Showing papers on "Absorption spectroscopy published in 2000"

Laser-Induced Shape Changes of Colloidal Gold Nanorods Using Femtosecond and Nanosecond Laser Pulses

Abstract: Gold nanorods have been found to change their shape after excitation with intense pulsed laser irradiation. The final irradiation products strongly depend on the energy of the laser pulse as well as on its width. We performed a series of measurements in which the excitation power was varied over the range of the output power of an amplified femtosecond laser system producing pulses of 100 fs duration and a nanosecond optical parametric oscillator (OPO) laser system having a pulse width of 7 ns. The shape transformations of the gold nanorods are followed by two techniques: (1) visible absorption spectroscopy by monitoring the changes in the plasmon absorption bands characteristic for gold nanoparticles; (2) transmission electron microscopy (TEM) in order to analyze the final shape and size distribution. While at high laser fluences (∼1 J cm-2) the gold nanoparticles fragment, a melting of the nanorods into spherical nanoparticles (nanodots) is observed when the laser energy is lowered. Upon decreasing the...

Blue shift in ultraviolet absorption spectra of monodisperse CeO2−x nanoparticles

Abstract: Blue shifts corresponding to the absorption edge in the UV-A (310–400 nm) range are obtained from ultraviolet (UV) absorption spectra of monodisperse CeO2−x (0

Local plasmon sensor with gold colloid monolayers deposited upon glass substrates.

Abstract: A new optical sensor that uses local plasmon resonance is proposed. A peak that is due to the local plasmon resonance appears in the absorption spectrum of a gold colloid suspension in the visible region, and its height and wavelength depend on the refractive index of the suspension. These properties are used for optical sensors. We used gold colloid monolayers in which colloidal gold particles a few tens of nanometers in diameter were immobilized upon a glass slide by a functional organic coupling agent. We measured the absorption spectra of the the gold colloid monolayers, which were immersed in liquid samples or coated with thin films. We observed increases of both the resonance wavelength and the absorbance as the refractive indices of the sample liquids or the thickness of the coated films increased. The proportional constants of the resonance wavelength to the film thickness were 3.6 and 5.7 for a 13.9- and a 20.2-nm gold colloid monolayer, respectively.

The thermal history of the intergalactic medium

Abstract: At redshifts z≳2, most of the baryons reside in the smooth intergalactic medium which is responsible for the low column density Lyα forest. This photoheated gas follows a tight temperature–density relation which introduces a cut-off in the distribution of widths of the Lyα absorption lines (b-parameters) as a function of column density. We have measured this cut-off in a sample of nine high-resolution, high signal-to-noise ratio quasar spectra and determined the thermal evolution of the intergalactic medium in the redshift range 2.0–4.5. At a redshift z∼3, the temperature at the mean density shows a peak and the gas becomes nearly isothermal. We interpret this as evidence for the reionization of He ii.

Temperature dependence of the absorption cross sections of formaldehyde between 223 and 323 K in the wavelength range 225–375 nm

Abstract: UV absorption cross sections of formaldehyde (HCHO) have been measured with a spectral resolution of 0.025 nm in the wavelength range 225–375 nm at 298 K using a diode array detector. At selected temperatures ranging from 223 to 323 K, measurements have been conducted to obtain temperature gradients in the wavelength range 250–356 nm. Error limits for the reported absorption cross sections are ±5% but at least ±3×10−22 cm2 molecule−1. For the temperature gradients, uncertainties are <8%. Spectra and temperature gradients are compared with earlier measurements.

“Raisin Bun”-Type Composite Spheres of Silica and Semiconductor Nanocrystals

Abstract: CdTe nanocrystals capped with 1-mercapto-2,3-propandiol, CdSe nanocrystals capped with sodium citrate, and core−shell CdSe/CdS nanocrystals capped with sodium citrate were synthesized in aqueous solutions, and their surface was modified by 3-mercaptopropyltrimethoxysilane (MPS) in water−ethanol mixtures. By addition of sodium silicate, “raisin bun”-type composite particles were formed, with either CdTe, CdSe, or CdSe/CdS nanocrystals being homogeneously incorporated as multiple cores into silica spheres of 40−80 nm size, accompanied by some alteration of optical properties of the nanoparticles and, in particular, the reduction of the luminescence quantum yield. Further, growth of larger silica spheres (100−700 nm) can be performed by the Stober technique using either MPS-modified semiconductor nanocrystals or “raisin bun”-type composite particles as seeds, which gives semiconductor-doped silica globules of desirable sizes in the submicrometer range. The composite spheres can be used as building blocks for...

Supported Gold Nanoparticles from Quantum Dot to Mesoscopic Size Scale: Effect of Electronic and Structural Properties on Catalytic Hydrogenation of Conjugated Functional Groups

Abstract: Titania- and zirconia-supported gold particles of 1−5 nm size, prepared by various routes of synthesis, were employed in the partial hydrogenation of acrolein. In-depth characterization of their structural and electronic properties by electron microscopy, electron paramagnetic resonance, and optical absorption spectroscopy aimed at disclosing the nature of the active sites controlling the hydrogenation of CO vs CC bonds. The structural characteristics of the catalysts, as mean particle size, size distribution, and dispersion, distinctly depend on the synthesis applied and the oxide support used whereby the highest gold dispersion (DAu = 0.78, Au/TiO2) results from a modified sol−gel technique. For extremely small gold particles on titania and zirconia (1.1 and 1.4 nm mean size), conduction electron spin resonance of the metal and paramagnetic F-centers (trapped electrons in oxygen vacancies) of the support were observed. Besides the influence of the surface geometry on the adsorption mode of the α,β-unsat...

Spectral measurement of absorption by spectroscopic frequency-domain optical coherence tomography.

Abstract: A new method of measurement that essentially combines Fourier-domain optical coherence tomography with spectroscopy is introduced. By use of a windowed Fourier transform it is possible to obtain, in addition to the object structure, spectroscopic information such as the absorption properties of materials. The feasibility of this new method for performing depth-resolved spectroscopy is demonstrated with a glass filter plate. The results are compared with theoretically calculated spectra by use of the well-known spectral characteristics of the light source and the filter plate.

New Class of Two-Photon-Absorbing Chromophores Based on Dithienothiophene

Abstract: Novel two-photon absorption (TPA) chromophores are synthesized; they have dithienothiophene (DTT) as a π-center which is attached by electron donor (D) or electron acceptor (A) at each end through a π-conjugation. Their TPA cross section, measured using nanosecond- as well as femtosecond-pulsed laser, exhibits one of the largest values known so far. This is attributable mainly to the unique electronic properties of DTT.

Effect of the Solvent Environment on the Spectroscopic Properties and Dynamics of the Lowest Excited States of Carotenoids

Abstract: The spectroscopic properties and dynamics of the lowest excited singlet states of peridinin, fucoxanthin, neoxanthin, uriolide acetate, spheroidene, and spheroidenone in several different solvents have been studied by steady-state absorption and fast-transient optical spectroscopic techniques. Peridinin, fucoxanthin, uriolide acetate, and spheroidenone, which contain carbonyl functional groups in conjugation with the carbon−carbon π-electron system, display broader absorption spectral features and are affected more by the solvent environment than neoxanthin and spheroidene, which do not contain carbonyl functional groups. The possible sources of the spectral broadening are explored by examining the absorption spectra at 77 K in glassy solvents. Also, carotenoids which contain carbonyls have complex transient absorption spectra and show a pronounced dependence of the excited singlet state lifetime on the solvent environment. It is postulated that these effects are related to the presence of an intramolecul...

Ligand K-Edge X-ray Absorption Spectroscopy: A Direct Probe of Ligand−Metal Covalency

Abstract: Ligand K-edge X-ray absorption spectroscopy (XAS) is a new experimental probe of the covalency of a metal−ligand bond. The intensity of the ligand pre-edge feature is proportional to the mixing of ligand orbitals into the metal d orbitals. The methodology to determine covalencies in one-electron (hole) and many-electron systems is described and demonstrated for a series of metal tetrachlorides [MCl4]n-, metal tetrathiolates [M(SR)4]n-, and dimeric iron−sulfur (Fe−S) clusters [Fe2S2(SR)4]2-. It is then applied to blue Cu proteins, the CuA site, hydrogen bonding in Fe−S clusters, and the delocalization behavior in [2Fe-2S] vs [4Fe-4S] clusters. The covalencies determined in these studies provide important electronic structure insight into function.

Film morphology and photophysics of polyfluorene

Abstract: We have studied the interplay between photophysics and film morphology of poly(9,9-dioctyl)fluorene (PFO) using a variety of optical probes. Upon slowly warming a spin-cast PFO film from 80 to 300 K, a fraction of the sample is transformed into a different solid phase, the $\ensuremath{\beta}$ phase. Absorption and electroabsorption measurements show that the $\ensuremath{\beta}$ phase has more extended conjugation than the glassy phase. As a consequence, excited states of the $\ensuremath{\beta}$ phase are redshifted and have higher polarizability. The photoinduced absorption spectrum of a glassy PFO film is dominated by triplet excitons, whereas both polarons and triplet excitons are seen in a sample containing a fraction of the $\ensuremath{\beta}$ phase. The dependence of the photoinduced absorption and photocurrent upon the excitation wavelength shows that there is a clear link between polaron and triplet photogeneration.

Femtosecond Excited-State Dynamics of an Iron(II) Polypyridyl Solar Cell Sensitizer Model

Abstract: Time-resolved electronic absorption spectroscopy on a ∼100 fs time scale has been used to study excited-state dynamics in an FeII polypyridyl complex. [Fe(tren(py)3)]2+, where tren(py)3 is tris(2-pyridylmethyliminoethyl)amine, forms a 1MLCT excited state upon irradiation at 400 nm and is known from previous studies to undergo relaxation to a low-lying ligand-field state having S = 2. Static absorption measurements on the low-spin parent complex and a high-spin analogue have been used to identify spectroscopic signatures for the S = 0 and S = 2 ligand-field states, respectively. Comparison of these data with femtosecond and nanosecond differential absorption spectra establishes that the net ΔS = 2 intersystem crossing is essentially complete in well under 1 ps. Spectroelectochemistry on [Fe(tren(py)3)]2+ has also been used to find an absorption feature characteristic of the initially formed 1MLCT state at λ ≳ 600 nm. Analysis of single-wavelength kinetics data in this spectral region reveals that the charg...

Selective interaction of a semiconjugated organic polymer with single-wall nanotubes

Abstract: Hybrid systems of a semiconjugated organic polymer and single-wall nanotubes have been characterized by optical absorption spectroscopy, electron microscopy, and Raman spectroscopy. It is demonstrated that solutions of the polymer are capable of suspending nanotubes indefinitely while the majority of the accompanying amorphous graphite precipitates out of solution. Electron microscopy and Raman scattering indicate that through an intercalation process, the ropes of nanotubes are destroyed, resulting in individual nanotubes being well dispersed within the polymer matrix. Moreover, Raman and absorption studies suggest that the polymer interacts preferentially with nanotubes of specific diameters or a range of diameters.

The photoprotector mechanism of mycosporine-like amino acids. Excited-state properties and photostability of porphyra-334 in aqueous solution.

Abstract: The photostability and photophysical parameters of an aqueous solution of the mycosporine-like amino acid (MAA) porphyra-334 have been determined. The excited-singlet state lifetime, measured by time-correlated single photon counting, was 0.4 ns. Laser flash photolysis experiments at 355 nm did not show any transient species. The triplet state of porphyra-334 was sensitized by triplet-triplet energy transfer. The T-T absorption spectrum was determined and the maximal absorption coefficient at 440 nm was estimated to be 1 x 10(4) M(-1) cm(-1). In this way an upper limit for the intersystem crossing quantum yield was determined. The very low quantum yield of fluorescence (phiF = 0.0016) and triplet formation (phiT < 0.05) together with a photodecomposition quantum yield of 2-4 x 10(-4), in the absence and the presence of oxygen respectively, can be explained by a very fast internal conversion process. These results support the photoprotective role assigned to this MAA in living systems.

Nature of the fundamental band gap in GaNxP1−x alloys

Abstract: The optical properties of GaNxP1−x alloys (0.007⩽x⩽0.031) grown by gas-source molecular-beam epitaxy have been studied. An absorption edge appears in GaNxP1−x at energy below the indirect ΓV–XC transition in GaP, and the absorption edge shifts to lower energy with increasing N concentration. Strong photomodulation signals associated with the absorption edges in GaNxP1−x indicate that a direct fundamental optical transition is taking place, revealing that the fundamental band gap has changed from indirect to direct. This N-induced transformation from indirect to direct band gap is explained in terms of an interaction between the highly localized nitrogen states and the extended states at the Γ conduction-band minimum.

Effect of Solvent on the Excited-state Photophysical Properties of Curcumin¶

Abstract: Photophysical properties of curcumin, 1,7-bis-(4-hydroxy-3-methoxy phenyl)-1,6-heptadiene-2,5-dione, a pigment found in the rhizomes of Curcuma longa (turmeric) have been studied in different kinds of organic solvent and also in Triton X-100 aqueous micellar media using time-resolved fluorescence and transient absorption techniques having pico and nanosecond time resolution, in addition to steady-state absorption and fluorescence spectroscopic techniques. Steady-state absorption and fluorescence characteristics of curcumin have been found to be sensitive to the solvent characteristics. Large change (delta mu = 6.1 Debye) in dipole moments due to photoexcitation to the excited singlet state (S1) indicates strong intramolecular charge transfer character of the latter. Curcumin is a weakly fluorescent molecule and the fluorescence decay properties in most of the solvents could be fitted well to a double-exponential decay function. The shorter component having lifetime in the range 50-350 ps and percent contribution of amplitude more than 90% in different solvents may be assigned to the enol form, whereas the longer component, having lifetime in the range 500-1180 ps with less than 10% contribution may be assigned to the di-keto form of curcumin. Our nuclear magnetic resonance study in CDCl3 and dimethyl sulfoxide-D6 also supports the fact that the enol form is present in the solution by more than about 95% in these solvents. Excited singlet (S1) and triplet (T1) absorption spectrum and decay kinetics have been characterized by pico and nanosecond laser flash photolysis. Quantum yield of the triplet is low (phi T < or = 0.12). Both the fluorescence and triplet quantum yields being low (phi f + phi T < 0.18), the photophysics of curcumin is dominated by the energy relaxation mechanism via the internal conversion process.

Optical spectroscopy of Eu3+ ions in lithium borate and lithium fluoroborate glasses

Abstract: Optical absorption, excitation and emission spectra of Eu3+ ions in lithium borate and lithium fluoroborate glasses have been investigated. Judd–Ofelt intensity parameters are derived from the integrated absorption spectra and also from the emission spectra under various constraints. The relative merits of thermal correction to the oscillator strengths of the transitions originating from the ground state ( 7 F 0 ) of Eu3+ ion observed in the absorption spectra have been discussed. The Judd–Ofelt parameters obtained from the emission spectra have been used to calculate the total spontaneous emission probabilities (A), lifetimes (τR) and branching ratios (βR) for eight excited levels that include, 5 K 6 , 3 P 0 , 5 H 3 , 5 L 7 , 5 D 3 , 5 D 2 , 5 D 1 and 5 D 0 . The predicted values of τR and βR are compared with the measured values for 5 D 0 level. The stimulated emission cross-sections (σ (λp)) are also evaluated for the 5 D 0 → 7 F J and 5 D 1 → 7 F J transitions. The variation of optical properties with compositional changes of lithium oxide and lithium fluoride contents in the glasses are discussed and compared with similar results.

In Situ XAS and XRD Studies on the Formation of Mo Suboxides during Reduction of MoO3

Abstract: Reduction of MoO3 with hydrogen (5−100 vol %) in the temperature range from 573 to 823 K was studied by in situ X-ray diffraction and X-ray absorption spectroscopy. The experiments performed focused on elucidating phase composition and evolution with time under isothermal as well as temperature-programmed reduction conditions. At reaction temperatures below 698 K, the reduction of MoO3 to MoO2 is a one-step process without the formation of crystalline intermediates. At reduction temperatures above 723 K and H2 concentrations higher than 10 vol %, Mo metal is the final product of the reduction of MoO3. In addition, at temperatures higher than 698 K, the formation of Mo4O11 was observed. However, Mo4O11 is not an intermediate in the reduction of MoO3 but is being formed in a parallel reaction from MoO3 and MoO2 at temperatures above 698 K. It is shown that Mo4O11 can be obtained from a reaction of MoO3 and MoO2 at temperatures above 773 K, affording the same phase ratio of monoclinic and orthorhombic Mo4O11...

Optical evidence for a nonmolecular phase of nitrogen above 150 GPa

Abstract: Optical spectroscopy techniques, including visible and near infrared (IR) Raman and synchrotron IR methods have been applied to study solid nitrogen at megabar pressures. We find that nitrogen becomes totally opaque above 150 GPa, accompanied by the disappearance of Raman and IR vibrational excitations, while new broad IR and Raman bands become visible. Optical absorption measurements reveal that the semiconducting absorption edge responsible for the change of color is characterized by the presence of a wide Urbach-like tail and a high-energy (Tauc) region. These data are consistent with the dissociation of molecular nitrogen into a nonmolecular (possibly amorphous) phase.

UV‐visible absorption cross sections of nitrous acid

Abstract: Nitrous acid, HONO, is a source of OH radicals in the polluted atmosphere. Although the atmospheric chemistry of HONO is qualitatively understood, not much quantitative information exists. The magnitude of the OH production by HONO photolysis depends on the spectrum of its absorption cross sections; therefore the knowledge of σ'HONO(λ) is essential. The spectrum of the differential cross sections σ'HONO(λ) is needed to detect HONO in the atmosphere by differential optical absorption spectroscopy (DOAS). Here we present measurements of the HONO UV-visible absorption cross sections with a spectral resolution better than 0.1 nm and a high signal-to-noise ratio. The maximum value of the absorption cross sections is σHONO (354 nm) = (5.19±0.26) × 10−19 cm2 and agrees well with literature data. Nevertheless, calculations based on data from this work and on literature data reveal that an uncertainty of ∼15% remains for the HONO photolysis rates. The new σHONO(λ) has been employed in DOAS measurements in Milan, Italy.

Exciton spectra of ZnO epitaxial layers on lattice-matched substrates grown with laser-molecular-beam epitaxy

Abstract: Optical properties in undoped-ZnO epilayers grown by the laser-molecular-beam epitaxy method on lattice-matched ScAlMgO4 substrates were investigated. The absorption spectrum at 5 K has two sharp peaks, both of which are attributed to resonances of A and B excitons, which reflect a small nonradiative damping constant of excitons as well as high film crystallinity accomplished by the virtue of lattice matching. The coupling strengths of exciton-acoustic phonon and of exciton–longitudinal-optical phonon were directly determined from the temperature dependence of exciton absorption spectra independently for A and B excitons, which are close in energy and obey the same selection rule for each other.

Conjugation Length Control in Soluble Poly[2-methoxy-5-((2‘-ethylhexyl)oxy)-1,4-phenylenevinylene] (MEHPPV): Synthesis, Optical Properties, and Energy Transfer

Abstract: Poly[2-methoxy-5-(($2^{\prime}$-ethylhexyl)oxy)-1,4-henylenevinylene] (MEHPPV) of varying conjugation length was prepared by the selective thermal elimination of one of the substituents in a suitable precursor polymer. The precursor, a dialkoxy poly(1,4-xylylene) derivative with varying amounts of acetoxy and methoxy groups, was prepared by a competitive nucleophilic substitution of the Wessling polyelectrolyte, using methanol and sodium acetate in acetic acid as nucleophiles. Selective thermal elimination(in solution) of the acetate groups alone yielded MEHPPV of varying conjugation lengths. The selective nature of the acetate elimination was confirmed by $^1H$ NMR spectroscopy. As expected, both the absorption and emission maxima of the eliminated samples shifted to the red with increasing conjugation length. While there was very little difference between the absorption spectra of thin film and solutions of MEHPPV-x, there was a significant bathochromic shift in the emission spectra of the thin films when compared to their dilute solution spectra. Additionally, separate emission from the various oligomers, which are occasionally visible in solution, is absent in thin films. Energy transfer from short to longer conjugated segments, within a single polymer chain in solution, was inferred by comparison of the fluorescence spectra of the partially conjugated polymers with those expected from a system where simultaneous independent emission occurs from a similar collection of noninteracting oligophenylenevinylene (OPV)molecules. The latter was calculated assuming a statistically random substitution/elimination process of the precursor in conjunction with the fluorescence spectral data of OPV's reported by previous workers. The extent of energy transfer increases as the average conjugation length increases. Furthermore, unlike in the model oligomers, in the case of polymers the fluorescence quantum yield in solution rapidly decreases with increase in the average conjugation length.

Wet chemical synthesis and spectroscopic study of CdHgTe nanocrystals with strong near-infrared luminescence

Abstract: Several series of CdHgTe composite nanocrystals were prepared using a wet-chemical colloidal technique. The synthesis began using CdTe nanocrystal precursors stabilised using 1-mercapto-2,3-propanediol (1-thioglycerol) to which subsequent layers of HgTe and CdTe were added in an attempt to form both CdTe/HgTe core/shell and CdTe/HgTe/CdTe quantum dot quantum well (QDQW) structures. The room temperature photoluminescence (PL) spectra of the resulting hybrid nanocrystals all exhibited a significant increase in quantum efficiency (QE) over the pure CdTe material. In addition, the position of the ‘excitonic’ PL peak was red-shifted to the near infrared to give emission wavelengths ranging from 600 to 1350 nm depending on the composition. The possibility of alloying, and a redistribution of the mercury throughout the interior of the particles is discussed, along with the high resolution transmission electron microscopy (HRTEM) of some selected samples.

General Sonochemical Method for the Preparation of Nanophasic Selenides: Synthesis of ZnSe Nanoparticles

Abstract: ZnSe nanoparticles of about 3 nm in size have been prepared by the sonochemical irradiation of an aqueous solution of selenourea and zinc acetate under argon. The ZnSe nanoparticles were characterized using techniques such as transmission electron microscopy, X-ray diffraction, absorption spectroscopy, differential scanning calorimetry, transmission and diffuse reflection spectroscopy, photoluminescence spectroscopy, and energy-dispersive X-ray analysis. The mechanism of the sonochemical irradiation is discussed. This sonochemical method was found to be a general method for the preparation of other selenides as well.

Spectral light attenuation and the absorption of UV and blue light in natural waters

Abstract: The spectral pattern of light attenuation in the ultraviolet (UV) and blue region (360‐500 nm) was analyzed for seven high Arctic lakes. The best description of Kd versus wavelength was obtained with an exponential model similar to the model used for absorption by chromophoric dissolved organic compounds (CDOM), but with an additional parameter (Kback) that accounts for background scattering: S(l 2l) 0 K (l) 5 K (l )e 1 K , dd 0 back where Kd(l) is the diffuse vertical attenuation coefficient at wavelength l and S is the exponential slope parameter that characterizes the decrease in attenuation with increasing wavelength. The inclusion of the background parameter gave a significantly better fit and eliminated the systematic deviations over the spectrum that occur in the absence of Kback. The resultant S values (mean 5 17.4 mm 21 ) were on average 47% higher than values calculated without a background parameter, and were more sensitive to between-lake differences. The same pattern was found when S was estimated from spectral Kd values in three literature data sets, so the new equation will generally increase the estimated values of S based on Kd and provide a more accurate guide to intersystem variability. A compilation of literature data for S (based on Kd and the new equation or on absorbance) showed that its mean value (6SE) is significantly higher in freshwaters (17.1 6 0.7 mm 21 ) than in the sea (14.0 6 0.4 mm 21 ). The variability in S was highest for low values of Kd or a (340 nm values below 3 m 21 ). This pattern may be due to instrument-related problems or more likely represents the real variability in the optical properties of CDOM in low colored systems. The analysis showed that S can vary significantly between and within systems (overall range 5 9.2‐36.2 mm 21 ) and that the value obtained also depends on the method of calculation, the wavelength range, and the type of optical measurement.

Surface-enhanced infrared spectroscopy: A comparison of metal island films with discrete and nondiscrete surface plasmons

Abstract: A study of the surface-enhanced infrared absorption (SEIRA) spectroscopy of para-nitrobenzoic acid (PNBA) adsorbed on thermally evaporated silver films has been conducted to determine the effect of film architecture on the magnitude of the SEIRA enhancement. Ordered arrays of uniformly sized silver nanoparticles, termed periodic particle arrays (PPAs), were prepared on several different infrared transparent substrates (germanium, silicon, and mica) by nanosphere lithography (NSL). It was found that the ordered arrays deposited by NSL produced well-defined and intense surface plasmon resonance (SPR) bands in the infrared at frequencies between 1500 and 4000cm -1. The peak frequency of these infrared SPR bands depended on the array architecture and the substrate material. By appropriate design of the nanoparticle array, the infrared SPR band can be made to be coincident with the SEIRA sensitive infrared bands of the PNBA. The trends in the infrared SPR peak frequencies and band shapes were consistent with predictions from electrodynamic theory. The SEIRA responses per unit area of deposited metal obtained with the PPA-type films were at best comparable to results obtained with disordered silver and gold films deposited on the same substrate materials by thermal evaporation (i.e., in the absence of any NSL masking spheres). The results of this study are most consistent with theories and models that attribute SEIRA to the dielectric constant and optical extinction spectrum of the metal film. Index Headings: Infrared spectroscopy; Surface-enhanced infrared absorption; Plasmon; SEIRA.