechanism predominately contributes to the cross sections at collision energies just above the effective energetic threshold for the abstraction and dissociation reactions; at higher collision energies, the contribution from the stripping mechanism increases and eventually dominates. At a collision energy of 9.5 eV, the cross sections for oxygen exchange, abstraction, and dissociation are 4.17 a02, 1.58 a02, and 0.68 a02, respectively. The lower reaction cross sections, higher effective reaction barrier, and product energy distribution of the stripping mechanism were attributed to the short lifetime (28 fs) of the OCOO species compared with that of the CO3 species (45 fs) that arises in the insertion-elimination mechanism. For the exchange reaction, it is found that roughly 40% of the reactant translational energy ends up in CO2 vibration, which provides a single-collision mechanism to produce highly excited CO2. We also studied intersystem crossing effects using trajectory surface hopping calculations and find no changes compared to single surface (triplet) calculations at energies below 7.5 eV; however, at 7.5 eV and higher the abstraction cross sections are changed by as much as 20%, and the (very small) dissociation cross sections are changed by factors of four or more.

Investigation of temperature-dependent photoluminescent properties of potassium perylene-3,4,9,10-tetracarboxylate (K4PTC), a molecule with no internal rotational degrees of freedom, shows aggregation-induced enhanced emission at room temperature. The different excitonic emission processes are dependent of temperature, some of which quenches in an intermediate temperature range (from 50 to 150 K). The exciton excited states switching phenomenon from "dark" to "bright" states is observed and its explained using Herzberg-Teller selection rule. K4PTC is a molecule comparable to the size of its precursor, perylene-3,4,9,10-tetracarboxylic anhydride (PTCDA) and is highly soluble in water, contrary to PTCDA, which is poorly soluble in most solvents. Powder x-ray diffraction measurements corroborate a lesser degree of ordering of bulk K4PTC compared to bulk PTCDA. The green luminescent molecule could, in principle, be used as a biomarker, or in photodynamic therapy, if further studies show relatively low toxicity.

We report a measurement of the photoionization cross-section of the lithium 2P3/2 state in a magneto-optical trap (MOT) by means of a single-frequency cw laser. Intensity of the photoionizing radiation seen by atoms is determined by means of averaging the intensity distribution of the photoionizing beam over the spatial distribution of trapped atoms. We use the photoionizing laser beam with large waist to reduce a possible misalignment between the photoionizing beam and the MOT density distribution. The excited state fraction is also accurately measured under our MOT conditions. The near-threshold photoionization cross-section of lithium-7 2P3/2 state at λPI = 349.846(1) nm is found to be equal to σ = 13.7(1.4) Mb, with better accuracy in comparison with the previous measurements. We study the variation of the photoionization cross section on the polarization of the ionizing beam. Further experiments are suggested.

Irradiation of dilute mixtures of NH3 and O2 dispersed in solid Ne at 3.6 K with light of wavelengths 200, 192.5, 173, and 143 nm from a synchrotron initiated photochemical dissociation of those precursors and the production of N, NH, NH2, O, O3, HO2, NO, NO2, N2O, H2O, HONO in both s-cisoid and s-transoid rotational isomers, and HONO2, detected according to their spectra in mid-infrared absorption from 450 to 4000 cm−1 and in absorption and emission from 200 to 1100 nm.

A series of platinum(II) complexes supported by terphenyl diacetylide as well as diimine or bis-N-heterocyclic carbene (NHC) ligands have been prepared. The diacetylide ligands adopt a cis coordination mode featuring non-planar terphenyl moieties as revealed by X-ray crystallographic analyses. The electrochemical, photophysical and photochemical properties of these platinum(II) complexes have been investigated. These platinum(II) diimine complexes show broad emission with peak maxima from 566 nm to 706 nm, with two of them having emission quantum yields >60% and lifetimes

We explore the photophysical properties of a family of Ru(II) complexes, Ru-ip-nT, designed as photosensitizers for photodynamic therapy (PDT). The complexes incorporate a 1H-imidazo[4,5-f][1,10]-phenanthroline (ip) ligand appended to one or more thiophene rings. One of the complexes studied herein, Ru-ip-3T (known as TLD1433), is currently in Phase II human clinical trials for treating bladder cancer by photodynamic therapy (PDT). The potent photocytotoxicity of Ru-ip-3T is attributed to a long-lived intraligand charge-transfer triplet state. The accessibility of this state changes upon varying the length (n) of the oligothiophene substituent. In this paper we highlight the impact of n on the ultrafast photoinduced dynamics in Ru-ip-nT, leading to the formation of the function-determining long-lived state. Femtosecond time-resolved transient absorption combined with resonance Raman data was used to map the excited-state relaxation processes from the Franck-Condon point of absorption to the formation of the lowest-energy triplet excited state, which is a triplet metal-to-ligand charge transfer ((3)MLCT) excited state for Ru-ip-0T-1T and an oligothienyl-localized triplet intraligand charge transfer ((3)ILCT) excited state for Ru-ip-2T-4T. We establish the structure-activity relationships with regard to changes in the excited state dynamics as a function of thiophene chain length, which alters the photophysics of the complexes and presumably impacts the photocytotoxicity of these photosensitizers.

In this work, a novel phenanthro[9,10-d]imidazole-zinc coordination complex (Zn(TPPI)2) is reported. This compound exhibits suitable physical properties for a host material. First, its highest occupied molecular orbital (HOMO) (− 5.33 eV) energy level is favorable for hole injection from transporting layer. Second, its small singlet–triplet splitting (0.31 eV) can reduce the intrinsic energy loss from singlet to triplet excited state and promote the device efficiency. Finally, its good thermal stability (decomposition temperature: 495 °C) favors evaporation preparation of uniform films. As a result, yellow–red and red phosphorescent devices which utilize Zn(TPPI)2 as host display high efficiencies (yellow–red: 58.35 cd/A, 70.52 lm/W, 20.82%) (red: 15.89 cd/A, 16.09 lm/W and 19.05%). The performance of red device is comparable to the best results of previous publications on corresponding emitter. Meanwhile, the undoped device of Zn(TPPI)2 exhibits high efficiencies (3.79 cd/A, 3.97 lm/W, 2.47%) in zinc-complex blue emitters. These results demonstrate that Zn(TPPI)2 is a good blue emitter and host material.

The development of NIR emitters based on earth‐abundant elements is an important goal in contemporary science. We present here Cr(0), Mo(0), and W(0) carbonyl complexes with a pyridyl‐mesoionic carbene (MIC) based ligand. A detailed photophysical investigation shows that all the complexes exhibit dual emissions in the VIS and in the NIR region. The emissive excited states are assigned to two distinct triplet states by time‐resolved emission and step‐scan FTIR spectroscopy at variable temperature, supported by density functional theory. In particular, the NIR emissive triplet state exhibits unprecedented lifetimes of up to 600±10 ns and quantum yields reaching 1.7 ⋅ 10−4 at room temperature. These are the first examples of Cr(0), Mo(0) and W(0) complexes that emit in the NIR II region., This work presents emissive Cr(0), Mo(0), and W(0) complexes that contain a bidentate pyridyl‐mesoionic carbene ligand and CO coligands. These systems exhibit dual vis and NIR II emissions at room temperature. The emissive excited triplet states were characterized by temperature‐dependent luminescence and step‐san FTIR spectroscopy in combination with density functional theory. The NIR quantum yield increases from Cr(0) over Mo(0) to W(0), reaching a very high value of 1.4 ⋅ 10−3 at room temperature.

In organic and organometallic solids, upon electronic excitation, most intermolecular structural relaxations follow a pathway along the π-π stacking direction or metal-metal bond with significant coupling strength. Differently, we discovered that the self-assembled platinum(II) complexes, Pt(fppz)2, exhibit an unusual interchain contraction. The ground-state and excited-state multiple local minima were distinguished by temperature-dependent excitation/emission spectra, indicating the existence of multiple local minima. The time-resolved emission decay revealed the excited-state structural relaxation lifetime with τobs = 41 ns at 298 K. Temperature-dependent X-ray diffraction analysis showed that the packing geometries contract 0.6 A along the interchain direction (a-axis) at 50 K compared to the geometries at 298 K. Such structural displacements render the slow internal conversion rate in the excited states. We thus demonstrate the correlation between the packing geometries and the excited-state dynamics of the self-assembled Pt(II) complexes, shedding light on the unique direction of interchain structural deformation of the molecular aggregates.

Previous work was successful in synthesizing a nickel amine, [CztBu(PyriPr)(NH2-PyriPr)], by double C-H activation and functionalization via irradiating a disphenoidal Ni(II) azido complex, [CztBu(PyriPr)2NiN3]. The present work seeks to expand upon the earlier research and to substitute the metal with iron or cobalt. Density functional theory (DFT)-B3LYP/6-31+G(d') and APFD/Def2TZVP-was used to simulate the generation of an intermediate with significant nitridyl radical character after the loss of N2 from the starting azido complex. DFT and time-dependent density functional theory (TDDFT) were also used to propose a detailed pathway comprised of intermediates of low, intermediate, or high spin multiplicity and photogenerated excited states for the reaction of the azido complex, [CztBu(PyriPr)2MN3], to form the amine complex [CztBu(PyriPr)M(NH2-PyriPr)], M = Co, Ni, or Fe.

A new praseodymium-based borate crystal Pr2CaB10O19 (PCB) has been grown through the high temperature solution method. PCB crystallizes in monoclinic space group C2 with unit cell parameters of a = 10.9475(10) A, b = 6.5343(7) A, c = 9.0336(8) A, β = 91.652(3)°, and Z = 2, in which B5O12 groups and PrO10 and CaO8 polyhedra constitute the three-dimensional framework. PCB exhibits a similar second harmonic response intensity to that of La2CaB10O19 and an intense orange fluorescence emission with a long fluorescence lifetime at about 610 nm excited by a xenon lamp light of 466 nm. The band gap, partial density of states, and birefringence have been investigated via theoretical calculations.

One of the rate limiting steps in catalytic ammonia synthesis is a nitrogen dissociation on a catalyst surface, which can be promoted by vibrational excitation of nitrogen molecules. In this work, the efficiency of plasma assisted heterogeneous nitrogen activation via vibrational excitation on the Ru surface is investigated. The analysis consists of two parts: in the first, ab initio calculations are performed for the adsorption and dissociation energy pathways of $${\text{N}}_{{\text{2}}}$$ on terrace and step sites and heterogeneous vibrational energy relaxation time of adsorbed nitrogen molecule is calculated using ab initio molecular dynamics. The second part includes the solution of the chemical kinetic equations for vibrationally excited molecules both in the gas phase and on the surface, and an estimation of energy cost of heterogeneous plasma activation of nitrogen. It is shown that heterogeneous vibrational energy relaxation of nitrogen molecule on the Ru surface is rather fast, and results in relatively high energy cost of vibrational nitrogen activation, which is 16 eV/molec for atmospheric pressure and 5 eV/molec for P = 4 Torr according to our calculations.

The effects of discharge conditions and catalysts on CO2 methanation under the plasma were investigated via In-Situ transmission FTIR and OES analysis. The bare Al2O3, Ni/Al2O3 and Ru/Al2O3 catalysts were coated on the ZnSe window using the modified sol–gel method for In-Situ transmission FTIR analysis. It was confirmed from the OES analysis that the intensity of excited hydrogen increased in all catalysts as the discharge frequency and voltage increased, and the increment of H+ peak intensity was the largest in the Ru/Al2O3 catalyst. In addition, it was found from the In-Situ transmission FTIR analysis that the O-H band was all disappeared as the frequency and voltage increased. In conclusion, the increased H+ with the decomposition of O–H led to the increase in the CH4 conversion, resulting in the highest CH4 conversion in the Ru/Al2O3 catalyst.

Yb:CaWO4 and Yb, Nb:CaWO4 single crystals have been grown by the Czochralski method in air and in protective atmospheres and subjected to additional annealing in air, in CO/CO2 atmosphere, and in forevacuum. The optical absorption spectra in the range from 250 to 1500 nm and the luminescence spectra of these crystals in the visible and near-IR spectral regions upon UV excitation have been investigated. It is shown that additional introduction of Nb5+ ions into Yb:CaWO4 crystal increases by an order of magnitude (almost to unity) the Yb3+ distribution coefficient between CaWO4 crystal and melt. It is found that optical excitation of the crystals in the range of 260–355 nm induces down-conversion luminescence of Yb3+ ions from the 2F5/2 level in the vicinity of 1 µm. An increase in the oxidative potential of synthesis atmosphere, as well as the introduction of niobium into the crystal composition, weakens this luminescence. A consistent pattern explaining the nature of the donor centers involved in down-conversion population of excited state 2F5/2 of Yb3+ in the crystals is proposed. Within this pattern, Yb2+ ions play the role of these donor centers. Another (much less efficient) mechanism of population of the 2F5/2 level is intracenter relaxation from the higher-lying charge transfer excited state within Yb3+ ions. At the same time, it is confirmed that color centers based on oxygen vacancies and partially reduced tungsten ions, as well as self-trapped excitons on tungstate complexes, are not involved in population of the excited state 2F5/2 of Yb3+ ions, and the optical centers formed in Yb:CaWO4 crystals as a result of vacuum annealing suppress ytterbium luminescence.

In the present study Eu2O3 doped Li2O–Si2O–B2O3 glasses (LSBE) were synthesized by the melt quench technique. The physical, thermal, and spectroscopic properties of prepared glasses by various techniques have been investigated in this work. The powder X-ray diffraction study confirms the amorphous nature of glass samples. The various absorption bands assigned were observed from ground level 7F0 to various excited states within the 4f shell. Emission spectra exhibit bands in the visible region from 450 to 750 nm. The spectra show some sharp peaks belongs to 4f electronic transitions of Eu3+ ion at 5D0 → 7F0 (578 nm), 5D0 → 7F1 (590 nm), 5D0 → 7F2 (614 nm), 5D0 → 7F3 (652 nm), and 5D0 → 7F4 (701 nm). The band at 614 nm corresponds to 5D0 →7F2 transition is hypersensitive among all bands. From the CIE chromaticity diagram, the glass sample LSBE-5 shows the highest emission intensity with color coordinates x = 0.56, y = 0.33 among all glass samples.

Ruthenium(II) complexes, like [(tbbpy)2Ru(dppz)]2+ (Ru-dppz; tbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine, dppz = dipyrido-[3,2-a:2',3'-c]phenazine), have emerged as suitable photosensitizers in photoredox catalysis. Since then, there has been ongoing interest in the design of π-extended Ru-dppz systems with red-shifted visible absorption maxima and sufficiently long-lived excited states independent of the solvent or pH value. Herein, we explore the photophysical properties of protonation isomers of the linearly π-extended [(tbbpy)2Ru(L)]2+-type complexes bearing a dppz ligand with directly fused imidazole (im) and methyl-imidazole units (mim) as L. Steady-state UV-vis absorption, resonance Raman, as well as time-resolved emission and transient absorption spectroscopy reveal that Ru-im and Ru-mim show desirable properties for the application in photocatalytic processes, i.e., strong visible absorbance and two long-lived excited states in the 3ILCT and 3MLCT manifold, at pH values between 3 and 12. However, protonation of the (methyl-)imidazole unit at pH ≤ 2 unit causes decreased excited-state lifetimes and an emission switch-off.

Developing highly active catalysts for hydrogen evolution reaction is vital for large-scale and efficient production of hydrogen through water splitting. In this study, we reported scale-up TiO2/LaFeO3 composite catalysts with multiple heterojunctions synthesized via facile solid-phase reaction and investigated their hydrogen evolution reaction (HER) performance in both acidic and alkaline solutions. To be excited, under AM1.5 simulated sunlight irradiation, the working electrode decorated by TiO2/LaFeO3 presents a higher current density with 10 mV/cm2 at 0.55 V in a 0.5 M H2SO4 solution, suppressing the corresponding performance with the occasion of pure electrocatalysis. Importantly, the hydrogen evolution efficiency can reach 7.62 mmol h−1 cm−2, overwhelming approximately 5.3 times higher than that of commercial P25 (1.43 mmol h−1 cm−2) with exceptional stability via imposing simulated sunlight and a bias of 500 mV. Therefore, such excellent catalysts could serve as an alternative to reach remarkable HER performance via fossil fuels free technology, potentially making contribution toward the goal of global “carbon neutral” by 2050.

Recently, a new production process of various metals and alloys from their oxides and ores by Cold Hydrogen Plasma (CHP) has been introduced. CHP is produced by using a microwave oven, using less power than the microwave ovens used domestically for cooking food. CHP is very efficient in producing metals and alloys from their oxides because of excited species. These excited species decrease the thermodynamic and kinetic barriers of reduction, making the reduction easier and faster. In the current investigation, nickel has been produced from nickel oxide (NiO) pellets of ~ 2.5 gm to ~ 7.5 gm. The hydrogen flow rate ranges from 70 ml/s to 150 ml/s, and power varies from 600 to 750 W. The time taken for reduction changed between 300 to 1200 s. CHP reduces very fast due to the active oxygen present in it. This faster production of nickel from pellets upto ~ 7.5 gm at such low power opens up the possibilities of upscaling the reduction of NiO by CHP.

Photodynamic therapy (PDT) involving the generation of cytotoxic reactive oxygen species under light in the presence of sufficient oxygen has been widely used in diagnosing and treating cancer. However, the ubiquitous hypoxia in many solid tumors due to their abnormal proliferation and vascularization has greatly compromised the therapeutic effect. We have designed and prepared a tumor therapeutic nanoplatform for improving PDT based on defective TiO[Formula: see text] (d-TiO[Formula: see text] with the consideration that the continuous PDT would cause hypoxic tumor microenvironment (HTM) in which many hypoxia-sensitive drugs might be activated to exert the antitumor activities. The inorganic d-TiO[Formula: see text] nanoparticles (NPs) were firstly prepared and then modified by APTES to obtain the mesoporous d-TiO[Formula: see text]@SiO2NPs. The organic photosensitizer pyropheophorbide-a (PPa) and hypoxic-sensitive agent 6-aminoflavone (AF) were then adsorbed in the mesoporous SiO2, followed by further hydrophilic PEGylation to improve the biocompatibility. Defective d-TiO[Formula: see text] and the PPa could simultaneously consume oxygen after light excitation, while the resulted HTM was utilized to activate the hypoxic-sensitive agent 6-aminoflavone (AF) to trigger anti-cancer effect. The prepared d-TiO[Formula: see text]@SiO2/PPa/AF@PEG NPs were stable in normal physiological environment, and could continuously release PPa and AF under slightly acidic conditions. The in vitro experiments against cancer cells suggested that the combination of PPa and AF displayed significantly enhanced antitumor activities than that of monotherapy. Therefore, this research offered a potential application for 6-aminoflavone in PDT-induced hypoxia to improve the antitumor effects.

A g-C3N4/CdSe quantum dot/[Fe2S2(CO)6] composite has been successfully constructed. The structure and chemical composition of the composite were investigated via, inter alia, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The ability of the assembly to act as a photocatalyst for proton reduction to form hydrogen gas was studied. With visible light irradiation for 4 h, the total H2 production catalyzed by the g-C3N4/CdSe quantum dot/[Fe2S2(CO)6] composite was found to be 9 times as high as a corresponding CdSe/[Fe2S2(CO)6] assembly and significantly higher than either the CdSe quantum dots or g-C3N4 alone. The g-C3N4 support/matrix was found to enhance the stability and efficiency of the CdSe quantum dot/iron carbonyl cluster assembly in the photocatalytic hydrogen evolution process. Results from recycling tests showed that the g-C3N4/CdSe quantum dot/[Fe2S2(CO)6] composite is a sustainable and robust photocatalyst, maintaining the same activity after three cycles. The photoinduced charge carrier transfer dynamics in the g-C3N4/CdSe quantum dot/[Fe2S2(CO)6] composite system has been investigated by transient absorption (TA) and time-resolved photoluminescence (TRPL) spectroscopies. The spectroscopic results indicate efficient hole transfer from the valence band of the excited CdSe quantum dots to the molecular iron carbonyl clusters and from the defect state of the quantum dots to g-C3N4 in the g-C3N4/CdSe quantum dot/[Fe2S2(CO)6] composite, which significantly inhibits the recombination of photogenerated charge carriers in CdSe quantum dots and boosts the photocatalytic activity and stability for hydrogen evolution. Energy transfer from g-C3N4 to the CdSe quantum dot/[Fe2S2(CO)6] assembly with a time constant of 0.7 ns also contributed to the charge transfer process.

The recent isolation of molecular tetravalent lanthanide complexes has enabled renewed exploration of the effect of oxidation state on the single-ion properties of the lanthanide ions. Despite the isotropic nature of the 8S ground state in a tetravalent terbium complex, [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4], preliminary X-band electron paramagnetic resonance (EPR) measurements on tetravalent terbium complexes show rich spectra with broad resonances. The complexity of these spectra highlights the limits of conventional X-band EPR for even qualitative determination of zero-field splitting (ZFS) in these complexes. Therefore, we report the synthesis and characterization of a novel valence series of 4f7 molecular complexes spanning three oxidation states (Eu2+, Gd3+, and Tb4+) featuring a weak-field imidophosphorane ligand system, and employ high-frequency and -field electron paramagnetic resonance (HFEPR) to obtain quantitative values for ZFS across this valence series. The series was designed to minimize deviation in the first coordination sphere from the pseudotetrahedral geometry in order to directly interrogate the role of metal identity and charge on the complexes' electronic structures. These HFEPR studies are supported by crystallographic analysis and quantum-chemical calculations to assess the relative covalent interactions in each member of this valence series and the effect of the oxidation state on the splitting of the ground state and first excited state.

Luminescent cuprous complexes are important coordination compounds due to their relative abundance, low cost and ability to display excellent luminescence. The structures of two CuIP2S-type cuprous complexes, namely, iodido(thiourea-κS)bis(triphenylphosphane-κP)copper(I), [CuI(CH4N2S)(C18H15P)2] or [CuI(TU)(TPP)2] (I), and (2,3-dihydrobenzimidazole-2-thione-κS)iodidobis(triphenylphosphane-κP)copper(I), [CuI(C7H6N2S)(C18H15P)2] or [CuI(DHBIT)(TPP)2] (II), are described. In these two structures, the complex molecules of both are constructed by one copper(I) centre, one iodide ion, two TPP ligands and one thione ligand (TU for I and DHBIT for II). The copper(I) centres of I and II are both located in a distorted CuIP2S tetrahedron and are coordinated by two P atoms from two TPP ligands, one S atom from the thione ligand and the I atom. The UV–Vis absorption and photoluminescence properties of these CuIP2S-type cuprous complexes have been studied using crystalline powder samples. Detailed time-dependent density functional theory (TD-DFT) calculations and wavefunction analysis reveal that the pale-blue–green phosphorescence emission should originate from intra-ligand (TPP for I and DHBIT for II) charge transfer, with a small component of the metal-to-ligand charge transfer 3(IL+ML)CT excited state.