Visible Excitation Research Articles

Photoelectrochemical Methanol Oxidation Under Visible and UV Excitation of TiO2-Supported TiN and ZrN Plasmonic Nanoparticles

TiN and ZrN refractory transition metal nitride nanoparticles (NPs) have recently emerged as an alternative to noble metals in plasmonic applications. However, plasmon-driven photocatalysis by ZrN NPs is largely unexplored. In this study, optical properties, morphology, crystal structure and surface composition of in-house synthesized and commercial ZrN nanoparticles (NPs) are vigorously characterized in order to select the best candidate material for evaluation of activity towards CH3OH photoelectrochemical oxidation. The photocatalytic activity of TiO2-supported ZrN NPs is compared to that of TiN/TiO2 as a function of NP loading and illumination wavelength. Our results indicate that optical properties and photocatalytic activity of ZrN/TiO2 are strongly affected by ZrN surface oxidation and agglomeration. We found that under visible illumination, both in-house synthesized 17 nm ZrN and commercial 30 nm TiN NPs promote TiO2 activity for CH3OH oxidation, while under visible + UV excitation, an inhibition effect is observed. The differences between the TiN/TiO2 and ZrN/TiO2 interfaces are discussed and the mechanisms of promotion/inhibition of TiO2 photocatalytic activity by ZrN and TiN NPs are proposed. Electromagnetic simulations are used to facilitate interpretation of experimental extinctions and photocatalytic activities.

Determination of ammonium in natural water using a quinoline-based o-dialdehyde fluorescent reagent with visible excitation wavelength.

In this paper, a novel and stable fluorescent reagent, quinoline-2,3-dicarbaldehyde (QDA), is synthesized as a probe to detect ammonium in natural water. Ammonium reacts with QDA in the presence of SO32- and Ca2+ to form a fluorescence product, which has maximum excitation and emission wavelengths at 429 nm and 518 nm. The concentration of reagents, the reaction temperature, the reaction time, and the pH in the final solution are investigated and optimized. The interferences of typical organic nitrogen and inorganic compounds are evaluated, and results prove that most volatile amines have little or negligible effect. Under the optimized conditions, this method provides a limit of detection of 0.065 μmol L-1, a calibration range of 0.216-9 μmol L-1, and reproducibility (with a relative standard deviation) of 1.9% for 1.5 μmol L-1 ammonium. For water sample analysis, the proposed method provides comparable results to those of the conventional o-phthalaldehyde method but has longer reagent stability (42 days).

Imaging and analysis of near-infrared fluorescence from tiger chert and Native American tiger chert artifacts

Tiger chert was used extensively by Native American people of the Clovis lithic industry as the source material for stone tools. Although tiger chert occurs naturally only within the Bridger Formation of Southwest Wyoming, tiger chert artifacts have been found throughout the American west. This paper explores the previously unreported near-infrared fluorescence emitted from tiger chert upon visible excitation. The two objectives of this study were to demonstrate the utility of near-infrared fluorescence imaging (NIRFI) to tiger chert artifacts and to identify the chemical origin of the observed fluorescence. Tiger chert was analyzed by visible and NIRFI, SEM-EDX, ICP-OES, and fluorescence spectroscopy. NIRFI can be easily used to discriminate between tiger chert artifacts and the environment, since most materials such as soil and most rocks appear black in the resultant image. This suggests NIRFI should be utilized by archeologists at any site where tiger chert has been previously identified. Additionally, NIRFI was used to differentiate between tiger chert artifacts and an artificially weathered, recently-knapped tiger chert point, suggesting that NIRFI could be used to distinguish genuine tiger chert artifacts from counterfeits. Tiger chert fluorescence was confined to the manganese-and-iron-rich surface, suggesting the presence of desert varnish; however, red agate from the same site did not exhibit fluorescence, instead implicating tiger-chert-specific weathering. Thus, the chemical origin of fluorescence was not conclusively identified.

A novel blue-emitting Sr2Gd8(SiO4)6O2:Bi3+ phosphor with oxyapatite structure

A series of Sr2Gd8(SiO4)6O2 (SGSO):xBi3+ (x = 0.005, 0.007, 0.010, 0.030 and 0.050) phosphors were successfully synthesized by a high-temperature solid-phase route. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared (FT-IR), ultraviolet–visible diffuse reflectance (UV–Vis DR), photoluminescence excitation (PLE) and emission (PL) spectra were utilized to evaluate the samples. The characterization results show that the PLE spectra monitored at 440 nm present a broad band with the maximum at 315 nm. Besides, the pure SGSO possesses the space group P63/m crystal structure, in which the low symmetry C3 or Cs sites favor the transition from 3P1 to 1S0 of Bi3+, thus produce strong blue emission. According to the calculation of concentration quenching, the critical distance of energy transfer (ET) between adjacent Bi3+ is 23.48 Å, and it is concluded that the quenching mechanism is attributed to d-d interaction. Eventually, the International Commission on Illumination (CIE) chromaticity coordinates of phosphors are located in blue region, which can be suitable for practical application in the field of the white light-emitting diode (WLED) and plasma display panels (PDPs).

Preventing Photomorbidity in Long-Term Multi-color Fluorescence Imaging of Saccharomyces cerevisiae and S. pombe.

Time-lapse imaging of live cells using multiple fluorescent reporters is an essential tool to study molecular processes in single cells. However, exposure to even moderate doses of visible excitation light can disturb cellular physiology and alter the quantitative behavior of the cells under study. Here, we set out to develop guidelines to avoid the confounding effects of excitation light in multi-color long-term imaging. We use widefield fluorescence microscopy to measure the effect of the administered excitation light on growth rate (here called photomorbidity) in yeast. We find that photomorbidity is determined by the cumulative light dose at each wavelength, but independent of the way excitation light is applied. Importantly, photomorbidity possesses a threshold light dose below which no effect is detectable (NOEL). We found, that the suitability of fluorescent proteins for live-cell imaging at the respective excitation light NOEL is equally determined by the cellular autofluorescence and the fluorescent protein brightness. Last, we show that photomorbidity of multiple wavelengths is additive and imaging conditions absent of photomorbidity can be predicted. Our findings enable researchers to find imaging conditions with minimal impact on physiology and can provide framework for how to approach photomorbidity in other organisms.

Comparison of Photocatalytic Activities of TiN and Zrn Nanoparticles Incorporated into TiO2matrix Under Visible Excitation

TiN and ZrN belong to a new class of refractory transition metal nitride plasmonic materials that exhibit a localized surface plasmon resonance in visible and near-infrared spectral regions [1, 2]. TiN and ZrN exhibit an optical response analogous to that of the extensively studied plasmonic Au nanostructures thereby offering inexpensive, chemically and mechanically robust material alternative to Au for plasmon-mediated photocatalytic reactions. When plasmonic nanoparticle (NP) is integrated with a semiconducting TiO2 support, properties of the interface become important. Prior research highlighted two significant differences between the TiN/TiO2 and Au/TiO2 interfaces [3]. First, TiN does not form a Schottky barrier with TiO2, leading to poor separation of photogenerated carriers in the absence of an external bias. However, under positive potential bias, higher efficiencies of hot carrier collection are observed for TiN/TiO2 system as compared to Au/TiO2 [4]. Second, photocarriers generated via interband transitions in TiN may play a major role in photoelectrochemical reactions at the TiN/TiO2 interface, in contrast to the intraband transitions in Au NPs at the Au/TiO2 interface [4, 5]. Herein, we extend our scope to the ZrN/TiO2 interface that is predicted to benefit from higher rates of hot carrier generation in ZrN (vs TiN) [6].The plasmonically-sensitized TiN/TiO2 and ZrN/TiO2 photocatalysts were investigated for methanol (CH3OH) photoelectrochemical oxidation under visible excitation. The effect of plasmonic NPs loading, applied potential, pH and CH3OH concentration were examined. Near-and far-field electrodynamic simulations and quantum calculations were performed to facilitate interpretation of photoelectrochemical experiments. Using COMSOL software, we computed both free-standing TiN and ZrN NPs, as well as embedded into a TiO2 matrix. The rates of resonant optical generation of over-barrier hot electrons were calculated using the quantum formalism.ZrN powder prepared in lab and commercial TiN NPs (PlasmaChem) were dispersed into a P25 TiO2 matrix by ultrasonically agitating metal nitride NPs and TiO2 powders in H2O overnight. ZrN NPs were synthesized by ammonolysis of Zr(NMe2)4 and subsequent annealing at 950 °C under NH3 flow; clean Zr(NMe2)4 was prepared following a literature protocol [7]. Electrochemical experiments were conducted in a three-electrode photoelectrochemical cell. Thin films of TiN/TiO2 and ZrN/TiO2 deposited onto fluorine-tin-oxide (FTO)-coated glass served as working electrodes. Platinum foil and Ag/AgCl in 3 M NaCl (BioLogic, Inc) were used as a counter and reference electrodes, respectively. Nine single-color LED lights were employed for illumination. The intensities varied between 10-100 mW/cm2, and 300-480 mW/cm2 in the wavelength range of 490-670 and 730-960 nm, respectively.

Rare Earth Doped Nanoparticles for Theranostics

In the biomedical field, research has recently focused on nanoparticle-based “theranostic” agents for the treatment of diverse diseases, including cancer. This new paradigm in personalized medicine intends to exploit nanoplatforms that carry both therapeutic and diagnostic (theranostic) modalities. Compared with delivering drugs or imaging agents separately, theranostic agents can simultaneously deliver them to specific sites, enabling detection and treatment of disease in a single procedure. Many theranostic nanoplatforms are triggered by light, however, the vast majority of these are limited in that the ultraviolet or visible excitation light used has minimal applicability in biological applications. Rare earth doped nanoparticles, on the other can be excited with biologically friendly near-infrared light (in the biological windows) and can emit in the ultraviolet, visible or near-infrared regions through a multiphoton upconversion process while simultaneously emitting in the near-infrared region (also in the 3 biological windows) through a Stokes or downshifted process. Hence, the upconversion luminescence can be used to trigger the therapeutic application (drug delivery, photodynamic therapy, etc.) while the near-infrared luminescence can be used for the diagnostic modality (bioimaging, nanothermometry/temperature sensing, etc).In this presentation, we will introduce rare earth doped nanoparticles and demonstrate their usefulness in theranostics. In particular, we will show that complex nanoparticle architectures can endow further functionality to these nanoparticles and discuss how they can be used for temperature sensing (nanothermometry) in biological systems.

Analysis of scarlet elf cup (Sarcoscypha coccinea) carotenoids in vivo by Raman spectroscopy

AbstractRaman spectroscopy, an established optical method of remote diagnostics of pigments and dyes, is applied here for the first time to the cup fungus Scarlet elf cup (Sarcoscypha coccinea or Plectania coccinea or Peziza coccinea) from the order Pezizales (Ascomycota). As‐collected fungi samples are investigated, not subject to any treatment. The dominant vibrational features in the acquired in vivo spectrum, around 1000, 1150, and 1500 cm−1, respectively, clearly indicate it is dominated by carotenoid(s). Contrary to most previous Raman studies of carotenoids, including few studies of fungi, which focused on the latter three strongest fundamental vibrations, we have resolved and analyzed in detail 30 vibrational bands, including rarely studied wavenumber range above 2000 cm−1. We discuss in detail the inferred from our spectral analysis carotenoid species in comparison with those previously reported for Sarcoscypha coccinea by other methods. In particular, we suggest two characteristic ring vibrations, at 1131 and 1283 cm−1, to be used as a measure of the ratio of astaxanthin and plectaniaxanthin to β‐carotene and lycopene in this and similar fungi. In addition, we report the fluorescence spectrum of this fungal species, present as background in the Raman spectrum at visible excitation. The results obtained in this work will facilitate subsequent more quantitative studies of carotenoid composition in other kinds of fungi and other microorganisms using Raman spectroscopy in combination with other techniques.

The Photoactive Excited State of the B12-Based Photoreceptor CarH.

We have used transient absorption spectroscopy in the UV-visible and X-ray regions to characterize the excited state of CarH, a protein photoreceptor that uses a form of B12, adenosylcobalamin (AdoCbl), to sense light. With visible excitation, a nanosecond-lifetime photoactive excited state is formed with unit quantum yield. The time-resolved X-ray absorption near edge structure difference spectrum of this state demonstrates that the excited state of AdoCbl in CarH undergoes only modest structural expansion around the central cobalt, a behavior similar to that observed for methylcobalamin rather than for AdoCbl free in solution. We propose a new mechanism for CarH photoreactivity involving formation of a triplet excited state. This allows the sensor to operate with high quantum efficiency and without formation of potentially dangerous side products. By stabilizing the excited electronic state, CarH controls reactivity of AdoCbl and enables slow reactions that yield nonreactive products and bypass bond homolysis and reactive radical species formation.

Experimental autoimmune orchitis induced by immunization with HSP in mice

A series of far-red-emitting Ca2M3(SiO4)2(PO4)O (M = La, Y) (CMSPO):xEu3+ (x = 0.05, 0.10, 0.20, 0.30, 0.40 and 0.50) phosphors were successfully synthesized by high-temperature solid-phase reaction. The fabricated samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared (FT-IR), ultraviolet–visible diffuse reflectance (UV–Vis DR), photoluminescence excitation (PLE) and emission (PL) spectra. Under 394 nm excitation, the samples show red emission locating at 618 nm, which is attributed to the 5D0 → 7F2 electric dipole (ED) transition. Also, a deep red-emitting originating from 5D0 → 7F4 transition matches well with the absorption spectra of PR and PFR regions. It is also found that the PL intensity of CLSPO:0.30Eu3+ is enhanced about 1.6 times compared with the CYSPO:0.20Eu3+. Additionally, the results demonstrated that the phosphors can provide reference for the development of Eu3+-doped phosphors that can be used for plant cultivation LEDs.

Down-conversion of YOF: Pr3+, Yb3+ phosphor

Abstract The photoluminescence (PL) of yttrium oxyfluoride (YOF) samples co-doped with praseodymium (Pr3+) and ytterbium (Yb3+) was investigated for possible down-conversion (DC) applications for c-Si solar cells (SCs). The optimum infrared (IR) emission obtained through DC was recorded with a Yb3+ content of 2% and a Pr3+ content of 0.3% and this was within the effective response range for Si SCs. YOF:Pr3+, Yb3+ samples were synthesized by the pyrolysis method with trifluoroacetate as precursor. The X-ray diffraction patterns indicated a crystalline phase of stoichiometric rhombohedral YOF (space group: R 3 ‾ m (166)) after annealing at 900 °C. X-ray photoemission spectroscopy's high resolution peak fits for the high concentration YOF: 0.3 mol % Pr3+, 6 mol % Yb3+ co-doped sample revealed two Pr oxidation states, Pr3+ and Pr4+. The presence of Pr4+ was due to the annealing in ambient air. The Pr3+ visible (VIS) emission's excitation spectra showed an intense 4f-5d band of Pr3+ at 250 nm accompanied with weaker 4f-4f peaks at 456, 470 and 483 nm. The VIS green PL emission was due to the 4f-4f [3P0 → 3H4] and [3P0 → 3F2] transitions at 498 nm and 659 nm, respectively. Quenching of the Pr3+ green emission was due to the energy transfer to Yb3+ ions through the cross-relaxation mechanism with a dipole-dipole interaction. The Yb3+ IR emission's excitation spectrum revealed a new band at 225 nm that overlapped with the 4f-5d band of Pr3+. The band at 225 nm was ascribed to the charge transfer band of Yb3+ due to electrons transferred from the O2− 3p6 level to the 4f13 level of Yb3+. Excitation with 250 nm showed multi-narrow peaks in the IR range between 885 nm and 1120 nm that corresponded to the Pr3+ 3P0 → 1G4 and 1D2 → 3F3, 3F4 transitions and to the 2F7/2 → 2F5/2 transition of Yb3+. Upon excitation of 225 nm, the IR emission showed only emission of Yb3+ transitions with almost no traces of Pr3+ emission. The decay times for VIS and IR emissions were calculated to be in the microseconds range.

Time-Resolved Vibrational Fingerprints for Two Silver Cluster-DNA Fluorophores.

DNA-templated silver clusters are chromophores in which the nucleobases encode the cluster spectra and brightness. We describe the coordination environments of two nearly identical Ag106+ clusters that form with 18-nucleotide strands CCCCA CCCCT CCCX TTTT, with X = guanosine and inosine. For the first time, femtosecond time-resolved infrared (TRIR) spectroscopy with visible excitation and mid-infrared probing is used to correlate the response of nucleobase vibrational modes to electronic excitation of the metal cluster. A rich pattern of transient TRIR peaks in the 1400-1720 cm-1 range decays synchronously with the visible emission. Specific infrared signatures associated with the single guanosine/inosine along with a subset of cytidines, but not the thymidines, are observed. These fingerprints suggest that the network of bonds between a silver cluster adduct and its polydentate DNA ligands can be deciphered to rationally tune the coordination and thus spectra of molecular silver chromophores.

Enhanced near-infrared downconversion luminescence in ZnxNb(1-x)O composite host co-doped Bi3+ /Yb3+ phosphor for Si solar cell applications

The spectral modification is noticed through near Infrared (IR) downconversion (DC) in Yb3+, Bi3+ co-doped ZnxNb(1-x)O composite host. A high-intensity blue emission centered at 450 nm is observed upon UV excitation at 270 nm for the host ZnxNb(1-x)O at x = 0.5 (ZN). Doping with the optimized concentration at 4 mol% of Yb3+ with ZN (YZN) initiates an energy transfer from the niobate group to two neighboring Yb3+ ions in a co-operative energy transfer (CET) process. The resulting Yb3+ emission spectrum is around 1000 nm, which matches well with the spectral response of Si solar cells. Introducing 1 mol% of trivalent Bi3+ ions as an additional sensitizer to YZN (BZN), the excitation wavelength is further extended from UV at 270 nm to visible at 450 nm region. As an effect of this, UV excitations at 270 nm, 330 nm, and visible excitation at 450 nm in BZN enhance the luminescence in the near IR region. The DC process observed in BZN is due to the CET process from both the niobate group and Bi3+ ions to Yb3+ ions. Solar panel coated with BZN shows an increase in conversion efficiency which in turn indicates that the synthesized phosphor is a promising material for increasing Si solar cell efficiency.

The color center of beryllium-treated yellow sapphires

Yellow color in gem corundum is commonly caused by Fe3+ impurity replacing Al3+ in the Al2O3 structure. For two decades beryllium-assisted heat treatment has been introduced to produce yellow sapphires from colorless, green, or light blue sapphires. The roles of beryllium atoms in corundum structure have been proposed in different ways either triggering structural defects or being as catalysts. Thus, the research experiments were conducted to evaluate these contradictions by applying the UV–vis excitation spectra and Fe K-edge x-ray absorption near edge structure spectra (XANES) of the samples, in combinations with Tauc plots of the UV–vis absorption spectra. The trace element content of the samples was analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). As a result, iron impurity in the samples has been confirmed as Fe3+ by XANES spectra, and hence, revealed as the cause of yellow color in natural yellow sapphire samples. Besides, the absorptions at 423 nm, 457 nm, 487 nm and 553 nm and emissions at 609 nm and 841 nm of Fe3+-Be2+ mixed donor states were detected by UV–vis excitation, which is the novel finding on the origin of yellow coloration in beryllium-treated sapphires. Therefore, an energy band model for mixed Fe3+-Be2+ donor states is proposed to be responsible for the yellow color center in beryllium-treated yellow sapphires, comparable to Fe3+ and Fe3+/Fe3+ states for the natural yellow sapphires commonly contain high iron.

Phenanthroline chromophore as efficient antenna for Tb3+ green luminescence: A theoretical study

The photophysical processes, from excitation in the UV range, energy migration pathways to luminescence of Tb(phen)2(NO3)3 complex in the Vis region have been studied by theoretical approaches and spectroscopic measurements. The UV–Vis absorption, diffuse reflectance, excitation and luminescence spectra indicated that the ligand 1,10-phenanthroline (phen) was a suitable antenna chromophore for Tb3+ luminescence at excitation of wavelength range 350–352 nm, corresponding to the S1 state of phen. The energy level diagram and character of the singlet and triplet excited states of the ligand-chromophore and Tb(phen)2(NO3)3 in gas phase and polar solution were obtained by the DFT/TDDFT/ωB97xD/B1 method and multireference ab-initio calculations with perturbative spin-orbit coupling corrections. It was also established that the vibro-electronic contribution to the excitation energy is important for correct reproduction and interpretation of the experimental absorption and emission spectra of Tb(phen)2(NO3)3. The rate constants for competitive singlet-triplet intersystem crossing relaxation transitions, as well as radiative and non-radiative deactivation of the ligand-centered excited states were qualitatively estimated and the fastest electronic relaxation mechanism was revealed. The excitation channel S0→S1→T2→T1→5D4 was predicted as the most probable one for effective phen→Tb3+ energy transfer. The sensitization results in a high luminescent quantum yield of 13%, which suggests energy transfer rates, sufficiently higher than the rates of radiative and non-radiative depopulation of the T1 state.

Structural and optical properties of green emitting Y2SiO5:Tb3+ and Gd2SiO5:Tb3+ nanoparticles for modern lighting applications

The optical and structural properties of Tb3+-doped yttrium and gadolinium oxyorthosilicate (Y2SiO5 and Gd2SiO5) phosphors were analyzed. The samples were synthesized via sol–gel combustion method using organic fuel. The phase purity and structural properties of the samples were determined via combined approach of powder X-ray diffraction, Fourier transformation infrared (FTIR) and transmission electron microscopy (TEM). X-ray measurements revel monoclinic crystal lattice with P21/c symmetry for both M2SiO5 (pure host) and M2SiO5:Tb3+ (doped) silicates, irrespective of the nature of metal (Y or Gd), presence or absence of Tb3+ in lattice and change in calcination temperature up to 1050 °C. FTIR analysis was applied to confirm the bonding of prepared materials. The appearance of bands corresponding to SiO4 tetrahedra (880–1020 cm−1) suggest the layered structure and support the diffraction measurements. TEM micrographs confirm the synthesis of spherical nanoparticles with filled morphology, narrow size distribution and slightly agglomerated crystallites of the samples. The elemental composition of prepared materials was determined using energy dispersive X-ray spectroscopy. The spectra show peaks only for elements assimilated within the host framework. The photoluminescence (PL) emission spectra of Tb3+-doped samples show 5D4 → 7FJ (J = 3–6) transitions under 254 nm-excitation. The dominant peak at 544 nm for 5D4 → 7F5 transition is responsible for the emission of green light on ultraviolet–visible excitation in both the Tb3+-doped host matrixes. Owing to advantageous properties like intense PL and high crystallinity, these nanophosphors could possess potential applications in the mercury free lighting sources and optoelectronic devices.

Synthesis and Characterization of a Novel Rambutan‐like ZnO@SrTiO3/TiO2 Microsphere

AbstractDesigning gradient energy levels is an effective method to improve the photocatalytic performance of the semiconductor materials. In this work, we propose a core‐shell structured material with micro‐sized spherical SrTiO3/TiO2 (abbreviated as SrT) as the core material, and the rod‐shaped ZnO shell attaching on the surface of SrT, which forms a hierarchical spherical composite with rambutan‐like shape. During the synthesis process, ZnO seeds are coated on the surface of SrT microspheres firstly, and then they transfer to nanorods with a diameter of 60–70 nm and a length of less than 100 nm under the growth solution medium at 90 °C with the volume ratio of zinc nitrate to hexamethylenetetramine (abbreviated as HMT) is 1 : 1 and the concentration is 0.05 mol/L. This structure may further facilitate the separation of the photo‐generated electron‐hole pairs and widen the photocatalytic applications of perovskite structured SrTiO3 or anatase structured TiO2 with visible excitation response.

Comparison and chemical structure-related basis of species discrimination of animal fats by Raman spectroscopy using near-infrared and visible excitation lasers

The objective of present study is mainly to compare the discrimination capabilities of near-infrared Fourier transform Raman (FT-Raman, λex~1064 nm) and visible-Raman (vis-Raman, λex~532 nm) spectroscopy for animal fats. All animal fats were analysed by gas chromatography and then the spectra were collected using FT-Raman and vis-Raman spectroscopy. Although vis-Raman spectra partly presented fluorescence interference, the resulting Raman spectra still had higher signal-to-noise ratio than the corresponding FT-Raman spectra. Animal fats from different species produced obvious differences in peak intensity ratios at 1653/1745 and 1653/1441 cm−1, as well as shoulders at 1298 and 1264 cm−1. Chemometric analysis demonstrated that vis-Raman spectroscopy possessed better discrimination capability for animal fat compared to FT-Raman spectroscopy. According to the chemical structure-related basis, the differing degrees of unsaturated fatty acid and relative cis/trans fatty acid contents could be sufficiently reflected in Raman spectra and were the important factors for the successful species discrimination of animal fat.

Lanthanide doped TiO2: Coexistence of discrete and continuous dopant distribution in anatase phase

Despite extensive studies on lanthanide (Ln) doped TiO2 nanoparticles, there is still considerable uncertainty as to whether Ln reside in the bulk (either as substitutional or interstitial dopant) or on the surface. Herein, new Ln (Eu, Sm, Nd and Er) discrete substitutional centers are identified in the anatase phase using low temperature, site selective time-gated luminescence spectroscopy. The excitation wavelength spanned UV (TiO2 host absorption) to visible excitation range into Ln f-f absorption transitions. The Ln multisite distribution is described in terms of fingerprint emission/excitation spectra and emission decays. The emission of Ln centers cover the visible (Eu, Sm) to near-infrared range (Nd, Er) and display narrow emission with full width at half maximum (FWHM) as small as 0.2 nm. The role of TiO2 host in sensitization of Ln emission is emphasized for each center. We have also found that besides discrete distribution, Ln distribute continuously on closely related anatase lattice sites. In this case, the Ln emission is significantly broader, with FWHM around 20 nm and change continuously in spectral shape and intensity with the excitation wavelength. The challenges encountered while identifying the Ln centers in TiO2 and comparison with case of CeO2 and SnO2 are also discussed.

Highly efficient visible light phenyl modified carbon nitride/TiO2 photocatalyst for environmental applications

Eco-sustainable solutions for the neutralization of air and water pollutants have increasingly gravitated toward the use of heterogeneous photocatalysts. This approach, which transforms pollutants into harmless substances through a light-driven chemical reaction on a catalytic surface, must comply with eco-sustainability requirements and be easily applicable. Semiconductor-based photocatalysis is a promising pathway for the degradation of environmental pollutants and, among all the various semiconductors used, titanium dioxide has proved itself to be the foremost material for environmental remediation due to its highly desirable photocatalytic properties. Titanium dioxide, however, poorly exploits the visible part of the electromagnetic spectrum due to the relatively large band-gap of its anatase phase, and as such, the UV portion of the solar spectrum is largely responsible for its photocatalytic activity. Herein, we demonstrate a highly efficient visible light hybrid catalyst based on titanium dioxide and phenyl carbon nitride (PhCN). With the organic component providing a broad absorption up to 600 nm and fast charge exchange to the conduction band of TiO2, the combination allows for the highly efficient photocatalytic degradation of Rhodamine B under visible excitation.