OH Band Research Articles

Non-Covalent Interactions in Molecular Systems: Thermodynamic Evaluation of the Hydrogen-Bond Strength in Amino-Ethers and Amino-Alcohols.

The intramolecular hydrogen bond (intra‐HB) is one of the best‐known examples of non‐covalent interactions in molecules. Among the different types of intramolecular hydrogen bonding, the NH⋅⋅⋅O hydrogen bond in amino‐alcohols and amino‐ethers is one of the weakest. In contrast to the strong OH⋅⋅⋅N intramolecular hydrogen bond, the strength of the NH⋅⋅⋅O bond can hardly be measured with conventional spectroscopic methods, even for simple amino‐alcohols, since the band belonging to the NH⋅⋅⋅O conformer merges with the free OH band. In this work, we developed a combination of G4 calculations, and a method based on experimental vaporization enthalpies to determine the NH⋅⋅⋅O hydrogen bonding strength. The archetypal compounds for this study are 2‐amino‐1‐ethanol and 3‐amino‐1‐propanol as well as their respective methoxy analogs. Based on these molecules, different series were studied to investigate various factors influencing NH⋅⋅⋅O intra‐HB strength. In the first series, the influence of alkylation near the hydroxy or methoxy group and the amino group in sterically hindered aminoalcohols was examined. In the second series, the influence of alkylation of the amino‐group was investigated. In the third series, the effect of extending the alkyl chain between functional groups was studied.

Two types of C[dbnd]O⋯HO hydrogen bonds and OH⋯OH (dimer, trimer, oligomer) hydrogen bonds in PVA with 88% saponification/PMMA and PVA with 99% saponification/PMMA blends and their thermal behavior studied by infrared spectroscopy

In this study, polyvinyl alcohol (PVA) with 88% and 99% degrees of saponification was blended with polymethyl methacrylate (PMMA) to investigate the intramolecular hydrogen bonding in PVA and the intermolecular hydrogen bonding between PVA and PMMA. Differential scanning calorimetry (DSC) results confirmed the miscibility of the PVA/PMMA blends. Temperature-dependent ATR-IR spectra revealed that in PVA with an 88% saponification degree, some CO groups were free while the others were involved in CO···HO hydrogen bonding. In the blends with 88% saponified PVA, two types of CO···HO hydrogen bonds formed: CO(PVA)···HO(PVA) and CO(PMMA)···HO(PVA). Since the glass transition temperature of PVA is lower than that of PMMA, CO(PVA)···HO(PVA) can be broken at a lower temperature than CO(PMMA)···HO(PVA). In the blends with 99% saponified PVA, peaks derived from the CO stretching modes of CO(PMMA)···HO(PVA) were observed for PVA:PMMA = 60:40 and 40:60. In the OH stretching region of PVA and the blends, a broad band was observed in the 3700–3000 cm−1 region, where in OH bands arising from OH···OH (dimer, trimer, oligomer) hydrogen bonds and from the two types of CO···HO hydrogen bonds were expected to appear. In the PVA/PMMA blends with 88% saponified PVA, two types of CO⋯HO hydrogen bonds, CO(PVA)···HO(PVA) and CO(PMMA)···HO(PVA), yielded an OH stretching band at around 3370 cm−1. By contrast, the PVA/PMMA blends with 99% saponified PVA showed only a band corresponding to CO(PMMA)···HO(PVA) hydrogen bonding.

Biogenic Silver Nanoparticles Fabricated by Euphorbia granulata Forssk’s Extract: Investigating the Antimicrobial, Radical Scavenging, and Catalytic Activities

The plants of Euphorbiaceae have high medicinal values and their phytochemical composition plays a major role in metal ion reduction. In this research, Euphorbia granulata (EG) the “spurge family” plant extract was used to reduce silver ions to silver nanoparticles (AgNPs). This nanoparticle formation was observed by UV‐VIS spectrophotometric analysis at different times and temperatures to achieve the most optimal conditions. The synthesized biogenic silver nanoparticles (EG‐AgNPs) were subjected to FTIR studies. The obtained low‐intensity bands of fingerprint region bands (612 cm-1) and aromatic OH bands (3385 cm-1) are identified that the reduction of silver ions (Ag+) into metallic silver (Ag0) nanoparticles. Further, the charge, size, and morphology of the synthesized EG‐AgNPs were studied using various spectroscopic methods including powder X‐ray diffraction (XRD), high‐resolution scanning electron microscope (HRSEM), FESEM‐EDX elemental mapping, and high‐resolution transmission electron microscope (HRTEM). The notable efficacy of the EG‐AgNPs in antimicrobial activity including minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) suggested the EG‐AgNPs are noteworthy material for biomedical applications. EG‐AgNPs exhibited an efficient photocatalytic activity by degrading environmental pollutants, methylene blue (MB), and methyl orange (MO) dyes. The antioxidant property by radical scavenging (DPPH) assay of synthesized AgNPs was studied. Furthermore, the studied antioxidant behavior of EG‐AgNPs by DPPH assay strongly supports that the EG‐AgNPs are highly suitable materials for anticancer agents.

Quantitative OH concentration measurement using OH(2,0) band bi-directional LIF method for high-pressure and high-temperature symmetrical flames

Quantitative OH concentration measurement using OH(2,0) band bi-directional LIF method for high-pressure and high-temperature symmetrical flames

Dissociative Excitation of Nitromethane Induced by Electron Impact in the Ultraviolet - Visible Spectrum.

The excitation of nitromethane (CH3 NO2 ), which is an important propellant and prototypic molecule for large class of explosives, has been investigated by electron impact and subsequent emission of photons in the UV-VIS spectral region between 300 nm and 670 nm. Emission spectrum of nitromethane was recorded at an electron energy of 50 eV. New dissociative excitation channels were observed through the appearance of different CH, CN, NH, OH and NO bands, and the Balmer series of atomic hydrogen. In addition, relative emission cross sections were recorded for the transitions of selected fragments. The emission spectrum was captured with significantly higher resolution in comparison to previous studies.

Rhodium nanoparticles confined in titania nanotubes for efficient Hydrogen evolution from Ammonia Borane

Designing efficient catalysts for hydrogen evolution from hydrolysis of ammonia borane (AB) have attracted considerable attention. Rhodium (Rh) based catalysts with rational design present remarkable catalytic performance for the reaction. Herein, we report the confined Rh@TiO2 catalysts synthesized by atomic layer deposition combining with the sacrificial template approach, in which the Rh nanoparticles are uniformly confined on the inner surface of the porous titania nanotubes. The optimized catalysts show high catalytic activity with a turnover frequency value of 334.1 molH2·molRh-1·min-1 and better durability. Mechanistic investigation demonstrates that the cleavage of OH bands in water should be the rate determining step, and the appropriate concentration of NaOH can further enhance the hydrogen evolution activity. The catalysts can also achieve the hydrogenation of various organic substrates using AB as the hydrogen source. In addition, our present strategy is general and can be extended to the synthesis of other confined catalysts for various catalytic reactions.

Investigation of the role of chemically active radicals in the antibacterial properties of a low-temperature plasma jet at ambient pressure mixed with argon and air

The work is devoted to the study of a low-temperature plasma jet of atmospheric pressure in a mixture of air with argon, used in plasma medicine. The intensities of the spectral emission bands of OH– (309 nm), N2 (337 nm), and N2 (356 nm) in different parts of the plasma jet were investigated depending on the argon flow rate and the amplitude of voltage pulses at the electrodes of the dielectric barrier discharge. The antibacterial effect of such a plasma jet on the surface of biological tissues has been experimentally investigated. Numerical simulation of ionization processes in the studied plasma source has been performed in the COMSOL Multiphysics software using. The dynamics of the distribution of excited molecules in the plasma torch as well as the kinetic plasma processes inside the plasma torch affecting the spatial distribution of its main characteristics have been analyzed.

Nitrogen as a Probe Molecule for the IR Studies of the Heterogeneity of OH Groups in Zeolites.

One of the methods of IR studies of the heterogeneity of Si–OH–Al groups in zeolites is the investigation of the frequency shift of the band of free OH bands restored upon the adsorption of ammonia and subsequent desorption at increasing temperatures. We extended this method by following the shift of the band of the OH group interacting by hydrogen bonding with nitrogen. The advantage of nitrogen, compared with CO, which has been commonly used as a probe molecule in studies on hydrogen bonding, is that for nitrogen the frequency shift is smaller than for CO and therefore there is no overlapping of shifted OH band with the bands of ammonium ions. For zeolites NaHY, HMFI, and HBEA, the frequency shift of IR bands of both free and hydrogen-bonded Si–OH–Al with the increase of ammonia desorption temperature evidences the heterogeneity of these hydroxyls. On the other hand, in zeolite HFAU of Si/Al = 31, Si–OH–Al were found to be homogeneous. Heterogeneity of OH groups may be explained both by the presence of Si–OH–Al of various number of Al near the bridge and of Si–OH–Al of various geometry.

Structure, Energetics, and Spectra for the Oxygen Vacancy in Rutile: Prominence of the Ti-HO-Ti Bond.

Under reducing conditions, rutile TiO2 develops O vacancies (VO) coupled to Ti3+ centers. It is favorable for H atoms to enter this system, either forming OH groups or occupying vacancy sites (denoted HO) that bond to two Ti atoms next to the vacancy. OH defects are well documented by the presence of infrared modes at ∼3300 cm-1, while HO is relatively underinvestigated. We report the energies, geometries, and vibrational frequencies of hydrogen defects in rutile predicted from quantum mechanics calculations, focusing on the coexistence of OH and HO. We find that HO is more stable than OH by 1.42 eV, leading to an infrared mode at ∼1200 cm-1. Introducing a second H forms an OH bond with an infrared mode at ∼3300 cm-1. These results suggest that assessments of hydrogen storage in mantle phases of rutile and similar minerals based on OH bands may significantly underestimate H concentrations.

Stable filamentary structures in atmospheric pressure microwave plasma torch

This paper experimentally investigates the processes governing the single- and multi-filament regimes in an atmospheric pressure microwave (MW) torch operated in argon. Optical emission spectroscopy and spectral imaging are the principal diagnostics techniques which are employed. MW power is found to be the main parameter controlling the number of filaments. The single-filament regime exhibits many properties typical for surface wave discharges, e.g. a linear decrease in electron density along the axis or the existence of a central dip in the radial/lateral emission profiles. Simple geometric quantities, such as the length or thickness of the filament(s), vary almost linearly with the input MW power, and exhibit discontinuities at successive filament splitting events. These take place at similar values of filament maximum thickness, and may be due to skin-depth limited power transfer. The presence and chemistry of a low-emission intensity plasma shell surrounding the filament(s) is also investigated. The gas temperature is estimated from the OH band and complemented by Schlieren imaging, which revealed that a much larger cone of gas is being heated by filaments than is their diameter.

Free water molecules and hydrogen bonding form the basis of variation in homeopathic potencies as revealed by vibrational spectroscopy

Objective: Using Fourier Transform Infrared spectroscopy (FTIR) we have demonstrated that homeopathic potencies of Natrum mur, Cantharis, Nux vomica and Sulphur show differences with respect to the number of free water molecules and strength of hydrogen bonding. The purpose of the present study is to confirm this phenomenon in three potencies of two more drugs Calcarea carb and Silicea. 
 Design: The potencies used for each of the two drugs were 30cH, 200cH and 1000cH. The control was 90% ethanol as also the potentized drugs. The control, as well as the potencies, were diluted with distilled water to reduce the level of ethanol to 0.03 molar fraction in each of them. FTIR spectra of all the potentized drugs, control and sterile distilled water (reference water) were taken in the wave number region of 4000-2800 cm-1. The full width at half maximum (fwhm) of OH band was measured for each spectrum. The width was divided into two in the middle. The difference spectrum (absorbance of drug solution - absorbance of reference water) for each potency and the control was obtained after normalization of the spectrum at 3410 cm-1. One difference spectrum so obtained for a potency was subtracted from another to find out if there is a difference between two different potencies.
 Results: The half width half maximum (hwhm) in both the high and low-frequency sides of the OH band is far less narrow in potencies than in the control as compared to that in water. The difference spectra for different potencies show different levels of fall in intensity at the wave number region of dip at 3630 cm-1. The level of dip at 3630 cm-1 and subsequent rise in intensity in the lower frequency region represent the quantity of free water molecules and strong alcoholic OH bond around 3250 cm-1, respectively. The results of subtraction between two different potencies are not zero but have marked positive or negative values. 
 Conclusion
 (i) Potencies have stronger intermolecular interactions and a higher number of chemical environments than the control, as revealed by the data on hwhm. 
 (ii) The three potencies of each of the two drugs show distinct variation in the number of free water molecules and strength of hydrogen bonding. 
 (iii) There exists both inter-drug and inter-potency variation as revealed by the difference spectra and results of subtraction between two difference spectra.

The Polarizable continuum potential model in the liquid state Calculations. Density functional computational analysis of the anharmonic vibrational spectrum of liquid water

A Density Functional calculation, using the Gaussian 03 W protocol with the B3LYP functional and the SCRF-Polarizable Continuum model (SCRF-PCM), has been performed on a pentameric unit, constituted by a central water molecule tetrahedrically coordinated to four other surrounding molecules by hydrogen bond (HB) interactions. The calculation has been aimed at reproducing vibrational distributions of the intra-molecular and intermolecular modes, which contribute at widening the stretching and bending OH bands in the liquid vibrational spectrum, and those at low frequencies, commonly considered intermolecular motions of O-H…O stretching and bending type, in the HB tetrahedral network of liquid water. The so called librational large distribution has been also nicely reproduced by this calculation. Energetic and geometrical considerations have been discussed for the equilibrium structure of this pentameric assembly, representing the basic unit presently used to simulate more space-extended structures of liquid water. These are constituted by different domains of ordered (open, or ice-like) and unordered (closed) patches of water clusters. Although the small cluster used in this calculation represents only an approximation to treat the real organization existing in the liquid water complex system, our results seems to reproduce quite well both the vibrational spectrum and the energetic and geometric situations for this very important liquid.

Enhancing thermal and dynamic‐mechanical properties of epoxy reinforced by amino‐functionalized microcrystalline cellulose

AbstractIn this study, microcrystalline cellulose (MCC) was chemically modified with 3‐(aminopropyl)triethoxysilane and added to epoxy to improve chemical, thermal and dynamic‐mechanical characteristics of the composites. The composites were manufactured aided by sonication with 1.0%, 2.5%, or 5.0% wt/wt of untreated MCC or amino‐functionalized MCC (MCC‐Si). The epoxy/MCC‐Si composites showed a decrease in the ─OH band by Fourier‐transform infrared spectroscopy, and X‐ray diffraction analysis indicated better dispersion. The incorporation of MCC‐Si in epoxy resin decreased the heat of reaction, increased activation energy values (Ea) and pre‐exponential factor (A), and did not affect thermal degradation. All conversion degree (α) versus temperature curves for the composites showed a sigmoidal shape. MCC‐Si composites showed better dynamic‐mechanical properties than the MCC counterparts, and the functionalization effect was evidenced in storage modulus (E') and loss modulus (E"). At 2.5% wt/wt of MCC‐Si content an increase of 119% in E' at the glassy region, 127% in E' at the rubbery region and 173% in E" was observed compared to the neat resin, whereas the Tg barely changed among samples. Good adhesion between the amino‐functionalized MCC and the epoxy matrix was observed at the fracture surface, evidencing that surface modification of MCC improves their chemical interaction.

Crystal chemistry and high-temperature vibrational spectra of humite and norbergite: Fluorine and titanium in humite-group minerals

AbstractThe humite-group minerals along the brucite-olivine join may be important dense hydrous magnesium silicate (DHMS) phases in the subducting slab. Fluorine and titanium can be incorporated into their structures through the substitutions (OH)– = F– and Mg2+ + 2(OH)– = Ti4+ + 2O2–. These substitutions have significant effects on the hydrogen bonding behavior in the structures. Structure refinements and in situ high-temperature Raman and Fourier transform infrared (FTIR) measurements were conducted on natural humite and norbergite crystals. Both minerals crystallize in space group Pbnm, and their isobaric Grüneisen parameters for the lattice and SiO4 internal vibrations are compared with those of chondrodite, clinohumite, brucite, and forsterite. For the humite-group minerals, the OH-stretching modes above 3450 cm–1 are affected by local H-H repulsion, whereas the behavior of those below 3450 cm–1 can be explained by F– and Ti4+ substitutions, either of which may relieve the H-H repulsion effect. The Raman-active OH bands below 3450 cm–1 are affected by Ti4+ substitution, while the IR-active bands can be affected by either F– or Ti4+ substitutions. Based on an analysis of the high-T Raman and FTIR spectra, the OH vibrations above and below 3450 cm–1 behave differently as a function of temperature, and similar behavior has also been observed for other dense hydrous silicate phases in the hydrous peridotite system. Hence, the lengths of the oxygen-oxygen edges in MgO6 octahedra where protonation can occur become similar to each other at elevated temperatures. This may provide an atomistic explanation for the electrical conductivity properties of DHMS phases at high temperatures.

New Insight into the Relationships Between Structural and Ftir Spectroscopic Features of Kaolinites

AbstractTo resolve the existing ambiguities in the interpretation of the OH-stretching vibrations of kaolinites, relationships were, for the first time, established between the structural and Fourier-transform infrared (FTIR) spectroscopic features for a set of kaolinite samples which differed in terms of their relative amounts of coexisting high- and low-ordered phases. For this purpose, a representative collection of kaolinites differing in origin, particle size, and degree of disorder was studied by powder X-ray diffraction (XRD) and FTIR spectroscopy. Modeling of the experimental XRD patterns based on the orthogonal layer unit cell having a mirror plane showed each sample to be a mixture of nearly defect-free high-ordered (HOK) and low-ordered (LOK) kaolinite phases, with HOK varying from 86 to 4%. The wavenumbers, heights, areas, and full widths at half-maximum (FWHM) were determined for the OH-stretching bands at ~3697 (ν1), ~3670 (ν2), ~3652 (ν3), and 3620 cm–1 (ν4) by decomposition and fitting of the FTIR spectra. The FWHM(ν1)/FWHM(ν4) and FWHM(ν3)/FWHM(ν2) values were related linearly to the HOK content, which may be associated with the in-phase and out-of-phase character of the corresponding pairs of vibrations, respectively. A novel interpretation was suggested for the variations in the relative integrated intensities of the OH bands with the amount of the HOK phase. The intensity distribution of the ν2 and ν3 bands is controlled by the triclinic structure symmetry in the defect-free kaolinite and the mirror symmetry of the layers in low-ordered structures, in agreement with the observed evolution of the corresponding band intensities. The ν1 and ν2 band positions for the low-ordered samples are within the wavenumber range for the high-ordered samples. In contrast, the ν3 and ν4 band positions for the low-ordered samples are shifted toward higher wavenumbers, indicating that some of the low-ordered kaolinites should contain dickite-like structural fragments distributed among kaolinite layers.

Hydroxylation of Apollo 17 Soil Sample 78421 by Solar Wind Protons

AbstractHydroxylation by solar wind protons has been simulated in our laboratory on Apollo 17 lunar sample 78421, a very mature regolith sample that is rich with agglutinates (68%). The goal of this study was to determine the rate of hydroxyl formation and their thermal stability by monitoring changes in the SiOH (hydroxyl) stretching band near 3 μm using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). A 2 keV H2+ ion beam was used to simulate proton implantation on 78421 and on a crushed fused silica sample. We find that the OH band does not change unless the samples have been annealed in vacuum prior to irradiation. Qualitatively, the OH bands for the fused silica and 78421 are very different. The OH band for fused silica is centered at 2.74 μm and is relatively sharp ranging from 2.67 to 3.1 μm at full width at half maximum (FWHM), while the OH band for 78421 is centered at 3.0 μm and ranges from 2.74 to 3.37 μm at FWHM. The increase in wavelength and broadened nature of the OH band in 78421 may be associated with the OH’s proximity to surface defects and/or lattice vacancies. The lack of the H2O bending mode at 6.1 μm indicates that any adsorbed terrestrial H2O is below our detection limit, and therefore the H2O stretching mode at 2.9 μm is not significantly contributing to the broad 3 μm OH band and implies that proton implantation by itself does not lead to water formation. To simulate the maximum dayside temperature on the lunar surface, the lunar sample was heated after proton irradiation. The proton induced OH concentration was reduced by as much as 25% after heating to 400 K (127°C).

The Functionalization Study of PVDF/TiO2 Hollow Fibre Membranes Under Vacuum Calcination Exposure

In this study, polyvinylidene fluoride (PVDF) hollow fibre membrane was modified by adding TiO2. TiO2 presence affects the membrane structure becomes more less hydrophobic which makes the membrane less fouling. Membranes were made via dry-wet spinning method and calcined under vacuum condition by furnace (100, 300, and 500 °C). Besides, PVDF-TiO2 uncalcined membrane were also prepared as comparison to investigated the effect of calcination on hollow fibre membrane’s functional groups. Fourier Transform Infrared (FT-IR) spectra indicated that all PVDF-TiO2 membranes have bands of OH in the TiO2 at ∼1600 cm−1. Peaks of α-phase PVDF crystals appeared at ∼876, ∼876, and ∼872 cm−1 for uncalcined, 100 and 300 °C, while for 500 °C the PVDF peak only shows at 874 cm−1. The peaks at ∼1200 cm−1 represent CF2 groups. Peaks at ∼1400 cm−1 assigned to CH2 groups, but it does not observed for 500 °C. Deconvolution by Fityk software that shows calcination using vacuum condition gives the compounds gradually decomposes. At high temperature calcination lead the CH2 peak extremely lost.

SINTESIS DAN TRANSISI ELEKTRONIK KOMPLEKS TEMBAGA (II)-KLOROFIL

The copper (II)-chlorophyll complex was prepared from the reaction between the chlorophyll isolated from cassava leaves and the metal ion precursor, CuSO4.5H2O in methanol under reflux for four hours. The FTIR spectra of the reaction product compared to the chlorophyll spectra show an indication of a complexation through metal coordination with the N atom from the phyrol ring replacing the magnesium (II) ion in chlorophyll.This assumption is drawn based on changes on FTIR spectra, i.e. vibration absorption originating from the CN and NH groups in the porphyrin ring and the appearance of the distinctive vibration band of nitrogen-metal bonds which is annotated as Cu-N groups at 599.88 cm-1. Another sign is the change in the OH and CO vibration bands which imply changes in aggregate properties that occur through inter-molecular interactions due to the introduction of copper (II) metal into the chlorophyll structure. The formation of copper (II)-chlorophyll compounds is also shown from the results of atomic absorption spectroscopy by recording copper metal in the product and reducing magnesium metal concentration. UV-vis spectra of chlorophyll in methanol show a characteristic band in the dark area (Soret band) at a maximum wavelength of 404 nm and the visible area (Q band) with the strongest intensity at 665 nm. These peaks appear to shift hypsochromically in the copper (II)-chlorophyll compound to 397 nm and 650 nm with higher absorptivity, indicating a change in the electronic transition of the chlorophyll after coordinating with the copper (II) ion. A new peak at 411 nm was also observed which is suggested to indicate that the copper (II) -chlorophyll complex is in an octahedral geometry in the aggregate coordinated via nitrogen atoms in the phyrol ring in place of the magnesium (II) ion.

Susceptibility of Staphylococcus epidermidis to Argon Cold Plasma Jet by Oxygen Admixture

Cold atmospheric pressure sterilization is one of the nominated and efficient techniques to prevent the spread of diseases. Reactive species such as O and OH and other radicals play a major role in the mechanism of plasma sterilization. Therefore, in this work, oxygen was mixed with different parentage from (0.2 to 1.2%) to argon to enhance the generation of the reactive species and increase the argon atmospheric pressure plasma sterilization efficacy. The emission spectra from the jet increase the radicle line intensities by increasing the percentage admixture of O2 with the argon gas to reach a maximum power at 0.8; then, it gradually decreases with a higher O2 percentage. The OH band intensity decreases with increasing the admixture of O2. The jet with different O2 percentages was tested against Gram-positive S. epidermidis, which is the causal agent of nosocomial infections. The maximum reduction in colony-forming units (CFU) was observed at 0.2% O2. No bacterial growth was observed at the later concentration applied for 8 min and the same case was detected at 0.4% O2 applied to 16 min.

Effects of Nitrogen Dioxide on the Oxidation of Levitated exo-Tetrahydrodicyclopentadiene (JP-10) Droplets Doped with Aluminum Nanoparticles.

Nitrogen dioxide (NO2) can significantly improve the combustion of hydrocarbon fuels, but the effect of NO2 on the ignition of fuels with energy densities enhanced by aluminum (Al) nanoparticles has not been studied. We therefore investigated the effects of NO2 on the ignition of JP-10 droplets containing Al nanoparticles initially acoustically levitated in an oxygen-argon mixture. A carbon dioxide laser ignited the droplet and the resulting combustion processes were traced in real time using Raman, ultraviolet-visible (UV-vis), and Fourier-transform infrared (FTIR) spectroscopies simultaneously with a high-speed optical or thermal imaging camera. Temperature temporal profiles of the ignition processes revealed that a 5% concentration of NO2 did not cause measurable differences in the ignition delay time or the initial rate of temperature rise, but the maximum flame temperature was reduced from 2930 ± 120 K to 2520 ± 160 K. The relative amplitudes of the UV-vis emission bands were used to deduce how NO2 affected the composition of the radical pool during the oxidation process; for example, the radicals NO, NH, and CN were detected and the OH (A 2Σ+-X 2Π) band at 310 nm was less prominent with NO2. Localized heating from a tightly focused infrared laser beam provided sufficient energy to activate chemical reactions between the JP-10 and NO2 without igniting the droplet. Raman spectra of the residue produced give information about the initial oxidation mechanisms and suggest that organic nitro compounds formed. Thus, in contrast to previous studies of hydrocarbon combustion without Al nanoparticles, NO2 was found not to enhance the ignition of an Al-doped JP-10 droplet ignited by a CO2 laser.