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With the goal of accurately detecting and quantifying the amounts of dopamine (DA) and serotonin (5-HT) in mixtures of these neurotransmitters without using any labelling, we present a detailed, comparative computational and Raman experimental study. Although discrimination between these two analytes is achievable in such mixtures for concentrations in the millimolar range, their accurate quantification remains unattainable. As shown for the first time in this work, the formation of a new composite resulting from their interactions with each other is the main reason for this lack of quantification. While this new hydrogen-bonded complex further complicates potential analyte discrimination and quantification at concentrations characteristic of physiological levels (i.e., nanomolar concentrations), it can also open new avenues for its use in drug delivery and pharmaceutical research. This remark is based not only on chemical interactions analyzed here from both theoretical and experimental approaches, but also on biological relationship, with consideration of both functional and neural proximity perspectives. Thus, this research constitutes an important contribution toward better understanding of neural processes, as well as toward possible future development of label-free biosensors.

Surfaces of AISI 304 austenitic stainless steel plates nitrided by plasma immersion ion implantation (PIII) technology were studied by means of Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) to determine the effect of the nitriding process on the surface and subjacent layers. Elemental compositions obtained by AES and XPS at varying depths indicate that the saturation of N is relatively constant as a function of depth, indicating the reliability of PIII technology for subsurface saturation. It is concluded that the concentrations of both Cr and O increase with depth, the subjacent oxide is driven by the Ar+ sputtering process used to access the lower layers, and then N is bound to Cr.

A combined theoretical and experimental analysis of dopamine (DA) is presented in this work with the objective of achieving more accurate detection and monitoring of this neurotransmitter at very low concentrations, specific to physiological levels. Surface-enhanced Raman spectroscopy on silver nanoparticles was employed for recording DA concentrations as low as 10−11 molar. Quantum chemical density functional calculations were carried out using Gaussian-09 analytical suite software. Relatively good agreement between the simulated and experimentally determined results indicates the presence of different DA molecular forms, such as uncharged DA±, anionic DA−, and dopaminequinone. Disappearance of the strongest bands of dopamine around 750 cm−1 and 790 cm−1, which suggests its adsorption onto the metallic surface, is not only consistent with all of these DA configurations, but also provides additional information about the analyte’s redox process and voltammetric detection. On the other hand, occurrence of the abovementioned Raman lines could indicate the formation of multilayers of DA or its presence in a cationic DA+ form. Thus, through coordinated experiment and theory, valuable insights into changes observed in the vibrational signatures of this important neurotransmitter can be achieved for a better understanding of its detection at physiological levels, which is crucial if further optovoltammetric medical device development is envisioned.

Combined theoretical and experimental analysis of dopamine is presented in this work to better understand phenomena related to this neurotransmitter's detection and monitoring at very low concentrations specific to physiological levels. Surface-enhanced Raman spectroscopy (SERS) on silver nanoparticles was employed for recording dopamine concentrations as low as 10−11 molar. Quantum chemical density functional calculations were carried out using Gaussian-09 analytical suite software. Relatively good agreement between the simulated and experimentally determined results indicates the presence of all dopamine molecular forms, such as neutral DA0, ionic DA− and DA+, and of dopaminequinone as well. Disappearance of the strongest bands of dopamine at 750 cm−1 and 795 cm−1, which suggests its adsorption onto the metallic surface, is consistent with the appearance of the latter molecular configuration. Thus, through coordinated experiment and theory, valuable insights into changes observed in the vibrational signatures of this important neurotransmitter can be analyzed and comprehended.

Boron-doped diamond (BDD) has seen a substantial increase in interest for use as electrode coating material for electrochemistry and studies of deep brain stimulation mechanism. In this study, we present an alternative method for determining important characteristics, including conductivity, carrier concentration, and time constant, of such material by the signature of Drude-like metallic behavior in the far-infrared (IR) spectral range. Unlike the direct determination of conductivity from the four-point probe method, using far-IR transmittance provides additional information, such as whether the incorporation of boron results in a large concentration of carriers or in inducing defects in the diamond lattice. The slightly doped to medium-doped BDD samples that were produced using chemical vapor deposition and analyzed in this work show conductivities ranging between 5.5 and 11 (Ω cm)−1. Different growth conditions demonstrate that increasing boron concentration results in an increase in the carrier concentration, with values between 7.2 × 1016 and 2.5 × 1017 carriers/cm3. Addition of boron, besides leading to a decrease in the resistivity, also resulted in a decrease in the time constant, limiting BDD conductivity. Investigations, by confocal Raman mapping, of the induced stress in the material due to interaction with the substrate or to the amount of doping are also presented and discussed. The induced tensile stress, which was distributed closer to the film-substrate interface decreased slightly with doping.

Although not yet ready for clinical application, methods based on Raman spectroscopy have shown significant potential in identifying, characterizing, and discriminating between noncancerous and cancerous specimens. Real-time and accurate medical diagnosis achievable through this vibrational optical method largely benefits from improvements in current technological and software capabilities. Not only is the acquisition of spectral information now possible in milliseconds and analysis of hundreds of thousands of data points achieved in minutes, but Raman spectroscopy also allows simultaneous detection and monitoring of several biological components. Besides demonstrating a significant Raman signature distinction between nontumorigenic (MCF-10A) and tumorigenic (MCF-7) breast epithelial cells, our study demonstrates that Raman can be used as a label-free method to evaluate epidermal growth factor activity in tumor cells. Comparative Raman profiles and images of specimens in the presence or absence of epidermal growth factor show important differences in regions attributed to lipid, protein, and nucleic acid vibrations. The occurrence, which is dependent on the presence of epidermal growth factor, of new Raman features associated with the appearance of phosphothreonine and phosphoserine residues reflects a signal transduction from the membrane to the nucleus, with concomitant modification of DNA/RNA structural characteristics. Parallel Western blotting analysis reveals an epidermal growth factor induction of phosphorylated Akt protein, corroborating the Raman results. The analysis presented in this work is an important step toward Raman-based evaluation of biological activity of epidermal growth factor receptors on the surfaces of breast cancer cells. With the ultimate future goal of clinically implementing Raman-guided techniques for the diagnosis of breast tumors (e.g., with regard to specific receptor activity), the current results just lay the foundation for further label-free optical tools to diagnose the disease.

We present a comparative microscopic and spectroscopic study of the morphology and composition of WO3 and W0.95Ti0.05O3 thin films, grown by radio-frequency magnetron reactive sputtering at substrate temperatures varied from room temperature to 500 °C, using atomic force microscopy (AFM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). With increasing growth temperature, the AFM results show increase in the average crystallite size and in the surface roughness for both undoped and doped samples. The AFM data, along with the Raman results, clearly indicate that for the given set of experimental conditions, higher growth temperatures are required to obtain crystalline Ti-doped WO3 films than for WO3 films. Also, the Raman results suggest a potential phase transformation from a monoclinic WO3 structure to an orthorhombic, but more probably a tetragonal, configuration in the W0.95Ti0.05O3 thin films. This remark is based on the observed shifting, with Ti doping, to lower frequencies of the Raman peaks corresponding to W–O–W stretching modes of WO3 at 806 and 711 cm−1 to 793 and 690 cm−1, respectively. XPS data indicate that the doped material has a reduced WO3−x stoichiometry at the surface, with the presence of W6+ and W5+ oxidation states; this observation could also be related to the existence of a different structural phase of this material, corroborating with the Raman measurements.

With its reputation as a high-energy density fuel, aluminum hydride (AlH3) has received renewed attention as a material that is particularly suitable, not only for hydrogen storage but also for rocket propulsion. While the various phases of AlH3 have been investigated theoretically, there is a shortage of experimental studies corroborating the theoretical findings. In response to this, we present here an investigation of these compounds based primarily on two research areas in which there is the greatest scarcity of information in the literature, namely Raman and infrared (IR) absorption analysis. To the authors' knowledge, this is the first report of experimental far-IR absorption results on these compounds. Two different samples prepared by broadly similar ethereal reactions of AlCl3 with LiAlH4 were analyzed. Both Raman and IR absorption measurements indicate that one sample is purely γ-AlH3 and that the other is a mixture of α-, β-, and γ-AlH3 phases. X-ray diffraction confirms the spectroscopic findings, most notably for the β-AlH3 phase, for which optical spectroscopic data are reported here for the first time. Copyright © 2010 John Wiley & Sons, Ltd.

Urolithiasis, the category of diseases associated with the formation of kidney stones, has many causes. However, only a few have been documented as aggravating calculi depositions and aggregations. This amply justifies continued work in developing effective and efficient inhibition and treatment techniques. The recent resurgence in reviews on plant antiurolithiatic activity has given credence to the application of modern spectroscopic analysis, and has led us to this study. Results obtained from Raman and infrared (IR) absorption analysis of inhibited calculi growth resulting from laboratory synthesis of calcium oxalate crystals accompanied by the natural infusion of Larrea tridentata are reported. A visible decrease in calcium oxalate crystal growth with increasing amounts of L. tridentata herbal infusion was observed in photomicrographs, as well as a color change from white-transparent for pure crystals to light orange-brown for crystals with inhibitor. Both Raman and IR absorption spectra reveal a monohydrate structure for the crystals grown alone, which transform to a dihydrate morphology with the addition of the L. tridentata inhibitor. Furthermore, the resulting data support the possibilities of the influences, in this complex process, of the nordihydroguaiaretic acid (NDGA) and its derivative compounds from L. tridentata and the bonding of the magnesium of the inhibitor with the oxalate ion on the surface of the calculi crystals. This assumption corroborates well with the micrographs obtained under higher magnification, which show that the separated small crystallites consist of a darker brownish core, which we attribute to the dominance of growth inhibition by NDGA, surrounded by light transparent thin shells, which possibly correspond to passivation of the crystals by magnesium oxalate. Copyright © 2010 John Wiley & Sons, Ltd.

We present a detailed study of the morphology and composition of tungsten oxide (WO3) thin films, grown by radio frequency magnetron reactive sputtering at substrate temperatures varied from room temperature (RT) to 500 °C, using infrared (IR) absorption, Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS). This work includes valuable new far-IR results about structural changes in microcrystalline WO3. Both IR absorption and Raman techniques reveal an amorphous sample grown at RT and initial crystallization into monoclinic structures for samples grown at temperatures between 100 and 300 °C. The Raman spectra of the samples grown at high temperatures indicate, apart from the monoclinic structure, a strain effect, with a distribution revealed by confocal Raman mapping. XPS indicates that the film surface maintains the stoichiometry WOx, with a value of x slightly greater than 3 at RT due to oxygen contamination, which decreases with increasing temperature.

Although herbal medicine is widely employed in inhibition of urinary calculi as an alternative and complementary curative method, the lack of detailed scientific studies that could provide insights into this complex process weakens its validity. The present work targets multitechnique spectroscopic investigations by Raman, infrared absorption, X-ray photoelectron spectroscopy (XPS), and photoluminescence on the effects of the herb Rotula Aquatica Lour (RAL) on the growth of synthetically prepared magnesium-based calculi. In addition to the standard magnesium phosphate-based sample, two other samples were prepared with incorporation of 1 and 2wt% RAL herbal extract. Both, Raman and infrared data show a newberyite structure for the crystals without and with inhibitor. The XPS measurements reveal an unexpected presence of Zn in the sample with bfRAL inhibitor, which, as suggested in the literature, may initiate rapid stone formation, and consequently, contribute to the inhibition process. Furthermore, the existence of metallic Zn can explain the reflectance of the incident light observed in the infrared transmission studies of the unground crystals. A significant increase in magnesium with addition of herbal extract is observed in the XPS data. Also, evidence for MgO binding between the inhibitor and the phosphate units of urinary calculus is found in XPS and Raman results. Similarity between our photoluminescence measurements and those of in vivo chlorophyll a corroborates to provide additional evidence of Mg-related inhibition. Copyright © 2009 John Wiley & Sons, Ltd.

Inorganic potassium dihydrogen phosphate (KDP) is widely known for its value as a nonlinear optical material. In this study, pure and l-arginine–doped KDP single crystals were grown by the slow solvent evaporation technique and further subjected to infrared absorption and Raman studies for the confirmation of chemical group functionalization and possible bonding between the organic and inorganic materials. The appearance in the infrared absorption spectra of additional vibrational lines, which mostly originate from disturbed N–H, C–H, and C–N bonds of the l-arginine–doped salt, confirm the interaction between KDP and the organic material. This affirmation is supported by more evidence from Raman measurements, where the disappearance of NH vibrations of the amino group is observed. We are thus led to the possibility of hydrogen bonding primarily between the nucleophilic O− of the phosphate unit of KDP and the amino group of the l-arginine.

In this investigation, we address the question of how organic thioindigo binds to inorganic palygorskite to form a pigment similar to Maya Blue. We also address how such binding, if it occurs, might be affected by varying the proportion of dye relative to that of the mineral, and by varying the length of heating time used in preparation of the pigment. In addition to samples of palygorskite and thioindigo both alone, four synthetic pigment samples were prepared; two samples of 8 wt.% dye, one heated at 170 °C for 3 h and one at 170 °C for 9 h, and two samples of 16 wt.% dye, one heated at 170 °C for 3 h and one at 170 °C for 9 h. All samples were examined using Fourier transform-infrared (FT-IR) and FT-Raman spectroscopy. For the pigment samples, FT-IR peaks at 1627 cm−1 are attributed to a downshifted CO stretching mode of thioindigo due to dye–clay interaction. This interpretation is corroborated by FT-Raman CO peaks with 14 cm−1 shifts to lower wavenumber for the pigment relative to thioindigo alone. Additional Raman scattering between 550 cm−1 and 650 cm−1 also suggests dye–clay interaction through metal–oxygen bonding. We are thus led to the possibility of mostly hydrogen bonding between silanol and carbonyl at lower dye concentration, with a predominance of metal–oxygen bonding at higher dye concentration. Copyright © 2008 John Wiley & Sons, Ltd.

Analysis of the induced stress on undoped and boron-doped diamond (BDD) thin films by confocal Raman microscopy is performed in this study to investigate its correlation with sample chemical composition and the substrate used during fabrication. Knowledge of this nature is very important to the issue of long-term stability of BDD coated neurosurgical electrodes that will be used in fast-scan cyclic voltammetry, as potential occurrence of film delaminations and dislocations during their surgical implantation can have unwanted consequences for the reliability of BDD-based biosensing electrodes. To achieve a more uniform deposition of the films on cylindrically-shaped tungsten rods, substrate rotation was employed in a custom-built chemical vapor deposition reactor. In addition to visibly preferential boron incorporation into the diamond lattice and columnar growth, the results also reveal a direct correlation between regions of pure diamond and enhanced stress. Definite stress release throughout entire film thicknesses was found in the current Raman mapping images for higher amounts of boron addition. There is also a possible contribution to the high values of compressive stress from sp2 type carbon impurities, besides that of the expected lattice mismatch between film and substrate.

An AlN film was grown using ammonia plasma and characterized with Auger electron spectroscopy in depth profile mode using argon sputtering. After growth of AlN on a 6061 Al substrate in a plasma chamber, the sample was removed from the vacuum and transported to an ultrahigh vacuum surface analysis system. Detailed AES spectra of Al, O and N are presented as a function of sputtering time (depth). Relative concentration changes were observed for the KLL O and KLL N signals but there were no significant lineshape changes, however significant relative concentration and lineshape changes associated with the LVV Al signal were observed. Lineshape analysis indicates the presence of the following bonds: Al-O (56 eV), Al-N (59 eV) and A1-A1 (68 eV).

An oxygen free polycrystalline 6061 aluminum alloy surface was obtained for the first time in an UHV environment ( 1×10 −9 to 3×10 −9 Torr) after dc ammonia plasma treatment in a separate vacuum system. The specimen was first sputtered and processed in the plasma chamber for about 1 h, transferred after air exposure into the UHV chamber, then cleaned by 2.8 keV Ar+ ion bombardment for about 10 min to remove the air-grown oxide. An oxygen free 6061 aluminum surface was observed using Auger electron spectroscopy. Regrowth of the oxide layer in the UHV environment was monitored versus time. A possible cleaning mechanism by the ammonia plasma is proposed. This oxygen free surface is key to achieving thin film growth/deposition on aluminum or its alloys.

In recent years, doped diamond-like carbon (DLC) coatings have been shown to solve some intrinsic application difficulties of DLC, esp. reducing internal stresses and improving thermal stability. Diamond-like nanocomposite (DLN), by incorporating an amorphous Si-O network into the DLC, is a special class of modified DLC coatings, which have many excellent properties and wide applications. In this paper, a diamond-like nanocomposite film was synthesized by an ion beam assisted deposition method in an acetylene atmosphere. The composition and microstructure of the DLN film were investigated by various spectroscopic analyses, including Fourier transform infrared absorption spectroscopy, Rutherford backscattering spectroscopy. Raman scattering spectroscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible absorption spectroscopy.

Composite films of aluminum nitride and alumina were fabricated on aluminum 6061 alloys in a DC plasma chamber. Samples were treated by three main processes. These were: (1) Ar plasma etching, (2) NH 3 /Ar plasma with low pressure and low current density, and (3) NH 3 plasma with high pressure and high current density. The oxygen-free Al surface was obtained after 10 min 2.8 keV Ar + sputtering in an ultrahigh vacuum analysis chamber after the sample was treated by processes 1 and 2. Composite films of aluminum nitride and alumina were obtained on samples treated by processes 1, 2 and 3. The surface compositions and bonding environments of the composite films were characterized by Auger electron spectroscopy and X-ray photoelectron spectroscopy. the thicknesses of the films were determined by argon sputtering in the ultra-high vacuum chamber. The surface morphologies of samples after fabrication processing in DC plasma were investigated by scanning electron microscopy. Al with the composite film not only shows a much better corrosion resistance in 1N HCl solution but also exhibits six times higher hardness than that of untreated Al. A possible formation mechanism of the composite film is proposed.

Objectives: We demonstrate that confocal Raman mapping spectroscopy provides rapid, detailed, and accurate neurotransmitter analysis, enabling millisecond time resolution monitoring of biochemical dynamics. As a prototypical demonstration of the power of the method, we present real-time in vitro serotonin, adenosine, and dopamine detection, and dopamine diffusion in an inhomogeneous organic gel, which was used as a substitute for neurologic tissue. Materials and Methods: Dopamine, adenosine, and serotonin were used to prepare neurotransmitter solutions in distilled water. The solutions were applied to the surfaces of glass slides, where they interdiffused. Raman mapping was achieved by detecting nonoverlapping spectral signatures characteristic of the neurotransmitters with an alpha 300 WITec confocal Raman system, using 532 nm neodymium-doped yttrium aluminum garnet laser excitation. Every local Raman spectrum was recorded in milliseconds and complete Raman mapping in a few seconds. Results: Without damage, dyeing, or preferential sample preparation, confocal Raman mapping provided positive detection of each neurotransmitter, allowing association of the high-resolution spectra with specific microscale image regions. Such information is particularly important for complex, heterogeneous samples, where changes in composition can influence neurotransmission processes. We also report an estimated dopamine diffusion coefficient two orders of magnitude smaller than that calculated by the flow-injection method. Conclusions: Accurate nondestructive characterization for real-time detection of neurotransmitters in inhomogeneous environments without the requirement of sample labeling is a key issue in neuroscience. Our work demonstrates the capabilities of Raman spectroscopy in biological applications, possibly providing a new tool for elucidating the mechanism and kinetics of deep brain stimulation.

In initial observations during Auger studies of NaCl, we have observed stable, clearly resolved Auger peaks. With time, however, some of the Auger spectra reveal the occurrence of strong negative charging. This charging appears to be a result of irradiation-induced accumulation of sodium metal on the sample surface. We report the dependence of the strong negatively charged state on temperature. The results are consistent with the above model; the strongly negatively charged surface cannot be maintained at temperatures sufficiently high that sodium metal evaporation occurs.

We observed diatomic hydrogen and nitrogen desorbing from Pt(111) surfaces covered with multilayer ammonia at 120 K during electron irradiation at 600 eV. Experiments were conducted to verify that the source of H2(g) and N2(g) species was indeed the electron-irradiated ammonia multilayer. This effect, which we describe as electron-stimulated associative desorption (ESAD), has not been previously reported.

An oxygen‐free 6061 aluminum surface was obtained for the first time in our knowledge in an ultrahigh vacuum (UHV) environment after ex situ ammonia dc plasma treatment. The specimen was first processed in an ammonia plasma chamber for 5 to 6 h then taken from the treatment chamber, mounted on a sample holder in air, and inserted into an UHV system through a sample transfer chamber. The sample was cleaned by 2.8 keV Ar+ ion bombardment for about 10 min to remove the oxide layer that had formed in air. A clean metallic aluminum Auger spectrum with no detectable oxygen peak was obtained under standard operating conditions with a Perkin‐Elmer Physical Electronics 560 spectrometer. The kinetic energy of the Auger electrons was calibrated using sputter‐cleaned Cu surfaces. The oxygen free Al surface is a key to thin film growth/deposition on aluminum or aluminum alloy surfaces.

Hydrogen gas was used as a probe to investigate the distribution of adsorption sites and their blocking by a submonolayer of carbon on a Rh(100) surface in ultra-high vacuum. TDS and AES results are consistent with a model in which carbon atoms residing only in four-fold hollow sites block the adsorption of hydrogen there.