Measurements Of Fluorescence Spectra Research Articles

Reflection-enhanced laser-induced fluorescence spectroscopy to improve the analytical sensitivity in liquids

The current work demonstrates a novel approach to enhancing the analytical sensitivity of the laser-induced fluorescence (LIF) technique in liquids. An increase in the fluorescence spectral band intensity of about sixfold compared to the conventional LIF has been achieved. Such betterment has been accomplished by having the fluorophore liquid in a cuvette having a reflecting mirror-like side facing the exciting incident laser beam. The silvered or aluminized reflecting side of the cuvette was tested. The pilot test of the proposed cuvette was performed using an excitation laser light of 405 nm wavelength and five mW average power on chlorophyll-a (Chl-a) samples of different concentrations. As a result, a pronounced improvement in the Chl-a fluorescence spectral band intensity is achieved. Such a novel approach, the reflection-enhanced laser-induced fluorescence (RELIF), has been used to analyze six Egyptian brands of extra virgin olive oil (EVOO). Compared to the LIF measurement results on the same EVOO, the RELIF was superior in terms of the fluorescence-spectrum intensity enhancement factor. Both Ag and Al coatings of the cuvette revealed similar results. Statistical analysis of the measured fluorescence spectra via the partial least square regression (PLSR) method for LIF and RELIF revealed a higher coefficient of determination R2 for both RELIF measurements (with silver and aluminum coating) than for LIF. The proposed novel RELIF approach can be utilized for other fluorophore liquids at higher analytical sensitivity than conventional LIF. On the other hand, the RELIF technique is straightforward, cost-effective, and does not complicate the traditional LIF setup.

Study of fluorescence spectroscopy and molecular mechanisms for the interaction of Hg2+ ions and R-phycoerythrin from marine algae (Porphyra yezoensis).

Heavy metal is a worldwide hazardous material, and many efforts were made to detect them sensitively and selectively. R-phycoerythrin (R-PE), a marine fluorescent protein, is abundant in red algae and participates in photosynthesis. In this work, the fluorescence spectroscopy and molecular mechanism of Hg2+ ions and R-PE were further explored through fluorescence spectrum measurements, time-resolved fluorescence lifetimes, peak fitting of Fourier transform infrared spectroscopy, and molecular docking simulation in this study. It was proved by fluorescent spectrum measurements that Hg2+ ions could lead to static fluorescence quenching. Besides, the interaction was a spontaneous and exothermic process driven by hydrogen bond and Van der Waals (VDW) force. Importantly, Hg2+ ions bound to 78LYS and 82CYS on the α chain and 73CYS and 82CYS on the β chain, which resulted in the structural changes of the peptide chain and affected the secondary structure contents of R-PE. This study further explained the effect of Hg2+ ions on marine fluorescent protein R-PE.

Excited-state dynamics of all-trans protonated retinal Schiff base in CRABPII-based rhodopsin mimics

The rhodopsin mimic is a chemically synthetized complex with retinyl Schiff base (RSB) formed between protein and the retinal chromophore that can mimic the natural rhodopsin-like protein. The artificial rhodopsin mimic is more stable and designable than the natural protein and hence has wider uses in photon detection devices. The mimic structure RSB, like the case in the actual rhodopsin-like protein, undergoes isomerization and protonation throughout the photoreaction process. As a result, understanding the dynamics of the RSB in the photoreaction process is critical. In this study, the ultrafast transient absorption spectra of three mutants of the cellular retinoic acid-binding protein II-based rhodopsin mimic at acidic environment were recorded, from which the related excited-state dynamics of the all-trans protonated RSB (AT-PRSB) were investigated. The transient fluorescence spectra measurements are used to validate some of the dynamic features. We find that the excited-state dynamics of AT-PRSB in three mutants share a similar pattern that differs significantly from the dynamics of 15-cis PRSB of the rhodopsin mimic in neutral solution. By comparing the dynamics across the three mutants, we discovered that the aromatic residues near the β-ionone ring structure of the retinal may help stabilize the AT-PRSB and hence slow down its isomerization rate. The experimental results provide implications on designing a rhodopsin-like protein with significant infrared fluorescence, which can be particularly useful in the applications in biosensing or bioimaging in deeper tissues.

Monitoring of natural water pollution by fluorescence spectroscopy

Introduction. Environmental monitoring of the state of water bodies is an important component of environmental protection. A promising direction for assessing the quality of water bodies is to determine their generalized indicators. Fluorescence spectroscopy can serve as a source of important information about the state of water bodies and sources of their pollution. Purpose of the study - to assess the water pollution of the Moskva River and its tributaries using the fluorescence spectroscopy method. To reveal the influence of oil products on the fluorescence spectra of river water. Materials and methods. The object of the study was water from the Moskva River and its tributaries: Pakhra, Kotlovka, Setun. Water samples from the Moskva River were taken in different parts of the city, which are characterized by varying degrees of pollution. Water fluorescence spectra were measured with SM2203 spectrofluorimeter (ZAO Solar, Belarus), total organic and inorganic carbon, on a TOC-VCHP total carbon analyzer (Shimadzu, Japan). Results. The nature of the fluorescence spectra of the Moskva River and its tributaries in the absence of significant anthropogenic pollution are characterized by relative constancy. Bacterial pollution and pollution with aromatic compounds of anthropogenic origin, including oil products, leads to an increase in the fluorescence intensity in the short-wavelength part of the spectrum. The correlation coefficient between the optical density at a wavelength of 254 nm and the content of dissolved organic carbon (DOC) for the studied samples was 0.66, and between the fluorescence intensity at a wavelength of 400 nm and DOC was 0.74. Limitations. The method cannot be used for the quantitative determination of individual substances; it is intended for a semi-quantitative assessment of water pollution. Conclusion. Measurement of fluorescence spectra and total organic carbon makes it possible to give a general assessment of the contamination of a water body (which is especially important for a sample of unknown composition) and to choose the optimal scheme for its targeted analysis. High dissolved organic carbon (DOC) values and high fluorescence intensity at 320 nm are highly likely to indicate chemical contamination of water, while DOC values characteristic of a water body and high fluorescence intensity at 320 nm indicate bacterial contamination.

Remote laser fluorescence method for oil leak detection at an excitation wavelength of 266 nm

Subject of study. The possibility of implementing a remote laser fluorescence method to detect oil leaks on the Earth’s surface at a fluorescence excitation wavelength of 266 nm was analyzed and substantiated. Method. Laser-induced fluorescence spectra of clean oil, oil spilled on different types of soil at different time intervals after leakage, and natural and anthropogenic terrain elements were investigated. The experimental setup for remote measurements of laser-induced fluorescence spectra of oil pollution on the Earth’s surface using a laser source with a wavelength of 266 nm, pulse energy of 0.3 mJ, and a single spectral channel of a detector with a central wavelength of 510 nm and a bandwidth of 84 nm is described. The detection possibility of oil pollution against a background of natural vegetation (shrubs and grass) and soil without oil pollution were investigated remotely at a distance of 75 m using emission with a fluorescence excitation wavelength of 266 nm. Main results. Laser-induced fluorescence spectra of commercial oil from the Ryazan oil refinery and oil from Almetyevsk oil field were obtained in addition to the fluorescence spectra of vegetation, soil, and asphalt. Analysis of the data in laser-induced fluorescence spectra indicates that the maximum of the oil spectra is in the range 450–550 nm. Laser-induced fluorescence from vegetation is the largest interference signal in the detection of oil leaks on the Earth’s surface. Remote detection of oil pollution against the background of vegetation and other landscape elements was experimentally demonstrated both immediately after pollution and two days later. Practical significance. The possibility of remote monitoring of oil pollution on the Earth’s surface was experimentally demonstrated at a fluorescence excitation wavelength of 266 nm at distances close to safe aircraft flying altitudes.

Optical Sensor System for Early Warning of Inflow Organic Matter Breach in Large-Scale Irrigation Systems and Water Treatment Systems

A growing world population together with a decrease in water resources have resulted in a deficit in water sources for agriculture. Nations with limited water resources are already using recycled treated water as a vital water source for irrigation. In 2019, treated wastewater made up 45% of the overall agricultural water consumption in Israel. Since recycling systems work continuously and are directly connected to irrigation reservoirs, there is a constant risk of irrigation system malfunctions in the treatment process. In cases of fecal origin, this may result in pathogens entering the irrigation water, the soil, and eventually the food chain. Early warning systems for biological water contamination are important in large-scale processing, yet less studied. This work proposes such a system, with a functional prototype for irrigation-water monitoring by measuring fluorescence spectra in the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$300-520 \textit {nm}$ </tex-math></inline-formula> at excitation wavelengths of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$280 \textit {nm}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$340 \textit {nm}$ </tex-math></inline-formula> , to capture both tryptophan-like fluorescence and humic-like fluorescence. The prototype was successfully tested under simulated field conditions with treated irrigation water as the base substance, and milk injections to simulate dissolved organic matter breaches. Near real-time operation enabled recording biological and chemical dynamics within the substance for the sake of monitoring drift in process control.

Visible-Light-Driven Sonophotocatalysis for the Rapid Reduction of Aqueous Cr(VI) Based on Zirconium-Porphyrin Metal-Organic Frameworks with csq Topology.

Photochemical treatment of highly toxic Cr(VI) is a desirable and ecofriendly method to protect the environment and human beings. In this study, a MOF-based sonophotocatalytic system is established, in which visible-light-driven sonophotocatalytic reduction of toxic Cr(VI) to Cr(III) in water is investigated using zirconium-porphyrin metal-organic frameworks (MOFs) structured as PCN-222(M) [M = H2, Zn(II), Fe(III), Co(II)]. In the view of the synergistic effect of sonochemistry and photocatalysis, PCN-222(M) exhibited enhanced activities for Cr(VI) reduction compared with the photocatalytic process. Kinetic studies showed that apparent reaction rate constants in the sonophotocatalytic system of PCN-222(M) are 1.5-3.3 times higher than those in photocatalysis. Fluorescence and UV-vis absorption spectra measurements demonstrate that the sonophotocatalytic process promotes the transfer of photoinduced electrons from PCN-222(M) to Cr(VI), thus enhancing the catalytic performance. The innovative combination of porous MOFs and sonophotocatalytic technology might become a feasible strategy to improve the existing MOF-based photocatalytic systems.

Design and fabrication of a new fluorescent film sensor towards uranyl ion via self-assembled monolayer

Uranium, as a naturally radioactive actinide element, plays a significant role in the nuclear industry. It is reasonably necessary to develop a fast and efficient approach for uranyl ions detection. In consideration of the practical application, fluorescent film sensor exhibits great advantages of convenience, ease of being made into portable devices, etc. Herein, a new film senor towards uranyl ion has been designed and fabricated via drawing into an AIE-active (aggregation-induced emission) tetraphenylethene moiety and a carbamoylphosphine oxide chelate moiety through a self-assembled monolayer on quartz glass. Fluorescence spectra measurements demonstrated that the film sensor could be used for detecting UO22+ in a simple way with the range of 0–0.5 μM, and the calculated limit of detection was as low as 32 nM. On the basis of the results from XPS, NMR, MS, time-resolved fluorescence spectra and absorption spectra measurements, the fluorescence quenching was arising from the UO22+ located around the tetraphenylethene molecules under the ground state. Furthermore, the film sensor exhibit higher selectivity toward UO22+ than the other metal ions. These results suggest that the film sensor can be applied as a convenient sensor for the UO22+ detection.

Visible to near-infrared broadband fluorescence from Ce-doped silica fiber

We investigate the fluorescence characteristics of a purely Ce-doped silica fiber and demonstrate broad-bandwidth fluorescence across the visible and near-infrared. The Ce-doped fiber is fabricated using standard modified chemical vapor deposition technology. Trace metal analysis by inductively coupled plasma mass spectrometry confirmed the purity of Ce-doping. The Ce valence state of 3+ was revealed by X-ray photoelectron spectroscopy. The optimum pump wavelength for the broadest luminescence from a fiber is scanned between 405 nm to 440 nm wavelength of diode lasers operating under continuous-wave regime. The strongest pump absorption is observed at the wavelength of 405 nm. Variation of pump power and fiber length results in the demonstration of broad-bandwidth fluorescence with spectral widths up to 301 nm (at -10 dB). The measured fluorescence spectra cover the wavelength range from ∼458 nm to ∼819 nm with spectral power densities of up to 2.4 nW/nm.

Unraveling the early petroleum migration of the Potiguar Basin, Brazil: Constraints from fluid inclusions of the Ubarana and Lorena oilfields

A coupled study of fluid inclusions and one-dimensional basin modeling allowed the reconstruction of the early hydrocarbon filling history of the main petroleum systems of the Potiguar Basin, Brazil. Confocal laser scanning microscopy, microthermometry and fluorescence spectra measurements were used to model PVTx properties of petroleum inclusions in samples from the onshore Lorena and the offshore Ubarana oilfields. The fluid inclusion data and basin modeling suggest that the initial filling of the Lorena reservoir (Pendência Formation) occurred during the rift stage in two scenarios at 62.7–80.6 °C (11–16.8 MPa): (i) the late rift phase in the Barremian–Early Aptian (ca. 129–124 Ma) or during the beginning of the uplifting phase in the Aptian (ca. 118–117 Ma). In the Ubarana Oilfield, hydrothermal fluids migrated alongside petroleum during the reservoir initial filling. Fluid inclusion homogenization temperatures for both the Açu (mode interval of homogenization temperatures, Th(LV→L)mode interval = 124–128 °C) and Ponta do Mel (Th(LV→L)mode interval = 115–130 °C) formations are higher than the present-day reservoir temperature (110 °C). Isochoric modeling of saddle dolomite-hosted fluid inclusions from the Ponta do Mel Formation indicates trapping temperatures between 128.9 and 133.1 °C and pressures between 10.6 and 12.9 MPa. Temperatures and salinities (16 and 20 mass % equivalent in NaCl + CaCl2) of aqueous inclusions hosted in saddle dolomite are similar to those of the fluid inclusions trapped in hydrothermal minerals in Mississippi Valley-Type Pb–Zn deposits. No specific timing can be suggested for the hydrothermal event in Ubarana Oilfield. However, this atypical (hydrothermal) petroleum system could be linked to two possible scenarios: (i) the onset of petroleum migration of the Alagamar Formation during the Cenozoic Macau (ca. 48–8.8 Ma) magmatic event; or (ii) an earlier activity of the petroleum system, prior to the peak oil generation (50–10 Ma).

Biochemical Study of Fibrinolytic Protease from Euphausia superba Possessing Multifunctional Serine Protease Activity.

Fibrinolytic protease from Euphausia superba (EFP) was isolated. Biochemical distinctions, regulation of the catalytic function, and the key residues of EFP were investigated. The serial inhibition kinetic evaluations coupled with measurements of fluorescence spectra in the presence of 4-(2-aminoethyl) benzene sulfonyl fluoride hydrochloride (AEBSF) was conducted. The computational molecular dynamics (MD) simulations were also applied for a comparative study. The enzyme behaved as a monomeric protein with a molecular mass of about 28.6 kD with Km BApNA = 0.629 ± 0.02 mM and kcat/Km BApNA = 7.08 s-1/mM. The real-time interval measurements revealed that the inactivation was a first-order reaction, with the kinetic processes shifting from a monophase to a biphase. Measurements of fluorescence spectra showed that serine residue modification by AEBSF directly caused conspicuous changes of the tertiary structures and exposed hydrophobic surfaces. Some osmolytes were applied to find protective roles. These results confirmed that the active region of EFP is more flexible than the overall enzyme molecule and serine, as the key residue, is associated with the regional unfolding of EFP in addition to its catalytic role. The MD simulations were supportive to the kinetics data. Our study indicated that EFP has an essential serine residue for its catalyst function and associated folding behaviors. Also, the functional role of osmolytes such as proline and glycine that may play a role in defense mechanisms from environmental adaptation in a krill's body was suggested.

Estimation of Theoretical Models of Photophysical Processes for Fluorescein Laser Dye with Ag Nanoparticles

In this study, a novel theoretical method for the absorption and fluorescence spectral estimations has been presented. These estimations have been based on experimental measurements of absorption and fluorescence spectra for the solutions of Fluorescein laser dye with Silver (Ag) nanoparticles in distilled water. The used concentration was (1x10-5 M) for Fluorescein dye, while the mass amounts were (0.003g, 0.005g, 0.0065g, 0.008g and 0.0085g) for Silver nanoparticles. A spectral absorption enhancement was detected in the case of increased Silver nanoparticle masses, which specify that the doped Fluorescein dye with Ag nanoparticles has an important effect on the dye absorption spectra. On the other hand, each fluorescence emission spectrum for the dye has quenched as Ag nanoparticle's mass amounts have increased. The related amounts of mass increase as a consequence of Förster resonance energy transfer (FRET). The novel approach of theoretical estimations has been based on curve fitting using Logistic Power Peak (LPP) function to estimate theoretical models for the absorption and fluorescence spectra of these samples. These rated models have excellent matching profiles with the experimental profiles so that the estimated models can replace the experimental measurements.

Characterization of tracers for two-color laser-induced fluorescence thermometry of liquid-phase temperature in ethanol, 2-ethylhexanoic-acid/ethanol mixtures, 1-butanol, and o-xylene.

The fluorescence spectra of dye solutions change their spectral signature with temperature. This effect is frequently used for temperature imaging in liquids and sprays based on two-color laser-induced fluorescence (2cLIF) measurements by simultaneously detecting the fluorescence intensity in two separate wavelength channels resulting in a temperature-sensitive ratio. In this work, we recorded temperature-dependent absorption and fluorescence spectra of solutions of five laser dyes (coumarin 152, coumarin 153, rhodamine B, pyrromethene 597, and DCM) dissolved in ethanol, a 35/65 vol.% mixture of ethanol/2-ethylhexanoic acid, ethanol/hexamethylsiloxane, o-xylene, and 1-butanol to investigate their potential as temperature tracers in evaporating and burning sprays. The dissolved tracers were excited at either 266, 355, and 532 nm (depending on the tracer) for temperatures between 296 and 393 K (depending on the solvent) and for concentrations ranging between 0.1 and 10 mg/l. Absorption and fluorescence spectra of the tracers were investigated for their temperature dependence, the magnitude of signal re-absorption, the impact of different solvents, and varying two-component solvent compositions. Based on the measured fluorescence spectra, the tracers were analyzed for their 2cLIF temperature sensitivity in the respective solvents. Coumarin 152 showed for single-component solvents the overall best spectroscopic properties for our specific measurement situation related to temperature imaging measurements in spray-flame synthesis of nanoparticles as demonstrated previously in ethanol spray flames [Exp. Fluids61, 77 (2020)10.1007/s00348-020-2909-9].

Empirical method for rapid quantification of intrinsic fluorescence signals of key metabolic probes from optical spectra measured on tissue-mimicking turbid medium.

.Significance: Optical fluorescence spectroscopy technique has been explored extensively to quantify both glucose uptake and mitochondrial metabolism with proper fluorescent probes in small tumor models in vivo. However, it remains a great challenge to rapidly quantify the intrinsic metabolic fluorophores from the optically measured fluorescence spectra that contain significant distortions due to tissue absorption and scattering.Aim: To enable rapid spectral data processing and quantify the in vivo metabolic parameters in real-time, we present an empirical ratio-metric method for rapid fluorescence spectra attenuation correction with high accuracy.Approach: A first-order approximation of intrinsic fluorescence spectra can be obtained by dividing the fluorescence spectra by diffuse reflectance spectra with some variable powers. We further developed this approximation for rapid extraction of intrinsic key metabolic probes (2-NBDG for glucose uptake and TMRE for mitochondrial function) by dividing the distorted fluorescence spectra by diffuse reflectance intensities recorded at excitation and emission peak with a pair of system-dependent powers. Tissue-mimicking phantom studies were conducted to evaluate the method.Results: The tissue-mimicking phantom studies demonstrated that our empirical method could quantify the key intrinsic metabolic probes in near real-time with an average percent error of .Conclusions: An empirical method was demonstrated for rapid quantification of key metabolic probes from fluorescence spectra measured on a tissue-mimicking turbid medium. The proposed method will potentially facilitate real-time monitoring of key metabolic parameters of tumor models in vivo using optical spectroscopy, which will significantly advance translational cancer research.

Evaluation of Interfacial pH Using Surface Forces Apparatus Fluorescence Spectroscopy.

The fluorescence spectrum measurement of a fluorescence pH probe, C. SNARF-4F, was performed for monitoring the interfacial pH of aqueous electrolytes between mica or silica surfaces while varying the surface separation (D) using surface force apparatus (SFA) fluorescence spectroscopy. The pH of the aqueous CsCl between mica exponentially decreased with decreasing D. The order of the decay lengths of the interfacial pH obtained from the exponential fitting (L) at various electrolyte concentrations was L1mM > L0.1mM ≈ L0.4mM > L10mM. For studying the mechanisms of these changes, we performed the electric double layer (EDL) model calculation of the interfacial pH based on the surface potentials, which were evaluated from the EDL forces between the substrates in aqueous electrolytes using the same SFA. The calculated pH value for the 0.1 mM aqueous electrolyte corresponded to the values obtained from fluorescence spectroscopy, indicating that the interfacial pH was attributed to only the general EDL effect. On the other hand, the measured pH value for the higher concentrations of aqueous electrolytes (0.4-10 mM) decreased in the longer D ranges than the values calculated from the model, indicating that there was an additional factor affecting the interfacial pH for those concentrations. We also studied the effects of the cationic species of the electrolytes (Cs+, Na+, and Li+) and of the silica substrate on the interfacial pH. The systematic studies of the interfacial pH revealed that it depended on all three factors studied here, that is, the electrolyte concentration, electrolyte species, and the substrates. The results also suggested that the interfacial pH was not only due to the simple EDL theory but could also be affected by an additional factor due to the ion adsorption at the interface and chemical states of the substrates.

A New Fluorometric Dosimetry for Low-medium Gamma Radiation Doses.

In this study, for the first-time, solutions of a Schiff base was evaluated as a possible chemical dosimeter for gamma-rays at low-medium dose ranges. The solutions of N-N'-bis(salicylidene)-1,3-propanediamine (LH2) were prepared at different ethanol/water compositions and the effect of various irradiation doses on the fluorometric response of these solutions were investigated. Fluorescence spectra of non-irradiated and irradiated solutions showed that fluorescence intensity of LH2 (λex = 375 nm, λem = 498 nm) decreased as the radiation dose increased. This decrease was observed over a wider dose range for the solutions that contain 40-60 % water. In order to increase the sensitivity of the method, LH2-Zn complexes were formed by adding Zn (II) to non-irradiated and irradiated LH2 solutions. After that, analytical parameters such as linearity, LOD, LOQ, repeatability and reproducibility were determined by measuring fluorescence spectra of these solutions (λex = 350 nm, λem = 444 nm). The performance characteristics of the chemical dosimetry system suggest that LH2 can be used as a dosimeter in dose range 0.04-5kGy. The proposed method is simple, sensitive, reproducible and cost-effective, and can be useful in measuring doses in food irradiation.

Assessment on the binding characteristics of residual marbofloxacin in animal-derived food to bovine/human serum albumin by spectroscopy and molecular modelling.

To assess the toxicity of residual marbofloxacin from animal-derived food, the interaction characteristics of marbofloxacin to bovine/human serum albumins (BSA/HSA) were explored using spectroscopic methods combined with molecular modelling. According to fluorescence spectra and time-resolved fluorescence spectra measurements, quenching of BSA/HSA fluorescence induced by marbofloxacin was characterized as static quenching. A 1:1 ground-state complex of marbofloxacin to BSA/HSA was formed with binding constant (Ka ) 1.66 × 104 /9.74 × 103 M-1 at 291 K. The location of marbofloxacin binding at site I within BSA/HSA was clarified by site marker competitive experiments. Molecular modelling demonstrated that the binding region for marbofloxacin to BSA and HSA were at site I with the lowest binding free energies of -22.86 and -21.60 kJ mol-1 , respectively. Hydrogen bonds and van der Waals forces were dominantly involved in the spontaneous binding. Nonradiation energy transferred from BSA and HSA to marbofloxacin, due to the close distance (r0 ) between marbofloxacin and Trp residues of BSA (4.28 nm) and HSA (3.34 nm). As explained by circular dichroism (CD) spectra, an increased BSA/HSA α-helix structure was observed after binding to marbofloxacin. Ultraviolet-visible (UV-vis) and Fourier transform infrared (FT-IR) spectra suggested that conformation of the two proteins was altered by marbofloxacin.

In-vivo measurement of the fluorescence spectrum of wild cochineal (Dactylopius opuntiae)

It is known that the harmful presence of the wild cochineal (Dactylopius opuntiae), unlike the fine cochineal (Dactylopius coccus), in prickly pear crops of farmers leads to consider it as one of the major pests for this crop. In this study, we present the implementation of an optical setup that ensures the measurement of the in-vivo fluorescence spectra of wild cochineals ranging in size from 440 to 1190 µm in their natural habitat achieved by developing a reproduction model adopted from available literature. It was observed that in-vivo fluorescence spectra of these insects were comprised in the spectral region of 570–760 nm, showing a proportional dependence between the fluorescence intensity emitted and the cochineal size. In addition, we have considered other spectral parameters to perform the comparison between fluorescence spectra of the different cochineal sizes. These results provide the basis for the development of novel methodologies and equipment aimed towards the early detection of this pest in prickly pear crops from its early growth stages (nymph I and II).

Physico-Chemical Characterization and Antimicrobial Properties of Hybrid Film Based on Saponite and Phloxine B.

This research was aimed at the preparation of a hybrid film based on a layered silicate saponite (Sap) with the immobilized photosensitizer phloxine B (PhB). Sap was selected because of its high cation exchange capacity, ability to exfoliate into nanolayers, and to modify different surfaces. The X-ray diffraction of the films confirmed the intercalation of both the surfactant and PhB molecules in the Sap film. The photosensitizer retained its photoactivity in the hybrid films, as shown by fluorescence spectra measurements. The water contact angles and the measurement of surface free energy demonstrated the hydrophilic nature of the hybrid films. Antimicrobial effectiveness, assessed by the photodynamic inactivation on hybrid films, was tested against a standard strain and against methicillin-resistant bacteria of Staphylococcus aureus (MRSA). One group of samples was irradiated (green LED light; 2.5 h) and compared to nonirradiated ones. S. aureus strains manifested a reduction in growth from 1-log10 to over 3-log10 compared to the control samples with Sap only, and defects in S. aureus cells were proven by scanning electron microscopy. The results proved the optimal photo-physical properties and anti-MRSA potential of this newly designed hybrid system that reflects recent progress in the modification of surfaces for various medical applications.

Design of Fiber-Optics Probe Based on Monte-Carlo Simulation and Application of the Probe in Fluorescence Spectrum Measurement of Nicotinamide Adenine Dinucleotide in Skin

Design of Fiber-Optics Probe Based on Monte-Carlo Simulation and Application of the Probe in Fluorescence Spectrum Measurement of Nicotinamide Adenine Dinucleotide in Skin