Optical Diffuse Reflectance Spectroscopy Research Articles

Sonochemical growth of antimony selenoiodide in multiwalled carbon nanotube

This paper presents, for the first time, the nanocrystalline, semiconducting antimony selenoiodide (SbSeI) grown in multi-walled carbon nanotubes (CNTs). It was prepared sonochemically using elemental Sb, Se, and I in the presence of ethanol under ultrasonic irradiation (35 kHz, 2.6 W/cm 2) at 323 K for 3 h. The CNTs filled with SbSeI were characterized by using techniques such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, high-resolution transmission electron microscopy, selected area electron diffraction, and optical diffuse reflection spectroscopy. These investigations exhibit that the SbSeI filling the CNTs is single crystalline in nature and in the form of nanowires. It has indirect allowed energy band gap E gIf = 1.61(6) eV.

Contact and contactless diffuse reflectance spectroscopy: potential for recovery monitoring of vascular lesions after intense pulsed light treatment

Optical fiber contact probe diffuse reflectance spectroscopy and remote multispectral imaging methods in the spectral range of 400 to 1100 nm were used for skin vascular malformation assessment and recovery tracing after treatment by intense pulsed light. The results confirmed that oxy-hemoglobin relative changes and the optical density difference between lesion and healthy skin in the spectral region 500 to 600 nm may be successfully used for objective appraisal of the therapy effect. Color redness parameter a* = 2 is suggested as a diagnostic border to distinguish healthy skin and vascular lesions, and as the indicator of phototreatment efficiency. Valuable diagnostic information on large area (>5 mm) lesions and lesions with uncertain borders can be proved by the multispectral imaging method.

The mechanism of the Fischer–Tropsch reaction over supported cobalt catalysts

Natural gas and coal are converted to fuels by the Fischer–Tropsch reaction, i.e., by reacting CO with H 2, the currently accepted mechanism involving surface carbide formation. We have monitored the adsorbed species and their evolution during Fischer–Tropsch reaction on the commercial catalyst Pt,Co/γ-Al 2O 3 (as a standard), on Co/alumina-pillared montmorillonite (Co,Al-EFW) and its beidellite analogue (both are tri-octahedral smectite clays, but beidellite possesses tetrahedrally coordinated Al in the sheets) via optical diffuse reflectance (DRS 1 1 Optical diffuse reflectance spectroscopy. ) and variable temperature in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS 2 2 Diffuse reflectance infrared Fourier transformation spectroscopy. ). We show that in this case over Pt/Co-γ-Al 2O 3, under model conditions, H 2 reacts with CO forming H–C O bridges over [Co-μO 2-Co] units; this transition state moiety also involves adjacent matrix Al–O–CO units. Subsequent stages provide differing oxygenate species via concerted acid–base reactions. The early stages of the Fischer–Tropsch synthesis thus do not involve surface carbide species and surface oxygenates are generated via concerted reaction of support surface Al-OH with the above HCO-bridging binuclear Co 2+ unit.

Using of sonochemically prepared components for vapor phase growing of SbI 3·3S 8

The using of sonochemically prepared components for growth of SbI 3·3S 8 single crystals from the vapor phase is presented for the first time. The good optical quality of the obtained crystals is important because this material is valuable for optoelectronics due to its non-linear optical properties. The products were characterized by using techniques such as X-ray crystallography, powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, high-resolution transmission electron microscopy, selected area electron diffraction, optical diffuse reflection spectroscopy and optical transmittance spectroscopy. The direct and indirect forbidden energy gaps of SbI 3·3S 8 illuminated with plane polarized light with electric field parallel and perpendicular to the c-axis of the crystal have been determined. The second harmonic generation of light in the grown crystals was observed.

Synthesis, crystal, luminescent properties and electronic structures of two copper(I) halide polymers based on Cu4I4 cubane tetramers

Abstract Two novel coordination polymers [Cu4I4(en)2]n 1 and [Cu4I4(pn)2]n 2 (en = 1,2-diaminoethane and pn = 1,3-diaminopropane) were prepared by hydrothermal methods and determined by single-crystal X-ray diffraction analysis. Compound 1 possesses a 3D zeolite-like architecture with infinite intersected channels, constructing from cubane Cu4I4 tetramers, which is simplified into a twofold interpenetrating dia network. Compound 2 with the similar Cu4I4 cores, features a 2D layer with parallelogram-shaped channels along the b axis, showing a uninodal sql net. Both exhibit luminescent emission bands at about 600 nm at room temperature when excited at 350 and 370 nm, respectively. Furthermore, thermogravimetric analyses, optical diffuse reflectance spectroscopy, and the theoretical calculations were discussed.

Sonochemical preparation of SbS 1−xSe xI nanowires

A sonochemical method for direct preparation of nanowires of SbS 1− x Se x I solid solution has been established. The SbS 1− x Se x I gel was synthesized using elemental Sb, S, Se and I in the presence of ethanol under ultrasonic irradiation (35 kHz, 2 W/cm 2) at 50 °C for 2 h. The product was characterized by using techniques such as powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray analysis, selected area electron diffraction, and optical diffuse reflection spectroscopy. The SEM and HRTEM investigations exhibit that the as-prepared samples are made up of large quantity nanowires with lateral dimensions of about 10–50 nm and lengths reaching up to several micrometers and single-crystalline in nature. The increase of molar composition of Se affects linear decrease of the indirect forbidden optical energy gap as well as the distance between (121) planes of the SbS 1− x Se x I nanowires.

Sonochemical growth of antimony sulfoiodide in multiwalled carbon nanotube

This paper presents for the first time the nanocrystalline, semiconducting ferroelectrics antimony sulfoiodide (SbSI) grown in multiwalled carbon nanotubes (CNTs). It was prepared sonochemically using elemental Sb, S and I in the presence of methanol under ultrasonic irradiation (35 kHz, 2.6 W/cm 2) at 323 K for 3 h. The CNTs filled with SbSI were characterized by using techniques such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, high-resolution transmission electron microscopy, selected area electron diffraction, and optical diffuse reflection spectroscopy. These investigations exhibit that the SbSI filling the CNTs is single crystalline in nature and in the form of nanowires. It has indirect forbidden energy band gap E gIf = 1.871(1) eV.

Sonochemical preparation of SbSeI gel

A novel sonochemical method for direct preparation of nanocrystalline antimony selenoiodide (SbSeI) has been established. The SbSeI gel was synthesized using elemental Sb, Se, and I in the presence of ethanol under ultrasonic irradiation (35 kHz, 2 W/cm 2) at 50 °C for 2 h. The product was characterized by using techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and optical diffuse reflection spectroscopy (DRS). The SEM and HRTEM investigations exhibit that the as-prepared samples are made up of large quantity nanowires with lateral dimensions of about 20–50 nm and lengths reaching up to several micrometers and single crystalline in nature.

Influence of the solvent on ultrasonically produced SbSI nanowires

The influence of the substitution of methanol in place of ethanol during the ultrasonic production of antimony sulfoiodide (SbSI) nanowires is presented. The new technology is faster and more efficient at temperatures greater than 314 K. The products were characterized by using techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), optical diffuse reflection spectroscopy (DRS) and IR spectroscopy. The coexistence of Pna2 1 (ferroelectric) and Pnam (paraelectric) phases at 298 K was observed in the SbSI nanowires produced in methanol. The methanol decomposes during the sonication or due to the adsorption process on SbSI nanowires.

Wavelength Identification and Diffuse Reflectance Estimation for Surface and Profile Soil Properties

Optical diffuse reflectance spectroscopy (DRS) has been used to estimate soil physical and chemical properties, but much of the previous work has been limited to surface soils or to samples obtained from a restricted geographic area. Our objectives in this research were: (1) to assess the accuracy of DRS for estimating variation in several important surface and profile soil properties across a wide range of soils from the U.S. Corn Belt, and (2) to determine the wavelength ranges and/or specific wavelengths that should be included in a DRS soil property sensor. Soil cores were obtained to a 120 cm depth from ten fields, two each in Missouri, Illinois, Michigan, South Dakota, and Iowa. Cores were segmented by pedogenic horizon and samples (n = 165 for the surface soil horizon, n = 697 for all soil horizons in the profile) were analyzed for texture fractions, cations (calcium, magnesium, and potassium) and cation exchange capacity (CEC), pH, total and organic carbon, and total nitrogen using standard laboratory procedures. Spectra were obtained on sieved, air-dried soils from 350 to 2500 nm using a commercial three-detector spectrometer. Reflectance data were related to soil properties using partial least squares (PLS) regression and stepwise multiple linear regression (SMLR). Calibration accuracies varied among the different soil properties, but for a given soil property, similar accuracies were generally obtained with PLS and SMLR. The most accurate estimates, with R2 values above 0.8, were obtained for organic carbon, clay, CEC, and calcium. When data from each of the three spectrometer detector ranges were analyzed separately with PLS, the third detector range (1770 to 2500 nm) provided results similar to those obtained using the complete spectral range. Discrete wavelength models that described 90% or more of the variance described by a full model were obtained using eight or fewer wavelengths for the profile dataset and six or fewer wavelengths for the surface dataset. Several wavelengths and wavelength ranges common to models for multiple soil properties were identified: 2070 nm, 1870 to 1915 nm, and 2220 to 2410 nm. Because additional wavelengths important for individual soil properties were dispersed across the 1770 to 2500 nm spectral range, a full-spectrum sensing approach is recommended for simultaneous estimation of multiple soil properties. A discrete-waveband sensor could be practical for estimating one or two individual soil properties.

Electromagnetic Spectroscopy of Normal Breast Tissue Specimens Obtained From Reduction Surgeries: Comparison of Optical and Microwave Properties

Techniques utilizing electromagnetic energy at microwave and optical frequencies have been shown to be promising for breast cancer detection and diagnosis. Since different biophysical mechanisms are exploited at these frequencies to discriminate between healthy and diseased tissue, combining these two modalities may result in a more powerful approach for breast cancer detection and diagnosis. Toward this end, we performed microwave dielectric spectroscopy and optical diffuse reflectance spectroscopy measurements at the same sites on freshly excised normal breast tissues obtained from reduction surgeries at the University of Wisconsin Hospital, using microwave and optical probes with very similar sensing volumes. We found that the microwave dielectric constant and effective conductivity are correlated with tissue composition across the entire measurement frequency range (|r| approximately 0.5-0.6, p<0.01) and that the optical absorption coefficient at 460 nm and optical scattering coefficient are correlated with tissue composition (|r| approximately 0.4-0.6, p<0.02). Finally, we found that the optical absorption coefficient at 460 nm is correlated with the microwave dielectric constant and effective conductivity (r=-0.55, p<0.01). Our results suggest that combining optical and microwave modalities for analyzing breast tissue samples may serve as a crosscheck and provide complementary information about tissue composition.

Sonochemical preparation of SbSI gel

A novel sonochemical method for direct preparation of nanocrystalline antimony sulfoiodide (SbSI) has been established. The SbSI gel was synthesized using elemental Sb, S and I in the presence of ethanol under ultrasonic irradiation (35kHz, 2W/cm2) at 50°C for 2h. The products were characterized by using techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and optical diffuse reflection spectroscopy (DRS). The SEM and HRTEM investigations exhibit that the as-prepared samples are made up of large quantity nanowires with diameters of about 10–50nm and lengths reaching up to several micrometers and single-crystalline in nature.

In Vivo Assessment of Radio Frequency Induced Thermal Damage of Kidney Using Optical Spectroscopy

Radio frequency ablation is a promising modality for treating small renal tumors. Several studies have been published showing its efficacy. A major drawback in the current management of renal tumors with radio frequency ablation is the lack of an effective modality to accurately monitor the progress of the ablation zone in real-time fashion. Previous studies have demonstrated the feasibility of using optical spectroscopy to assess tissue thermal damage, especially in hepatic lesions. We examined the feasibility of this technology in the setting of renal radio frequency ablation. A portable spectroscopic system was used to acquire in vivo fluorescence and diffuse reflectance spectra from porcine renal tissue undergoing radio frequency ablation in real-time fashion with simultaneous temperature recordings. Fluorescence and diffuse reflectance spectral data were then correlated with various degrees of thermal damage and temperature recordings. The most noticeable change in fluorescence characteristics of renal tissue resulting from thermal coagulation was a strong decrease in fluorescence intensity between 400 and 550 nm. When fully coagulated, a significant increase in diffuse reflectance intensity was observed between 500 and 800 nm. Optical spectroscopy, specifically fluorescence and diffuse reflectance spectroscopy, differs significantly in porcine renal tissues with varying degrees of thermal damage from radio frequency ablation in an in vivo setting. Future clinical studies with sufficient sample size are required to validate the potential of these findings. Optical diagnostics may prove to be a rapid, noninvasive, low cost option for monitoring the tumor response to radio frequency based ablative techniques. It may be integrated into future radio frequency ablation probes.

Hemodialysis monitoring in whole blood using transmission and diffuse reflection spectroscopy: a pilot study

Visible and near infrared transmission and diffuse reflection spectroscopy were used to monitor changes in whole blood resulting from hemodialysis treatment for end-stage renal disease. Blood samples from 8 patients on chronic hemodialysis therapy were measured in the 500- to 1700-nm wavelength range immediately before and after a single treatment. Principal component scores characteristic of each spectrum were derived, and mean pre- and posttreatment scores of the first principal component indicated a significant treatment-dependent change in both optical transmission (P = 0.004) and diffuse reflection (P < 0.001). Significant treatment-induced change persisted (P < 0.05) when the first four principal components were used to account for >97% of the treatment-dependent spectral variation. Some blood spectral changes expressed in terms of difference spectra (posttreatment - pretreatment) were consistent with standard clinical indicators of weight reduction, urea reduction, and potassium change, with probable origins at a molecular level. The results indicate the feasibility of using optical transmission and diffuse reflection spectroscopy to characterize clinically relevant blood changes for the future development of more comprehensive indicators of hemodialysis efficacy and long-term clinical outcomes. Moreover, the optical techniques employed are adaptable for potential online monitoring of blood changes during the hemodialysis treatment.

The Interaction of O2, NO, and N2O with Surface Defects of Dispersed Titanium Dioxide

A combined study of intrinsic structural defects in reduced TiO2 was performed using mass spectrometry, optical diffuse-reflectance spectroscopy, and UV photoelectron spectroscopy (UPS). It was found that the reduction of TiO2 resulted in the appearance of absorption in the region 0.50 ≤ hν ≤ 3.50 eV (400 ≤ λ ≤ 2500 nm), which is formed by absorption due to free electrons (a continuum at hν ≤ 1.50 eV), local centers—Ti3+ ions (a band at 2.00 eV), and oxygen vacancies (bands at 1.17, 2.81, and 2.55 eV). The spectrum of induced occupied electronic states in the forbidden gap and the position of oxygen vacancy levels with respect to the Fermi level were determined by UPS. The absorption of reduced TiO2 was stable on the sample to T = 800 K in a vacuum; however, it weakened in contact with O2, NO, and N2O molecules beginning at T = 300 K (surface sites) and T ≥ 400 K (subsurface sites) as a result of filling oxygen vacancies with atomic oxygen in the course of dissociative adsorption. The adsorption complexes formed by the interaction of O2, NO, and N2O with defects were analyzed by temperature-programmed desorption. The distribution of sites over the energies of oxygen binding was found with the use of a nonuniform surface model, and specific oxygen adsorption species were revealed. It was found that the irradiation of TiO2 activates the formation and decay of sites and results in the formation of specific O2 and N2O adsorption species.

Sonochemical fabrication and characterization of stibnite nanorods.

Regular stibnite (Sb(2)S(3)) nanorods with diameters of 20-40 nm and lengths of 220-350 nm have been successfully synthesized by a sonochemical method under ambient air from an ethanolic solution containing antimony trichloride and thioacetamide. The as-prepared Sb(2)S(3) nanorods are characterized by employing techniques including X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, transmission electron microscopy, selected area electron diffraction, high-resolution transmission electron microscopy, and optical diffuse reflection spectroscopy. Microstructural analysis reveals that the Sb(2)S(3) nanorods crystallize in an orthorhombic structure and predominantly grow along the (001) crystalline plane. High-intensity ultrasound irradiation plays an important role in the formation of these Sb(2)S(3) nanorods. The experimental results show that the sonochemical formation of stibnite nanorods can be divided into four steps in sequence: (1) ultrasound-induced decomposition of the precursor, which leads to the formation of amorphous Sb(2)S(3) nanospheres; (2) ultrasound-induced crystallization of these amorphous nanospheres and generation of nanocrystalline irregular short rods; (3) a crystal growth process, giving rise to the formation of regular needle-shaped nanowhiskers; (4) surface corrosion and fragmentation of the nanowhiskers by ultrasound irradiation, resulting in the formation of regular nanorods. The optical properties of the Sb(2)S(3) amorphous nanospheres, irregular short nanorods, needle-shaped nanowhiskers, and regular nanorods are investigated by diffuse reflection spectroscopic measurements, and the band gaps are measured to be 2.45, 1.99, 1.85, and 1.94 eV, respectively.

Synthesis and characterization of the wide band-gap compound Pr 2Te 4O 11

Single crystals of Pr 2Te 4O 11 have been grown through the reaction of Pr 6O 11 and TeO 2 in a CsCl flux at 1123 K. This compound, which is isostructural with Nd 2Te 4O 11 and Ho 2Te 4O 11, crystallizes in space group C2/ c of the monoclinic system with four formula units in a cell of dimensions at 153 K of a=12.6880(6) Å, b=5.2361(3) Å, c=16.2920(8) Å, β=106.052(1)°, and V=1040.17(9) Å 3. The three dimensional structure is made from the interconnection between ∞ 2[Pr 2O 10 14−] and ∞ 2[Te 4O 11 6−] networks. Pr 2Te 4O 11 is a Curie–Weiss paramagnetic with an effective magnetic moment of 3.59(2) μ B. Optical diffuse reflectance spectroscopy shows typical 4f–4f optical transitions for Pr(III), in addition to a wide band gap of 3.65 eV.

Incorporation of Cr 3+ in dickite: a spectroscopic study

We have investigated a well-ordered sample of natural Cr-bearing dickite from Nowa Ruda (Lower Silesia, Poland) using electron paramagnetic resonance (EPR) at X- and Q-band frequencies (9.42 and 33.97 GHz, respectively) and optical diffuse reflectance spectroscopy. The observation of the spin-forbidden transitions at 15500 and 14690 cm−1 allows us to unambiguously identify the major contribution of octahedrally coordinated Cr3+ ions in the optical spectrum. The X- and Q-band EPR spectra show two superposed Cr3+ signals. The corresponding fine-structure parameters were determined at room temperature and 145 K. These results suggest the substitution of Cr3+ for Al3+ in equal proportions in the two unequivalent octahedral sites of the dickite structure. In kaolin group minerals, the distortion around Cr3+ ions (λ≈ 0.2–0.4) in Al sites is significantly less rhombic than that observed around Fe3+ ions (λ≈ 0.6–0.8).

Hydrothermal Synthesis and Characterization ofM2Te3O8(M=Mn, Co, Ni, Cu, Zn): A Series of Compounds with the Spiroffite Structure

Several compounds isotypic to the mineral spiroffite were obtained as high quality single crystals via hydrothermal reactions. These materials, which have the general formulaM2Te3O8, crystallize in the monoclinic space groupC2/cand contain divalent transition metal ions and tellurite building blocks. Typical synthetic conditions for the preparation of these materials are 375°C for 3–5 days in an aqueous NH4Cl solution. This structure type is based on slabs containing Te2O6groups joined byMcations. These Te2O6groups are made up of two edge-sharing TeO3+1polyhedra. The metal tellurite slabs are connected to one another through tellurium(IV) atoms, which are coordinated by four oxygen atoms in a regular TeO4trigonal bipyramidal configuration. A detailed structural characterization via single crystal X-ray diffraction was performed on four compounds (Co2Te3O8:a=12.690(1) Å,b=5.211(2) Å,c=11.632(2) Å,β=98.98(1)°,V=759.7(3) Å3,R(Rw)=0.023 (0.046); Ni2Te3O8:a=12.407(1) Å,b=5.207(1)Å,c=11.509(1) Å,β=98.723(9)°,V=735.0(2) Å3,R(Rw)=0.025 (0.033); Cu2Te3O8:a=11.8368(8) Å,b=5.266(2) Å,c=12.2419(8) Å,β=100.316(6)°,V=750.7(2) Å3,R(Rw)=0.025 (0.032); Zn2Te3O8:a=12.681(2) Å,b=5.200(2) Å,c=11.786(2) Å,β=99.60(1)°,V=766.3(3) Å3,R(Rw)=0.031 (0.041)). The manganese analog (a=12.896(5) Å,b=5.398(2) Å,c=11.907(5) Å,β= 98.14(4)°) was identified via powder diffraction patterns. The cobalt, nickel, and copper compounds were observed to have an antiferromagnetic transition by DC magnetic susceptibility measurements. The band gaps were obtained by optical diffuse reflectance spectroscopy and show that these compounds are all wide band gap materials.

Zeolite Chemistry of CuZSM-5 Revisited

The recently reported interesting behavior of the EPR spin intensity as freshly prepared CuZSM-5 is dehydrated has been confirmed, and the interpretation offered in explanation has been tested by extending the data. Magnetic susceptibility and optical diffuse reflection spectroscopy have been used to show that the anomalous EPR data correspond to changes in symmetry rather than disproportionation of [CuOH]+ into Cu+ and Cu2+O- as H2O is removed, as previously suggested. Moreover, the relatively small negative Weiss constants suggest that antiferromagnetic coupling through the supposedly EPR silent conventional bridge species, [Cu2+−O2-−Cu2+]2+, cannot be responsible for the relatively large changes in observed EPR spin intensity on dehydration. EPR measures selectively individual paramagnetic species and ignores those of low symmetry, while magnetic susceptibility integrates over all magnetic species in the sample. The changes in the EPR intensities were much larger than those observed by magnetic susceptibility. Furthermore, those from EPR occurred as the first H2O was removed, before any significant change in susceptibility occurred. The EPR data reflected those expected for the decrease in symmetry accompanying dehydration. Support for these views was found in the magnetic susceptibility and optical reflectance data. Evidence for CuO formation concomitant with dehydration was obtained.