Energy Dispersive X-ray Spectroscopy Studies Research Articles

Atomic Layer Deposition of Al-Doped MoS2: Synthesizing a p-type 2D Semiconductor with Tunable Carrier Density.

Extrinsically doped two-dimensional (2D) semiconductors are essential for the fabrication of high-performance nanoelectronics among many other applications. Herein, we present a facile synthesis method for Al-doped MoS2 via plasma-enhanced atomic layer deposition (ALD), resulting in a particularly sought-after p-type 2D material. Precise and accurate control over the carrier concentration was achieved over a wide range (1017 up to 1021 cm–3) while retaining good crystallinity, mobility, and stoichiometry. This ALD-based approach also affords excellent control over the doping profile, as demonstrated by a combined transmission electron microscopy and energy-dispersive X-ray spectroscopy study. Sharp transitions in the Al concentration were realized and both doped and undoped materials had the characteristic 2D-layered nature. The fine control over the doping concentration, combined with the conformality and uniformity, and subnanometer thickness control inherent to ALD should ensure compatibility with large-scale fabrication. This makes Al:MoS2 ALD of interest not only for nanoelectronics but also for photovoltaics and transition-metal dichalcogenide-based catalysts.

Development of tungsten diselenide/polyaniline composite nanofibers as an efficient electrocatalytic counter electrode material for dye-sensitized solar cell

In this work, polyaniline nanofibers (PANI NFs) were prepared by a chemical oxidative polymerization method and the tungsten diselenide nanoparticles (WSe2 NPs) were prepared by a simple hydrothermal method. By making use of both these materials, WSe2/PANI (1:1, 1:2 and 2:1 wt%) composite nanofibers were prepared by mixing them at various ratios with the help of ultrasonication method to use as an efficient counter electrode (CE) for dye-sensitized solar cell (DSSC). The physio-chemical behaviour of pristine PANI, WSe2, std. Pt and WSe2/PANI composite nanofibers were investigated through X-ray diffractometer (XRD), Raman spectroscopy, field emission scanning microscope (FESEM) and energy-dispersive X-ray spectroscopy (EDAX) studies. The electrocatalytic activity of PANI, WSe2, Std. Pt and WSe2/PANI CEs were studied by using cyclic voltammetry (CV), electrochemical impedance and Tafel polarization studies. From the electrochemical studies, we observed that WSe2/PANI (1:1 wt%) CE has good electrocatalytic behaviour towards the reduction of iodide/triiodide (I-/I3-) than WSe2/PANI (1:2 and 2:1 wt%), pristine PANI, WSe2, and Std. Pt. Finally, WSe2/PANI (1:1 wt%), pristine PANI, WSe2, and std. Pt CEs based DSSC were fabricated and tested. The WSe2/PANI (1:1 wt%) exhibits an outstanding photoconversion efficiency (PCE) of 8.22%. It revealed that WSe2/PANI (1:1 wt%) CE has excellent electrocatalytic activity than the pristine PANI, WSe2, and std. Pt and could be used as an alternative to Pt CE for DSSC.

Experimental investigation of structural, surface, optical and electrical properties of gallium sesquioxide doped tausonite compounds

We report that 1% and 3% wt concentration of gallium sesquioxide (Ga2O3) doped tausonite (SrTiO3) compounds have been developed by mechanochemical synthesis followed by calcination process and their microstructural, spectral and opto-electrical characterization are discussed for the first time. The lattice parameter values of the Ga2O3 doped SrTiO3 samples were examined using the X- ray Diffraction (XRD) and Williamson-Hall (W-H) plot. The cubic structure of SrTiO3 is confirmed by the XRD and Raman studies. The Field Effect-Scanning Electron Microscopy (FE-SEM) images of the Ga2O3 doped SrTiO3 samples were composed of spherical particles with agglomeration throughout the surface. The chemical elements and chemical states of the prepared compound have been tested in the Fourier Transform Infrared (FT-IR), Energy Dispersive X-ray (EDX) and X-ray Photoelectron Spectroscopy (XPS) studies. The optical spectra displayed that the absorption wavelength shifted near the red shift with the increase of the Ga2O3 doped SrTiO3. The dielectric and electrical conductivity responses of the 1% and 3 wt % Ga2O3 doped SrTiO3 materials were investigated in the dielectric and electrical studies.

ZnO/CuO hybrid films synthesized by sequential application of electrochemical and spin coating technique

The synthesis of ZnO/CuO films on ITO substrate was realized in two steps, first ZnO was deposited electrochemically and then CuO nanoparticles were precipitated with help of spin coating technique. ZnO nanorods were obtained in aqueous Zn(NO3)2 solution, in presence of KCl as capping agent. Spin coating technique yielded CuO nanoparticles on these nanorods, particle size was employed by copper (II) acetate and ethanolamine in 2-methoxyethanol. In addition, field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy studies were also realized for understanding the structure. UV–Visible spectrophotometer study results revealed that the bandgap value of bilayered structure was governed by presence of CuO nanoparticles. Mott–Schottky analysis was realized for characterization of prepared semiconductor materials, which indicated to + 0.571 for ZnO/CuO(3), while these values were + 0.532 V and − 0.360 V for CuO and ZnO, respectively. Electrochemical measurements were realized with help of solar simulator, for testing photocatalytic activity of ZnO/CuO as photocathode material, in aqueous solution.

Growth, characterisation and antibacterial activity of LHCdBr single crystal

ABSTRACT Single crystals L– Histidine Cadmium Bromide (LHCdBr) have been grown successfully by solution growth method. Transparent crystal was obtained in the period of 2 weeks. The single crystal X-ray diffraction shows that the crystal is triclinic in structure. Powder X-ray diffraction analysis was carried to identify the intense peak. The various functional groups present were confirmed by Fourier Transform Infrared spectroscopy. By using Energy Dispersive X-ray Spectroscopy studies presence of elemental composition was confirmed. From the optical studies the cut-off length is found to be 315 nm. The mechanical properties of the LHCdBr crystal have been analysed. The dielectric study was carried out and reported in this paper. By the Kurtz powder method the second harmonic generation was confirmed and it is 0.9 times greater than that of KDP crystal. LHCdBr shows good antibacterial activity against various standard bacterial strains (E. coli, Shigella flexneri, Salmonella typhi and Staphylococcus aureus).

High-temperature oxidation behavior of the Crofer 22 APU steel coated with (La,Sr)(Co,Fe)O3 film prepared by pulsed laser deposition

The La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF48) film was deposited on Crofer 22 APU ferritic stainless steel using the pulsed laser deposition (PLD) technique. The LSCF48 film with a thickness of about 1.1 μm was dense and homogeneous, with good adhesion to the metallic substrate. Transmission electron microscopy combined with the energy-dispersive X-ray spectroscopy studies showed that the stoichiometry of the target was precisely transferred to the film by pulsed laser deposition. Oxidation studies of bare Crofer 22 APU steel, and steel with the LSCF48 film were carried out in laboratory air at 1073 K under both isothermal and cyclic oxidation conditions. The calculated parabolic rate constant kp after oxidation for 200 h for the steel with LSCF48 film was approximately three times lower than the oxidation rate of the steel without surface modification. The oxide scale formed on Crofer 22 APU steel consisted of two layers: an inner layer built of chromia and an outer layer consisting of the Mn1.5Cr1.5O4spinel. In the case of the steel with LSCF48 film, the oxide scale was two times thinner and had a similar phase composition. In both cases, the presence of an internal oxidation zone with SiO2 and Al2O3 precipitates was observed. In addition, small amounts of spinel crystals were observed on the film surface. After 2400 h of oxidation at 1073 K under thermal cyclic conditions, the total mass gain was 1.04 mg · cm−2 and 0.67 mg · cm−2 for the respectively bare and coated substrate. The results indicated that the spallation of the oxide scale and/or the film did not occur. In both cases, the composition of the scales was similar to the scales formed on the samples after isothermal oxidation. Studies of the electrical properties show, that Crofer 22 APU steel with LSCF48 film deposited by PLD method meets criteria for the interconnector materials for intermediate-temperature solid oxide fuel cells applications.

Transparent conducting SnO2 thin films synthesized by nebulized spray pyrolysis technique: Impact of Sb doping on the different physical properties

The impact of antimony (Sb) doping concentration on the different physical properties of transparent conducting tin oxide (SnO2) thin films synthesized through nebulized spray pyrolysis (NSP) method have been explored systematically. X-ray diffraction (XRD) results reveal the tetragonal cassiterite structure of single phase SnO2 and the decrement of crystallite size with rising Sb doping concentration. Uniform and compact surface morphology with continuous distribution of grains and reduction of grain size with increasing dopant amount are illustrated by scanning electron microscopy (SEM). The stoichiometry of SnO2 film with 2% Sb doping is confirmed by energy dispersive X-ray spectroscopy (EDS) study. The optical transmittance is more than 85% in the visible region for undoped film and enhanced in the near infrared (NIR) spectral region for all the films. The transparency is reduced and the optical band gap is found to increase from 3.69 eV to 3.90 eV upon Sb inclusion. The extinction coefficient, refractive index, dielectric constant, dissipation factor, volume energy loss function, surface energy loss function, optical conductivity and optical density of the films are determined and interpreted for different dopant concentrations. The photoluminescence (PL) spectrum demonstrates the enhancement of emission intensity with increasing Sb incorporation representing its suitability in the application of solid state lighting. The lowest resistivity of 6.435 × 10−4 Ω cm and the highest carrier concentration of 1.316 × 1021 cm−3 are achieved for the film with 8% Sb doping concentration. The mobility of the studied degenerated films is varied from 54.743 cm2/Vs for undoped films to 7.378 cm2/Vs for 8% Sb doped film and limited by ionized impurity scattering. The film deposited with 2% Sb doping level exhibits the highest figure of merit values in both visible and NIR wavelength region indicating its better role in optoelectronic applications.

ZnWO4 :Eu3+ phosphor with intense blue LED excitation: photoluminescence and electron density distribution analysis.

A high intensity 464 nm excitable ZnWO4 :Eu3+ red-emitting phosphor for warm white lighting applications was prepared using a solid-state reaction method by varying the dopant Eu3+ concentration. Crystalline purity and phase identification was confirmed and revealed using powder X-ray diffraction and Rietveld refinement analysis. The surface morphology of Zn1-x Eux WO4 (x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05) was examined using scanning electron microscopy (SEM) techniques. From SEM analysis, the ZnWO4 :Eu3+ phosphor prepared at 1-3% molar Eu3+ concentrations exhibited a small pebble-like morphology with a smooth surface. On increasing the molar concentration of Eu3+ to >3%, the pebble stone morphology disappeared and a large, smooth irregular polygon-shaped granular-like morphology was obtained. Of the higher mol% Eu3+ , the 4% Eu3+ -doped ZnWO4 showed the best photoluminescence properties with high intensity and sharp excitation at 395 and 464 nm, followed by red emission centred at 615 nm with excellent CIE coordinates (x = 0.58 and y = 0.41) in the core red region. Elemental composition and chemical state analysis were carried out for the 4% Eu3+ -doped ZnWO4 phosphor using X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy studies. Based on all the above analyses, the Eu3+ -doped ZnWO4 phosphor was found to be a very efficient red-emitting phosphor under near-UV light as well as under visible light excitation and could be used for white LED and field emissive displays applications.

A Sulfur-Infused Separator for Boosting Areal Capacity of Li-S Batteries.

This study presents a new approach for enabling the development of high-performance lithium-sulfur (Li-S) cells by simply inserting a sulfur-infused separator (SIS) between a common S cathode and a Li metal anode. All solid sulfur electrically isolated from the cathode is electrochemically reduced to polysulfides during the first discharge. Notably, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) studies have demonstrated that the S in the separator disappears completely even when the cell is discharged to 2.1 V in the first cycle. The combination of a SIS with a typical S cathode results in the doubling of the areal capacity with superior cycling stability upon comparison with the control cell. This result demonstrates that the introduction of additional active materials, such as elemental sulfur, to a separator is a highly effective method for the fabrication of Li-S cells with a high areal capacity.

Correlation between surface chemistry and morphology of PtCu and Pt nanoparticles during oxidation-reduction cycle

Process conditions during catalytic reactions induce significant changes in surface chemistry and structure of bi- (mono) metallic nanoparticles leading to their deactivation, and this can ultimately affect the reactions long-term performance. Here PtCu and Pt model nanoparticles are prepared by microwave synthesis and characterized by X-ray diffraction (XRD). Surface chemical and morphological changes of the nanoparticles during high-temperature oxidation and reduction treatments cycle are correlated by near in situ X-ray photoelectron spectroscopy (XPS) and ex situ transmission electron microscopy (TEM) - energy-dispersive X-ray spectroscopy (EDS) studies. At 300 °C the surface atomic composition of the PtCu nanoparticles switches reversibly upon the cycle and at the same time their morphology and composition are maintained. At 400 °C, the surface atomic composition does not fully restore and, while the shape is maintained, the size and composition are not. This occurs by a mechanism of Cu leaching out from the nanoparticles. These data delineate potential operating conditions for stable PtCu nanocatalysts.

Effect of arsenic on exopolysaccharide production in a diazotrophic cyanobacterium

The Bengal Delta Plain (BDP), located across India and Bangladesh, is one of the worst arsenic (As)-affected regions, including contaminated agricultural lands. The effect of As on the growth and exopolysaccharide (EPS) production was investigated in Nostoc ellipsosporum, a diazotrophic cyanobacterium isolated from a paddy field located in BDP. The cells were exposed to 0 (control), 50, 200, and 400 μM concentrations of sodium arsenite salt and monitored for 21 days. For 50 and 200 μM arsenite treatments, cellular growth was found to be stimulated, whereas, at 400 μM treatment, a characteristic growth behavior was observed compared with growth in control culture. There was an inhibition phase for the first 9 days, followed by a steady increase of growth. During the initial 9 days, the released EPS production (normalized to cell density) in 400 μM As-treated culture was very high compared with that of the lower As treatments. Based on microscopy, it was observed that there was an aggregation of cell filaments in 400 μM treatment culture. In case of capsular EPS, no difference was observed in 50 μM treatment. However, in 200 and 400 μM treatments, capsules were disintegrated after 12 and 15 days of incubation, respectively. Energy-dispersive X-ray spectroscopy (EDS) study showed the binding potential of released and capsular EPS toward As. The adaptive capabilities of N. ellipsosporum, including behavior of multicellularity and protective role of EPS from As stress, can be useful for incorporating in cost-effective bioremediation strategies to remove As from agricultural fields.

A scalable method for preparing Cu electrocatalysts that convert CO2 into C2+ products

Development of efficient catalysts for selective electroreduction of CO2 to high-value products is essential for the deployment of carbon utilization technologies. Here we present a scalable method for preparing Cu electrocatalysts that favor CO2 conversion to C2+ products with faradaic efficiencies up to 72%. Grazing-incidence X-ray diffraction data confirms that anodic halogenation of electropolished Cu foils in aqueous solutions of KCl, KBr, or KI creates surfaces of CuCl, CuBr, or CuI, respectively. Scanning electron microscopy and energy dispersive X-ray spectroscopy studies show that significant changes to the morphology of Cu occur during anodic halogenation and subsequent oxide-formation and reduction, resulting in catalysts with a high density of defect sites but relatively low roughness. This work shows that efficient conversion of CO2 to C2+ products requires a Cu catalyst with a high density of defect sites that promote adsorption of carbon intermediates and C–C coupling reactions while minimizing roughness.

Facile microwave synthesis of bismuth molybdate nanostructures and their characterization for optoelectronic applications

Facile microwave synthesis of monophasic bismuth molybdate (α-Bi2Mo3O12) nanoparticles/nanosheets were achieved with different contents of Cetrimonium bromide (CTAB) as surfactants. The effect of CTAB contents on physical properties of α-Bi2Mo3O12 has been studied. X-ray diffraction (XRD) and FT-Raman studies approved the monophasic synthesis of α-Bi2Mo3O12 without any additional impurity or separate phase. Energy dispersive X-ray spectroscopy (EDX) study further confirm the synthesis of bismuth molybdate. The morphology of α-Bi2Mo3O12 was strongly affected by CTAB contents and it was transformed from nanoparticles to nanosheets like structure, however, no separate phase was observed. For optical band gap analysis diffused reflectance spectra were measured and Kubelka-Munk theory was employed to determine energy gap and noticed between 2.76 and 3.10 eV. Furthermore, dielectric constant (ε’), loss (ε’‘), and ac electrical conductivity (σac) was determined and discussed. The values of ε’ were noticed between 17 and 27. The electrical conduction mechanism was also discussed through calculating the frequency exponent values.

Fabrication and Characterization of Zein/Hydroxyapatite Composite Coatings for Biomedical Applications

Stainless steel is renowned for its wide use as a biomaterial, but its relatively high corrosion rate in physiological environments restricts many of its clinical applications. To overcome the corrosion resistance of stainless steel bio-implants in physiological environments and to improve its osseointegration behavior, we have developed a unique zein/hydroxyapatite (HA) composite coating on a stainless steel substrate by Electrophoretic Deposition (EPD). The EPD parameters were optimized using the Taguchi Design of experiments (DoE) approach. The EPD parameters, such as the concentration of bio-ceramic particles in the polymer solution, applied voltage and deposition time were optimized on stainless steel substrates by applying a mixed design orthogonal Taguchi array. The coatings were characterized by using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and wettability studies. SEM images and EDX results indicated that the zein/HA coating was successfully deposited onto the stainless steel substrates. The wettability and roughness studies elucidated the mildly hydrophilic nature of the zein/HA coatings, which confirmed the suitability of the developed coatings for biomedical applications. Zein/HA coatings improved the corrosion resistance of bare 316L stainless steel. Moreover, zein/HA coatings showed strong adhesion with the 316L SS substrate for biomedical applications. Zein/HA developed dense HA crystals upon immersion in simulated body fluid, which confirmed the bone binding ability of the coatings. Thus the zein/HA coatings presented in this study have a strong potential to be considered for orthopedic applications.

Thermally Stable Phosphor KBa2(PO3)5:Eu2+ with Broad-Band Cyan Emission Caused by Multisite Occupancy of Eu2.

The relationship between the structure and properties is always a hot topic in the luminescent material field. In this work, a new phosphor KBa2(PO3)5:Eu2+ (KBP:Eu) was prepared by a high-temperature solid-state reaction method and characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, photoluminescence (PL), and electroluminescence studies. The polyphosphate host KBP offers three lattice environments (K1, Ba1, and Ba2) for Eu2+ ions to realize broad-band emission from 380 to 700 nm under 345 nm excitation. The distributions of Eu2+ in the three lattice sites can be proven by low-temperature PL and transient fluorescence spectroscopy. Furthermore, temperature-dependent luminescence studies for phosphor KBP:0.02Eu reveal that its luminescence intensity at 150 °C retains about 97% of the initial value at 25 °C. By composing a 365 nm UV chip and KBP:0.02Eu, CaAlSiN3:Eu2+ phosphors, a warm white-light-emitting diode (WLED) was obtained with a correlated color temperature of 5146 K and chromaticity coordinates (0.3404, 0.3384). Therefore, KBP:Eu phosphor is a potential cyan-emitting phosphor used for high-power WLEDs.

Impact of rare earth europium (RE-Eu3+) ions substitution on microstructural, optical and magnetic properties of CoFe2−xEuxO4 nanosystems

In this study, pure cobalt ferrite (CoFe2O4) nanoparticles and europium doped CoFe2O4 (CoFe2−xEuxO4; x = 0.1, 0.2, 0.3) nanoparticles were synthesized by the precipitation and hydrothermal approach. The impact of replacing trivalent iron (Fe3+) ions by trivalent rare earth europium (RE-Eu3+) ions on the microstructure, optical and magnetic properties of the produced CoFe2O4 nanoparticles was studied. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectra exposed the consistency of a single cubic phase with the evidence of Eu2O3 phases for x ≥ 0.2. FTIR transmittance spectra showed that, the all investigated samples have three characteristic metal-oxygen bond vibrations corresponding to octahedral B-site (υ1 and υ2) and tetrahedral A-site (υ3) around 415 cm−1, 470 cm−1 and 600 cm−1 respectively. XRD and energy dispersive X-ray spectroscopy studies affirmed the integration of RE-Eu3+ ions within CoFe2O4 host lattice and decrease of average crystals size from 13.7 nm to 4.7 nm. Transmission electron microscopy (TEM) analysis showed the crucial role played by RE-Eu3+ added to CoFe2O4 in reducing the particle size below 5 nm in agreement with XRD analysis. High resolution-TEM (HR-TEM) analysis showed that the as-synthesized spinel ferrite, i.e., CoFe2−xEuxO4, nanoparticles are single-crystalline with no visible defects. In addition, the HR-TEM results showed that pure and doped CoFe2O4 have well-resolved lattice fringes and their interplanar spacings matches that obtained by XRD analysis. Magnetic properties investigated by the vibrating sample magnetometer technique illustrated transformation of magnetic state from ferromagnetic to superparamagnetic at 300 K resulting in introducing RE-Eu3+ in CoFe2O4 lattice. At low temperature (~5 K) the magnetic order was ferromagnetic for both pure and doped CoFe2O4 samples. Substitution of Fe3+ ions in CoFe2O4 nanoparticles with RE-Eu3+ ions optimizes the sample nanocrystals size, cation distribution and magnetic properties for many applications.

Phosphate Coatings Enriched with Copper on Titanium Substrate Fabricated Via DC-PEO Process.

The present paper covers the possible ways to fabricate advanced porous coatings that are enriched in copper on a titanium substrate through Direct Current Plasma Electrolytic Oxidation (DC-PEO) with voltage control, in electrolytes made of concentrated orthophosphoric acid with the addition of copper(II) nitrate(V) trihydrate. In these studies, solutions containing from 0 to 650 g salt per 1 dm3 of acid and anodic voltages from 450 V up to 650 V were used. The obtained coatings featuring variable porosity could be best defined by the three-dimensional (3D) parameter Sz, which lies in the range 9.72 to 45.18 μm. The use of copper(II) nitrate(V) trihydrate in the electrolyte, resulted, for all cases, in the incorporation of the two oxidation forms, i.e., Cu+ and Cu2+ into the coatings. Detailed X-Ray Photoelectron Spectroscopy (XPS) studies layers allowed for stating that the percentage of copper in the surface layer of the obtained coatings was in the range of 0.24 at% to 2.59 at%. The X-Ray Diffraction (XRD) studies showed the presence of copper (α-Cu2P2O7, and Cu3(PO4)2) and titanium (TiO2-anatase, TiO3, TiP2O7, and Ti0.73O0.91) compounds in coatings. From Energy-Dispersive X-Ray Spectroscopy (EDS) and XPS studies, it was found that the Cu/P ratio increases with the increase of voltage and the amount of salt in the electrolyte. The depth profile analysis by Glow-Discharge Optical Emission Spectroscopy (GDOES) method showed that a three-layer model consisting of a top porous layer, a semi-porous layer, and a transient/barrier layer might describe the fabricated coatings.

Growth Rate of Intermetallics in Aluminum to Copper Dissimilar Welding

The use of aluminum and copper materials increases due to their excellent electrical and thermal characteristics. The growth and the type of intermetallic compounds were varied with the various conditions in fusion welding. The present study focuses on the joining of aluminum to copper by friction welding to characterize the intermetallic layer in the interface. Heat treatment was applied for the welds using a constant temperature of 300 °C for the duration of 6 h, 12 h and 24 h. The growth of the intermetallics and their characteristics were examined by microscopic and energy-dispersive X-ray spectroscopy studies. The interdiffusion, growth rate and thickness of the intermetallic compounds were evaluated according to the heating time. The tensile strength and resistance of the welds gradually reduced with increasing the thickness of the intermetallic compounds. The fracture morphology of the welds was investigated by scanning electron microscopy on both sides of the welds.

A search for apatite crystals in the gap zone of collagen fibrils in bone using dark-field illumination.

Bright-field transmission electron microscope (TEM) images of ion milled or focused ion beam (FIB) sections of cortical bone sectioned parallel to the long axis of collagen fibrils display an electron-dense phase in the gap zones of the fibrils, as well as elongated plates (termed mineral lamellae) comprised of apatite crystals, which surround and lie between the fibrils. Energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) studies by others have shown that the material in the gap zones is calcium phosphate. Dark-field (DF) images are capable of revealing the projected position of crystals of apatite in a section of bone. We obtained bright field (BF) images of ion milled sections of bovine femoral cortical bone cut parallel to fibril axes (longitudinal view), and compared them with DF images obtained using the (002) apatite reflection to test a widely held theory that most of the mineral in bone resides in the gap zones. Most apatite crystals which were illuminated in DF images and which projected onto gap zones were extensions of crystals that also project onto adjacent overlap zones. However, in BF images, overlap zones do not appear to contain significant amounts of mineral, implying that the crystals imaged in DF are actually in the interfibrillar matrix but projected onto images of fibrils. However a small number of "free" illuminated crystals did not extend into the overlap zones; these could be physically located inside the gap zones. We note that projections of gap zones cover 60% of the area of any longitudinal field of view; thus these "free" crystals have a high random probability of appearing to lie on a gap zone, wherever they physically lie in the section. The evidence of this study does not support the notion that most of the mineral of bone consists of crystals in the gap zone. This study leaves uncertain what is the Ca-P containing material present in gap zones; a possible candidate material is amorphous calcium phosphate.

The effect of hydrochloric acid (HCl) on permanent molars: A scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) study

It is well established that acid disposal is a potentially effective method used by criminal syndicates to hinder the identification of victims. This study documents the effects of continuous immersion in hydrochloric acid (HCl, 37%) on molars using macroscopic analysis, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The goal of this study is to aid in distinguishing visually unrecognizable fragments of dental remains when drastic changes in morphology have occurred as a result of acid exposure. Macroscopic, SEM, and EDS analysis were conducted on seven maxillary molars before and after HCl treatment. Molars reduced in weight relative to the length of time immersed in HCl and the dissolution time was over 40 hours longer than reported in previous studies, at just over 66 hours. SEM and EDS analysis showed acid-treated teeth exhibited morphological patterns such as cracking and layering visible at high magnification. Calcium/phosphorous ratios fell within the expected range of 1.6-2.5, indicating that HCl-treated teeth are still identifiable as osseous or dental tissue even when not visually identifiable as teeth. This is the first study to present SEM images of molar cementum before and after immersion in HCl and to present EDS results. This information can assist researchers and investigators in determining the presence of dental tissue in a forensic context associated with acid disposal.