UV Vis Near-infrared Research Articles

Near-infrared absorbing dyes at 1064 nm: Soluble dithiolene nickel complexes with alkylated electron-donating groups as Peripheral substituents

Soluble dithiolene nickel complexes are designed and synthesized as near-infrared (NIR) absorbing dyes through the introduction of strong electron-donating groups at the molecular periphery. The resulting complexes are characterized by 1H/13C NMR, IR, ESI-MS, UV–vis–NIR, TG, DSC, XPS and elemental analysis. The identification results are in accord with the chemical structure of designed dithiolene nickel complexes. The XPS results suggested that the dithiolene ligands in carbazole-containing nickel complex take a radical monoanion, which depends on the substituent electron-donating ability to a large extent. The TG and DSC measurements indicated that the resulting complexes have an excellent thermal stability and take on a glassy state at low temperature. The laser transmittance measurement suggested that the optical filters fabricated through static solution-casting approach with dithiolene nickel complexes as NIR absorbing dyes could be well applied to the NIR laser protection at 1064 nm.

Synthesis of poly(8-aminopyrene-1,3,6-trisulfonic acid)/CNT Nanocomposite for Electrochemical Detection of Caffeine

We synthesized nanocomposite of polymerized 8-aminopyrene-1,3,6-trisulfonic acid (APTA) and single-walled carbon nanotubes (SWCNTs). To prepare the nanocomposite, SWCNTs were dispersed in aqueous solution of APTA (monomers) using a probe sonicator. The as-prepared APTA/SWCNTs dispersion was characterized using Raman, FT-IR, and UV-visible-near infrared (UV-vis-NIR) spectroscopies. Cyclic voltammetry measurements indicated that polymerization of APTA occurred during probe sonication due to the oxidation of APTA molecules. Using the poly(APTA)/SWCNTs dispersion, a conducting thin film was prepared on a glassy carbon electrode (GCE) and its electrochemical and catalytic properties were studied. The poly(APTA)/SWCNTs film coated electrode exhibited excellent electrochemical catalytic activity toward the oxidation of caffeine (CAF) with a linear range from 10 μM to 0.76 mM with a linear regression equation; Ipa (mA) = 0.015 mM + 5.84 × 10−7 (R2 = 0.993). In addition, the other common electroactive biomolecules such as dopamine (DA) and ascorbic acid (AA) did not interfere with the CAF oxidation peak. Well-defined oxidation peaks (with high catalytic currents) of AA (+0.49 V), DA (+0.53 V) and CAF (+1.47 V) were simultaneously observed at the poly(APTA)/SWCNTs sensor. Selective detection of CAF in fruit juices was also demonstrated.

Toward NIR driven photocatalyst: Fabrication, characterization, and photocatalytic activity of β-NaYF4:Yb3+,Tm3+/g-C3N4 nanocomposite

The β-NaYF4:Yb3+,Tm3+/g-C3N4 (NYT/C3N4) photocatalyst has been successfully fabricated by a stepwise method. Firstly, the advanced near-infrared (NIR) driven photocatalyst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV–Vis–NIR diffuse reflectance spectroscopy. It was found that NYT/C3N4 photocatalyst consisted of uniform hexagonal phase NaYF4 nanocrystals with about 20nm diameter distributed on surface of g-C3N4 sheets, and the NYT/C3N4 composite exhibited strong near-infrared light absorption and the energy transfer from β-NaYF4:Yb3+,Tm3+ to g-C3N4 was confirmed. Secondly, the photocatalytic activities of the catalysts were evaluated by the degradation of methyl blue dye and colorless phenol under the irradiation of 980nm laser. The results suggested that NYT/C3N4 nanocomposite is an advanced NIR-driven photocatalyst. Moreover the NYT/C3N4 photocatalyst showed good stability for photocatalytic decoloration of dye in the recycled tests. This study suggested a promising system to utilize the NIR energy of sunlight for photochemical and photoelectrical applications based on g-C3N4, which will contribute to the utilization of solar energy in the future.

Syntheses, structures and photophysical properties of Zn–Ln coordination polymers

Eight novel coordination polymers, {[LnZn(2,3-pydc)2(ox)0.5(H2O)3]·3H2O}n (Ln=Pr 1, Nd 2, Ho 3, Er 4, Yb 5, Sm 6, Eu 7, Tb 8) (2,3-H2pydc=pyridine-2,3-dicarboxylic acid, H2ox=oxalic acid) are synthesized by the hydrothermal method and their structures are determined by single-crystal X-ray diffraction. They are isomorphous and crystallized in the triclinic system, with space group P1¯. In crystals, Ln(III) and Zn(II) ions are linked into 2D layers by 2,3-pydc2− ligands adopting two coordination modes, and neighboring layers are bridged into 3D network structure through oxalate ligands in bridging tetradentate coordination mode. The IR, UV–Vis–NIR absorption spectra and emission spectra in the visible and near-infrared (NIR) region of polymers are determined and analyzed. All of polymers exhibit characteristic emission bands of corresponding Ln(III) ions, which should be attributed to sensitization from the d-block (Zn–ligand moiety) and ligands after introducing Zn(II) ion into the system of Ln(III) complexes.

Near-infrared optical constants and optical polarization properties of ZnO thin films

The optical characteristics of ZnO thin films deposited on Si (111) and quartz at temperature <50°C using reactive RF sputtering deposition were examined within the near-infrared (NIR) region. From the X-ray diffraction observations, it was found that the films show a polycrystalline structure. X-ray photoelectron spectroscopy analysis shows the chemical bonding states of zinc and oxygen in the surface of the films and confirms the formation of Zn–O bonds. The field emission scanning electron microscopy and the atomic force microscopy images of the films shown an almost uniform distribution and the surfaces are smooth with grains of the order of 40–60nm. The average surface roughness was in the range of 3.15–24.33nm. Over a wavelength range 700–2500nm, the optical constants of the films were obtained by analysis of the measured ellipsometric spectra using the Cauchy–Urbach model. Refractive indices and extinction coefficients of the ZnO films were determined to be in the range n=1.65–1.73 and κ=0.0060–0.029, respectively. Also, the s- and p-polarized optical properties (transmittance and reflectance) of the films have been measured at different angles of incidence in the UV–Vis–NIR spectral range. In addition, calculations have been carried out in order to determine the optical absorptance by using the conservation of energy. The films reveal a high transmittance (85%–95%), low reflectance (5%–15%), and very low absorptance (<1%) at normal incidence. This means that the sputtered polycrystalline ZnO films could be good candidates for antireflection (AR) optical coatings.

Optical characterization of hafnium oxide thin films for heat mirrors

HfO2 thin films (80nm) fabricated at various substrate temperatures (25–120°C) using an electron beam evaporation technique and thermally annealed at 500°C were characterized through X-ray diffraction, atomic force microscopy and UV–vis–NIR spectroscopy. X-ray diffraction results illustrate that as-deposited HfO2 films are amorphous, which transform to polycrystalline (monoclinic) structure on annealing. Films reveal various morphologies and crystallite orientations, which seem to be responsible for variations in surface roughness (5–12nm), mean crystallite size (5.2–6.3nm), refractive index (1.43–1.79), extinction coefficient (0.066–0.103) etc. In addition, better reflectivity (5–10%) of annealed HfO2 films in near infrared (NIR) region has been improved by inserting a metallic Ag layer to form insulator-metal-insulator structure useful for heat mirror applications. Optical characterization of such HfO2(10nm)/Ag(5nm)/HfO2(10nm) structure illustrates minimum transmittance (~35%) in the visible region and maximum reflectance (~90%) in the visible (vis) and near infrared regions.

Carbon quantum dots/hydrogenated TiO2 nanobelt heterostructures and their broad spectrum photocatalytic properties under UV, visible, and near-infrared irradiation

To make the best and highest use of solar light is the main direction and object of photocatalysis and water-splitting. Although UV and visible active photocatalysts have been extensively investigated, the use of near-infrared (NIR) wave band of solar light remains a nearly blank area. Here we report the UV–visible–NIR broad spectrum active photocatalytic property of CQDs/hydrogenated TiO2 (H-TiO2) nanobelt heterostructures. The improved UV and visible photocatalytic property can be attributed to improved optical absorption, charge carrier trapping, and hindering of the photogenerated electron–hole recombination of oxygen vacancies and Ti3+ ions in TiO2 nanobelts created by hydrogenation. The NIR photocatalytic activity is from photo-induced electron transfer, electron reservoir, and up-converted PL properties of CQDs, which can absorb NIR light and convert into visible light and transfer to visible photocatalytic active H-TiO2 nanobelts. This work offers a simple strategy for the fabrication of a wide spectrum of active heterostructured photocatalysts by assembling CQDs on the surface of UV–visible photocatalysts, which opens a door for photodegradation, photocatalytic water splitting, and enhanced solar cells using sunlight as light source.

Application of artificial neural networks coupled to UV–VIS–NIR spectroscopy for the rapid quantification of wine compounds in aqueous mixtures

Ultraviolet–visible (UV–VIS) and near-infrared (NIR) spectroscopy coupled to artificial neural networks (ANNs) was used as a non-destructive technique to quantify ethanol, glucose, glycerol, tartaric acid, malic acid, acetic acid and lactic acid in aqueous mixtures. Spectral data were obtained for 152 samples. Differing pre-treatments were applied to the spectra and ANN models were obtained using raw and pre-treated data to evaluate several spectral wavelength groupings and ANN training conditions. Feasible calibration models were obtained for ethanol, malic acid and tartaric acid. To validate the process, 120 new samples were measured using the best ANN models. The determination coefficients for the three compounds using this validation set were above 0.9. The results showed the importance of good parameter selection when training the ANN to obtain reliable models. Coupling UV–VIS–NIR spectroscopy to ANN could provide an alternative to conventional chemical methods for determining ethanol, tartaric acid and malic acid in wines.

Green colored nano-pigments derived from Y2BaCuO5: NIR reflective coatings

A green colored nano-pigment Y2BaCuO5 with impressive near infra-red (NIR) reflectance (61% at 1100 nm) was synthesized by a nano-emulsion method. The developed nano-crystalline powders were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), UV–vis–NIR diffuse reflectance spectroscopy and CIE-L*a*b* 1976 color scales. The XRD and Rietveld analyses of the designed pigment powders reveal the orthorhombic crystal structure for Y2BaCuO5, where yttrium is coordinated by seven oxygen atoms with the local symmetry of a distorted trigonal prism, barium is coordinated by eleven oxygen atoms, and the coordination polyhedron of copper is a distorted square pyramid [CuO5]. The UV–vis spectrum of the nano-pigment exhibits an intense d–d transition associated with CuO5 chromophore between 2.1 and 2.5 eV in the visible domain. Therefore, a green color has been displayed by the developed nano-pigment. The potential utility of the nano-pigments as “Cool Pigments” was demonstrated by coating on to a building roofing material like cement slab and PVC coatings.

Multifunctional hybrid silica nanoparticles based on [Mo6Br14]2− phosphorescent nanosized clusters, magnetic γ-Fe2O3 and plasmonic gold nanoparticles

We report on the synthesis, characterization and photophysical study of new luminescent and magnetic hybrid silica nanoparticles. Our method is based on the co-encapsulation of single maghemite γ-Fe2O3 nanoparticles and luminescent molybdenum cluster units [Mo6Bri8Bra6]2− through a water-in-oil (W/O) microemulsion technique. The as-prepared core–shell [Cs2Mo6Br14-γFe2O3]@SiO2 nanoparticles (45–53nm) possess a single magnetic core (6, 10.5 or 15nm) and the cluster units are dispersed in the entire volume of the silica sphere. The [Cs2Mo6Br14-γFe2O3]@SiO2 nanoparticles have a perfect spherical shape with a good monodispersity and they display red and near-infrared (NIR) emission in water under UV excitation, whose intensity depends on the magnetic core size. The hybrid nanoparticles have been characterized by transmission electron microscopy (TEM), high annular angular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDX), UV–Vis–NIR spectroscopy and magnetometer SQUID analysis. Small gold nanoparticles were successfully nucleated at the surface of the hybrid silica nanoparticles in order to add plasmonic properties.

Ilmenite mapping of the lunar regolith over Mare Australe and Mare Ingenii regions: An optimized multisource approach based on Hapke radiative transfer theory

AbstractWe model lunar ilmenite abundances over Mare Australe and Mare Ingenii regions using a new approach; we integrate Lunar Reconnaissance Orbiter Wide Angle Camera (WAC) and Clementine UV‐visible/near‐infrared (UVVIS/NIR) data to obtain a 14‐band mosaic (320‐2000 nm). We use Hapke's radiative transfer equations to compute spectra for various mixtures of orthopyroxene, clinopyroxene, plagioclase, olivine, and ilmenite, with varying grain size, chemistry, and degree of maturity, and find the closest match between the modeled spectra and the spectra of the less mature pixels (optical maturity ≥ 0.2) in the 14‐band mosaic. We calculate a “maximum stoichiometrically possible ilmenite content”, using Clementine‐derived TiO2 abundances and the amount of TiO2 in stoichiometric ilmenite, and use it as a constraint in our model. We validate our methodology with lunar soil spectra of known composition. Our results show that the integrated WAC‐UVVIS/NIR data and the UVVIS/NIR data overestimate ilmenite abundances by 8.80 wt % and 7.97 wt %, respectively, when a fixed maximum of 20 wt % ilmenite is used. When the maximum stoichiometrically possible ilmenite content is used as a constraint, the integrated WAC‐UVVIS/NIR data give slightly more accurate ilmenite abundance estimation (±2.87 wt %) than when using only UVVIS/NIR data (± 3.04 wt %). We find ilmenite concentrations of 0−11 wt % in Mare Australe and 0−6 wt % in Mare Ingenii region. Ilmenite abundances between 4 and 7 wt % are exposed in Mare Australe, whereas ilmenite abundances between 7 and 11 wt % are found on the walls of 0.6‐11.8 km diameter craters within Mare Australe.

Spectroscopy and visible frequency upconversion in Er3+–Yb3+: TeO2–ZnO glass

The UV–Vis–NIR absorption studies of the Er3+/Er3+–Yb3+ doped/codoped TeO2–ZnO (TZO) glasses fabricated by the melting and quenching method has been performed. The spectroscopic radiative parameters viz. radiative transition probabilities, branching ratios and lifetimes have been determined from the absorption spectrum by using Judd–Ofelt theory. The near infrared (NIR) to visible frequency upconversion (UC) have been monitored by using an excitation of 976nm wavelength radiation from a CW diode laser. The effect of codoping with Yb3+ ions on the intensity of the UC emission bands from the Er3+ ions throughout visible region has been studied. The mechanism responsible for the observed upconversion emissions in the prepared samples have been explained on the basis of excited state absorption and efficient energy transfer processes.

Au Nanorod Design as Light-Absorber in the First and Second Biological Near-Infrared Windows for in Vivo Photothermal Therapy

Photothermal cancer therapy using near-infrared (NIR) laser radiation is an emerging treatment. In the NIR region, two biological transparency windows are located in 650-950 nm (first NIR window) and 1000-1350 nm (second NIR window) with optimal tissue transmission obtained from low scattering and energy absorption, thus providing maximum radiation penetration through tissue and minimizing autofluorescence. To date, intensive effort has resulted in the generation of various methods that can be used to shift the absorbance of nanomaterials to the 650-950 nm NIR regions for studying photoinduced therapy. However, NIR light absorbers smaller than 100 nm in the second NIR region have been scant. We report that a Au nanorod (NR) can be designed with a rod-in-shell (rattle-like) structure smaller than 100 nm that is tailored to be responsive to the first and second NIR windows, in which we can perform hyperthermia-based therapy. In vitro performance clearly displays high efficacy in the NIR photothermal destruction of cancer cells, showing large cell-damaged area beyond the laser-irradiated area. This marked phenomenon has made the rod-in-shell structure a promising hyperthermia agent for the in vivo photothermal ablation of solid tumors when activated using a continuous-wave 808 m (first NIR window) or a 1064 nm (second NIR window) diode laser. We tailored the UV-vis-NIR spectrum of the rod-in-shell structure by changing the gap distance between the Au NR core and the AuAg nanoshell, to evaluate the therapeutic effect of using a 1064 nm diode laser. Regarding the first NIR window with the use of an 808 nm diode laser, rod-in-shell particles exhibit a more effective anticancer efficacy in the laser ablation of solid tumors compared to Au NRs.

Syntheses, structures and near-infrared luminescent properties of a series of Ln(III) coordination polymers

Abstract Using aromatic carboxylic acids as main ligands, four Ln(III) coordination polymers, [Er(CH3C6H4COO)2(Ac)(H2O)]n (1), [Yb(β-C10H7COO)2(Ac)(H2O)]n (2), [Nd(C9H7O2)3]n (3) and [Ho(C9H7O2)3]n (4) (CH3C6H4COO = p-toluylate, Ac = acetate, β-C10H7COO = β-naphthoyloxy, C9H7O2 = cinnamate), were synthesized by hydrothermal method and their structures were studied by single-crystal X-ray diffraction. Polymers 1 and 2 possess 2D layer structures, and polymers 3 and 4 possess 1D chain structures. At room temperature in the solid state, the IR, UV–Vis–NIR spectra and the emission spectra in the visible and near-infrared (NIR) regions of the four polymers were determined. In the NIR region, polymers 1–4 show characteristic emission bands of the corresponding Ln(III) ions which exhibit shift, splitting or broadness in comparison with their theoretical emission bands. This can be confirmed by their UV–Vis–NIR spectra and discussed emphatically.

Effects of Ultrasonic Dispersion on the Separation of Single-Walled Carbon Nanotubes

Recently, gel chromatography has been demonstrated as an effective method for the separation of single-walled carbon nanotubes (SWCNTs) according to their electronic type and structure. The separation of SWCNTs was thought to result from the different affinity forces between the gel and various SWCNTs. Based on this method, we investigated the effect of ultrasonic time on the dispersion and separation of metallic and semiconducting SWCNTs. At a low ultrasonic power, with the increase of ultrasonic time, better monodispersed SWCNTs in sodium dodecylsulfate (SDS) aqueous solution were obtained. The UV-visible-near infrared (UV-Vis-NIR) absorption, Raman and photoluminescence (PL) spectroscopic characterizations confirmed that under the condition of ultrasonication (2 h), higher-purity metallic tubes and semiconducting tubes with different diameter distributions could be obtained. We believe that the control of the ultrasonication time may tune the mono-dispersity and the length of SWCNTs, which would further influence the difference in affinity forces between various SWCNTs and the gel, therefore leading to different separation results.

Optical and Phase Transition Properties of Ti&lt;sub&gt;&lt;em&gt;x&lt;/em&gt;&lt;/sub&gt;V&lt;sub&gt;1-&lt;em&gt;x&lt;/em&gt;&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; Thin Films

TixV1-xO2 (0 <= x <= 1) thin films with different molar ratios of V/Ti were prepared on c-plane sapphire (0001) substrates by radio frequency magnetron sputtering. The microstructure and optical properties of the thin films were determined by X-ray diffraction (XRD), Raman spectroscopy, and UV-visible-near infrared (UV-Vis-NIR) spectroscopy. The width of the optical band gap was calculated and the integrated solar transmittance of the films was characterized. As the content of titanium was increased, infrared regulation and thermal hysteresis were gradually reduced until they disappeared. The results show that the band gap of the thin films broadens as the content of titanium increases, causing the optical absorption edge to exhibit a blue shift. Conversely, the band gap narrows as the proportion of vanadium is increased, which causes a red shift of the optical absorption edge.

Near-infrared reflecting inorganic pigments based on molybdenum and praseodymium doped yttrium cerate: Synthesis, characterization and optical properties

A series of novel environmentally benign near-infrared (NIR) reflecting inorganic pigments based on yttrium cerate doped with metal ions such as Mo 6+ or Pr 4+ have been developed and characterized using XRD, UV–vis–NIR diffuse reflectance spectroscopy and CIE 1976 L ⁎ a ⁎ b ⁎ color scales. The substitution of Mo 6+ for Ce 4+ in Y 2Ce 2O 7 changed the color from ivory-white to yellow and the band gap decreased from 3.01 to 2.44 eV due to O 2p–Mo 4d charge-transfer transitions. Most importantly the molybdenum doped pigments exhibit bright yellow hue with high NIR solar reflectance (>90%) in the range 700–2500 nm. In contrast, replacing Pr 4+ for Ce 4+ drastically shifts the absorption edge of the pigments from 410 to 725 nm and as a result the band gap of the compounds changes from 3.01 to 1.70 eV. Interestingly, the praseodymium doped pigments not only exhibits colors ranging from brick-red to dark-brown but also shows significant NIR solar reflectance. The ability of the pigments to transfer their NIR reflectance properties to a roofing material like asbestos cement sheet was evaluated.

Syntheses, structures and photophysical properties of heteronuclear Zn–Ln coordination complexes

Four heteronuclear Zn–Ln coordination complexes, [Nd 2Zn 2( p-toluylate) 10(phen) 2] ( 1), [Ln 2Zn 2( p-toluylate) 10(phen) 2]·2(HAc) 1/2 (Ln=Tb 2, Ho 3) and [PrZn 2( p-toluylate) 5(Ac) 2(phen) 2] ( 4) (phen=1, 10-phenanthroline), are synthesized by the hydrothermal method and their structures are measured by single-crystal X-ray diffraction. The IR and UV–vis–NIR absorption spectra and the emission spectra in the visible and near-infrared (NIR) regions of the four complexes are determined at room temperature. In the NIR region (or in the visible region), the complexes show the characteristic emission bands of Ln 3+ ions, which may be attributed to sensitization from the ligands (the ligand directly-coordinated to Ln 3+ ions and d-block) to Ln 3+ ions after forming the Zn–Ln complexes. It is reported for the first time in this paper that the Zn–Pr complex 4 can exhibit the broad emission band in the NIR region. In addition, the shift, split or broadness of the ff emission bands in the NIR region of complexes 1, 3 and 4 are discussed.

Preparation of CIGS Thin Films by Electrodeposition Method Using Ethanol as a Solvent

We prepared copper indium gallium diselenide (CIGS) thin films by potentiostatic electrodeposition in an ethanol solution. The thin films were characterized by scanning electron microscopy (SEM), X-ray energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and UV-visible-near infrared (UV-VIS-NIR) spectrophotometry to determine their morphology, composition, crystal structure, and absorption properties. The results show that the chalcopyrite structured CuIn0.7Ga0.3Se2 thin films can be obtained by annealing the electrodeposited films at-1.6 V (vs SCE) at 450 °C. The obtained thin film has uniform morphology, good crystallinity, and a bandgap of about 1.17 eV. We found that ethanol as a solvent can effectively avoid the hydrogen evolution phenomenon, which often occurs in aqueous solution and reduces the deposition potential limitation.

Comparison of thermal protective performance of aluminized fabrics of basalt fiber and glass fiber

AbstractRapid progress has been made in the field of fire protection during the past few decades, nevertheless, the development of fire protective clothing with prolonged durability has always been a matter for public attention. In order to prevent or minimize skin burn damage resulting from flashover, a kind of thermal protective composite fabric, the surface of which is aluminized, has been upgraded and developed. Using the UV–Vis–NIR (ultraviolet–visible–near infrared) spectrophotometer, the thermal radiation protective performance of aluminized fabrics made of basalt fiber and glass fiber were evaluated and compared. The aluminized fabrics and the substrate fabrics used were exposed to a fire environment generated by burning liquified gas for a few minutes, aiming at evaluating the protective effect of the aluminum coating and characterizing the thermal insulating performance. The results showed that the spectral reflectance of aluminized fabrics present obvious differences over a wide range of wavelengths, perhaps due to the different yarn parameters and weave structure. The fire exposure experiment indicated that the aluminized fabric of basalt fiber had better thermal protective performance than the substrate fabrics. Although the thermal insulating performance of aluminized fabrics is insufficient to provide enough time for people to focus on his/her job, the aluminized fabrics exhibit great potential application in the fields of firefighting and military. Copyright © 2010 John Wiley &amp; Sons, Ltd.