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We utilize a novel, high-power, tunable, continuous wave (CW) deep UV laser to measure resonance Raman spectra of phenolate solutions with high signalto-noise ratios (SNR). In UV resonance Raman (UVRR), increased coupling of the excitation light with a chromophore can transfer molecules into excited states that cause increased heating and photochemistry. Deep UV lasers have traditionally utilized high peak powers to enable efficient single-pass nonlinear conversion from visible into near infrared light. Nonlinear phenomena such as the formation of transient radical species, Raman saturation, thermal heating, and dielectric breakdown can introduce extraneous light sources that can complicate the interpretation of the Raman spectrum. Dielectric breakdown can increase the baseline, increase noise, and sometimes saturate the detector, preventing Raman detection. Spontaneous Raman scattering intensities should scale linearly with the excitation light intensity. However, this linear behavior does not always occur with pulsed laser excitation. This occurs because stimulated Raman scattering can cause a superlinear intensity response, or transient absorption can cause sublinear intensity responses. CW laser excitation excites samples with electric fields that are much lower than typical pulsed laser excitation. This eliminates the nonlinear responses. The geometry of our new CW laser enables high gain in the harmonic generation cavities that achieve high harmonic generation efficiencies. Average power in the deep UV is >30 mW for wavelengths as short as 206 nm. In the work here, we demonstrate that CW excitation is ideal for resonance Raman measurements in general to reduce spectral complexity. [ABSTRACT FROM AUTHOR]

We developed a state-of-the-art, high-sensitivity, low-stray-light standoff deep-ultraviolet (DUV) Raman spectrometer for the trace detection of resonance Raman-enhanced chemical species. As an excitation source for Raman measurements, we utilized our recently developed, second-generation, miniaturized, diode-pumped, solid-state neodymium-doped gadolinium orthovanadate (Nd:GdVO4) laser that generates quasi-continuous wave 228 nm light. This 228 nm excitation enhances the Raman intensities of vibrations of NOx groups in explosive molecules, aromatic groups in biological molecules, and various aromatic hydrocarbons. Our DUV Raman spectrograph utilizes a custom DUV f /8 Cassegrain telescope with an ∼200 mm diameter primary mirror, high-efficiency DUV transmission gratings, custom DUV mirrors, and a custom 228 nm Rayleigh rejection filter. We utilized our new standoff DUV Raman spectrometer to measure high signal-to-noise ratio spectra of ∼50 μg/cm2 drop-cast explosives: ammonium nitrate (AN), trinitrotoluene, pentaerythritol tetranitrate as well as aromatic biological molecules: lysozyme, tryptophan, tyrosine, deoxycytidine monophosphate, deoxyadenosine monophosphate at an ∼3 m distance within 10–30 s accumulation times. We roughly estimate the average ultraviolet resonance Raman (UVRR) detection limits for the relatively homogeneous drop-cast films of explosives and biological molecules to be ∼1 μg/cm2 when utilizing a continuous raster scanning that averages Raman signal over ∼1 cm2 sample area to avoid quick analyte depletion due to ultraviolet (UV) photolysis. We determined 3 m standoff UVRR detection limits for drop-cast AN films and identified factors impacting UVRR detection limits such as analyte photochemistry and analyte morphology. We found a detection limit of ∼0.5 μg/cm2 for drop-cast AN films on glass substrates when the Raman signal is averaged over ∼0.5 cm2 of sample surface using a continuous raster scan. For a step raster scan, when the probed sample area is limited to the laser spot size, the detection limit is approximately tenfold higher (∼5 μg/cm2) due to the impact of UV photochemistry. Graphical abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

We are developing photonic crystal glucose sensing materials to continuously monitor relatively high glucose concentrations, such as found in blood. We modified our synthetic fabrication methodologies in order to increase the glucose concentration range and to increase the reproducibility of our PCCA fabrication. We have also advanced our understanding of the sensing response by developing a mechanical method to independently determine the hydrogel cross-link density. Our investigation of the sensing mechanism indicates that glucose binding depends mainly on the boronic acid concentrations and affinities. We determined the binding constant Of 2-fluoro-5-aminophenyl boronic acid for glucose under physiological conditions. We have examined the dependence of glucose sensing upon interferences by other species that ligand to boronic acids, such as lactate and human serum albumin. We examined the stability of our sensors over a period of weeks at room temperature and demonstrated that we could further stabilize our sensing materials by reversibly dehydrating them for storage.

The vibrational interactions between adjacent peptide units are studied in the peptide bond angles of neutral trialanine. The amide I vibrations show a strong coupling in [alpha]-helical conformation than in PPII conformation of trialanine.

Ultraviolet resonance Raman (UVRR) spectroscopy exciting at ~200 nm was used within the peptide bond pi -> pi* transitions to selectively study the amide vibrations of peptide bonds during alpha-helix melting. Results show that the [3.sub.10]-, and pi-helix/bulge conformations melt prior to melting of pure alpha helices, even though these conformations are proposed to be intermediates, indicating they are much more transient at the higher alpha-helix melting temperature.

We developed new photonic crystal polymerized crystalline colloidal array (PCCA) glucose sensing materials, which operate on the basis of formation of cross-links in the hydrogel. These materials are composed of hydrogels that embed an array of ~100-nm-diameter monodisperse polystyrene colloids that Bragg diffract light in the visible spectral region. The hydrogels change volume as the glucose concentration varies. This changes the lattice spacing, which changes the wavelength of the diffracted light. In contrast to our previous glucose sensing photonic crystal materials, we no longer require [Na.sup.+] chelating agents. These photonic crystal materials are being designed for use in glucose sensing contact lens for people with diabetes mellitus. We describe methods to speed up the response kinetics of these PCCA sensing materials. Rapid-response kinetics is achieved by controlling the elasticity and the hydrophilic--hydrophobic balance of the hydrogel system. A more hydrophobic hydrogel composition is obtained by copolymerizing n-hexylacrylate into an acrylamide--bisacrylamide hydrogel. The response rate significantly increases to where it fully responds within 90 s to the average glucose concentrations found in blood (5 mM) and within 300 s to the average glucose concentrations found in tear fluid (0.15 mM). We find unusual temperature-dependent kinetics, which derive from glucose mutarotation in solution. It is shown that a-D-glucose is the glucose anomer binding to the boronic acid derivative. Care must be taken in any glucose determination to ensure that the glucose mutarotation equilibrium has been established. We have demonstrated that the sensor is responsive to ~0.15 mM glucose concentrations in artificial tear fluid solution.

A study to quantitatively correlate the peptide bond AmIII frequency to its Psi Ramachandran angle and to the number and types of amide hydrogen bonds at different temperatures using UV resonance Raman (UVRR) spectroscopy is conducted. The results allow us to develop a family of relationships to directly estimate Psi Ramachandran angle from measured UVRR AmIII frequencies for peptide bonds with known hydrogen bonding.

The solution conformation of poly-L-lysine (PLL) and poly-L-glutamic acid (PGA) in their non-alpha-helical states is examined by using the UV resonance Raman (UVR) spectroscopy. A method is also developed to estimate the distribution of Psi Ramachandran angles for these conformations, which are used to estimate a Psi Ramachandran angle energy landscape.

We developed a polymerized crystalline colloidal array (PCCA) photonic crystal sensing material that senses the organophosphorus compound parathion at ultratrace concentrations in aqueous solutions. A periodic array of colloidal particles is embedded in a hydrogel network with a lattice spacing such that it Bragg diffracts visible light. The molecular recognition agent for the sensor is the enzyme acetylcholinesterase (ACHE), which binds organophosphorus compounds irreversibly, creating an anionic phosphonyl species. This charged species creates a Donnan potential, which swells the hydrogel network, which increases the embedded particle array lattice spacing and causes a red-shift in the wavelength of light diffracted. The magnitude of the diffraction red-shift is proportional to the amount of bound parathion. These AChE-PCCAs act as dosimeters for parathion since it irreversibly binds. Parathion concentrations as low as 4.26 fM are easily detected.

The transport of [Pb.sup.2+] through a sensory gel, a polymerized crystalline colloidal array hydrogel with immobilized benzo-18-crown-6, is important for understanding and optimizing the sensor. Square wave voltammetry at a Hg/ Au electrode reveals many parameters. The partition coefficient for [Pb.sup.2+] into a control gel (no crown ether), [K.sub.p], is 1.00 [+ or -] 0.018 (errors reported are SEM). The porosity, [epsilon], of the gel is 0.90 [+ or -] 0.01. Log [K.sub.c ]for complexation in the gel is 2.75 [+ or -] 0.014. Log [K.sub.c] in aqueous solution for [Pb.sup.2+] with the ligand 4-acryloylamidobenzo-18-crown-6 is 3.01 [+ or -] 0.010 with dissociation rate [k.sub.d] = (8.34 [+ or -] 0.45) x [10.sup.2] [s.sup.-1] and association rate [k.sub.f] = (8.79 [+ or -] 0.025) x [10.sup.7] [M.sup.-1] [s.sup.-1]. The partition coefficient of the ligand 4-acryloylamidobenzo-18-crown-6 into the control gel, [K.sub.p,L] is 2.07 [+ or -] 0.15. The diffusion coefficient of [Pb.sup.2+] in the control gel is 6.72 x [10.sup.-6] [+ or -] 0.12 [cm.sup.2]/s. For the sensor gel, but not control gel, diffusion coefficients are location dependent. The range of diffusion coefficients for [Pb.sup.2+] in the probed locations was found to be (6.1112.60) x [10.sup.-7] [cm.sup.2]/s for 0.91 mM [Pb.sup.2+] and (2.84 - 9.39) x [10.sup.-7] [cm.sup.2]/s for 0.35 mM [Pb.sup.2+]. Lead binding in the sensor gel is slightly less avid than in solution. This is attributed, in part, to the demonstrated affinity of the ligand 4-acryloylamidobenzo-18-crown-6 to the gel. Diffusion coefficients determined for the sensor gel were found to be location dependent. This is attributed to heterogeneities in the crown concentration in the gel. Analysis of diffusion coefficients and rate constants show that diffusion and not chemical relaxation will limit the time response of the material.

Adenylyl cyclase (AC) is a prototypical cell-signaling molecule expressed in virtually all organisms form bacteria to man. 7Clb-S meets basic criteria to serve as a model protein for the Clb region and may be used as a prototype to develop other isoform Clb soluble model proteins.

A versatile procedure to synthesize mono disperse hollow polymer colloid particles which can self-assemble into a crystalline colloidal array (CCA) is developed. These help in confining the reaction inside the hollow particles to fabricate.

A combination of a highly efficient 213 nm Rayleigh rejection filter (RRF) and a miniaturized 213 nm neodymium-doped vanadate laser enables portable deep ultraviolet (UV) Raman spectrometers. We demonstrate the high efficiency of 213 nm RRF manufactured by Green Optics Co., Ltd by utilizing our compact 213 nm vanadate laser to measure high signal-to-noise ratio UV Raman spectra of Teflon and UV resonance Raman (UVRR) spectra of solid ammonium nitrate. We also demonstrate UVRR detection of trace amounts of ammonia formed during ammonium nitrate UV photolysis. We roughly estimate the ammonia UVRR detection limit of ∼10 ng under our experimental conditions. [ABSTRACT FROM AUTHOR]

We developed an optrode sensing device that utilizes a polymerized colloidal array (PCCA) photonic crystal material. This array diffracts light in the visible spectral region due to the periodic spacing of colloidal particles. The PCCA changes diffraction wavelength due to binding of [Pb.sup.2+] to an 18-crown-6 ether molecular recognition agent. This optrode consists of a probe assembly that contains the PCCA [Pb.sup.2+] sensing film. An inexpensive, commercial diode array spectrometer and a fiber-optic reflectance probe monitors the wavelength of light back diffracted by the PCCA. Liquid inlet and outlet connections are provided to introduce the sample solution and to exchange out nonbinding ions. In low ionic strength solutions, diffraction wavelength shifts are actuated by the binding of the [Pb.sup.2+] to the crown ether to immobilize the [Pb.sup.2+] counterions. In these low ionic strength solutions, a Donnan potential forms to cause an osmotic pressure, which swells the PCCA in proportion to the number density of bound [Pb.sup.2+]. This Donnan potential disappears at high ionic strengths. Thus, no response of the PCCA occurs. Our optrode design allows for the fast removal of nonbound ions from the PCCA by washing with pure water. Since the bound [Pb.sup.2+] ions have a slow off rate from the crown ether, the bound [Pb.sup.2+] PCCA diffraction transiently red shifts during washing, directly in proportion to the sample [Pb.sup.2+] concentration. This transient diffraction red-shift can be used to quantitatively determine Pb2+ concentrations in high ionic strength solutions such as bodily fluids.

We demonstrate a colorimetric glucose recognition material consisting of a crystalline colloidal array embedded within a polyacrylamide--poly(ethylene glycol) (PEG) hydrogel, or a polyacrylamide--15-crown-5 hydrogel, with pendent phenylboronic acid groups. We utilize a new molecular recognition motif, in which boronic acid and PEG (or crown ether) functional groups are prepositioned in a photonic crystal hydrogel, such that glucose self-assembles these functional groups into a supramolecular complex. The formation of the complex results in an increase in the hydrogel cross-linking, which for physiologically relevant glucose concentration blue shifts the photonic crystal diffraction. The visually evident diffraction color shifts across the visible spectral region over physiologically important glucose concentration ranges. These materials respond to glucose at physiological ionic strengths and pH values and are selective in their mode of response for glucose over galactose, mannose, and fructose. Thus, we have developed a new recognition motif for glucose that shows promise for the fabrication of noninvasive or minimally invasive in vivo glucose sensing for patients with diabetes mellitus.

We developed a polymerized crystalline colloidal array photonic material that senses metal cations in water at low concentrations (PCCACS). Metal cations such as [Cu.sup.2+], [Co.sup.2+], [Ni.sup.2+], and [Zn.sup.2+] bind to 8-hydroxyquinoline groups covalently attached to the PCCACS. At low metal concentrations (< [micro]M), the cations form bisliganded complexes with two 8-hydroxyquinolines that cross-link the hydrogel and cause it to shrink, which blue shifts the photonic crystal diffraction. These bisliganded cross-links break at higher cation concentrations due to the formation of monoliganded cation complexes. This red shifts the diffraction. We have extended hydrogel volume phase transition theory in order to quantitatively model the diffraction dependence upon metal concentration. These materials can be used as a dosimeter to sense extremely low metal cation concentrations or as a sensor material for concentrations greater than 1 [micro]M. Metal cation concentrations can be determined visually from the color of the diffracted light or can be determined by reflectance measurements using a spectrophotometer. This sensing material could be used in the field to visually determine metal cation concentrations in drinking water. A color chart would be used to relate the diffracted color to the metal cation concentration.

A carbohydrate sensing material is developed, which consists of a crystalline array incorporated into a polyacrylamide hydrogel (PCCA) with pendent boronic acid groups. The PCCA photonic crystal sensing material responds to glucose in low ionic strength aqueous solutions by swelling and red shifting its diffraction as the glucose concentration increases.

The first synthesis of mesoscopic, monodisperse particles that contain nanoscopic inclusions of ferromagnetic cobalt ferrites is reported. These monodisperse ferromagnetic composite particles readily self-assemble into magnetically responsive photonic crystals that efficiently diffract incident light.