Gross morphology and adhesion-associated physical properties of Drosophila larval salivary gland glue secretion.

One of the major functions of the larval salivary glands (SGs) of many Drosophila species is to produce a massive secretion during puparium formation. This so-called proteinaceous glue is exocytosed into the centrally located lumen, and subsequently expectorated, serving as an adhesive to attach the puparial case to a solid substrate during metamorphosis. Although this was first described almost 70 years ago, a detailed description of the morphology and mechanical properties of the glue is largely missing. Its main known physical property is that it is released as a watery liquid that quickly hardens into a solid cement. Here, we provide a detailed morphological and topological analysis of the solidified glue. We demonstrated that it forms a distinctive enamel-like plaque that is composed of a central fingerprint surrounded by a cascade of laterally layered terraces. The solidifying glue rapidly produces crystals of KCl on these alluvial-like terraces. Since the properties of the glue affect the adhesion of the puparium to its substrate, and so can influence the success of metamorphosis, we evaluated over 80 different materials for their ability to adhere to the glue to determine which properties favor strong adhesion. We found that the alkaline Sgs-glue adheres strongly to wettable and positively charged surfaces but not to neutral or negatively charged and hydrophobic surfaces. Puparia formed on unfavored materials can be removed easily without leaving fingerprints or cascading terraces. For successful adhesion of the Sgs-glue, the material surface must display a specific type of triboelectric charge. Interestingly, the expectorated glue can move upwards against gravity on the surface of freshly formed puparia via specific, unique and novel anatomical structures present in the puparial's lateral abdominal segments that we have named bidentia.

Redox features of hexaammineruthenium(III) on MXene modified interface: Three options for affinity biosensing.

In this article we describe construction of a bioreceptive interface for detection of a breast cancer biomarker carbohydrate antigen CA15-3. The conductive interface was patterned by a 2D nanomaterial MXene, to which a mixed layer containing sulfobetaine and carboxybetaine was electrochemically grafted through a diazonium moiety. Such a modified interface was then applied for covalent immobilisation of anti-CA15-3 antibody as a bioreceptive probe for detection of a breast cancer biomarker. Two different strategies were applied for final construction of an immunosensor i.e. an interface finally blocked by bovine serum albumin or an immunosensor without such modification. Finally, electrochemical reading was accomplished using a soluble redox probe Ru(NH3)63+ ion for detection of CA15-3 in a clinically relevant range up to 50 U mL-1. The results indicate that immunosensor based on non-blocked interface can be applied for biosensing using two modes of action: 1. differential pulse voltammetry (a plot of a peak current vs. analyte concentration) and 2. an electrochemical impedance spectroscopy (a plot of a charge transfer resistance vs. analyte concentration). The electrode blocked by bovine serum albumin (BSA) can be used by additional 3. mode of action: through detection of changes in the potential (a plot Epvs. c). Additionally, we reveal and explain that Ru(NH3)63+ is redox probe, which can be applied as interfacial molecular nanoscale ruler to distinguish negatively charged protein molecules present in the close proximity (≤ 6 nm) of the electrode (in our case adsorbed BSA molecules) from the negatively charged protein molecules at a larger distance (>12 nm) from the electrode (i.e. CA15-3 analyte).

Electrochemical Investigation of Interfacial Properties of Ti3C2T x MXene Modified by Aryldiazonium Betaine Derivatives.

For efficient and effective utilization of MXene such as biosensing or advanced applications, interfacial modification of MXene needs to be considered. To this end, we describe modification of Ti3C2Tx MXene by aryldiazonium-based grafting with derivatives bearing a sulfo- (SB) or carboxy- (CB) betaine pendant moiety. Since MXene contains free electrons, betaine derivatives could be grafted to MXene spontaneously. Kinetics of spontaneous grafting of SB and CB toward MXene was electrochemically examined in two different ways, and such experiments confirmed much quicker spontaneous SB grafting compared to spontaneous CB grafting. Moreover, a wide range of electrochemical methods investigating non-Faradaic and Faradaic redox behavior also in the presence of two redox probes together with contact-angle measurements and secondary ion mass spectrometry (SIMS) confirmed substantial differences in formation and interfacial presentation of betaine layers, when spontaneously grafted on MXene. Besides spontaneous grafting of CB and SB toward MXene, also electrochemical grafting by a redox trigger was performed. Results suggest that electrochemical grafting provides a denser layer of SB and CB on the MXene interface compared to spontaneous grafting of SB and CB. Moreover, an electrochemically grafted SB layer offers much lower interfacial resistance and an electrochemically active surface area compared to an electrochemically grafted CB layer. Thus, by adjusting the SB/CB ratio in the solution during electrochemical grafting, it is possible to effectively tune the redox behavior of an MXene-modified interface. Finally, electrochemically grafted CB and SB layers on MXene were evaluated against non-specific protein binding and compared to the anti-fouling behavior of an unmodified MXene interface.

Two-color symmetry breaking in laser-based secondary neutral mass spectrometry.

RATIONALE: An alternative method of analysis for laser-based secondary neutral mass spectrometry is introduced. METHODS: By mixing a fundamental 1240 nm wavelength of the near-infrared laser field with an intensity of 1 × 1015 W/cm2 with its second harmonic generation wavelength of 620 nm, control is attained over the ion yield in secondary neutral mass spectrometry for a native silver surface and a surface covered with silver nanoparticles. RESULTS: The ion yields of selected species in the mass spectra, such as a C2 H4 O2 surfactant fragment ion and the Ag ion, are enhanced or suppressed by a factor of 8 or 23, respectively, in comparison with single color post-ionization. In addition, a significant suppression of ion fragmentation is demonstrated for both the silver sample and silver nanoparticles. Periodic variation of the ion yield with a modulation depth of 4% is observed depending upon the relative phase between the fundamental and second harmonic generated fields. These variations are explained in terms of tunneling ionization with symmetry-broken fields. CONCLUSIONS: An additional degree of freedom in a form of additional second color is introduced in laser-based secondary neutral mass spectrometry. Ion yield control is extended in a form of symmetry-broken fields.

Fluorescence responsiveness of unicellular marine algae Dunaliella to stressors under laboratory conditions.

We examined the responsiveness of unicellular green alga Dunalliela tertiolecta to selected stressors employing confocal- and time-resolved imaging of endogenous fluorescence. Our aim was to monitor cell endogenous fluorescence changes under exposure to heavy metal Cd, acidification, as well as light by laser-induced photobleaching. The accumulation of Cd in algae cells was confirmed by the secondary ion mass spectroscopy technique. For the first time, custom-made computational techniques were employed to evaluate separately the fluorescence in the flagella vs. the body region. In the presence of Cd, we recorded increase in the green fluorescence in the flagella region in the form of opacities, without change in the fluorescence lifetimes, suggesting higher availability of the fluorescent molecules. Under acidification, we noted significant rise in the green fluorescence in the flagella region, but associated with longer fluorescence lifetimes, pointing to changes in the algae environment. Photobleaching experiments corroborated gathered observations. Obtained data support a differential responsiveness of the flagella vs. the body region to stressors and enable us to better understand the pathophysiological changes of algal cells in culture under stress conditions.

A Graphene-Based Glycan Biosensor for Electrochemical Label-Free Detection of a Tumor-Associated Antibody.

The study describes development of a glycan biosensor for detection of a tumor-associated antibody. The glycan biosensor is built on an electrochemically activated/oxidized graphene screen-printed electrode (GSPE). Oxygen functionalities were subsequently applied for covalent immobilization of human serum albumin (HSA) as a natural nanoscaffold for covalent immobilization of Thomsen-nouvelle (Tn) antigen (GalNAc-O-Ser/Thr) to be fully available for affinity interaction with its analyte-a tumor-associated antibody. The step by step building process of glycan biosensor development was comprehensively characterized using a battery of techniques (scanning electron microscopy, atomic force microscopy, contact angle measurements, secondary ion mass spectrometry, surface plasmon resonance, Raman and energy-dispersive X-ray spectroscopy). Results suggest that electrochemical oxidation of graphene SPE preferentially oxidizes only the surface of graphene flakes within the graphene SPE. Optimization studies revealed the following optimal parameters: activation potential of +1.5 V vs. Ag/AgCl/3 M KCl, activation time of 60 s and concentration of HSA of 0.1 g L-1. Finally, the glycan biosensor was built up able to selectively and sensitively detect its analyte down to low aM concentration. The binding preference of the glycan biosensor was in an agreement with independent surface plasmon resonance analysis.

Remarkable differences in the voltammetric response towards hydrogen peroxide, oxygen and Ru(NH3)63+ of electrode interfaces modified with HF or LiF-HCl etched Ti3C2Tx MXene.

An electrochemical study was performed on the behavior of Ti3C2Tx MXenes prepared by using either HF (MXene1) or LiF/HCl as etchants (MXene2). The use of two redox probes indicates the presence of a higher negative charge density on MXene2 in comparison to MXene1. The characterization of two nanomaterials shows that titanium and fluoride are present higher by one order of magnitude at the interface of MXene2, compared to MXene1. The high Ti and F content is accompanied by a 82-fold larger (249 µA·cm-2 vs. 5.64 µA·cm-2) anodic peak at the peak potential near 0.4 V (vs. Ag/AgCl). Similarly, the peak current on MXene2 is 317-fold higher for the oxygen reduction at pH 7.0 (at a voltage of -0.84 V) and 215-fold higher for the reduction of H2O2 at -0.89 V, when compared to MXene1. Graphical abstractDifference in electrochemical behavior of MXene prepared by HF (MXene1) and LiF/HCl (MXene2) as etchants.

Rat liver intoxication with CCl4: biochemistry, histology, and mass spectrometry.

This work provides complex characterisation of cirrhotic rat liver tissue induced by carbon tetrachloride using biochemical and histopathological analyses, and also presents a novel approach, secondary ion mass spectrometry (SIMS). According to our knowledge, this is the first report that compares these three different approaches in study of liver damage. We observed increased levels of triacylglycerols and total cholesterol in the liver and decreased levels of those parameters in the plasma. Histopathological observations include fat accumulation in the cells and changes in internal configuration of cells such as shift of position of organelles from the centre to the edge. The damage to the rat tissue is additionally determined by SIMS analysis, which characterizes, among other substances, diacylglycerols, cholesterol and fatty acids, such as linoleic and oleic acids. Interestingly, unlike other observed particles, a marked difference in SIMS intensity for diacylglycerol C37H69O4 positive fragment at 575.5 m/u was observed. In fact, there was one order of magnitude difference between intoxicated liver samples and controls and this molecular signal seems to be a potential chemical indicator of the damage. The SIMS images are consistent with histopathological results and they additionally provide information about distribution of chemical compound which is a new potential tool for the liver disease characterisation on molecular level.

Linear and Multi-Photon Fluorescence of Thiophene Based Copolymer with Electron-Accepting Side Chains.

A novel copolymer poly(thiophene-2,5-diyl-2,5-di-n-octyloxycarbonyl-1,4-phenylene), denoted as P33, is introduced as potential material for photovoltaics, polymer light-emitting diodes, and/or organic transistors. P33 dissolved in chloroform is investigated by steady-state absorption, linear/non-linear fluorescence spectroscopies and time-resolved fluorescence spectroscopy. Molar extinction coefficient, fluorescence quantum yield, and singlet fluorescence lifetime of P33 are determined to be 18,315 M-1 cm-1, 0.4, and 810 ps, respectively. The P33 fluorescence fast components of decay times are 1.2 ps, 2.0 ps, and 0.5 ps for increasing wavelengths of 480 nm, 500 nm, and 520 nm, respectively. The fast component is attributed to a transport of nearly instantaneously formed excitons to localized states known as downhill energy transfer. Additionally multi-photon excited fluorescence is observed for pumping with wavelengths of 800 nm and 1200 nm. Two-photon absorption cross-section is determined to be 6.9 GM. These spectroscopic studies provide basic fluorescence characteristics of the novel thiophene copolymer P33.

Electrochemical performance of Ti3C2Tx MXene in aqueous media: towards ultrasensitive H2O2 sensing.

An extensive characterization of pristine and oxidized Ti3C2Tx (T: =O, -OH, -F) MXene showed that exposure of MXene to an anodic potential in the aqueous solution oxidizes the nanomaterial forming TiO2 layer or TiO2 domains with subsequent TiO2 dissolution by F- ions, making the resulting nanomaterial less electrochemically active compared to the pristine Ti3C2Tx. The Ti3C2Tx could be thus applied for electrochemical reactions in a cathodic potential window i.e. for ultrasensitive detection of H2O2 down to nM level with a response time of approx. 10 s. The manuscript also shows electrochemical behavior of Ti3C2Tx modified electrode towards oxidation of NADH and towards oxygen reduction reactions.

Nonphasematched broadband THz amplification and reshaping in a dispersive chi(3) medium.

We theoretically investigate non-phasematched broadband THz amplification in dispersive chi(3) media. A short 100 fs pump pulse is interacting with a temporally matched second harmonic pulse and a weak THz signal through the four wave mixing process and a significant broadband THz amplification and reshaping is observed. The pulse evolution dynamics is explored by numerically solving a set of generalized Nonlinear Schroedinger equations. The influence of incident pulse chirp, pulse duration and the role of wavelength, THz seed frequency and losses are evaluated separately. It is found that a careful choice of incident parameters can provide a broadband THz output and/or a significant increase of THz peak power.

Adaptive Control of Ion Yield in Femtosecond Laser Post-ionization for Secondary Ion Mass Spectrometry.

Secondary ion mass spectrometry is an excellent technique of analytical chemistry, where primary ions sputter a solid sample generating the secondary ions which are determined. Although the ion yield is inherently low, it can be enhanced by using a post-ionization of sputtered neutral species. Our novel approach integrates this technique with a near infrared femtosecond laser post-ionization based on an adaptive control through a laser pulse shaper. The shaping of the laser pulse provides adaptive control to select a mass peak of interest and to enhance this peak intensity. Versatility is confirmed by optimizing the ion yield for different molecules (tryptophan, anthracene, polyethylene, and oxalic acid) with focus on parent ion enhancement, fragmentation process, sublimation effect, and excited secondary species. This proof-of-concept experiment provides not only a nonspecific increase of the overall ion yield, but also the selection of specific secondary species and the adaptive enhancement of their intensities on the order of 100, potentially simplifying data interpretation. Such tailored spectra might advance the (secondary ion) mass spectrometry to new capabilities.

Surface Nanostructures Composed of Thiolated Cyclodextrin/Au and Fe Species: Gas- and Liquid-Phase Preparation.

Supramolecular surface nanostructures have application potential as functional devices. The complex combination of thiolated cyclodextrin, chemisorbed on an Au surface (Au-S-CD), with deposited Fe species is studied by secondary ion mass spectrometry. The Fe species are prepared by pulsed laser ablation in water and thermal effusion in vacuum. Using laser ablation in water, the solution of Fe species is dropped on Au-S-CD, where mass peaks at 1227 m/z, 1243 m/z, and 1260 m/z are observed and assigned to C42 H68 O34 SNa-Fe(+) , C42 H68 O34 SK-Fe(+) together with C42 H68 O34 SNa-FeO(+) , and C42 H68 O34 SK-FeO(+) , respectively. On the other hand, laser ablation directly linked to the Au-S-CD surface results in desorption of CD-S. Thermal effusion, even with a cooled surface, was negative with respect to the complex observation. Laser ablation results in the formation of a supramolecular host-guest complex of the form Au-S-CD-Fe, and in the formation of an adduct of the form Au-S-CD-FeO.

Carboxybetaine Modified Interface for Electrochemical Glycoprofiling of Antibodies Isolated from Human Serum.

Impedimetric lectin biosensors capable of recognizing two different carbohydrates (galactose and sialic acid) in glycans attached to antibodies isolated from human serum were prepared. The first step entailed the modification of a gold surface by a self-assembled monolayer (SAM) deposited from a solution containing a carboxybetaine-terminated thiol applied to the subsequent covalent immobilization of lectins and to resist nonspecific protein adsorption. In the next step, Sambucus nigra agglutinin (SNA) or Ricinus communis agglutinin (RCA) was covalently attached to the SAM, and the whole process of building a bioreceptive layer was optimized and characterized using a diverse range of techniques including electrochemical impedance spectroscopy, cyclic voltammetry, quartz crystal microbalance, contact angle measurements, zeta-potential assays, X-ray photoelectron spectroscopy, and atomic force microscopy. In addition, the application of the SNA-based lectin biosensor in the glycoprofiling of antibodies isolated from the human sera of healthy individuals and of patients suffering from rheumatoid arthritis (RA) was successfully validated using an SNA-based lectin microarray. The results showed that the SNA lectin, in particular, is capable of discriminating between the antibodies isolated from healthy individuals and those from RA patients based on changes in the amount of sialic acid present in the antibodies. In addition, the results obtained by the application of RCA and SNA biosensors indicate that the abundance of galactose and sialic acid in antibodies isolated from healthy individuals is age-related.

Fluorescence Dynamics of Monocyclodextrin- and Bis(thiol-cyclodextrin)-Coumarin C153 Complexes.

The solvation and confinement of coumarin C153 within supramolecular host/guest complexes based on ß-cyclodextrin (ß-CD) and 6-deoxy-6-thio-ß-cyclodextrin (ß-CD-SH) in water are studied by fluorescence spectroscopy. For ß-CD/C153, the 1:1 complex is proposed, and for ß-CD-SH/C153 both the 1:1 and 2:1 complexes are believed to be formed. The 2:1 ß-CD-SH/C153 complex has an association constant of 4.2×10(5) M(-1) and a C153 population of 82 %, which are interestingly high values, indicating that the proposed ß-CD-SH dimers structure are connected by covalent disulfide bonds; this is supported by mass spectrometry. Solvation related to fast hydrogen-bond rearrangement as a part of fluorescence relaxation is determined by the ultrafast components of time-resolved spectroscopy to be 3 and 7 ps for the 1:1 ß-CD/C153 and 2:1 ß-CD-SH/C153 complexes, respectively.

Preparation of Cyclodextrin-Iron Species in Water by Laser Ablation: Secondary Ion Mass Spectrometry.

Supramolecular complexes between cyclodextrin and iron species are studied by using secondary ion mass spectrometry. The iron species are prepared by pulsed-laser ablation of bulk iron in water; this gives Fe(+) (56 m/z) and Fex Oy (+) (x, y=1-7) species. Cyclodextrin is added to the water either before or after the laser ablation. When it is added before laser ablation, molecular fragments of cyclodextrin are detected as dehydrated glucopyranose units (C6 H8 O4 (+) ) associated with Fe(+) , FeO(+) , and Fe2 O(+) species. The focus is to observe supramolecular host-guest complexes or adducts between intact molecules of cyclodextrin and iron species. When cyclodextrin is added after laser ablation, the relevant peak at 1210 m/z is observed and assigned as C42 H67 O35 FeNa(+) , which corresponds to a cyclodextrin molecule minus three H atoms. Two possible explanations of this finding are the presence of the host-guest C42 H67 O35 Na-Fe complex, in which Fe is in the cavity, or the presence of the adduct C42 H67 O34 Na-FeO with FeO on the outer surface; the formation of these complexes are supported by the hydrophobicity of Fe and hydrophilicity of FeO, respectively. Due to the presence of 12 % of intact C42 H70 O35 Na-Fe complex and an estimated Fe/FeO ratio of approximately 10(2) , host-guest formation is assumed to be more significant.

Formation mechanism of a silane-PVA/PVAc complex film on a glass fiber surface.

Mechanical properties of glass fiber reinforced composite materials are affected by fiber sizing. A complex film formation, based on a silane film and PVA/PVAc (polyvinyl alcohol/polyvinyl acetate) microspheres on a glass fiber surface is determined at 1) the nanoscale by using atomic force microscopy (AFM), and 2) the macroscale by using the zeta potential. Silane groups strongly bind through the Si-O-Si bond to the glass surface, which provides the attachment mechanism as a coupling agent. The silane groups form islands, a homogeneous film, as well as empty sites. The average roughness of the silanized surface is 6.5 nm, whereas it is only 0.6 nm for the non-silanized surface. The silane film vertically penetrates in a honeycomb fashion from the glass surface through the deposited PVA/PVAc microspheres to form a hexagonal close pack structure. The silane film not only penetrates, but also deforms the PVA/PVAc microspheres from the spherical shape in a dispersion to a ellipsoidal shape on the surface with average dimensions of 300/600 nm. The surface area value Sa represents an area of PVA/PVAc microspheres that are not affected by the silane penetration. The areas are found to be 0.2, 0.08, and 0.03 µm(2) if the ellipsoid sizes are 320/570, 300/610, and 270/620 nm for silane concentrations of 0, 3.8, and 7.2 µg mL(-1), respectively. The silane film also moves PVA/PVAc microspheres in the process of complex film formation, from the low silane concentration areas to the complex film area providing enough silane groups to stabilize the structure. The values for the residual silane honeycomb structure heights (Ha ) are 6.5, 7, and 12 nm for silane concentrations of 3.8, 7.2, and 14.3 µg mL(-1), respectively. The pH-dependent zeta-potential results suggest a specific role of the silane groups with effects on the glass fiber surface and also on the PVA/PVAc microspheres. The non-silanized glass fiber surface and the silane film have similar zeta potentials ranging from -64 to -12 mV at pH's of 10.5 and 3, respectively. The zeta potentials for the PVA/PVAc microspheres on the glass fiber surface and within the silane film significantly decrease and range from -25 to -5 mV. The shapes of the pH-dependent zeta potentials are different in the cases of silane groups over a pH range from 7 to 4. A triple-layer model is used to fit the non-silanized glass surface and the silane film. The value of the surface-site density for Γ(Xglass) and Γ(Xsilane), in which X denotes the Al-O-Si group, differs by a factor of 10(-4), which suggests an effective coupling of the silane film. A soft-layer model is used to fit the silane-PVA/PVAc complex film, which is approximated as four layers. Such a simplification and compensation of the microsphere shape gives an approximation of the relevant widths of the layers as the follows: 1) the layer of the silane groups makes up 10% of the total length (27 nm), 2) the layer of the first PVA shell contributes 30% to the total length (81 nm), 3) the layer of the PVAc core contributes 30% to the total length (81 nm), and finally 4) the layer of the second PVA shell provides 30% of the total length (81 nm). The coverage simulation resulted in a value of 0.4, which corresponds with the assumption of low-order coverage, and is supported by the AFM scans. Correlating the results of the AFM scans, and the zeta potentials sheds some light on the formation mechanism of the silane-PVA/PVAc complex film.

Fluorescence dynamics of coumarin C522 as a function of micelle confinement along with cyclodextrin supramolecular complex formation.

Our aim is to doubly confine a molecule of coumarin C522 in a host-guest supramolecular complex with ß-cyclodextrin in a reverse sodium dioctyl sulfosuccinate (AOT) micelle using nonpolar n-heptane and polar water solvents. Varying the volumes of coumarin C522 and ß-cyclodextrin dissolved in water allows us to control the water-pool diameters of the reverse micelle in n-heptane with values of w=3, 5, 10, 20, and 40, where w is the ratio of water concentration to AOT concentration in n-heptane. To study the fluorescence dynamics of coumarin C522, the spectral steady-state and time-resolved dependences are compared for the two systems coumarin C522(water)/AOT(n-heptane), denoted C522/micelle, and coumarin C522/ß-cyclodextrin(water)/AOT(n-heptane), referred to as C522/CD/micelle. The formation of the supramolecular host-guest complex CD-C522 is indicated by a blue shift, but in the micelle, the shift is red. However, the values of the fluorescence maxima at 520 and 515 nm are still way below the value of 535 nm representing bulk water. The interpretation of the red shift is based on two complementary processes. The first one is the confinement of CD and C522 by the micelle water pool and the second is the perturbation of the micelle by CD and C522, resulting in an increase of the water polarity. The fluorescence spectra of the C522/micelle and C522/CD/micelle systems have maxima and shoulders. The shoulder intensities at 440 nm, representing the C522 at n-heptane/AOT interface, decrease as the w values decrease. This intensity shift suggests that the small micelle provides a stronger confinement, and the presence of CD shifts the equilibrium from n-heptane towards the water pool even more. The fluorescence emission maxima of the C522/micelle and C522/CD/micelle systems for all w values clearly differentiate two trends for w=3-5, and w=10-40, suggesting different interaction in the small and large micelles. Moreover, these fluorescence maxima result in 7 and 13 nm differences for w=3 and w=5, respectively, and provide the spectral evidence to differentiate the C522 confinement in the C522/micelle and C522/CD/micelle systems as an effect of the CD molecule, which might be interpreted as a double confinement of C522 in CD within the micelle. The ultrafast decay in the case of w=3 ranges from 9.5 to 16 ps, with an average of 12.6 ps, in the case of the C522/micelle system. For C522/CD/micelle, the ultrafast decay at w=3 ranges from 9 to 14.5 ps, with an average of 11.8 ps. Increasing w values (from 10 to 40) result in a decrease of the ultrafast decay values in both cases to an average value of about 6.5 ps. The ultrafast decays of 12.6 and 11.8 ps for C522/micelle and C522/CD/micelle, respectively, are in the agreement with the observed red shift, supporting a double confinement in the C522/CD/micelle(w=3) system. The dynamics in the small and large micelles clearly show two different trends. Two slopes in the data are observed for w values of 3-5 and 10-40 in the steady-state and time-resolved data. The average ultrafast lifetimes are determined to be 12.6 and 6.5 ps for the small (w=3) and the large (w=40) micelles, respectively. To interpret the experimental solvation dynamics, a simplified model is proposed, and although the model involves a number of parameters, it satisfactory fits the dynamics and provides the gradient of permittivity in the ideal micelle for free water located in the centre (60-80) and for bound water (25-60). An attempt to map the fluorescence dynamics of the doubly confined C522/CD/micelle system is presented for the first time.

Infrared femtosecond laser preionization in secondary ion mass spectrometry of silver surface.

An alternative secondary ion mass spectrometry utilizing laser preionization is introduced. The native Ag sample surface is first irradiated with laser pulse (100 fs duration, 10(10)-10(11) W/cm(2) intensity, 1240 nm wavelength) and subsequently bombarded with primary ions (Bi(3)(+), 10 ns duration, 25 keV energy). Multiple correlation patterns are observed in the mass spectra, confirming the mutual laser-secondary ion mass spectrometry (SIMS) interplay in the preionization mechanism. The Ag(+), C(3)H(5)(+), C(3)H(5)O(3)(+), and AgOH(+), C(4)H(5)O(4)(+) are observed with the shallow and steep increasing of intensities at 1.3 × 10(11) W/cm(2) and 1.5 × 10(11) W/cm(2), respectively. Two ionization mechanisms are identified, the ion sputtering regime for intensities of less than 1.4 × 10(11) W/cm(2) and the multiphoton ionization at higher intensities. The Ag saturation intensity obtained from fitting is 2.4 × 10(13) W/cm(2), close to the one reported for postionization. The proposed preionization approach might eliminate the need for high peak power/high intensity laser source and, moreover, the experiment geometry ensures that large areas of the sample are affected by the laser beam.

Fullerenes, nanotubes, and graphite as matrices for collision mechanism in secondary ion mass spectrometry: determination of cyclodextrin.

A technique for improving the sensitivity of high mass molecular analysis is described. Three carbon species, fullerenes, single walled carbon nanotubes, and highly ordered pyrolytic graphite are introduced as matrices for the secondary ion mass spectrometry analysis of cyclodextrin (C(42)H(70)O(35), 1134 u). The fullerene and nanotubes are deposited as single deposition, and 10, 20, or 30 deposition films and cyclodextrin is deposited on top. The cyclodextrin parent-like ions and two fragments were analyzed. A 30 deposition fullerene film enhanced the intensity of cationized cyclodextrin with Na by a factor of 37. While the C(6)H(11)O(5) fragment, corresponding to one glucopyranose unit, increased by a factor of 16. Although fragmentation on fullerene is not suppressed, the intensity is twice as low as the parent-like ion. Deprotonated cyclodextrin increases by 100× and its C(8)H(7)O fragment by 10×. While the fullerene matrix enhances secondary ion emission, the nanotubes matrix film generates a basically constant yield. Graphite gives rise to lower intensity peaks than either fullerene or nanotubes. Scanning electron microscopy and atomic force microscopy provide images of the fullerene and nanotubes deposition films revealing flat and web structured surfaces, respectively. A "colliding ball" model is presented to provide a plausible physical mechanism of parent-like ion enhancement using the fullerene matrix.