Reflectance Spectroscopy Measurements Research Articles

Combined reflectance spectroscopy and coherent light backscattering measurement differentiate cervical cancer from normal epithelial tissue in a xenograft mouse model.

Cervical cancer is a type of slow-growing cancer associated with high mortality rates. Early detection can enable lifesaving early intervention. Current cervical premalignant lesion detection methods suffer from both high miss rates and excessive referrals for unnecessary biopsies. Herein, coherent light backscatter and modifications in reflected white-light spectra were measured to specifically discriminate between cervical tumors and normal squamous epithelial tissues resected from a mouse xenograft model. The combined measurements resulted in 92% sensitivity and 93% specificity in discrimination between the two tissues. These methods can be used to develop a noninvasive portable optical probe for sensitive and objective detection of precancer and cancer epithelial lesions in the cervix and other accessible epithelial tissues.

Rapid atomic layer etching of Al2O3 using sequential exposures of hydrogen fluoride and trimethylaluminum with no purging

A dramatic increase in the Al2O3 atomic layer etching (ALE) rate versus time was demonstrated using sequential, self-limiting exposures of hydrogen fluoride (HF) and trimethylaluminum (TMA) as the reactants with no purging. The normal purging expected to be required to prevent chemical vapor etching or chemical vapor deposition (CVD) is not necessary during the Al2O3 ALE. This purgeless, rapid atomic layer etching (R-ALE) was studied from 250 to 325 °C using various techniques. In situ quartz crystal microbalance (QCM) measurements monitored Al2O3 R-ALE at 300 °C. The Al2O3 R-ALE process produced linear etching versus number of R-ALE cycles. Each HF exposure fluorinates the Al2O3 substrate to produce an AlF3 surface layer. Each subsequent dose of TMA then undergoes a ligand-exchange transmetalation reaction with the AlF3 surface layer to yield volatile products. Using reactant partial pressures of HF = 320 mTorr and TMA = 160 mTorr, the fluorination and ligand-exchange reactions produced a mass change per cycle (MCPC) of −32.1 ng/(cm2 cycle) using sequential, 1 s exposures for both HF and TMA with no purging. This MCPC equates to a thickness loss of 0.99 Å/cycle or 0.49 Å/s. Comparison experiments using the same reactant exposures and purge times of 30 s yielded nearly identical MCPC values. These results indicate that the etch rates for Al2O3 R-ALE are much faster than for normal Al2O3 ALE because of shorter cycle times with no purging. Smaller MCPC values were also observed at lower reactant pressures for both Al2O3 R-ALE and Al2O3 ALE. The QCM studies showed that the Al2O3 R-ALE process was self-limiting versus reactant exposure. Ex situ spectroscopic ellipsometry and x-ray reflectivity (XRR) measurements revealed temperature-dependent etch rates from 0.02 Å/cycle at 270 °C to 1.12 Å/cycle at 325 °C. At lower temperatures, AlF3 growth was the dominant mechanism and led to an AlF3 atomic layer deposition (ALD) growth rate of 0.33 Å/cycle at 250 °C. The transition temperature between AlF3 growth and Al2O3 etching occurred at ∼270 °C. XRR scans showed that the Al2O3 ALD films were smoothed by Al2O3 R-ALE at temperatures ≥270 °C. Additionally, patterned wafers were used to compare Al2O3 R-ALE and normal Al2O3 ALE in high aspect ratio structures. Scanning electron microscope images revealed that the etching was uniform for both processes and yielded comparable etch rates per cycle in the high aspect ratio structures and on flat wafers. The HF and TMA precursors were also intentionally overlapped to explore the behavior when both precursors were present at the same time. Similar to ALD, where precursor overlap produces CVD, precursor overlap during Al2O3 ALE leads to AlF3 CVD. However, any AlF3 CVD growth that occurs during precursor overlap is removed by spontaneous AlF3 etching during the subsequent TMA exposure. This spontaneous AlF3 etching explains why no purging is necessary during R-ALE. R-ALE represents an important advancement in the field of thermal ALE by producing rapid etching speeds that will facilitate many ALE applications.

On the Effect of Thin Film Growth Mechanisms on the Specular Reflectance of Aluminium Thin Films Deposited via Filtered Cathodic Vacuum Arc

The optimisation of the specular reflectance of solar collectors is a key parameter to increase the global yield of concentrated solar power (CSP) plants. In this work, the influence of filtered cathodic vacuum arc deposition parameters, particularly working pressure and deposition time, on the specular and diffuse reflectance of aluminium thin films, was studied. Changes in specular reflectance, measured by ultraviolet–visible and near-infrared spectroscopy (UV-vis-NIR) spectrophotometry, were directly correlated with thin film elemental concentration depth profiles, obtained by Rutherford backscattering spectrometry (RBS), and surface and cross-sectional morphologies as measured by scanning electron microscopy (SEM) and profilometry. Finally, atomic force microscopy (AFM) provided information on the roughness and growth mechanism of the films. The two contributions to the total reflectance of the films, namely diffuse and specular reflectance, were found to be deeply influenced by deposition conditions. It was proven that working pressure and deposition time directly determine the predominant factor. Specular reflectance varied from 12 to 99.8% of the total reflectance for films grown at the same working pressure of 0.1 Pa and with different deposition times. This transformation could not be attributed to an oxidation of the films as stated by RBS, but was correlated with a progressive modification of the roughness, surface, and bulk morphology of the samples over the deposition time. Hence, the evolution in the final optical properties of the films is driven by different growth mechanisms and the resulting microstructures. In addition to the originally addressed CSP applications the potential of the developed aluminium films for other application rather than CSP, such as, for example, reference material for spectroscopic diffuse reflectance measurements, is also discussed.

Quantitative in vivo detection of adipose tissue browning using diffuse reflectance spectroscopy in near‐infrared II window

White adipose tissue (WAT) and brown adipose tissue (BAT) biologically function in an opposite way in energy metabolism. BAT induces energy consumption by heat production while WAT mainly stores energy in the form of triglycerides. Recent progress in the conversion of WAT cells to "beige" or "brown-like" adipocytes in animals, having functional similarity to BAT, spurred a great interest in developing the next-generation therapeutics in the field of metabolic disorders. Though magnetic resonance imaging and positron emission tomography could detect classical BAT and WAT in animals and humans, it is of a great challenge in detecting the "browning" process in vivo. Here, to the best of our knowledge, for the first time, we present a simple, cost-effective, label-free fiber optic-based diffuse reflectance spectroscopy measurement in the near infrared II window (~1050-1400 nm) for the quantitative detection of browning in a mouse model in vivo. We could successfully quantify the browning of WAT in a mouse model by estimating the lipid fraction, which serves as an endogenous marker. Lipid fraction exhibited a gradual decrease from WAT to BAT with beige exhibiting an intermediate value. in vivo browning process was also confirmed with standard molecular and biochemical assays.

Intraoperative liver steatosis characterization using diffuse reflectance spectroscopy

BackgroundLiver steatosis is associated with poor outcome after liver transplantation and liver resection. There is a need for an accurate and reliable intraoperative tool to identify and quantify steatosis. This study aimed to investigate whether surface diffuse reflectance spectroscopy (DRS) measurements could detect liver steatosis on humans during liver surgery. MethodsThe DRS instrumentation setup consists of a computer, a high-power tungsten halogen light source and two spectrometers, connected through a trifurcated optical fiber to a hand-held probe. Patients scheduled for open resection for liver tumors were considered for inclusion. Multiple DRS measurements were performed on the liver surface after mobilization. ResultsIn total, 1210 DRS spectra originated from 38 patients, were analyzed. When applying the data to an analytical model the volumetric absorption ratio factor of fat and water specified an explicit distinction between mild to moderate, and moderate to severe steatosis (p < 0.001). There were significant differences between none-to-mild and moderate-to-severe steatosis grade for the following parameters: reduced scattering coefficient (p < 0.001), Mie to total scattering fraction (p < 0.001), Mie slope (p = 0.003), lipid/(lipid + water) (p < 0.001), blood volume (p = 0.044) and bile volume (p < 0.001). ConclusionThis study shows that it is possible to evaluate steatosis grades with hepatic surface diffuse reflectance spectroscopy measurements.

Nanostructured BiOI for air pollution control: Microwave-assisted synthesis, characterization and photocatalytic activity toward NO transformation under visible light irradiation

In the last decades, air pollution control has received much attention due to the increase of environmental and health problems. The design of new materials with potential applications in air pollution control systems is a challenge nowadays. In this work, BiOI nanostructured materials were synthesized and used for photocatalytic oxidation of nitric oxide (NO). A microwave-assisted solvothermal method was successfully applied for BiOI synthesis at 126 °C, using ethylene glycol (EG) as a solvent. Several samples were prepared by varying the microwave irradiation time between 5 and 120 min. Resulting materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N2 adsorption-desorption isotherms, diffuse reflectance spectroscopy (DRS) and photoluminescence measurements (PL). The photocatalytic activity of BiOI samples was evaluated in the photo-oxidation reaction of nitric oxide (NO) in gas phase under visible light irradiation. BiOI sample synthesized after 15 min of microwave exposition shows the highest photocatalytic activity, even greater than that obtained when TiO2Evonik P-25 is used. This nanostructured material was applied into the formulation of two types of materials (ceramic paint and stucco) for its potential use in the construction industry. Preliminary results show that the application of nanostructured BiOI into stucco formulation has a great potential to develop commercial products to remove NO from air.

Hydrogen Generation Over Cobalt Containing Microporous Aluminohosphates Photo-Catalyst

Novel photo-catalytic materials based on cobalt type aluminophosphate molecular sieves have been elaborated in AEL and AFI structure by hydrothermal method. The photo-catalytic activity of CoAlPO4-5 and CoAlPO4-11 were evaluated for hydrogen production via water reduction under visible irradiation.The synthesizedmaterials werecharacterized thoroughly with respect toelemental analysis, X-Ray diffraction (XRD), scanning electron microscopy(SEM), fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DR), N2 adsorption (BET) and NH3 desorption measurement. Electrical conductivity, electrochemical and photo-electrochemical measurementssuch as cyclic voltammetry, currents-potential, Mott-schottky and Nykist were also studied.SinceAlPO4 materials possess a unique chemical composition as well as structural and micro-morphological characteristics. The photo-catalystshave shown a more negative flat band potential (Vfb = 0.31 eV) and a remarkable surface area -- 183 and 258 m2 g-1 which lead to a better accelerationof the charge (e-/h ) transfer by increasing the number of surface reaction sites.In this approach, hydrogen was produced at atmospheric pressure and a temperature of 50 °C. Under visible light, the photo-catalysts exhibited a good photo-catalytic activity for hydrogen production with a yield of 64 and 1260 µmol g-1min-1 for CoAlPO4-5 and CoAlPO4-11, respectively.

In vivo percutaneous reflectance spectroscopy of fatty liver development in rats suggests that the elevation of the scattering power is an early indicator of hepatic steatosis

This study assessed whether there was a scattering spectral marker quantifiable by reflectance measurements that could indicate early development of hepatic steatosis in rats for potential applications to pre-procurement organ evaluation. Sixteen rats were fed a methionine-choline-deficient (MCD) diet and eight rats were fed a normal diet. Direct assessment of the liver parenchyma of rats in vivo was performed by percutaneous reflectance spectroscopy using a single fiber probe at the beginning of diet-intake and arbitrary post-diet-intake times up to 11 weeks to render longitudinal comparison. Histological sampling of the liver over the duration of diet administration was performed on two MCD-diet treated rats and one control rat euthanized after reflectance spectroscopy measurement. The images of hematoxylin/eosin-stained liver specimens were analyzed morphometrically to evaluate the lipid size changes associated with the level of steatosis. The MCD-diet-treated group ([Formula: see text]) had mild steatosis in seven rats, moderate in three rats, severe in six rats, and no other significant pathology. No control rats ([Formula: see text]) developed hepatic steatosis. Among the parameters retrieved from per-SfS, only the scattering power (can be either positive or negative) appeared to be statistically different between MCD-treated and control livers. The scattering power for the 16 MCD-diet-treated livers at the time of euthanasia and presenting various levels of steatosis was [Formula: see text], in comparison to [Formula: see text] of the eight control livers [Formula: see text]. When evaluated at days 12 and 13 combined, the scattering power of the 16 MCD-diet-treated livers was [Formula: see text], in comparison to [Formula: see text] of the eight control livers ([Formula: see text]). All of four MCD-treated livers harvested at days 12 and 13 presented mild steatosis with sub-micron size lipid droplets, even though none of the MCD-treated livers were sonographically remarkable for fatty changes. The elevation of the scattering power may be a valuable marker indicating early hepatic steatosis before the steatosis is sonographically detectable.

Structural, morphological and dielectric investigations on NiO/CuO/ZnO combined semiconductor metal oxide structures based ternary nanocomposites

NiO/CuO/ZnO combined semiconductor metal oxide structures based ternary nanocomposites were synthesized in 2:1:1, 1:2:1 and 1:1:2 molar ratios using a simple and combined co-precipitation - hydrothermal method without utilizing any fuels, capping agents or surfactants. The structural, bonding, band gaps and morphological behaviour of the synthesized ternary nanocomposites were investigated using x-ray diffraction, Fourier transform infrared spectroscopy, UV-Diffuse reflectance spectroscopy and atomic force microscopic measurements. The dielectric properties recorded for these combined semiconductor metal oxide structures are valid with Maxwell-Wagner (M-W) model which is based on the dielectric nature in conducting grains layered with poorly conducting grain boundaries. The higher values of dielectric constant were observed for the ternary nanocomposite ratio 1:2:1 and the reduction in the values of dielectric constant of other ternary nanocomposite ratios (1:1:2 and 2:1:1) at lower frequencies is due to the fact the grain boundaries are preferably occupied by more Cu2+ ions than Ni2+ and Zn2+ ions. This kind of attempt in investigating the physical insights of combined semiconductor metal oxide structures is needed for the development of novel semiconducting devices.

Reduction in the band gap of anodic TiO2 nanotube arrays by H2 plasma treatment

Abstract Influence of the hydrogen (H2) plasma treatment on the anodic titanium dioxide (TiO2) nanotubes physical properties was studied. The Titanium substrates were anodized in an ethylene-glycol-based electrolyte solution containing 0.3 wt% ammonium fluoride (NH4F) and 3 vol% deionized (DI) water at a potential of 50 V for 1 h at room temperature. The TiO2 nanotubes arrays hold a great potential as the electrode materials for high-performance electrochemical applications. However, TiO2 nanotubes poor electronic conductivity limits their applications. Here, TiO2 nanotubes were treated with H2 plasma to improve the optical properties of the TiO2 nanotubes. The morphology, crystal structure, and optical band gap of the anodic TiO2 nanotubes were investigated. The morphology of the TiO2 nanotubes was studied by using field-emission scanning electron microscopy (FESEM). The roughness of the treated TiO2 nanotubes walls were enhanced compared to non-treated TiO2 nanotubes and also diameter of the H2 plasma treated nanotubes decreased. UV–Vis diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) measurements revealed that the H2 plasma treated TiO2 nanotubes have slightly lower band gap energy compare to the non-treated TiO2 nanotubes.

Charge Carrier Dynamics in TiO2 Mesocrystals with Oxygen Vacancies for Photocatalytic Hydrogen Generation under Solar Light Irradiation

There is a great concern about black TiO2 prepared by H2 treatment because of its ability to enhance light harvesting of TiO2. Black TiO2 shows different photocatalytic activities compared with white TiO2. However, the mechanism of photocatalytic reaction has not been clearly understood. Here, femtosecond time-resolved diffuse reflectance (fs-TRDR) spectroscopy and single-particle photoluminescence measurements were applied to gain better understanding about the relation between oxygen vacancy, charge transfer, lifetime of photogenerated charge, and photocatalytic activity. We prepared reduced TiO2 mesocrystals (R-TMC) through simple solid-state chemical reduction at moderate temperature 350 °C. R-TMC has nearly two times higher photocatalytic activity for H2 production under solar light irradiation. The presence of oxygen vacancies and Ti3+ was studied by electro paramagnetic resonance and X-ray photoelectron spectroscopy. This work confirms the findings of previous studies that enhancement of light abso...

Anodic growth of Nitrogen-doped Titanium dioxide nanotubes by anodization process of elemental Titanium in ethylene glycol based electrolyte solution with different water contents

Anatase Nitrogen-doped Titanium Dioxide (Nitrogen-doped TiO2) nanotubes were grown via an anodization process in an ethylene-glycol based electrolyte solution containing ammonium fluoride (NH4F) and different water contents (2–4 vol%). These electrolyte solutions act as the dopants sources of Nitrogen in anodic TiO2 nanotubes. The influence of different water content of electrolyte solution on physical properties of the Nitrogen-doped TiO2 nanotubes was studied. It was observed that the diameter of the Nitrogen-doped TiO2 nanotubes was increased by the water content increasing of the electrolyte solution. Also, the Nitrogen-doped TiO2 nanotubes which grown in the electrolyte solution with 3 vol% water content had maximum length. An energy dispersive X-Ray analysis (EDX) revealed that the TiO2 nanotubes were heavily doped with Nitrogen. UV–Vis diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) measurements showed that the Nitrogen-doped TiO2 nanotubes had narrow band gap energy (lower than 3 eV).

Effective Shielding of NaYF4:Yb3+,Er3+ Upconverting Nanoparticles in Aqueous Environments Using Layer-by-Layer Assembly.

Aqueous solutions are the basis for most biomedical assays, but they quench the upconversion luminescence significantly. Surface modifications of upconverting nanoparticles are vital for shielding the obtained luminescence. Modifications also provide new possibilities for further use by introducing attaching sites for biomolecule conjugation. We demonstrate the use of a layer-by-layer surface modification method combining varying lengths of negatively charged polyelectrolytes with positive neodymium ions in coating the upconverting NaYF4:Yb3+,Er3+ nanoparticles. We confirmed the formation of the bilayers and investigated the surface properties with Fourier transform infrared and reflectance spectroscopy, thermal analysis, and ζ-potential measurements. The effect of the coating on the upconversion luminescence properties was characterized, and the bilayers with the highest improvement in emission intensity were identified. In addition, studies for the nanoparticle and surface stability were carried out in aqueous environments. It was observed that the bilayers were able to shield the materials’ luminescence from quenching also in the presence of phosphate buffer that is currently considered the most disruptive environment for the nanoparticles.

Multiwavelength time-resolved near-infrared spectroscopy of the adult head: assessment of intracerebral and extracerebral absorption changes.

An optical technique based on diffuse reflectance measurement combined with indocyanine green (ICG) bolus tracking is extensively tested as a method for the clinical assessment of brain perfusion at the bedside. We report on multiwavelength time-resolved diffuse reflectance spectroscopy measurements carried out on the head of a healthy adult during the intravenous administration of a bolus of ICG. Intracerebral and extracerebral changes in absorption were estimated from an analysis of changes in statistical moments (total number of photons, mean time of flight and variance) of the distributions of times of flight (DTOF) of photons recorded simultaneously at 16 wavelengths from the range of 650-850 nm using sensitivity factors estimated by diffusion approximation based on a layered model of the studied medium. We validated the proposed method in a series of phantom experiments and in-vivo measurements. The results obtained show that changes in the concentration of the ICG can be assessed as a function of time of the experiment and depth in the tissue. Thus, the separation of changes in ICG concentration appearing in intra- and extracerebral tissues can be estimated from optical data acquired at a single source-detector pair of fibers/fiber bundles positioned on the surface of the head.

Fabrication of Novel n-SrTiO3/p-BiOI Heterojunction for Degradation of Crystal Violet Under Simulated Solar Light Irradiation

Novel n-SrTiO3/p-BiOI heterojunction composites were successfully fabricated by loading SrTiO3 particles onto the surface of BiOI nanoflakes via a two-step method. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy-disperse X-ray spectroscopy (EDS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), diffuse reflectance spectroscopy (DRS) and electrochemical measurements. The results show that the n-SrTiO3/p-BiOI heterojunction composites are composed of perovskite structure SrTiO3 and tetragonal phase BiOI. The composites exhibit excellent photocatalytic performance for the degradation of crystal violet (CV) solution under simulated solar light irradiation, which is superior to that of pristine BiOI and SrTiO3. The 30[Formula: see text]wt.%SrTiO3/BiOI composite is found to be the optimal composite, over which the dye degradation reaches 92.5% for 30[Formula: see text]min of photocatalysis. The photocatalytic activity of the 30[Formula: see text]wt.%SrTiO3/BiOI composite is found to be 3.94 times and 28.2 times higher than that of bare BiOI and SrTiO3, respectively. The reactive species trapping experiments suggest that [Formula: see text] and holes are the main active species responsible for the CV degradation. In addition, the electrochemical measurements elucidate the effective separation of photoinduced electron–hole pairs. Moreover, on the basis of experimental and theoretical results, a possible mechanism for the enhanced photocatalytic performance of the SrTiO3/BiOI heterojunction composites is also proposed.

A novel method for the synthesis of Ag3VO4/Ag2VO2PO4 heterojunction photocatalysts with improved visible-light photocatalytic properties

Abstract Ag3VO4/Ag2VO2PO4 heterostructure with highly enhanced visible light photocatalytic activity were synthesized by using Ag2VO2PO4 as the sacrificed template in different concentration of ammonia solution. Their crystalline structure, morphology, optical, and electrochemical properties were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, infrared spectroscopy, and electrochemical measurements. The photocatalytic degradation activities of as-prepared samples were evaluated by the photocatalytic of methylene blue (MB), methyl orange (MO) and imidacloprid in the aqueous phase. Compared with bare Ag2VO2PO4, the etched samples Ag3VO4/Ag2VO2PO4 exhibit the significantly enhanced photocatalytic activity under visible light irradiation. The Ag3VO4/Ag2VO2PO4 with 0.15 M etched sample exhibits the highest activity, which are nearly 3.8, 8.6 and 9 times higher than bare Ag2VO2PO4 for removal of MB, MO and imidacloprid, respectively. The improved photocatalytic performance of Ag3VO4/Ag2VO2PO4 can be attributed to the formation of Ag2VO2PO4/Ag3VO4 heterojunction, which suppresses the recombination of photoinduced charges and prolongs the lifetime of the charges. Moreover, the photostability and dominant active species were investigated.

Construction of Eu2O3/g‐C3N4 Redox Heterojunctions Containing Eu3+/Eu2+ Self‐Redox Centers for Boosted Visible‐Light Photocatalytic Activity

The in‐built self‐redox couple in a heterojunction can indeed boost its photocatalytic activity. Herein, to obtain highly efficient visible‐light photocatalysis, a new Eu2O3/g‐C3N4 redox heterojunction is designed and fabricated by a facile in situ growth strategy. Compared with pure g‐C3N4, the as‐prepared Eu2O3/g‐C3N4 redox heterojunction shows extremely enhanced photocatalytic performance for the decontamination of organic contaminants under visible‐light irradiation. The presence of the Eu3+/Eu2+ self‐redox couple is identified by X‐ray photoelectron spectroscopy spectra analysis, before and after photoreaction. The boosted photocatalytic mechanism is explored systematically through UV/Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and photocurrent measurements. Moreover, the radical trapping and electron paramagnetic resonance experiments reveal that ·O2– and h+ are the main active species, and a small amount of ·OH radical is also generated. The boosted photocatalytic performance is derived from the effective separation of photogenerated e–/h+ pairs by forming a Eu2O3/g‐C3N4 heterostructure with a self‐redox center. In particular, the self‐redox couple of Eu3+/Eu2+ can lead to more effective separation of the photogenerated charge carriers, as well as to sustainable production of ·O2–. It is anticipated that our study could provide new insight into the development of g‐C3N4‐based redox heterojunctions with high visible‐light photocatalytic performance.

Hybrid Diffuse Reflectance Spectroscopy: Non-Erythemal in vivo Testing of Sun Protection Factor

Background/Aims: In order to define a label sun protection factor (SPF) of topically applied sunscreens, in vivo test methods like ISO 24444, FDA guideline, or the Australian standard are used worldwide. The basis of all these methods is provoking an erythemal skin reaction by UV irradiation to find the level of unprotected and protected minimal erythemal doses (MED). In vitro methods replacing the human skin by any kind of non-human material are still not available. Thus, offering the new hybrid diffuse reflectance spectroscopy (HDRS) technique that is able to stay on an in vivo level for SPF testing but meanwhile neglecting the UV-dose-related erythemal skin reaction is a perfect combination to take care of sun protection and any ethical concerns in SPF testing nowadays. Methods: HDRS is a combination of in vivo diffuse reflectance spectroscopy (DRS) measurements on the skin and in vitro transmission measurements of a sunscreen on a roughened polymethylmethacrylate plate. By this technique, the in vivo behavior of the investigated sunscreen on the skin is measured as well as the UVB absorption, which is still non-visible in the reflectance technique. In order to establish an alternative method for in vivo SPF testing, a huge number of sunscreens (80 samples) was measured by HDRS and compared to the worldwide accepted standard ISO 24444. The variety of sunscreens measured reflects a wide range of different types of formulations as well as a wide range of SPFs (5–120) to validate this new alternative SPF testing procedure. Results: The applied quantity of product as well as skin color dependencies of signal generation are shown to support any basic correlation of DRS signal generation and sun protection expectations. Far-reaching statistical data analyses show an excellent link of the new non-erythemally driven HDRS-SPF technique and ISO 24444 results. In the same way, HDRS-UVA-PF results can be correlated with UVA-PF values calculated from ISO 24443. Conclusion: Due to the elimination of any erythemal relevant UVB and UVA doses, absolutely no skin reaction occurs. Consequently there is no need to define a MED any more. For the first time an alternative way to SPF is shown without any ethical concerns of SPF testing in vivo and/or any restriction of SPF testing in vitro. Regardless of the type of formulation or the level of protection, an excellent correlation of SPF_HDRS and SPF₂₄₄₄₄ for sunscreen labeling could be found. By this new alternative non-erythemal technique, not only SPF values can be measured, but also UVA-PF values can be calculated with an excellent correlation to ISO 24443 from the same set of data. For the first time a robust alternative test method of SPF- and UVA-PF values is described, taking into account the interaction of sunscreen formulation and skin.

Improving grade control efficiency with rapid on-line elemental analysis

Flotation circuit control is typically based on regular on-line elemental analyses. In base metal applications the conventional assaying method is X-ray fluorescence (XRF), which has proven to be a reliable and accurate technology. However, in large flotation plants with many sample streams to be analyzed, the measurement frequency for individual assays decreases because a centralized XRF analyzer can only measure one stream at a time. This results in unnecessary delays that reduce the control performance. Nevertheless, by integrating reflectance spectroscopy measurement with the conventional XRF technology, a practically continuous assay can be obtained. In this paper the advantages of improved analysis cycle to process performance via faster automated higher level flotation circuit control are demonstrated. The presented technology enables capturing and reacting to grade fluctuations that may have been missed with longer measurement intervals. Moreover, response time to drastic changes in flotation circuit operation is significantly reduced which results in better process performance.

CO2 to Liquid Fuels: Photocatalytic Conversion in a Continuous Membrane Reactor

The photocatalytic reduction of CO2 into value-added chemicals using sunlight is a promising approach to promote energy-bearing products, mitigating the adverse effects of anthropogenic CO2 emissions. In this work, exfoliated C3N4 was incorporated into Nafion matrix and used in a continuous photocatalytic reactor for converting CO2 into liquid fuels. Comprehensive structural and morphological diffuse reflectance spectroscopy (DRS), FT-IR, ATR-IR, and SEM measurements were performed for C3N4-loaded Nafion membrane and then compared with those of a Nafion membrane without any catalyst. The synergic effect of C3N4 organic catalyst embedded in a Nafion dense matrix and a continuous operating mode of the photoreactor was successfully accomplished for the first time, as yet absent in the literature, analyzing the reactor performance as a function of key parameters such as contact time and H2O/CO2 feed molar ratio. The reactor performance was analyzed under UV–vis light in terms of productivity, selectivity, and...