UV Vis NIR Absorption Research Articles

Synthesis of NiS nanoparticles using a sugar-ester nonionic water-in-oil microemulsion

Nickel sulfide (NiS) nanoparticles were prepared in water-in-oil (w/o) microemulsion system containing sucrose ester as the surfactants. The commercial food grade sucrose monoester (abbreviated S-1170) is a biodegradable and non-toxic surfactant, which can be adopted to form w/o microemulsion system in the presence of 1-butanol as co-solvent. The pseudo-ternary phase diagram for the inverse microemulsion region has been determined by the titration method. It was found that the studied system forms clear and homogenous microemulsion when heated to 37 °C but gradually becomes turbid at room temperature due to the phase separation. The as-prepared NiS nanoparticles were characterized by energy filter transmission electron microscopy (EFTEM), UV–VIS–NIR absorption spectroscopy and X-ray photoelectron spectroscopy (XPS). The results showed that the synthesized nanoparticles have regular shape, monodispersed and in the size range of 3–12 nm.

Spectral analysis of Ho3+: TeO2–B2O3–Li2O glass

A highly transparent and little yellow-coloured Ho3+ doped TeO2–B2O3–Li2O glass was prepared in order to study its optical properties from the measured UV–VIS–NIR absorption, emission and up-conversion emission spectra. We observed a prominent and bright red colour when this optical glass was brought under a UV lamp. The recorded up-conversion emissions revealed a strong green colour along with blue and violet colours upon excitation with λexc=643 nm, and the mechanism was explained by an energy level diagram as a three photon absorption process.

Optical properties of the LB multilayer films of 5-amino-3-octadecylimino-1,2,6,7-tetracyano-3 H-pyrrolizine

We report on the preparation and optical characterization of Langmuir–Blodgett (LB) films of the octaldecylimino derivative of 5-amino-3-imino-1,2,6,7-tetracyano-3 H-pyrrolizine. Multilayers (up to 30 layers) were deposited from toluene solutions onto hydrophobic quartz substrates. We studied the electronic absorption and anisotropy behavior in the LB films by using UV–Vis–Nir absorption spectroscopy with nonpolarized and polarized light, respectively. The optical investigations reveal a good quality and well-ordered structure in our LB films.

A new tetranuclear iron complex with a [Fe4O6]6+ core: synthesis, structure, spectroscopic and magnetic properties

The reaction of 2,6-bis(hydroxymethyl)-4-tert-butylphenol (H3L) with [Fe(III)(acac)3] in acetonitrile in the presence of NEt3 yields [Fe(III)4(HL)6(acac)2](HNEt3)2·3CH3CN (1) or after subsequent addition of [NEt4]Cl [Fe(III)4(HL)6(acac)2](NEt4)2 (2) as reddish-brown crystalline solids. The molecular structure of 1 was established by single crystal X-ray diffraction. The dianion of complex 1 contains an [Fe4O6]6+ core with two μ3-bridging benzylalcoholato ligands and four μ2-bridging benzylalcoholato ligands. This is the first structurally characterized example for a benzylalcoholato ligand bound to an octahedrally coordinated iron ion. The core of 1 can be considered as two face-sharing cuboidal [Fe3O4]5+ units. Compound 2 has been examined by FTIR, UV–Vis–NIR-absorption, 57Fe Mössbauer, and magnetochemical measurements. Compound 2 has an St=0 ground state indicative of antiferromagnetic interactions between the high-spin Fe(III) metal ions. The spin topology resembles that of the known [Fe4O2]8+ core with a ‘butterfly’ disposition of the four iron ions. Fitting of the data to the appropriate spin-Hamiltonian yields exchange-coupling constants between the ‘inner’ (‘body’) iron ions of Jbb=−10.0±0.1 cm−1 and between the ‘inner’ iron ions and ‘outer’ (‘wing-tip’) iron ions of Jwb=−6.2±1.0 cm−1. The differences of the spectroscopic and magnetochemical properties between the [Fe4O6]6+ core and the [Fe4O2]8+ core with an inversion of the superexchange pathways are discussed.

Single-wall carbon nanotubes with diameters approaching 6 nm obtained by laser vaporization

Single-wall carbon nanotubes (SWNTs) with large diameters from 2 to 5.6 nm were prepared by pulsed laser vaporization of carbon rods doped with Co, Ni and FeS in an atmosphere of Ar:H 2. The SWNT material was characterized by SEM, HRTEM, Raman, IR, UV–VIS–NIR absorption spectroscopy and thermogravimetric analysis.

Effect of the molecular weights on the optical and mechanical properties of poly(vinyl alcohol) films

Pure Poly(vinylacohol) (PVA) films with molecular weights (5000, 17000, 72000, 125000 gm/mol) were prepared by a casting technique. The thickness of the prepared films was 0.21 mm. Optical absorption and mechanical properties were measured. The UV–Vis–NIR absorption spectra gave the same band positions but the absorption intensity varies in a reverse trend with increasing molecular weight. The dependence of the absorption coefficient, α, on the photon energy, hν, has been determined and the band tails and energy gaps were calculated. It was found that the band tail increases, while the optical gaps, Young’s modulus and the strength at the break for PVA films decrease as the molecular weight is increased.

Isolation and spectroscopic characterization of Sm-containing metallofullerenes

We report the first isolation of a series of Sm-containing metallofullerenes, Sm@C 74, Sm@C 76(I, II), Sm@C 78, Sm@C 80, Sm@C 82(I, II, III) and Sm@C 84(I, II, III), and their characterization by UV–VIS–NIR absorption spectroscopy and electron energy-loss spectroscopy (EELS). The UV–VIS–NIR absorption spectra of Sm@C 74, Sm@C 80, Sm@C 82(I, II, III) and Sm@C 84(I, II) are quite similar to those of the corresponding Ca-, Sr-, Ba-, Eu-, Tm-, Yb-based metallofullerenes. In contrast, the absorption spectra of Sm@C 76(I, II), Sm@C 78 and Sm@C 84(III) show a novel feature: the onset for Sm@C 78 is observed ∼2600 nm, which corresponds to a small band gap (∼0.5 eV). Furthermore, the oxidation state of Sm atom in Sm@C 82(II) is investigated by EELS, which reveals that the Sm atom takes +2 oxidation state in this fullerene cage.

Excited state absorption processes in Sm 3+ doped GdOCl

The FT-Raman spectrum of the polycrystalline GdOCl doped with 1 mol% Sm 3+ was measured at room temperature using a cw Nd:YAG laser with the excitation wavelength of 1064 nm (9400 cm −1). Besides the very weak Stokes and anti-Stokes Raman lines the additional strong lines were concluded to result from luminescence processes. The UV–Vis–NIR absorption spectra of GdOCl:Sm 3+ ( x Sm=0.06) and the energy level simulation of Sm 3+ in SmOCl yielded the energy level scheme of Sm 3+. The additional lines could be assigned to the IR and visible Stokes and anti-Stokes luminescence of Sm 3+. Absorption of the 9400 cm −1 photons leads first to transition to the 6F 9/2 and then to the 4F 3/2 energy level of Sm 3+. The lines corresponding to luminescence at 13 596 and 12 310 cm −1 could then be assigned to the anti-Stokes transitions from the 4F 3/2 energy level to the 6H 13/2 and 6H 15/2 levels, respectively. Also lines in the Stokes emission originate from the luminescence processes of Sm 3+. However, all the extra lines in the Raman spectrum have not yet been explained by the luminescence processes.

Production and isolation of the isomers of dimetallofullerenes, HoTm@C 82 and Tm 2@C 82

Metallofullerenes encapsulating Ho and Tm atoms were isolated by using the HPLC method with two different columns. Three isomers of HoTm@C 82 and five isomers of Tm 2@C 82 were identified. The UV–VIS–NIR absorption spectra of these isomer species were similar to those of the corresponding isomers of Er 2@C 82. This suggests that the cages of HoTm@C 82 and Tm 2@C 82 have the same charge as that of Er 2@C 82 and that Tm takes the trivalent state in HoTm@C 82 and Tm 2@C 82, contrary to the divalent state in Tm@C 82.

Metallofullerenes Sc 2@C 82(I, II) and Sc 2@C 86(I, II): isolation and spectroscopic studies

The first isolation of Sc 2@C 82(I, II) and Sc 2@C 86(I, II) and their characterization by UV–Vis–NIR absorption spectroscopy are reported. The absorption spectra of Sc 2@C 82(I) and Sc 2@C 86(I) are markedly different from those of Sc 2@C 82(II) and Sc 2@C 86(II), respectively, indicating that the electronic structures of di-scandium metallofullerenes are dominated by the fullerene cages rather than the encapsulated atoms. Both UV–Vis–NIR absorption spectrometry and theoretical studies suggest that Sc 2@C 82(I) is a small band-gap metallofullerene. Furthermore, an ab initio calculation reveals that its electronic structure can be described as Sc 2 4+@C 82 4− similar to Sc 2@C 84.

Nanocomposites glass/conductive polymers

We report on the preparation and characterization of two glass/conducting polymer nanocomposites obtained by the in situ oxidative polymerization of pyrrole and aniline inside the pores of Porous Vycor Glass (PVG). Oxidative polymerization of pyrrole was done via Cu 2+ cation impregnated in the PVG pores. The polymerization of aniline was undertaken by impregnating PVG with the monomer, followed by an acid solution of (NH 4) 2S 2O 8. These nanocomposites were characterized by diffuse reflectance FT infrared spectroscopy, UV–Vis–NIR absorption spectroscopy, thermogravimetric analysis, Raman spectroscopy, solid state 13 C and 29 Si CP-MAS-NMR, scanning electron microscopy, transmission electron microscopy, cyclic voltammetry and conductivity measurements. The results showed that both polymers are formed inside the PVG pores in their oxidized conductive state, with the Si–O − groups of the glass surface acting as counter-anions. The dimensions of the pores of the glass preclude cross-linking of the polymers, allowing only formations of linear chains. The results suggest the formation of polymeric wires in the bulk of the glass substrate.

Optical properties of the Dy3+ ion in DyOCl

A detailed analysis of the energy level scheme of the Dy3+ ion with the 4f9 electron configuration was carried out in the DyOCl matrix. The UV–vis-NIR absorption spectra of the tetragonal DyOCl were measured at selected temperatures between 9 and 300 K. The emission spectra of the Dy3+ ion in the LaOCl and GdOCl matrices were obtained at 77 K and room temperature. The experimental energy level scheme of 179 c.f. components representing 57 SLJ states was successfully simulated according to the C4v site symmetry by a phenomenological model using 14 free ion and five c.f. parameters with an RMS deviation of 21 cm−1. The results for DyOCl are consistent with those for other RE3+ ions in RE oxychloride hosts.

Analysis and simulation of the optical spectra of the stoichiometric NdOF

The UV–VIS–NIR absorption of the rhombohedral NdOF was measured at selected temperatures between 9 and 300 K. The emission spectra of NdOF, LaOF:Nd3+ and GdOF:Nd3+ were obtained at 4.2, 9, 77 and 300 K. The energy level scheme of the Nd3+ ion (the 4 configuration) derived from the optical spectra was simulated with a phenomenological model taking simultaneously into account both the free ion interactions and the crystal field (c.f.) effect for the C3v point symmetry of the Nd3+ site in NdOF. The simulation yielded a good correlation (rms deviation 17 cm-1) between the experimental and calculated energy level schemes of 122 Kramers doublets of a total of 182. The c.f. parameters show only slight distortion from the cubic Oh symmetry. The fourth and sixth rank c.f. effects have an important contribution to the overall c.f. interaction, while the contribution of second rank crystal field is small which indicates an important electrostatic interaction between the cation and anions. A comparison to Pr3+ (4), Sm3+ (4), Eu3+ (4), Tb3+ (4) and Dy3+ (4 electron configuration) in LnOF (Ln=lanthanide) shows a smooth evolution of the c.f. effect.

Production and isolation of the C80-based group 2 incar-fullerenes: iCaC80, iSrC80 and iBaC80

We report the first production and isolation of mono-incar-fullerenes based on the missing fullerene C80, and their characterisation by UV–VIS–NIR absorption spectroscopy.

EPR/ENDOR detection of stable Ti III and Ti IV radical products generated by single electron transfer from (PriO)3TiCH3

Single electron transfer reactions between the stereoselective carbanion source methyltriisopropoxy-titanium(IV) as donor and α-diimines, ketones or α-dicarbonyls as π acceptor substrates exhibit a dichotomy with respect to the EPR-detectable paramagnetic ‘escape’ products. Substrates with very negative reduction potentials such as 2,2′-bipyridine yield TiIII species, whereas more easily reducible molecules such as dinucleating 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine react to yield EPR-detectable TiIV complexes of the corresponding anion radicals. A very stable paramagnetic product has been isolated from the reaction between 3,5-di-tert-butyl-o-quinone (dtbq) and (PriO)3TiCH3; this first thermally stable, but apparently configurationally labile, TiIV semiquinone complex [(dtbq–1)Ti(OPri)3]˙ was studied by UV–VIS–NIR absorption and EPR/ENDOR spectroscopy.