Raman Peak Intensity Research Articles

Effect of ion interactions on the Raman spectrum of NO3−: Toward monitoring of low-activity nuclear waste at Hanford

Raman spectroscopy is a valuable in-situ technique for many applications. The concentrations of species in complex ionic mixtures of nuclear waste can be estimated using Raman measurements. However, it has been experimentally observed that ion interactions can cause a modification of Raman peak intensities and positions. The present work explores the nonlinear behavior associated with the nitrate anion, NO3−, which is present in abundance in low activity nuclear waste. We examine changes in the main Raman peak of the nitrate anion in the presence of other ions. A wide range of concentrations are covered, including those expected during direct-feed low-activity waste (DFLAW) processing at the Hanford site in the State of Washington. The experiments showed that the ions interact and associate to form ion pairs, which results in a blue shift (i.e., a shift towards higher wavenumbers) in the main Raman peak of nitrate. The results indicate that cation concentration is a better predictor of the peak shift, compared to ionic strength, both for binary and multicomponent mixtures. These findings have direct implications on the development of spectra-to-composition models for the DFLAW system, since they show deviations from the linearity assumptions used in common chemometric models.

Spatially selective nanoplasmonic response in Ag embedded GLAD TiO2 nanocomposite thin films

The nanoplasmonic behaviour of Ag decorated TiO2 film structure was spatially varied across the sample surface by utilizing the tailored optical response of the underlying dielectric TiO2 thin film prepared using a novel collimated glancing angle deposition technique (collimated-GLAD). A blue shift in maximum attenuation coefficient region and minimum film transmittance region of the Ag/collimated-GLAD TiO2 nanocomposite coating with increase in height from the evaporation source was detected. The presence of minimum transmittance region was found to have occurred due to localized surface plasmon resonance (LSPR) phenomenon with additional contribution from thin film interference. The measured transmittance spectra showed spatial selectivity in LSPR wavelength of ∼22 nm with increase in height from the evaporation source. The variation of surrounding medium's (i.e. the TiO2 layer) refractive index (with height from the evaporation source) of the Ag nanostructures was the key factor responsible for the spatially varying nanoplasmonic response of Ag/collimated-GLAD TiO2 film across the sample surface. The Surface enhanced Raman scattering (SERS) characterization of the Ag/collimated-GLAD TiO2 film revealed photocatalysis driven dimerization conversion of p-aminothiophenol (p-ATP) molecules to p,p’-dimercaptoazobisbenzene (DMAB) due to the localized surface plasmons of the film structure along with the substantial enhancement in the Raman peak intensities compared to the blank substrate.

Dynamic insights into increasing antibiotic resistance in Staphylococcus aureus by label-free SERS using a portable Raman spectrometer

Rapid and quantitative detection of bacterial antibiotic resistance is of great significance for the prevention and treatment of infections and understanding drug-resistant mechanism. In this study, label-free surface-enhanced Raman spectroscopy (SERS) technology was applied to dynamically explore oxacillin/cefazolin-derived resistance in Staphylococcus aureus using a portable Raman spectrometer. The results showed that S. aureus rapidly responded to oxacillin/cefazolin stimulation and gradually developed different degrees of drug resistance during the 21 days of exposure. The molecular changes that accumulated in the drug-resistant strains were sensitively recorded by SERS in a whole-cell manner. Principal components-linear discriminant analysis correctly distinguished various degrees of drug-resistant strains. The typical Raman peak intensities of I734/I867 showed a negative and non-linear correlation with the minimum inhibitory concentration (MIC). The correlation coefficient reached above 0.9. The target sites of oxacillin/cefazolin on S. aureus clearly reflected on SERS profiles. The results collected by SERS were further verified by other biological methods including the antibiotic susceptibility test, MIC determination, and PCR results. This study indicates that SERS technology provides a rapid and flexible alternative to current drug susceptibility testing, laying a foundation for qualitative and quantitative evaluation of drug resistance in clinical detection.

Optical constants of diamond-like carbon films formed by gas cluster ion beam assisted deposition

We investigated the refractive index (n) and extinction coefficient (k) of diamond-like carbon (DLC) films formed by gas cluster ion beam (GCIB)-assisted deposition. DLC films are classified into four types based on n and k values (at λ = 2.25 eV). We formed the nonclassified DLC film which has high n (2.4–3.0) and k (0.75–1.0) values. The Raman peak intensity ratio (I D/I G) of this film was 0.601, which corresponds to the value of a-C:H or ta-C:H. The film density was 2.71 g cm−3. The nonclassified DLC film has intermediate properties between a-C:H and ta-C:H with respect to the density and k.

Sulfurization temperature induced enhancement in thermoelectric properties of polycrystalline WS2 nanomaterials

We have presented an interesting study about the evolution of vibrational modes in WS2 nanostructures and their effect on material thermoelectric performance. High purity polycrystalline nanostructures of WS2 were prepared by sulfurizing the hydrothermally prepared WS2 powders at different temperatures. The effect of sulfurization temperature on the structure of WS2 nanomaterials was probed by XRD and Raman Spectroscopy. XRD data confirmed the crystal structure of WS2 along with the presence of WO3 based secondary phases. An experimental investigation of the phase changes with sulfurization temperature has been made by Raman scattering methods. Both in Plane (E12g) and out of plane (A1g) Raman modes exhibited red shift by 45 and 11 cm−1 respectively and variation in Raman peak intensity with sulfurization temperature was also observed. For all samples, the room temperature thermoelectric measurements reveal that an increase in sulfurization temperature from 300 to 823 k resulted in the enhancement of electrical conductivity and the Seebeck coefficient. The observed thermoelectric data was linked with the structural changes occurred during the increase of sulfurization temperature. Power factor of WS2 nanostructures increase up to 5.09x 10−3 Wm−1K−2 with increasing sulfurizing temperature.

Ag-decorated TiO2 Nanofibers for Surface-enhanced Raman Scattering

In this report, SERS substrates based on Ag-decorated TiO2 nanofibers electrospun on a glass substrate (Ag/TiO2/glass) were successfully prepared using electrospinning and photodeposition methods. XRD pattern demonstrated that the crystalline structure of TiO2 nanofibers (TiO2 NFs) consisted of both anatase and rutile phase. SEM images show that the randomly oriented on glass substrate TiO2 NFs’ diameters are in the range of 150 nm-300 nm and their lengths are up to a few micrometers. After 15-minute photodeposition, Ag NPs with average diameter of about a few tens of nanometers were uniformly and densely decorated on TiO2 NFs surface. The Ag/TiO2/glass SERS substrate was then immersed in 0.01 mM, 0.1 mM, and 1 mM 4-mercaptobenzoic acid (4-MBA) solution, and was afterwards investigated by UV-Vis absorption and Surface-enhanced Raman Scattering (SERS) spectra. The preliminary results show that the change in UV-Vis absorption corresponds well to the Raman peak intensity upon the adsorption of probed molecules. This might open up a pathway in the detection and identification of probed molecules based on colorimetric-sensing and SERS-sensing.

Raman spectroscopic analysis of skin as a diagnostic tool for Human African Trypanosomiasis.

Human African Trypanosomiasis (HAT) has been responsible for several deadly epidemics throughout the 20th century, but a renewed commitment to disease control has significantly reduced new cases and motivated a target for the elimination of Trypanosoma brucei gambiense-HAT by 2030. However, the recent identification of latent human infections, and the detection of trypanosomes in extravascular tissues hidden from current diagnostic tools, such as the skin, has added new complexity to identifying infected individuals. New and improved diagnostic tests to detect Trypanosoma brucei infection by interrogating the skin are therefore needed. Recent advances have improved the cost, sensitivity and portability of Raman spectroscopy technology for non-invasive medical diagnostics, making it an attractive tool for gambiense-HAT detection. The aim of this work was to assess and develop a new non-invasive diagnostic method for T. brucei through Raman spectroscopy of the skin. Infections were performed in an established murine disease model using the animal-infective Trypanosoma brucei brucei subspecies. The skin of infected and matched control mice was scrutinized ex vivo using a confocal Raman microscope with 532 nm excitation and in situ at 785 nm excitation with a portable field-compatible instrument. Spectral evaluation and Principal Component Analysis confirmed discrimination of T. brucei-infected from uninfected tissue, and a characterisation of biochemical changes in lipids and proteins in parasite-infected skin indicated by prominent Raman peak intensities was performed. This study is the first to demonstrate the application of Raman spectroscopy for the detection of T. brucei by targeting the skin of the host. The technique has significant potential to discriminate between infected and non-infected tissue and could represent a unique, non-invasive diagnostic tool in the goal for elimination of gambiense-HAT as well as for Animal African Trypanosomiasis (AAT).

Correlation between Contact Angle and Surface Roughness of Silicon Carbide Wafers

Two-inch diameter 6H-SiC wafers were sliced from a SiC ingot and the wafers were ground and polished using different diamond slurries (1 μm and 0.1 μm in particles size) to investigate their dependence on wetting on surface roughness (Ra) and polarity using precisely dispensed de-ionized (DI) water drops. The Ra of the Si-face (0001) SiC wafer, after grinding and polishing, was 5.6 and 1.6 nm, respectively, as measured by atomic force microscopy (AFM). For C-face (000–1) SiC wafers, the Ra was 7.2 nm after grinding and 3.3 nm after polishing. The average contact angle measurement of the SiC wafers after final polishing showed clear differences between surface polarity; the contact angle for the Si-face (0001) was ~7o greater than that for the C-face (000–1). The difference in contact angles between the Si-face (0001) and the C-face (000–1) tends to increase as the reduction of surface roughness approaches the final stage of polishing. The uniformity of Raman peak intensity in the folded transverse optical phonon band at ~780 cm−1 in scanned areas correlated well with the surface roughness measured by AFM. The contact angle measurement can be used as a convenient surface polarity and surface roughness testing technique for SiC wafers.

Altering magnetic and optical features of rare earth orthoferrite LuFeO3 ceramics via substitution of Ir into Fe sites

LuFeO3 and LuFe1-xIrxO3 ceramics with x ​= ​0.05 and 0.10 have been obtained by solid-state reaction process. Scanning electron microscope (SEM) analyses have revealed the existence of both particle agglomeration and porosity of nature of the studied samples. The X-ray photoelectron spectroscopy (XPS) investigations have revealed that while Lu has 3+, Fe has mix valence states, 2+ and 3+. On the other hand, the Ir dopant has metallic and 4+ valence states in the study samples. The Raman investigations unveiled i) the Raman peak intensity reduces with Ir doping until ∼600 ​cm−1, ii) the peaks appearing between 200 ​cm−1 and 600 ​cm−1 wavenumbers shift toward the smaller values. Magnetic measurements, conducted by vibrating sample magnetometer (VSM), have shown the spin re-orientation (SR) transition temperature around 47 ​K for all the investigated samples. Furthermore, it is noticed the 5 ​mol % Ir doped sample has higher magnetization than other samples owing to existence of magnetic impurities such as Lu3Fe5O12. M ​− ​H loops have unveiled that Ir doping advances both Hc and Mr values compared to the undoped LFO sample. This increase in both Hc and Mr values could be due to 1) the variation of the canted angels of Fe3+ moments, 2) the advancement of energy of magnetocrystalline anisotropy, and 3) formation of secondary phases such as Lu3Fe5O12 and Fe3O4. Furthermore, the optical band gap examinations have revealed that the band gap of LFO reduces from 2.19 ​eV to 2.

High temperature surface graphitization of CVD diamond films and analysis of the kinetics mechanism

A plasma arc generator was used to heat treat the free-standing CVD diamond films at 1450–1900 °C. An Arrhenius curve was fit according to trends in the measured Raman peak intensity ratio of diamond to graphite as a function of heat treatment temperature, and the curve was extrapolated linearly. It was found that the extrapolation lines intersected at the Debye temperature, ΘD = 2021 K. By comparing the activation energies of diamond graphitization in literature and from different measurement modes in our study, it was found that the graphitization mechanisms were different on both sides of Debye temperature due to differences in the excited lattice vibration modes. When the heat treatment temperature was just below the Debye temperature, the graphitization process was promoted by generating vacancies or the breaking of single CC bonds, and the apparent activation energy was 366 ± 60 kJ·mol−1. When the heat treatment temperature was above the Debye temperature, the graphitization process was promoted by the simultaneous breaking of multiple CC bonds, and the apparent activation energy was 887 ± 141 kJ·mol−1. In combination with the morphology changes on the surface of the CVD diamond film after high temperature heat treatment, the mechanism of the micro-cyclic phase transition on the surface of the diamond film at temperatures lower than Debye temperature was summarized as follows. First, CC bonds on the diamond surface were activated and broken at high temperatures, and some diamond carbon atoms dissociated from solid phase sites to the gas phase by forming hydrocarbon free radicals. Then, the carbon atoms from these hydrocarbons entered the graphite lattice step by step to complete the spontaneous deposition of sp2 clusters.

Raman Spectral Shifts in Naturally Faulted Rocks

AbstractRaman spectral shifts of carbonaceous materials arising from faulted rocks produce varied and complex results. By analyzing faulted and adjacent non‐faulted samples from three discrete localities in France, Italy, and Morocco, we assess changes in specific Raman parameters, including G‐peak width, G‐peak position, and peak intensity ratios. We consistently observe a shift in Raman parameters between faulted and non‐faulted samples; however, the direction and magnitude of this shift varies. Raman peak intensity ratios are shown to both increase and decrease on fault planes. The majority of samples exhibit decreasing peak width and peak position in the faulted samples, but this is not consistent; in two samples an increase is observed, but the shift tends to be small. These data are compared to published Raman spectral shifts from experimental fault data. Our results suggest that fault zone deformation processes may measurably change the carbon nanostructure in faulted rocks. The inconsistent nature of Raman spectral shifts in the fault rock samples analyzed, and those published suggest that a complex set of factors control carbon nanostructure changes in fault rocks. These factors, although not discriminated here, likely include, background temperature, frictional heating, strain, carbonaceous material type, amongst others. We have shown that Raman Spectral shifts occur in faulted rocks with implications for how Raman data are used to predict maximum temperatures in faulted sedimentary rocks. We recognize the potential for a range of fault zone processes to modify Raman spectral shifts, however, systematic sampling across individual fault zones is critical.

Identification of biomarkers on kidney failure by Raman spectroscopy

AbstractChronic kidney disease (CKD) is a global health problem. Our study employed Raman spectroscopy for the first time to analyze potential biomarker such as tryptophan (Trp) on kidney failure and show the difference between normal and CKD groups. Adenine model of CKD characterized most of the physiological changes observed in human CKD. For that, 6‐week‐old Wistar male rats were assigned to the two groups: the control group, 0.5% carboxymethyl cellulose (CMC) was administered; the CKD group, adenine was administered to rats at a dose 600 mg/kg for 10 days. The Raman spectra were obtained in the spectral range of 100–2500 cm−1. The excitation source was 532 nm, the laser power was ~40 mW, and the analyzed tissue area was 10.02 × 82.12 μm2. The results showed a significant reduction in the case of Raman peak intensities at 748, 1359, 1554, and 1636 cm−1, which can be assigned as Trp. Moreover, it was shown that tyrosine at 1169 cm−1 and phenylalanine at 1001 cm−1 decreased in the CKD group. Trp and kynurenine (Kyn) levels in kidney tissue and plasma were analyzed by using the high‐performance liquid chromatography (HPLC). The Trp concentrations in plasma and kidney tissue significantly decreased in CKD 7.4 μg/ml and 0.1 μg/mg, respectively. However, Kyn level was not a statistically significant change in kidney tissue. In this work, we showed that Raman spectroscopy usage in CKD model and Raman spectroscopy can be considered a promising technique for semi‐quantitative analysis of potential biomarkers such as phenylalanine, tyrosine, and Trp of renal function because of the little or no need for sample preparation, and it is easily observing several biomarkers at the same time. The utilization of multivariate analysis method, such as partial least square analysis can be considered as a promising tool for the discrimination of control and CKD groups.

Quantitative evaluation of cement paste carbonation using Raman spectroscopy

Carbonation induced corrosion is one of the major durability issues for reinforced concrete structures. To address this issue, it is essential to understand the underlying mechanism of carbonation by detecting the ingress of the CO2 and carbonation depth quantitatively. This paper demonstrates the potential of Raman spectroscopy, as a powerful technique, to implement quantification analysis of cement paste carbonation. In present work, the correlation between the content of the CO32− and the Raman peak intensity was initially established by using several standard specimens premixed with certain amount of CO32−. The established correlation was then used to investigate the carbonation of the cement paste in a CO2 diffusion scenario, and the results show a good agreement with that obtained by thermogravimetry measurements. Therefore, the feasibility of the Raman spectroscopy to quantify the carbonation degree of the cement paste can be demonstrated.

Molecular and micro-scale heterogeneities in Raman modes of a relaxing polymer glass

We have used Raman spectroscopy to study relaxation dynamics at two different length scales, molecular level and micro-scale in order to probe the presence of cooperative rearranging regions in a polymer glass. Response to slow thermal cycles and fast quench through the glass transition temperature (T g) is analyzed for film and unprocessed forms of polyvinyl acetate (PVAc). In PVAc film, enhanced disorder and molecular mobility lead to peak broadening by about a factor of 10 compared to unprocessed PVAc. Thermal cycles (10 K min−1) produce hysteresis in integrated Raman peak intensity (loop area ). values of film are two orders of magnitude more than unprocessed, indicating more configurational mosaics with higher interfacial energy dissipations. Ageing after 60 K min−1 quench manifests as heterogeneous molecular dynamics of film Raman modes with significant peak-width variations, differentiating high mobility and low mobility modes. Two-dimensional mapping of film Raman modes after quench reveal micro-scale clusters of average size ≈250 molecules having fractal boundaries with fractal dimension d f = 1.5, resembling d f of percolation clusters below percolation threshold. During thermal cycling and relaxation after a quench, cooperative segmental dynamics with large correlations between skeletal C–C stretch and side branch modes is observed. The observations are analyzed in the context of the random first order transition theory of glasses, which attributes heterogeneous relaxations in glasses to the presence of clusters of variable configurational states.

−22-Fold of 1H signal enhancement in-situ low-field liquid NMR using nanodiamond as polarizer of overhauser dynamic nuclear polarization

Nanodiamond (ND) polarizer can be used for dynamic nuclear polarization (DNP), owing to unpaired electrons provided by surface defects. However, 1H enhancement via Overhauser DNP (ODNP) using ND in-situ liquid has been found much smaller than traditional radicals. Herein, we study the surface properties of ND using electron spin resonance (ESR) and Raman methods firstly. Then the enhancement of 1H ODNP is explored using ND as polarizer with different nanoparticle sizes and concentrations at home-built 0.06 T DNP spectrometer. The surface of ND with the size of 30 nm is further modification via high temperature air oxidized and the enhancement was measured. The results show that nanoparticle sizes and Raman peak intensity ratio of sp2/sp3 hybridization are approximate negative correlation and positive correlation to enhancement, respectively. Furthermore, there is no significant enhancement in the oxidation group, and a −22.5-fold 1H ODNP enhancement is achieved in-situ liquid at room temperature, which demonstrate the ND can be used as an efficient enhancer. We expect ND to play a greater role in biomedical research, especially for multimodal imaging with improving the performance of ND surface.

The Degradation of Carbon Electrode for Rechargeable Zinc-Air Battery at an Initial State of Cycling Revealed By in-Situ Raman Measurement

With the burgeoning energy consumption, the rechargeable zinc-air battery has attracted the worldwide attention owing to its intrinsic safety, low material cost and high theoretical specific energy density [1]. For its practical application, the degradation of air electrode made of carbon is necessary to be systematically explained for developing applicable electrode with long cycle life. Recent progresses in high-precision methods for surface analysis allow us to approach to mechanistic understanding of the electrode degradation, while normal ex-situ measurements require the rinsing and other processing which might be destructive. Hereby in this work, in-situ Raman measurements are carried out to observe the changes in chemical states of the carbon electrode in the zinc-air battery during the charging and discharging processes. Unlike other commercial air electrode with multi-component catalysts, the air electrode used for this study is the specially prepared carbon electrode with only Co3O4 particles to facilitate the Raman measurements. For the charging and discharging processes, the electrolyte of 8 M KOH solution with saturated ZnO as well as the current density of 20 mA/cm2 are applied, following the standard of zinc-air battery. Moreover, a three-electrode cell with Pt wire as the counting electrode and Hg/HgO as the reference electrode is utilized. In particular, a homemade setup is developed for the electrode so that the Raman spectra of both gas diffusion layer and catalytic layer can be easily detected from the cross-sectional view.In the first place, distinct carbon-related peaks are clearly observed at 1348 cm-1, 1579 cm-1 and 2695 cm-1. Other shoulder peaks are also assigned to the structural defects of the carbon material. Besides, the Raman peaks at 684 cm-1, 616 cm-1, 519 cm-1, 481 cm-1 and 194 cm-1 which only shown in the near-electrolyte area are attributed to the Co3O4 particles in the catalytic layer. Then, in order to activate the carbon electrode and facilitate the electrolyte infiltrating into the catalytic layer, 6 cycles of charging and recharging with low current density of 10 mA/cm2 are conducted as a pretreatment. Consequently, new peaks at 1060 cm-1 and 440 cm-1 appear, which can be attributed to the carbonate formation and ZnO precipitation respectively [2, 3]. It is interesting that the degradation of electrode is initiated from this unexpected early state of cycling, which has not been addressed yet. We consider the carbonate might be caused by the dissolution of atmospheric CO2 and the chemical corrosion of carbon in high-concentration KOH solution.CO2 + 2OH- →CO3 2- + H2OC + 6OH- → CO3 2- + 3 H2O + 4e- We also confirm that the ZnO arises from the decomposition of zincate ions in electrolyte, as the Raman peak intensity of ZnO increases while the intensity of OH- decreases during the charging process. Moreover, spectra from further cycling process suggest that the precipitation species on the electrode would long-lasting block the charging/discharging reaction sites.Zn(OH)4 2- → ZnO + 2OH- + H2OWe believe this in-situ work would be instructive for future optimization on zinc-air battery and other metal-air battery systems that prolong the cycle life of battery. Acknowledgements This research was partially supported by the “Development of Systems and Technology for Advanced Measurement and Analysis”, and the “Research & Development Initiative for Scientific Innovation of New Generation Batteries (RISING 2)” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Raman Spectroscopic Assessment of Myocardial Viability in Langendorff-Perfused Ischemic Rat Hearts.

Spontaneous Raman spectroscopy, which senses changes in cellular contents of reduced cytochrome c, could be a powerful tool for label-free evaluation of ischemic hearts. However, undetermined is whether it is applicable to evaluation of myocardial viability in ischemic hearts. To address this issue, we investigated sequential changes in Raman spectra of the subepicardial myocardium in the Langendorff-perfused rat heart before and during ligation of the left coronary artery and its subsequent release and re-ligation. Under 532-nm wavelength excitation, the Raman peak intensity of reduced cytochrome c at 747 cm−1 increased quickly after the coronary ligation, and reached a quasi-steady state within 30 min. Subsequent reperfusion of the heart after a short-term (30-min) ligation that simulates reversible conditions resulted in quick recovery of the peak intensity to the baseline. Further re-ligation resulted in resurgence of the peak intensity to nearly the identical value to the first ischemia value. In contrast, reperfusion after prolonged (120-min) ligation that assumes irreversible states resulted in incomplete recovery of the peak intensity, and re-ligation resulted in inadequate resurgence. Electron microscopic observations confirmed the spectral findings. Together, the Raman spectroscopic measurement for cytochrome c could be applicable to evaluation of viability of the ischemic myocardium without labeling.

Enhancement of defects induced optical nonlinearity in Al: ZnO thin films by electron beam

Controlling and understanding effects induced by electron beam irradiation is quite important to validate the enhanced optical nonlinearity exhibited by Al: ZnO thin films. Herein, we report the generation and controlling of defects by electron beam irradiation in Al: ZnO thin films. The X-ray photoelectron spectroscopy studies on the films confirm the reduction in oxygen-related radiative defect concentration on electron beam irradiation. The structural studies by glancing angle x-ray diffraction shows inclusion of lattice stress in the films upon electron beam irradiation. A drastic increase in the Raman peak intensity along with a shift and broadening of peaks were observed upon irradiation. The increment in the Raman modes intensity endorses that irradiation treatment has enhanced the structural defect centers in the films. The PL studies show a decrement in the emission intensity confirming the decrement of radiative defects in the films. The optical nonlinearity of the films shows an increment in signal intensity attributed to the variation in ground state dipole moments of the atoms investigated using laser stimulated third harmonic generation technique. The Z-scan studies endorses electron beam assisted enhancement in thermal lensing mechanism and free-carrier absorption induced two-photon absorption resulted in the enhancement of third-order optical susceptibility from 6.81 × 10-4 esu to 31.3 × 10-4 esu.

Identification and visualisation of microplastics / nanoplastics by Raman imaging (iii): algorithm to cross-check multi-images

We recently developed the Raman mapping image to visualise and identify microplastics / nanoplastics (Fang et al. 2020, Sobhani et al. 2020). However, when the Raman signal is low and weak, the mapping uncertainty from the individual Raman peak intensity increases and may lead to images with false positive or negative features. For real samples, even the Raman signal is high, a low signal-noise ratio still occurs and leads to the mapping uncertainty due to the high spectrum background when: the target plastic is dispersed within another material with interfering Raman peaks; materials are present that exhibit broad Raman peaks; or, materials are present that fluoresce when exposed to the excitation laser. In this study, in order to increase the mapping certainty, we advance the algorithm to combine and merge multi-images that have been simultaneously mapped at the different characteristic peaks from the Raman spectra, akin imaging via different mapping channels simultaneously. These multi-images are merged into one image via algorithms, including colour off-setting to collect signal with a higher ratio of signal-noise, logic-OR to pick up more signal, logic-AND to eliminate noise, and logic-SUBTRACT to remove image background. Specifically, two or more Raman images can act as “parent images”, to merge and generate a “daughter image” via a selected algorithm, to a “granddaughter image” via a further selected algorithm, and to an “offspring image” etc. More interestingly, to validate this algorithm approach, we analyse microplastics / nanoplastics that might be generated by a laser printer in our office or home. Depending on the toner and the printer, we might print and generate millions of microplastics and nanoplastics when we print a single A4 document.

Study on the effect of Ni co-doping on structural, micro-structural and optical properties of transparent AZO thin films

Abstract Optically transparent Zn0.97-xAl0.03NixO thin films were prepared using spin coating technique. The role of Ni concentration on the structural, microstructural, composition and optical properties were studied by means of XRD, SEM-EDS, RAMAN, UV–Visible spectroscopy. The prepared preferred crystalline orientation along the (002) plane (c-axis) with Ni concentration is seen in the prepared films. The findings of FESEM –EDX demonstrates the homogeneous, uniform and smooth texture of the prepared films with strong adherence to the glass substrate and the presence of nominal values of elements. In addition, the findings of Raman also confirm the absence of Ni related impurity phases. Furthermore, Raman peak shift and intensity variations of Raman spectra suggests that the prepared films have a high degree of crystallinity with lower residual stresses. Optical results suggested that spin coated thin films have optical transparency nearly 90% in the visible wavelength region. It was also observed that the energy bang-gap decreases with the concentration of Ni ions in the host ZnO matrix. Results examined indicate that spin-coated thin films are possible candidates for TCO applications.