Optical Fluorescence Spectroscopy Research Articles

Initial evaluation of waste phosphogypsum for its use as a precursor for bioceramic materials

In this study, the phosphogypsum waste taken from various places in the factory dump located in Kėdainiai (Lithuania) was reinspected and characterised by different physico-chemical characterisation methods. The results of X-ray diffraction analysis, thermogravimetric analysis and differential scanning calorimetry, Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis, elemental analysis using inductively coupled plasma optical emission and X-ray fluorescence spectroscopy confirmed that the main crystalline phase of the phosphogypsum waste is gypsum (CaSO4·2H2O). The surface morphology of the investigated materials was analysed using scanning electron microscopy. The specific surface area was determined by the Brunauer–Emmet–Teller method. The pore size distribution of the material produced was obtained using the Barrett–Joyner–Halenda method. This study also demonstrated that the phosphogypsum waste could be successfully used as a precursor for the dissolution-precipitation synthesis of high quality bioceramic calcium hydroxyapatite.

Application of nondestructive techniques for peach (Prunus persica) quality inspection: A review.

Peaches are highly valued for their rich nutritional content. Traditional fruit quality accessing methods (i.e., manual squeezing the fruit for firmness) are both subjective and destructive, which tend to diminish the integrity of fruit samples, consequently undermining their market value. Compared to traditional detection methods, nondestructive technology offers efficient and noninvasive solutions for rapidly and accurately assessing internal external quality of peaches. This can significantly enhance product classification and quality assurance while reducing the need for extensive human resources and minimizing potential physical damage to peaches. This review provided a comprehensive overview of nondestructive techniques for peach quality evaluation, including visible/near-infrared spectroscopy, machine vision technology, hyperspectral imaging, dielectric and optical properties, fluorescence spectroscopy, electronic nose/tongue, and acoustic vibration methods. It also evaluates the effectiveness of each technique in assessing internal quality, maturity, and disease detection of peaches. The advantages and limitations of each method were also summarized. This study focuses specifically on peaches and encompasses all existing nondestructive testing methods, providing valuable insights and references for future studies in the field of peach quality analysis using nondestructive testing methods.

Temporal fiber-optic fluorescence study of FAD-NADH interactions in phantoms for potential applications in rapid liquid optical biopsy procedures

Body fluids carry several biomarkers and genetic material that enable the detection of carcinogenesis and tumor metastasis. Owing to this, liquid biopsy is gaining importance and entering clinical practice as an adjunct modality to the current standard of practice in cancer detection. Liquid biopsy involving specimens such as urine is non-invasive and has biomarkers reflecting the tumor microenvironment. We investigate the normal and altered levels of cellular metabolic by-products in liquid phantoms and demonstrate their photon-induced excited-state interaction behaviour for potential diagnostic applications. Short-span temporal analysis of metabolic by-products FAD and NADH in liquid phantoms with fiber optic fluorescence spectroscopy is carried out. The mixed liquid phantom of FAD and NADH, showed excited state interactions that manifested as simultaneous inverse variation in the fluorescence emission from FAD and NADH in varying pH environments. Linear discriminant analysis of the time-varying integrated fluorescence intensity resulted in a 100% accuracy in classifying liquid samples between high and low metabolite concentrations. An extension of application of the experiment model for analysis of body fluids such as urine is also discussed.

Acenaphto[1,2-k]fluoranthene: Role of the Carbon Framework Transformation for Tuning Electronic Properties

Acenaphtho[1,2-k]fluoranthene (1) is synthesized via tandem cyclization during the dehydrofluorination of 1,4-di(1-naphthyl)-2,5-difluorobenzene (2) on activated γ-Al2O3. Presence of residual hydroxyl groups in alumina reduce the yield of target product 1 because of the side hydrolysis of fluoroarenes with the formation a product of partial cyclization, 9-(1-naphthyl)fluoranthen-8-ol (1b). The formation of negative ions (NI) of compounds 1 and 2 in the gas phase is studied by means of dissociative electron attachment (DEA) spectroscopy. Long-lived molecular NIs 1 and 2 are registered at the thermal energies of electrons, and patterns of their fragmentation are established. The adiabatic electron affinities of compounds 1 and 2 are estimated in the Arrhenius approximation and equal 1.17 ± 0.12 and 0.71 ± 0.07 eV, respectively, which agree with data from quantum chemical modeling at the level of the density functional theory (DFT). Electronic transitions for compounds 1 and 2 are studied via optical absorption and fluorescence spectroscopy. Fluorescence quantum yields are measured, and the resulting data are interpreted according to the time dependent DFT. The electrochemical properties of compounds 1, 1b, and 2 are studied via cyclic voltamperometry, and the levels of boundary molecular orbitals are estimated on the basis of their formal potentials of reduction and oxidation.

Acenaphto[1,2-k]fluoranthene: Role of the Carbon Framework Transformation for Tuning Electronic Properties

Acenaphtho[1,2-k]fluoranthene (1) is synthesized via tandem cyclization during the dehydrofluorination of 1,4-di(1-naphthyl)-2,5-difluorobenzene (2) on activated γ-Al2O3. Presence of residual hydroxyl groups in alumina reduce the yield of target product 1 because of the side hydrolysis of fluoroarenes with the formation a product of partial cyclization, 9-(1-naphthyl)fluoranthen-8-ol (1b). The formation of negative ions (NI) of compounds 1 and 2 in the gas phase is studied by means of dissociative electron attachment (DEA) spectroscopy. Long-lived molecular NIs 1 and 2 are registered at the thermal energies of electrons, and patterns of their fragmentation are established. The adiabatic electron affinities of compounds 1 and 2 are estimated in the Arrhenius approximation and equal 1.17 ± 0.12 and 0.71 ± 0.07 eV, respectively, which agree with data from quantum chemical modeling at the level of the density functional theory (DFT). Electronic transitions for compounds 1 and 2 are studied via optical absorption and fluorescence spectroscopy. Fluorescence quantum yields are measured, and the resulting data are interpreted according to the time dependent DFT. The electrochemical properties of compounds 1, 1b, and 2 are studied via cyclic voltamperometry, and the levels of boundary molecular orbitals are estimated on the basis of their formal potentials of reduction and oxidation.

Glycine methyl ester based Schiff base bearing long alkoxy arm and its zinc(II) and copper(II) complexes: Synthesis, mesomorphism, photoluminescence, CT-DNA interaction and DFT study

A new photoluminescent mesogenic glycine methyl ester based Schiff base ligand and its zinc(II) and copper(II) complexes have been synthesised. The compounds were characterized by elemental analyses, Fourier transform infrared spectroscopy (FT-IR), 1H, 13C nuclear magnetic resonance (NMR), ultraviolet–visible spectroscopy (UV–Vis), ESI-MS, MALDI-TOF, EDX and thermogravimetric analysis (TGA). The polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) study revealed that the ligand and zinc(II) complex possess SmecticA mesophase on heating but copper(II) complex is non-mesogenic. The optical absorption and fluorescence spectroscopy studies of zinc(II) complex indicate the existence of aggregation/ de-aggregation species in the presence of non-coordinating and coordinating solvents. The Density Functional Theory (DFT) study was carried out using LanL2DZ and 6–31 G (d, p) basis set with meta-hybrid Truhlar's functional M06–2X to obtain a stable, optimized structure, HOMO-LUMO energy gap and chemical hardness. As designed, the combination of both the –CN- and -COO- linkages plays significant role to influence the mesomorphic behaviour as well as biogenic properties of the compounds. The in vitro interactions of the compounds with CT-DNA has been investigated using UV–Vis and fluorescence spectroscopy. To the best of our knowledge, this is one of the few report on DNA binding studies of mesogenic amino acid Schiff base, which is having binding constant in the same range with the gold standard compound, ethidium bromide.

Non-Invasive Characterisation of the Wall Paintings in the Byzantine Church of Palazzo Simi (Bari, Italy) and Digital Photogrammetric Survey for a Pigment Mapping

The paper illustrates the results of a non-invasive characterisation of pigments and their mixtures in the pictorial surfaces of the wall paintings (10th century) found in the Byzantine church of Palazzo Simi in Bari (Italy). The investigation techniques included portable digital polarised microscopy, fibre optic reflectance spectroscopy (FORS) and X-ray fluorescence spectroscopy (XRF). Data comparison supported the recognition of red and yellow ochres, green earth, vine black, minium and Egyptian blue. The presence of some pigment mixtures demonstrated the recurrence of specific technical expedient used by local medieval artists in order to simulate more expensive pigments, which enabled contribution to the understanding of the valuable artistic tradition of the Apulian Middle Age. Both for purposes of conservation and fruition of the site, which is not always accessible, and due to the complexity in taking suitable photographs for the representation of results, the latter was performed on orthophotos extracted from a digital photogrammetric 3D model of the whole archaeological site. By means of chromatic overlapped layers, an interactive compositional map of the pictorial surfaces was produced.

A narrative review of imaging tools for imaging subgingival calculus.

The conventional method of detecting subgingival calculus involves using a periodontal probe to sense tactile differences on the dental root surface. Although efficient, this method can result in false positives and false negatives. This literature review explores alternative detection techniques that can detect subgingival calculus with improved accuracy and consistency. The accumulation of dental calculus below the gingival margin can foster periodontitis-inducing bacterial growth. Conventional methods of locating subgingival calculus are often inaccurate and highly dependent on clinician skill. This literature review evaluates techniques used to improve the accuracy of imaging and detecting subgingival calculus. Google Scholar, PubMed and PubMed Central databases were searched for peer-reviewed original articles evaluating subgingival calculus imaging and detection techniques. A total of 46 relevant articles ranging from 1981 to 2021 were included. This narrative review discusses the subgingival calculus detection and imaging capabilities of periodontal endoscopy in an in vivo study and of optical coherence tomography (OCT), fluorescence spectroscopy, and differential reflectometry in in vitro settings. Each technique has unique benefits and limitations that distinguishes it from the others. In vitro studies have revealed that techniques including periodontal endoscopy, OCT, fluorescence spectroscopy, or differential reflectometry allow for a more accurate diagnosis of subgingival calculus deposits in comparison to detection via periodontal probing. Despite the improved results, the common limitations of these techniques include longer operation times and expensive equipment. Further studies are needed to transition these imaging and detection methods to clinical environments.

Synthesis, structural and optical properties of Ni doped CuO nanoparticles

In this study, Ni-doped CuO nanoparticles were prepared without an inert gas by using the chemical reduction method. XRD, SEM, EDAX, UV–Visible, and FTIR characterization techniques were used to investigate the structural, morphological, and optical properties of prepared nanoparticles. The single-stage CuO nanoparticles formation is confirmed by the XRD patterns. As nickel fixation increased, it was seen that molecule size, cross-sectional boundaries, and cell volume all decreased. SEM reveals the mill morphology of unadulterated and Ni doped CuO nanoparticles. Optical absorbance and fluorescence spectroscopy were used to understand the optical properties. Detailed research on these nanomaterials was reported in this paper.

The colours of Segesta. Searching for the traces of the lost pigments

• Non invasive, multianalytical approach and in situ analysis for the investigation of traces of pigments. • Optical microscopy, UV-fluorescence, XRF and FORS spectroscopy for the analysis of traces of pigments. • Interchangeability of XRF and FORS for identification of general type of pigments polychromy of Greek temples. • Example of fruitful cooperation between chemists, archaeologists and the public institutions for the safeguarding of archaeological heritage. Many monuments and objects of the ancient civilizations were painted, but unfortunately the pigments are not still present and sometimes only small traces are evident. The analysis of the traces requires a multianalytical approach through the use of non-invasive techniques and only if necessary of a microsampling. Here, the study of the traces of colours found in some architectural elements and findings belonging to the Archeological Park of Segesta (Trapani, Italy) is reported. The traces are identified and characterised via several techniques such as Optical Microscopy, UV-Fluorescence Imaging, Fiber Optical Reflectance Spectroscopy (FORS), X-ray Fluorescence (XRF) and FT-IR Spectroscopy. Various pigments were identified, some of which are no longer clearly visible to the naked eye: hematite, umber, vegetable black and bone black. Despite the small amount of detectable pigment, the performed investigations allowed us to define part of the pictorial palette to imagine and relive the past in one place.

Label-Free Optical Spectroscopy for Early Detection of Oral Cancer.

Oral cancer is the 16th most common cancer worldwide. It commonly arises from painless white or red plaques within the oral cavity. Clinical outcome is highly related to the stage when diagnosed. However, early diagnosis is complex owing to the impracticality of biopsying every potentially premalignant intraoral lesion. Therefore, there is a need to develop a non-invasive cost-effective diagnostic technique to differentiate non-malignant and early-stage malignant lesions. Optical spectroscopy may provide an appropriate solution to facilitate early detection of these lesions. It has many advantages over traditional approaches including cost, speed, objectivity, sensitivity, painlessness, and ease-of use in clinical setting for real-time diagnosis. This review consists of a comprehensive overview of optical spectroscopy for oral cancer diagnosis, epidemiology, and recent improvements in this field for diagnostic purposes. It summarizes major developments in label-free optical spectroscopy, including Raman, fluorescence, and diffuse reflectance spectroscopy during recent years. Among the wide range of optical techniques available, we chose these three for this review because they have the ability to provide biochemical information and show great potential for real-time deep-tissue point-based in vivo analysis. This review also highlights the importance of saliva-based potential biomarkers for non-invasive early-stage diagnosis. It concludes with the discussion on the scope of development and future demands from a clinical point of view.

Fluorescent melamine-formaldehyde/polyamine coatings for microcapsules enabling their tracking in composites

This study aimed the development of fluorescent melamine-formaldehyde (MF)/polyamine coatings for labelling of prefabricated microcapsules and their tracking in composites. The composition of the fluorescent MF coatings was studied by FTIR spectroscopy, thermogravimetric analysis, and elemental analysis. The characteristics of the coatings and its deposition on different surfaces were investigated using optical and fluorescence microscopy and fluorescence spectroscopy. MF prepolymers were polymerised with tri- and polyamines yielding in fluorescent coatings without addition of fluorescent dyes. Both, MF/poly(ethylene imine) and MF/poly(vinyl amine) (PVAm) coated glass beads showed maximum fluorescence at an excitation wavelength of λ max = 360 nm with the emission maxima at λ max = 490 nm and λ max = 410 nm, correspondingly. The MF/PVAm polymer was coated on diuron-poly(methyl methacrylate) microcapsules and tracked in highly filled composites (water-based plaster/paint) to show its applicability. MF/polyamine coatings were identified as promising materials for the fluorescent labelling of prefabricated microcapsules.

Application of Optical Fluorescence Spectroscopy for Studying Bee Abundance in Tropaeolum majus L. (Tropaeolaceae).

Simple SummaryTropaeolum majus L. is a medicinal plant popularly known as capuchinha. It produces flowers of different colors and hence attracts various groups of floral visitors. Since these groups may be potential pollinators, they are major for biodiversity conservation. In this regard, our study aimed to verify potential relationships between corolla colors and visiting bee abundance using optical fluorescence spectroscopy and climatic analyses. Orange and yellow flowers were the most visited and showed higher temperatures and fluorescence emissions than did flowers of other colors. This might be due to the presence of compounds such as hydroxycinnamic acid and kaempferol that emit fluorescence around 470 to 620 nm, which are within the visible spectrum for these bee species.Tropaeolum majus L. species produce flowers with all sorts of colors, from yellow to red. This work aimed to apply optical fluorescence spectroscopy to study bee abundance in T. majus, answering the following questions: (1) do corolla temperature and weather conditions affect the abundance of visiting bee species? (2) do flower color and corolla fluorescence affect the abundance of visiting bee species? (3) do red flowers attract more visiting bees? (4) is there a relationship between bee visits and flower compounds? The bee species Apis mellifera, Paratrigona lineata, and Trigona spinipes were the most observed in T. majus flowers. The latter was more active in the morning and preferred orange and yellow flowers. These colors also had higher temperatures and fluorescence emissions than did the red ones and those with yellow-red and orange-red nectar guides. Orange flowers emitted a broadband UV spectrum (between 475 and 800 nm). This range might be due to compounds such as hydroxycinnamic acid, flavonols, isoflavonoids, flavones, phenolic acid, and chlorophyll. Extracts from different T. majus corolla colors showed that flowers emit specific fluorescent signals, mainly related to bee color vision and learning, thus acting as a means of communication between bees and flowers. In this way, this information evidences the interaction between bees and T. majus flowers, allowing conservation actions for pollinators.

Deep UV Led Dynamic Optical Imaging and Fluorescence Spectroscopy of the Protein Corona in a Plasmonic Solution and the Effect of Near-Infrared Laser Heating

Deep UV Led Dynamic Optical Imaging and Fluorescence Spectroscopy of the Protein Corona in a Plasmonic Solution and the Effect of Near-Infrared Laser Heating

Fluorescence spectroscopy and multispectral imaging for fingerprinting of aflatoxin-B1 contaminated (Zea mays L.) seeds: a preliminary study

Cereal seeds safety may be compromised by the presence of toxic contaminants, such as aflatoxins. Besides being carcinogenic, they have other adverse health effects on humans and animals. In this preliminary study, we used two non-invasive optical techniques, optical fiber fluorescence spectroscopy and multispectral imaging (MSI), for discrimination of maize seeds naturally contaminated with aflatoxin B1 (AFB1) from the uncontaminated seeds. The AFB1-contaminated seeds exhibited a red shift of the emission maximum position compared to the control samples. Using linear discrimination analysis to analyse fluorescence data, classification accuracy of 100% was obtained to discriminate uncontaminated and AFB1-contaminated seeds. The MSI analysis combined with a normalized canonical discriminant analysis, provided spectral and spatial patterns of the analysed seeds. The AFB1-contaminated seeds showed a 7.9 to 9.6-fold increase in the seed reflectance in the VIS region, and 10.4 and 12.2-fold increase in the NIR spectral region, compared with the uncontaminated seeds. Thus the MSI method classified successfully contaminated from uncontaminated seeds with high accuracy. The results may have an impact on development of spectroscopic non-invasive methods for detection of AFs presence in seeds, providing valuable information for the assessment of seed adulteration in the field of food forensics and food safety.

Study of β-lactam-based drug interaction with albumin protein using optical, sensing, and docking methods.

The quality and strength of drug and albumin interaction affecting the drug-free concentration and physiological activity are important issues in pharmacokinetic research. In the present study, not only did we evaluate the binding strength of ceftriaxone and ceftizoxime to bovine serum albumin (BSA), but we also investigated the kinetic and thermodynamic parameters including KD, KA, ΔS, and ΔH. We applied in vitro optical fluorescence spectroscopy and surface plasmon resonance (SPR) sensing approaches as well as molecular docking analyses. The kinetic and thermodynamic investigations were done using different concentrations of drugs at three temperatures. Thermodynamic parameters visibly demonstrated that the binding was an exothermic and spontaneous process. The obtained negative values of both enthalpy change (ΔH) and entropy change (ΔS) in fluorescence and SPR and also molecular docking investigations showed that the major binding force involved in the complexation of drugs to BSA was hydrogen bonding. Static quenching was the foremost fluorescence quenching mechanism between them. Furthermore, the results of ΔG and KD values proved that the interaction of ceftriaxone-BSA was stronger than ceftizoxime-BSA. Finally, molecular docking confirmed that the preferable binding sites of ceftizoxime and ceftriaxone were site IIA and site IB of albumin, respectively.

Incorporation of Europium into (Ba,Ca)2[formula omitted

Synchrotron-based powder diffraction measurements in combination with inductively coupled plasma optical emission spectrometry, Raman and fluorescence spectroscopy show that (Ba,Ca)2(CO3)2 can incorporate significant amounts (up to 6 ​mol%) of europium. This solid solution is therefore of potential interest for the solidification of nuclear waste streams involving aqueous nitrate solutions of lanthanides. Europium replaces Ba/Ca on lattice sites and is not incorporated as an interstitial defect. Charge compensation is likely due to the presence of OH−-groups as we could exclude a coupled substitution involving Na+. The Eu-containing compound is stable to at least 723 ​K. We show that the one-phase-field of (Bax,Ca(1−x))CO3 solid solutions at ambient conditions is larger (0.36 <x< 0.51) than previously thought. The synthesis routes employed here lead to compounds which have similar molar volumes than those of the naturally occurring (Ba,Ca)-double carbonates, in noted contrast to another synthetic phase, “balcite”.

Improved borate fusion technique for determination of rare earth elements in electronic waste components

ABSTRACT The information regarding the abundance of rare earth elements (REEs) in electronic waste components (EWC) helps the recycling industry. However, after the end of use, improper disposal may be detrimental to the environment by releasing toxic substances. An optimised alkaline borate fusion method for REEs determination in electronic waste (e-waste) was developed. It is divided into three phases. Firstly, the sample preparation stages were investigated. Secondly, the optimisation of experimental particulars comprises the choice of oxidiser, flux composition, non-wetting agents, fusion time, and sample to flux ratio. The third phase consists of spectroscopic determination by inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray fluorescence (XRF) spectroscopy. The highest REEs recovery (mg/g of e-waste) were found more in fine fractions of less than 0.09 mm compared to gross fractions. The optimum and safe fusion conditions for e-waste were achieved after slow thermal decomposition up to 550°C, pulverisation to 90% of –53 µm, flux composition (90%LiBO2 + 10% Li2B4O7), 3:1 oxidant ratio of Na2CO3: NaNO3, LiBr as the non-wetting agent. Also, a sample to flux ratio of 1:15 and a total fusion time of 10 min was optimised. The newly improved alkaline fusion results compared better to those obtained from classical mineral acid dissolution with at most 5% RSD on REEs studied. The alkaline borate fusion results in smartphones e-waste were at least 15% and 25% higher than in four acid digest and microwave-assisted digest techniques, respectively. The results indicated enrichment of REEs in smartphones followed by non-smartphones and computer waste.

Qualitative and Quantitative Evaluation of Different Types of Orthodontic Brackets and Archwires by Optical Microscopy and X-ray Fluorescence Spectroscopy

The wear behaviour and chemical composition of orthodontic components influence the mechanical characteristics of a fixed orthodontic treatment. The purpose of this paper is to evaluate the surface alterations of different types of brackets (aesthetic, metallic, and conventional self-ligating) and archwires (superelastic and thermal) subjected to wear tests through optical microscopy and, subsequently, to identify the chemical elements of accessories by X-ray fluorescence. The cycles (5000 for each bracket and 10,000 for each wire) of the tribological test were carried out in dry conditions inside a machine that allows alternating sliding. The results of the study highlighted different wear behaviours even within the same type of brackets and archwires. The monocrystalline sapphire brackets maintain their aesthetic properties despite traces of wear inside the slots and contain minimal amounts of nickel. Superelastic NiTi archwires have a better overall rating than thermal wires, as they do not show significant surface wear alterations.

Commercial milk discrimination by fat content and animal origin using optical absorption and fluorescence spectroscopy

Distinguishing milk products by fat content and animal origin is important as it can address problems in quality control in the dairy industry and in adulteration testing for regulatory bodies. Optical spectroscopy, combined with statistical analysis methods, can be useful in such analyses, being fast, non-destructive and cheaper compared with conventional analytical methods. In this study we discriminate commercial (supermarket) cow, goat and sheep milk based on their fat content and animal origin, by applying three spectroscopic techniques: ultraviolet absorption, Fourier-transform infrared reflectance (FTIR) and fluorescence. Orthogonal partial least-squares discriminant analysis (OPLS-DA) of the data grouped the samples by animal origin and fat content. All techniques exhibit at least 70% success rates in grouping the samples. UV absorption works best in fat-based discrimination (96% success), while fluorescence and UV are the most successful in animal-based discrimination (both 91% success).