Optical Diffuse Reflectance Research Articles

Broadband Near-Infrared Photoluminescence and Strong Visible Up-Conversion Emission in BaTiO3-(Na0.5Er0.5)TiO3 Lead-Free Piezoelectric Ceramics

For checking photoluminescence properties of BaTiO3-(Na0.5Er0.5)TiO3 lead-free piezoelectric ceramics, optical diffuse reflection spectra, visible up-conversion luminescence spectra, 1.55 μm near-infrared photoluminescence spectra, and optical temperature sensing performances under the excitation of 980 nm laser were investigated systematically. Broadband near-infrared (˜1.55 μm, FWHM˜90 nm) emission and strong visible up-conversion (˜550 nm) emission were observed under the 980 nm excitation in the ceramics at room temperature. Near-infrared emission and visible up-conversion emission became stronger with increasing (Na0.5Er0.5)TiO3 concentration below quenching point above which it will degrade. The optimal emission intensity was obtained when (Na0.5Er0.5)TiO3 content was 7 mol%. These ceramics with excellent ferro-/piezoelectric and photoluminescence properties may be useful for ultrasonic transducer, optical temperature sensor, optical amplifier, and other relative applications.

A Correlation Study between Two Adjacent Same-Meridian Acupoints after Laser-Needle Acupuncture with Optical Coherence Tomography and Diffuse Reflectance Spectra.

This study is to investigate the correlations among Sanjian (LI3), Hegu (LI4), and Yangxi (LI5) acupoints and their corresponding nonacupoints on the Yangming Large Intestine Meridian of Hand before and after laser irradiation using optical coherence tomography (OCT) and diffuse reflectance spectra. The experiment was conducted on 10 healthy people. A 658 nm laser with 50 mW output power was used for irradiating LI4, LI5 acupoints and their corresponding nonacupoints. As to LI4 acupoint with laser irradiation for duration of 15 or 45 minutes, the OCT backscattered light intensities of LI4 and LI5 acupoints increased significantly, and the reflectance intensities (RIs) of the LI3, LI4, and LI5 acupoints decreased significantly. As to LI5 acupoint with laser irradiation for duration of 15 or 45 minutes, the changes of OCT backscattered light intensities of the corresponding irradiated acupoint and LI4 acupoint increased significantly, and the RIs decreased significantly. However, the OCT backscattered light intensities and RIs for their nonacupoints were almost not changed. The results show that an association exists between two adjacent same-meridian acupoints on the same meridian after laser-needle acupuncture to some extent.

Challenges and Limitations of Narrow-Band Optical Imaging for Intra-Operative Parathyroid Identification

Background: Surgical resection of the parathyroid glands can be challenging due to poor visual contrast between the parathyroid and surrounding tissues. We hypothesized that narrow-band imaging (NBI) could enhance subtle differences in the colors of these tissues for improved visual contrast during parathyroid surgery. Methods: The diffuse optical reflectances of parathyroid, fat, muscle, and thyroid tissue were measured in vivo as a function of wavelength during six surgical procedures, using a fiber-optic probe and spectrophotometer. Analysis of these data led to three candidate NBI wavelength bands which exhibited the largest differences in reflectance between parathyroid and other tissue types. Color filters at these wavelength bands were attached to the surgeon’s loupes for qualitative visual assessment, and also to a digital camera for quantitative assessment of tissue contrast in seven additional surgeries. Results: Spectroscopic measurements showed that diffuse optical reflectance at green (515 - 565 nm), yellow (570 - 613 nm), and red (604 - 644 nm) wavelengths showed the greatest difference in intensity (appearing brighter or darker) between parathyroid and surrounding tissues. However, visual and digital NBI of the parathyroid using these wavebands generated measured intensities which were not significantly improved as compared to white light, providing only minimal contrast enhancement for the surgeon. Conclusions: Narrow-band color filters can be added to conventional loupes to selectively view the surgical field with light at specific wavelengths. When the parathyroid is viewed with filters chosen to maximize visual contrast between tissue types, there appears to be little benefit in contrast enhancement between tissues due to diminished overall brightness. J Curr Surg. 2016;6(1):14-20 doi: http://dx.doi.org/10.14740/jcs295w

The synthesis of a Ag–ZnO nanohybrid with plasmonic photocatalytic activity under visible-light irradiation: the relationship between tunable optical absorption, defect chemistry and photocatalytic activity

In this work, a visible-light-driven plasmonic Ag–ZnO nanohybrid photocatalyst was prepared by a one-pot approach with the aim of tailoring its structural, electronic and photocatalytic properties. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis optical diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy and electron spin resonance (ESR) spectroscopy. The effects of silver loading on the electronic structure and photodegradation of a rhodamine B dye solution were investigated experimentally and theoretically. It was found that the Ag–ZnO nanohybrid showed an enhanced photocatalytic activity for the degradation of the rhodamine B dye solution under visible-light irradiation and the photocatalytic performance was optimized at an Ag/Zn molar ratio of 0.05. The enhancement of the photocatalytic activity was attributed to the effective charge transfer from the plasmon-excited Ag nanoparticles to ZnO, which suppresses the charge recombination during the photocatalytic process. Optionally, the effective recycling of the photocatalyst was achieved by visible light illumination, free of secondary environmental contamination. This work may provide a new insight into the design and preparation of advanced ZnO-based visible-light photocatalytic materials.

Structural and optical properties of Fe-doped SnS2 nanoflakes prepared by molten salt solid state reaction

Tin (IV) disulfides (SnS2) doped with Fe ions are prepared through the molten salt solid state reaction at 280°C and the effect of the Fe-doping on their structural and optical properties is reported. They were found to be nanocrystalline hexagonal structure with nanoflakes morphology with an average size 30nm. The analysis of the optical data showed that all the samples are indirect semiconductors. Two absorption bands are observed in their optical diffuse reflectance spectra which indicate setting of two photons absorption processes due to formation of Fe intermediate band. The band gaps EgHInd and EgLInd that correspond to the two photons absorptions are found to vary from 1.49 to 1.09eV and 0.76 to 0.93eV, respectively. The most significant findings is that the sum of EgHInd and EgLInd has values between 2.25 and 2.02eV which reproduces or slightly enhances the band gap value of the parent SnS2 (2.01eV). This finding is directly related with the perseveration of the output voltage (Vo) which is a major condition required for realization of intermediate band solar cells with high solar conversion efficiency.

Electroporation-assisted penetration of zinc oxide nanoparticles in ex vivo normal and cancerous human colon tissue

In this study, we presented the research of the penetration of zinc oxide nanoparticles (ZnO NPs) (30 and 90 nm), and electroporation (EP) assisted penetration of the ZnO NPs in the human normal colon (NC) and adenomatous colon (AC) tissues studied with optical coherence tomography (OCT) and diffuse reflectance (DR) measurement. The results have shown that the attenuation coefficient of colon tissue after the application of 30 or 90 nm ZnO NPs alone decreased approximately by 28% and 14% for NC tissue, 35% and 22% for AC tissue, respectively; while the attenuation coefficient of colon tissue after combined application of 30 or 90 nm ZnO NPs/EP decreased approximately by 46% and 30% for NC tissue, and 53% and 42% for AC tissue, respectively. The results illustrate EP can significantly increase the penetration of ZnO NPs in the colon tissue, especially in AC tissue. Through the analysis of attenuation coefficient and reflectance intensity of the colon tissue, we find that the accumulation of the ZnO NPs in the colon tissue greatly influenced the tissue optical properties.

Spectroscopy and structural characteristics of Eu3+-activated perovskite tungstate Ba2La2ZnW2O12

Eu3+-doped tungstate Ba2La2ZnW2O12 was prepared by the high-temperature solid-state reaction method. The x-ray powder diffraction (XRD) patterns indicate that the matrix has a perovskite structure. The samples were characterized by the scanning electron microscope (SEM), by optical diffuse reflection, photoluminescence (PL) spectra and by their decay curves. Eu3+-activated Ba2La2ZnW2O12 shows red luminescence under the excitation of near-ultraviolet and blue light. Laser site-selective excitation and emission spectroscopy technology was applied to investigate the spectroscopic and microstructural properties. The excitation spectra were tested by monitoring the emission from 5D0 → 7F0–4 transitions. Accordingly the emission spectra and decay curves (lifetime) were measured by the excitation in the 5D0 → 7F0 wavelength region using a pulsed, tunable, and narrow-band dye laser. We have detected two Eu3+ sites in Ba2La2ZnW2O12 with the temperature region ranging from 10 K to below 300 K. On the spectra data of the site-selective emission and decay, the Stark energy levels of Eu3+ at two different sites were determined. The lifetimes of Eu3+ ions at the two sites were compared. The energy transfer and crystallographic assignments for the Eu3+ sites were discussed.

Does Laser Surgery Interfere with Optical Nerve Identification in Maxillofacial Hard and Soft Tissue?--An Experimental Ex Vivo Study.

The protection of sensitive structures (e.g., nerves) from iatrogenic damage is of major importance when performing laser surgical procedures. Especially in the head and neck area both function and esthetics can be affected to a great extent. Despite its many benefits, the surgical utilization of a laser is therefore still limited to superficial tissue ablation. A remote feedback system which guides the laser in a tissue-specific way would provide a remedy. In this context, it has been shown that nerval structures can be specifically recognized by their optical diffuse reflectance spectra both before and after laser ablation. However, for a translation of these findings to the actual laser ablation process, a nerve protection within the laser pulse is of utmost significance. Thus, it was the aim of the study to evaluate, if the process of Er:YAG laser surgery—which comes with spray water cooling, angulation of the probe (60°) and optical process emissions—interferes with optical tissue differentiation. For the first time, no stable conditions but the ongoing process of laser tissue ablation was examined. Therefore, six different tissue types (nerve, skin, muscle, fat, cortical and cancellous bone) were acquired from 15 pig heads. Measurements were performed during Er:YAG laser ablation. Diffuse reflectance spectra (4500, wavelength range: 350–650 nm) where acquired. Principal component analysis (PCA) and quadratic discriminant analysis (QDA) were calculated for classification purposes. The clinical highly relevant differentiation between nerve and bone was performed correctly with an AUC of 95.3% (cortial bone) respectively 92.4% (cancellous bone). The identification of nerve tissue against the biological very similar fat tissue yielded good results with an AUC value of 83.4% (sensitivity: 72.3%, specificity: of 82.3%). This clearly demonstrates that nerve identification by diffuse reflectance spectroscopy works reliably in the ongoing process of laser ablation in spite of the laser beam, spray water cooling and the tissue alterations entailed by tissue laser ablation. This is an essential step towards a clinical utilization.

Magnetic and optical properties of Co-doped ZnO nanocrystalline particles

We carried out a systematic study on the effect of Co doping on the structural, magnetic and optical properties of ZnO nanocrystalline particles, using x-ray diffraction, x-ray photoelectron spectroscopy (XPS), Quantum Design PPMS-9 magnetometry, and Ultra Violet-Visible spectroscopy. The Zn1-xCoxO nanoparticles with 0≤x≤0.1 were successfully prepared by the formal solid-state reaction method. The XPS results and the XRD analysis with full structural Rietveld refinement reveals that all Zn1-xCoxO nanocrystalline particles in this Co-doping range have hexagonal wurtzite structure. Co atoms have been successfully incorporated in tetrahedral sites and no secondary phases or Co rich clusters were detected. For all Co-doped ZnO nanoparticles under investigation, the field dependence of the magnetization curves exhibits ferromagnetic behavior with relatively small coercive fields at room temperature. The coercive fields increased with Co-doping and decreased with temperature, as expected. In addition, we found a signature for antiferromagnetic ordering between the Co ions. We also observed a strong correlation between the magnetic and optical behavior of the Co-doped ZnO nanoparticles. Optical diffuse reflectance and absorption spectra exhibit a red shift at room temperature in the absorption band edge with increasing Co-doping. The red shift is attributed to the sp-d exchange interaction between free charge carriers in ZnO band and the localized magnetic moments.

Influence of geometrical thickness of SnO2 based photoanode on the performance of Eosin-Y dye sensitized solar cell

In the present study, efforts have been taken to tune the optical parameters of SnO2 photoelectrode film to enhance the performance SnO2 based Dye Sensitized Solar Cell (DSSC). Influence of geometrical thickness of SnO2 based photoelectrode on light scattering magnitude and light harvesting capability was investigated using optical diffused reflectance and electrochemical impedance measurements. The short circuit current density (JSC) of the DSSC assembled using these photoanodes was apparently the decisive photovoltaic parameter in finalizing its photovoltaic efficiency (η). The variation in the light harvesting efficiency and the electron transfer yield were studied as a function of thickness of the photoanode by virtue of the light scattering magnitude in the films. These two factors appeared to have profoundly influenced JSC and so the photovoltaic performance of DSSC.

Biophotonic endoscopy: a review of clinical research techniques for optical imaging and sensing of early gastrointestinal cancer.

Detection, characterization, and staging constitute the fundamental elements in the endoscopic diagnosis of gastrointestinal diseases, but histology still remains the diagnostic gold standard.New developments in endoscopic techniques may challenge histopathology in the near future. An ideal endoscopic technique should combine a wide-field, “red flag” screening technique with an optical contrast or microscopy method for characterization and staging, all simultaneously available during the procedure. In theory, biophotonic advances have the potential to unite these elements to allow in vivo “optical biopsy.”These techniques may ultimately offer the potential to increase the rates of detection of high risk lesions and the ability to target biopsies and resections, and so reduce the need for biopsy, costs, and uncertainty for patients. However, their utility and sensitivity in clinical practice must be evaluated against those of conventional histopathology.This review describes some of the most recent applications of biophotonics in endoscopic optical imaging and metrology, along with their fundamental principles and the clinical experience that has been acquired in their deployment as tools for the endoscopist. Particular emphasis has been placed on translational label-free optical techniques, such as fluorescence spectroscopy, fluorescence lifetime imaging microscopy (FLIM), two-photon and multi-photon microscopy, second harmonic generation (SHG) and third harmonic generation (THG) imaging, optical coherence tomography (OCT), diffuse reflectance, Raman spectroscopy, and molecular imaging.

Thermoelectric transport properties of CuFeInTe3

In this paper we report on the preparation of CuFeInTe3 and its thermoelectric properties. Optical diffuse reflectance and Raman scattering spectroscopies, as well as X-ray powder diffraction were also carried out. Unprecedented for CuFeInTe3, a direct and an indirect band gap were found from its absorption spectrum. From Hall effect measurements at 300 K the carrier concentration (n), electrical conductivity (σ) and mobility (μ) were determined. In order to investigate whether this material is suitable for thermoelectric applications, the Seebeck coefficient (S), the thermal conductivity (κ) and σ as a function of temperature were measured. The measurements of Hall and Seebeck coefficients showed that alloying CuInTe2 with Fe2+ produces a change from the original p-type to n-type conductivity and causes a decrease in the κ value, while leaving σ unchanged. Relatively large S values were found for CuFeInTe3, with respect to CuInTe2, which were explained on the basis of a probable electron effective mass increase due to Fe2+ incorporation. It was also found, that thermal and electrical conductivities decrease with increasing temperature in the range between 300 and 450 K, while the figure of merit (zT) reaches values of 0.075 and 0.126 at 300 and 450 K respectively. Thus, the zT of CuFeInTe3 increases with temperature, reaching values larger than those reported for CuInTe2.

Novel metal-organic hybrid materials constructed by ferrocenyl terpyridine derivatives and ZnIIX2 (X = Cl−, Br−, I−, SCN− and CH3COO−)

Five novel Zinc (II) metal-organic hybrid materials, [(ZnCl2L)6·6(H2O)·6(CHCl3)] (1), [(ZnBr2L)6·6(H2O)·6(CHCl3)] (2), [ZnI2L·2(CHCl3)]n (3), [Zn(SCN)2L·(CHCl3)]n (4), and [Zn(CHCOO)2L·2(H2O)]n (5), have been assembled by a novel ligand 4′-ferrocenyl-4, 2′: 6′, 4″-terpyridine and different zinc salts under ambient conditions, and their structures have been confirmed by single-crystal X-ray diffraction analysis. The results indicate that both complexes 1 and 2 adopt a metallohexacycle consisting of six ligands and six zinc ions, and complexes 3, 4 and 5 are all one-dimensional polymers. The supramolecular frameworks are constructed by complexes 1–5 through the C–H⋯X (X = Cl, Br, I, S, O or π) or π–π intermolecular interactions. In addition, the optical band gaps were confirmed by use of the optical diffuse reflectance spectra, and the results show that the ligand and complexes 1–5 should have semiconductor properties.

Broadband and high diffuse reflectivity of hollow mesoporous silica nanospheres and their UV light shielding ability for light-labile peroxides

We herein report the optical diffuse reflection properties of hollow mesoporous silica nanospheres (HMSNs). The HMSNs reflect more than 90% of the UV and visible light in the wide range of 240–800nm and more than 70% of the UV light shorter than 240nm, which are significantly higher than that of the bulk silica. The high reflectance of the HMSNs mainly arises from multiple scattering, which is caused by the disordered arrangement of nanospheres with thickness up to several hundred nanometers. Besides, the unique microstructure of HMSNs and the comparable size of HMSNs with UV light may also contribute to their high reflection according to the Mie scattering principles. Unlike semiconductor materials which shield UV light by absorbing UV light and generating reactive species, the HMSNs display extremely low absorption in the UV light region. The high UV light reflection properties as well as the specific hollow mesoporous structures of the HMSNs indicate their superior applications in UV light shielding devices.

Effects of titanium dioxide nanoparticles coupled with diode laser on optical properties of in vitro normal and cancerous human lung tissues studied with optical coherence tomography and diffuse reflectance spectra.

The objective is to investigate the effects of two different sized (60 and 100 nm) titanium dioxide (TiO2) nanoparticles (NPs) penetration and accumulation in in vitro human normal lung (NL) tissue, lung squamous cell carcinoma (LSCC) tissue, and 650-nm diode laser-pretreated tissue on their optical properties studied with optical coherence tomography monitoring and diffuse reflectance (DR) spectra measurement. As with TiO2 NPs penetrating into the tissues, the intensities of DR of the samples increase, and then the enhancements of DR and the attenuation coefficients of the tissues were quantitatively calculated. The results suggest that 650-nm diode laser pretreatment increased the amounts of TiO2 NPs penetration and accumulation in NL and LSCC tissues, and the tissue optical properties were significantly influenced by accumulation of TiO2 NPs.

Synthesis and crystal structure of a novel layered barium antimonate Ba2Sb7O13(OH) with mixed-valence antimony

The compound of Ba2Sb7O13(OH) was synthesized by using hydrothermal method from starting reagents of Ba(OH)2·8H2O, Sb2O3 and KCl. The crystal structure of Ba2Sb7O13(OH) was determined and characterized by single crystal X-ray diffraction method. Ba2Sb7O13(OH) represents a novel two-dimensional layered structure which is composed of SbVO6 and SbIIIO4 polyhedra through sharing corner oxygen atoms. Two types of Sb cations with Sb3+ in sphenoid SbO4 polyhedra and Sb5+ in octahedral SbO6 fashion are mixed in the crystal structure. First-principles electronic structure calculations based on the density functional theory (DFT), as well as the optical diffuse reflectance spectroscopy measurements, indicate that the compound belongs to an indirect band semiconductor with optical band gap of 2.7 eV.

Role of mechanochemical milling in FeVO4 synthesis

Single phase, a FeVO4 triclinic crystalline structure was successfully synthesized by annealing the mechanochemically milled xV2O5·(1−x)α-Fe2O3 composites (x=0.5) at 550°C for 1h. X-ray powder diffraction (XRD), simultaneous differential scanning calorimetry and thermogravimetric analysis (DSC–TGA), Mössbauer spectroscopy, scanning electron microscopy (SEM), and optical diffuse reflectance spectroscopy were combined for a detailed study of the assisting role of the mechanochemical milling process. Mechanochemical milling homogeneously mixed the starting materials of α-Fe2O3 and V2O5 and substantially decreased their average grain sizes. The Mössbauer spectroscopy studies showed that the spectrum of the mechanochemically milled composites consisted of three sextets and one doublet, indicating the occurrence of V5+–Fe3+ ion substitutions in the corresponding α-Fe2O3 and V2O5 lattices, respectively. The partially V5+-substituted α-Fe2O3 phase and Fe3+-substituted V2O5 could be the important intermediate phases in the production of FeVO4 single phase. The synthesized FeVO4 phase had a slightly distorted nature with an unequal ratio in Fe3+ population in three inequivalent sites. Simultaneous DSC–TGA studies indicated that the synthesized FeVO4 is thermally stable up to 600°C. SEM images of the formed FeVO4 confirmed the wide particles size distribution range composed of nano-grains. Optical diffuse reflectance spectroscopy studies showed that the synthesized FeVO4 phase had semiconductor properties, with the band gap energy of ~2.44eV.

ChemInform Abstract: β‐BaGa[B4O8(OH)](H2O) and Ba4Ga [B10O18(OH)5](H2O): New Barium Galloborates Featuring Unusual [B4O8(OH)]5‐ and [B10O18(OH)5]11‐ Clusters.

AbstractThe new title compounds (III) and (V) are characterized by single crystal XRD, IR, UV/VIS, and optical diffuse reflectance spectroscopy, second harmonic generation measurements, and DFT electronic band structure calculations.

Synthesis, structure and enhanced photoluminescence properties of two robust, water stable calcium and magnesium coordination networks.

Two new 3D coordination networks Ca(cca)·H2O (1) and Mg(cca)·2H2O (2) (H2cca = 4-carboxycinnamic acid) are synthesized by solvothermal reactions and characterized by single crystal and powder X-ray diffraction, thermogravimetric analysis, optical diffuse reflection, photoluminescence spectroscopy, and internal quantum yield measurements. Crystal structure analysis reveals that compound 1 is built from edge-sharing chains of seven-coordinated calcium polyhedra, which are connected by the cca ligand to form a 2D layered structure. Compound 2 contains isolated magnesium polyhedra layers. These layers are linked by cca ligands to complete the 3D connectivity. Both compounds 1 and 2 have high thermal stability and remain intact in aqueous solutions of a broad range of pH values ranging from 3 to 11. Both compounds also show significantly enhanced luminescence with respect to the free ligand, giving rise to an increase in quantum yield by as much as 4-fold.

Simultaneous doping and heterojunction of silver on Na2Ta2O6nanoparticles for visible light driven photocatalysis: the relationship between tunable optical absorption, defect chemistry and photocatalytic activity

In this work, we report the synthesis of Na2Ta2O6/Ag heterojunctions with the aim of tailoring their structural, electronic and photocatalytic properties. The as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, UV-vis optical diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The effects of silver doping and heterojunctions on the electronic structure and photodegradation of a rhodamine B dye solution were investigated experimentally and theoretically. It was found that silver played critical roles in modulating the electronic structure, defect chemistry and visible light photocatalytic activity. Partial incorporation of Ag ions into the Na2Ta2O6 host lattice led to a monotonous lattice expansion and introduced an interband for band gap narrowing. Meanwhile, some of the Ag ions were reduced, and crystallized into Ag nanoparticles on Na2Ta2O6 surfaces that can promote the visible light absorption efficiency of Na2Ta2O6/Ag heterojunctions. Moreover, the doping and heterojunction of silver can also result in the modulation of defective oxygen species that have a great impact on photocatalytic performance. As a consequence of the well-controlled electronic structure, surface defect chemistry, Ag particle size, BET surface area, and Ag+ doping effects, the photocatalytic performance of the Na2Ta2O6/Ag heterojunctions was optimized at an as-measured Ag/Ta molar ratio of 1.17.