spectroscopy was used to investigate the temperature dependence
of thermally active ethylene-vinyl acetate | multiwall carbon nanotube
(EVA|MWCNT) films. The data shows systematic variations of intensities
with increasing temperature. Molecular orbital assignment of interplaying
intensities identified the 1s → π*C=C and 1s → π*C=O transitions as the
main actors during temperature variation. Furthermore, enhanced near-edge
interplay was observed in prestrained composites. Because macroscopic
observations confirmed enhanced thermal-mechanical actuation in prestrained
composites, our findings suggest that the interplay of C=C
and C=O π orbitals may be instrumental to actuation.
Gold nanoparticles provide a template for preparing supported lipid layers with well-defined curvature. Here, we utilize the localized surface plasmon resonance (LSPR) of gold nanoparticles as a sensor for monitoring the preparation of lipid layers on nanoparticles. The LSPR is very sensitive to the immediate surroundings of the nanoparticle surface and it is used to monitor the coating of lipids and subsequent conversion of a supported bilayer to a hybrid membrane with an outer lipid leaflet and an inner leaflet containing hydrophobic alkanethiol. We demonstrate that both decanethiol and propanethiol are able to form hybrid membranes and that the membrane created over the shorter thiol can be stripped from the gold along with the lipid leaflet using β-mercaptoethanol. The sensitivity of the nanoparticle LSPR to the refractive index (RI) of its surroundings is greater when the shorter thiol is used (37.8 ± 1.5 nm per RI unit) than when the longer thiol is used (27.5 ± 0.5 nm per RI unit). Finally, C-reactive protein binding to the membrane is measured using this sensor allowing observation of both protein-membrane and nanoparticle-nanoparticle interactions without chemical labeling of protein or lipids.
Novel experimental techniques allow
for the manipulation and interrogation
of biomolecules between metallic probes immersed in micro/nanofluidic
channels. The behavior of ions in response to applied fields is a
major issue in the use of these techniques in sensing applications.
Here, we experimentally and theoretically elucidate the behavior of
background currents in these systems. These large currents have a
slowly decaying transient response, as well as noise that increases
with ionic concentration. Using mechanically controllable break junctions
(MCBJ), we study the ionic response in nanogaps with widths ranging
from a few nanometers to millimeters. Moreover, we obtain an expression
for the ionic current by solving time-dependent Nernst–Planck
and Poisson equations. This expression shows that after turning on
an applied voltage, ions rapidly respond to the strong fields near
the electrode surface, screening the field in the process. Ions subsequently
translocate in the weak electric field and slowly relax within the
diffusion layer. Our theoretical results help to explain the short-
and long-time behavior of the ionic response found in experiments,
as well as the various length scales involved.
the ongoing search for ever-brighter surface-enhanced Raman scattering
(SERS) nanoprobes, gold nanostars (AuNSs) have emerged as one of the
best geometries for producing SERS in a nonaggregated state. Despite
their high enhancement factor, optical extinction from plasmon-matched
nanoparticles can greatly attenuate the overall SERS intensity. Herein,
we report the development of a new hybrid bimetallic NS-based platform
that exhibits superior resonant SERS (SERRS) properties. In this new
nanoplatform, coating AuNSs with a subtotal layer of silver (AuNS@Ag)
can further increase their SERRS brightness by an order of magnitude
when being interrogated by an off-resonant excitation source. Silica-encapsulated
AuNS@Ag nanoprobes were injected intradermally into a rat pelt, where
SERRS was readily detected with higher signal-to-noise than nanoprobes
prepared from AuNS. Moreover, these off-resonance AuNS@Ag nanoprobes
did not cause any gross photothermal damage to tissue, which was observed
with the plasmon-matched AuNSs. This novel SERRS-active hybrid nanoprobe
exhibits high SERRS brightness and offers promising properties for
future applications in sensing and molecular imaging.
X-ray Photoelectron Spectroscopy (XPS) was used to characterize the nitrogen species in perfluorophenylazide (PFPA) self-assembled monolayers. PFPA chemistry is a novel immobilization method for tailoring the surface properties of materials. It is a simple route for the efficient immobilization of graphene, proteins, carbohydrates and synthetic polymers onto a variety of surfaces. Upon light irradiation, the azido group in PFPA is converted to a highly reactive singlet nitrene species that readily undergoes CH insertion and C=C addition reactions. Here, the challenge of characterizing the PFPA modified surfaces was addressed by detailed XPS experimental analyses. The three nitrogen peaks detected in the XPS N1s spectra were assigned to amine/amide (400.5 eV) and azide (402.1 and 405.6 eV) species. The observed 2:1 ratio of the areas from the 402.1 eV to 405.6 eV peaks suggests the assignment of the peak at 402.1 eV to the two outer nitrogen atoms in the azido group and assignment of the peak at 405.6 eV to the central nitrogen atom in the azido group. The azide decomposition as the function of x-ray exposure was also determined. Finally, XPS analyses were conducted on patterned graphene to investigate the covalent bond formation between the PFPA and graphene. This study provides strong evidence for the formation of covalent bonds during the PFPA photocoupling process.
PFPA; XPS; Surface Characterization; Graphene
spectroscopy, experimental thermodynamic measurements,
and computational studies were performed to investigate the properties
of molecular hydrogen binding to the organometallic fragments [MHdppe2]+ (M = Fe, Ru, Os; dppe =1,2-bis(diphenylphosphino)ethane)
to form the dihydrogen complex fragments [MH(η2-H2)dppe2]+. Mössbauer spectroscopy
showed that the dehydrogenated complex [FeHdppe2]+ adopts a geometry consistent with the triplet spin state, transitioning
to a singlet state complex upon addition of the dihydrogen molecule
in a manner similar to the previously studied dinitrogen complexes.
From simulations, this spin transition behavior was found to be responsible
for the strong binding behavior experimentally observed in the iron
complex. Spin-singlet to spin-singlet transitions were found to exhibit
thermodynamics consistent with the 5d > 3d > 4d binding trend
for other transition metal dihydrogen complexes. Finally, the method
for distinguishing between dihydrogen and dihydride complexes based
on partial quadrupole splittings observed in Mössbauer spectra
was confirmed, providing a tool for further characterization of these
unique species for Mössbauer active compounds.
Biological polymers hybridized with single-walled carbon nanotubes (SWCNTs) have elicited much interest recently for applications in SWCNT-based sorting as well as biomedical imaging, sensing, and drug delivery. Recently, de novo designed peptides forming a coiled-coil structure have been engineered to selectively disperse SWCNT of a certain diameter. Here we report on a study of the binding strength and structural stability of the hybrid between such a “HexCoil-Ala” peptide and the (6,5)-SWCNT. Using the competitive binding of a surfactant, we find that affinity strength of the peptide ranks in comparison to that of two single-stranded DNA sequences as (GT)30-DNA > HexCoil-Ala > (TAT)4T-DNA. Further, using replica exchange molecular dynamics (REMD), we show that the hexamer peptide complex has both similarities with and differences from the original design. While one of two distinct helix-helix interfaces of the original model was largely retained, a second interface showed much greater variability. These conformational differences allowed an aromatic tyrosine residue designed to lie along the solvent-exposed surface of the protein instead to penetrate between the two helices and directly contact the SWCNT. These insights will inform future designs of SWCNT-interacting peptides.
SWCNT; Peptide; DNA; Molecular Dynamics; Stability
This work reports on the observation of a delocalized surface plasmon resonance (DSPR) phenomenon in linear chains of square-shaped silver nanoparticles (NP) as a function of the chain length and the distance between the nanoparticles in the chain. Transmission spectra of the silver nanoparticle chains reveal the emergence of new, red-shifted extinction peaks that depend strongly on the spacing between the nanoparticles and the polarization of the exciting light with respect to the chain axis. As the spacing between the nanoparticles in the linear chain decreases and the number of nanoparticles in the linear chain increases, the strength of the new extinction features increase strongly. These changes can be described by a tight-binding model for the coupled chain, which indicates that the origin of the phenomenon is consistent with an increased coupling between the nanoparticles. FDTD calculations reveal that the electric field is strongly enhanced between the nanoparticles in the chain. The DSPR response is found to be much more sensitive to dielectric changes than the localized surface plasmon resonance (LSPR).
Nanoparticle Chains; Plasmon; FDTD; LSPR; Nanoparticle Coupling
Multicomponent nanostructures with individual geometries have attracted much attention because of their potential to carry out multiple functions synergistically. The current work reports a simple method using particle lithography to fabricate multicomponent nanostructures of metals, proteins, and organosiloxane molecules, each with its own geometry. Particle lithography is well-known for its capability to produce arrays of triangular-shaped nanostructures with novel optical properties. This paper extends the capability of particle lithography by combining a particle template in conjunction with surface chemistry to produce multicomponent nanostructures. The advantages and limitations of this approach will also be addressed.
Recently, small (<5 nm diameter) nanoparticles (NPs) have shown improved in vivo biocompatibility compared to that of larger (>10 nm) NPs. However, the fate of small NPs under physiological conditions is poorly understood and remains unexplored. Here, the long-term aggregation behavior of gold nanoparticles (AuNPs) exposed to serum proteins in a near-physiological setup is studied using continuous photon correlation spectroscopy and computer simulations. It is found that the medium, temperature, and NP concentration affect the aggregation of AuNPs, but the observed aggregates are much smaller than previously reported. Simulations show that a single layer of albumin is deposited on the NP surface, but the properties of the aggregates (size, shape, and internal structure) depend critically on the charge distribution on the proteins, which changes with the conditions of the solution. These results explain the seemingly conflicting data reported in the literature regarding the size of aggregates and the morphology of the albumin corona. The simulations suggest that controlling the concentration of NPs as well as the pH and ionic strength of the solution prior to intravenous administration may help to preserve properties of the functionalized NPs in the bloodstream.
A new setup for pump-flow-probe X-ray absorption spectroscopy has been implemented at the SuperXAS beamline of the Swiss Light Source. It allows recording X-ray absorption spectra with a time resolution of tens of microseconds and high detection efficiency for samples with sub-mM concentrations. A continuous wave laser is used for the photoexcitation, with the distance between laser and X-ray beams and velocity of liquid flow determining the time delay, while the focusing of both beams and the flow speed define the time resolution. This method is compared with the alternative measurement technique that utilizes a 1 kHz repetition rate laser and multiple X-ray probe pulses. Such an experiment was performed at beamline 11ID-D of the Advanced Photon Source. Advantages, limitations and potential for improvement of the pump-flow-probe setup are discussed by analyzing the photon statistics. Both methods, with Co K-edge probing were applied to the investigation of a cobaloxime-based photo-catalytic reaction. The interplay between optimizing for efficient photoexcitation and time resolution as well as the effect of sample degradation for these two setups are discussed.
XTA; Time-resolved spectroscopy; cobaloxime; XANES; Photocatalysis; cobaloxime; XANES; pump-probe; LITR XAS
vapor-deposited on the SrTiO3(110) surface was studied
using scanning tunneling microscopy, photoemission spectroscopy (PES),
and density functional theory calculations. This surface forms a (4
× 1) reconstruction, composed of a 2-D titania structure with
periodic six- and ten-membered nanopores. Anchored at these nanopores,
Ni single adatoms are stabilized at room temperature. PES measurements
show that the Ni adatoms create an in-gap state located at 1.9 eV
below the conduction band minimum and induce an upward band bending.
Both experimental and theoretical results suggest that Ni adatoms
are positively charged. Our study produces well-dispersed single-adatom
arrays on a well-characterized oxide support, providing a model system
to investigate single-adatom catalytic and magnetic properties.
We use quantum coherence in a system consisting of one metallic nanorod and one semi-conductor quantum dot to investigate a plasmonic nanosensor capable of digital optical detection and recognition of single biological molecules. In such a sensor the adsorption of a specific molecule to the nanorod turns off the emission of the system when it interacts with an optical pulse having a certain intensity and temporal width. The proposed quantum sensors can count the number of molecules of the same type or differentiate between molecule types with digital optical signals that can be measured with high certainty. We show that these sensors are based on the ultrafast upheaval of coherent dynamics of the system and the removal of coherent blockage of energy transfer from the quantum dot to the nanorod once the adsorption process has occurred.
Quantum dots; quantum coherence; metallic; nanorods; nanosensors; dynamics
Alamethicin has been extensively studied as an antimicrobial peptide (AMP) and is widely used as a simple model for ion channel proteins. It has been shown that the antimicrobial activity of AMPs is related to their cell membrane orientation, which may be influenced by the phase of the lipid molecules in the cell membrane. The “healthy” cell membranes contain fluid phase lipids, while gel phase lipids can be found in injured or aged cells or in some phase separated membrane regions. Thus, investigations on how the phase of the lipids influences the membrane orientation of AMPs are important to understand more details regarding the AMP’s action on cell membranes. In this study, we determined the orientational changes of alamethicin molecules associated with planar substrate supported single lipid bilayers (serving as model cell membranes) with different phases (fluid or gel) as a function of peptide concentration using sum frequency generation (SFG) vibrational spectroscopy. The phase changes of the lipid bilayers were realized by varying the sample temperature. Our SFG results indicated that alamethicin lies down on the surface of fluid and gel phase 1,2-dimyristoyl(d54)-sn-glycero-3-phosphocholine (d-DMPC) lipid bilayers when the lipid bilayers are in contact with a peptide solution with a low concentration of 0.84 μM. However, at a medium peptide concentration of 10.80 μM, alamethicin inserts into the fluid phase lipid bilayer. Its orientation switches from a transmembrane to an in-plane (or lying down) orientation when the phase of the lipid bilayer changes from a fluid state to a gel state. At a high peptide concentration of 21.60 μM, alamethicin adopts a transmembrane orientation while associated with both fluid and gel phase lipid bilayers. We also studied the structural changes of the fluid and gel phase lipid bilayers upon their interactions with alamethicin molecules at different peptide concentrations.
sum frequency generation; alamethicin; supported lipid bilayers; membrane orientation; lipid phase
Two C60-(antenna)x analogous compounds having branched hybrid triad C60(>DPAF-C18)(>CPAF-C2M) and tetrad C60(>DPAF-C18)(>CPAF-C2M)2 nanostructures were synthesized and characterized. The structural design was intended to facilitate the ultrafast fs intramolecular energy-transfer from photoexcited C60[>1(DPAF)*-C18](>CPAF-C2M)1or2 or C60(>DPAF-C18)[>1(CPAF)*-C2M]1or2 to the C60> cage moiety upon two-photon pumping at either 780 or 980 nm, respectively. The latter nanostructure showed approximately equal extinction coefficients of optical absorption over 400–550 nm that corresponds to near-IR two-photon based excitation wavelengths at 780–1100 nm for broadband nonlinear optical (NLO) applications. Aside from their enhanced two-photon absorption (2PA) activity at 780 nm, we also demonstrated ultrafast photo-responses at 980 nm showing 2PA cross-section (σ2) values of 995–1100 GM for the hybrid tetrad. These σ2 values were correlated to the observed good efficiency in reducing fs light-transmittance down to 35% at the light intensity of 110 GW/cm2. Accordingly, 2PA characteristics of these nanostructures at multiple NIR wavelengths provided support for their suitability in uses as broadband NLO nanomaterials at 600–1100 nm that includes the 2PA ability of two antenna, DPAF (700–850 nm) and CPAF (850–1100 nm), and the fullerene cage at shorter wavelengths (600–700 nm).
C60-(antenna)x nanostructures; ultrafast intramolecular energy-transfer; NIR two-photon absorption; broadband NLO materials; femtosecond light-transmittance reduction
Directional control over fluorescence emission is important for improving the sensitivity of fluorescence based techniques. In recent years, plasmonic and photonic structures have shown great promise in shaping the spectral and spatial distribution of fluorescence, which otherwise is typically isotropic in nature and independent of the observation direction. In this work we have explored the potential of metal-dielectric-metal (MDM) structures composed of Au, Ag or Al in steering the fluorescence emission from various probes emitting in the NIR, Visible or UV/blue region. We show that depending on the optical properties of the metal and the thickness of the dielectric layer, the emission from randomly oriented fluorophores embedded within the MDM substrate is transformed into beaming emission normal to the substrate. Agreement of the observed angular emission patterns with reflectivity calculations reveals that the directional emission is due to the coupling of the fluorescence with the electromagnetic modes supported by the MDM structure.
Metal-Dielectric-Metal; Fluorescence; Directional Emission; Surface-Plasmon-Coupled Emission; Fabry-Perot Mode
Gd(III) associated with carbon nanomaterials relaxes water proton spins at an effectiveness that approaches or exceeds the theoretical limit for a single bound water molecule. These Gd(III)-labeled materials represent a potential breakthrough in sensitivity for Gd(III)-based contrast agents used for magnetic resonance imaging (MRI). However, their mechanism of action remains unclear. A gadographene library encompassing GdCl3, two different Gd(III)-complexes, graphene oxide (GO), and graphene suspended by two different surfactants and subjected to varying degrees of sonication was prepared and characterized for their relaxometric properties. Gadographene was found to perform comparably to other Gd(III)-carbon nanomaterials; its longitudinal (r1) and transverse (r2) relaxivity is modulated between 12–85 mM−1s−1 and 24–115 mM−1s−1, respectively, depending on the Gd(III)-carbon backbone combination. The unusually large relaxivity and its variance can be understood under the modified Florence model incorporating the Lipari-Szabo approach. Changes in hydration number (q), water residence time (τM), molecular tumbling rate (τR), and local motion (τfast) sufficiently explain most of the measured relaxivities. Furthermore, results implicated the coupling between graphene and Gd(III) as a minor contributor to proton spin relaxation.
gadolinium; graphene; graphene oxide; relaxivity; modified Florence NMRD program
der Waals (vdW) forces play a fundamental role in the structure
and behavior of diverse systems. Because of development of functionals
that include nonlocal correlation, it is possible to study the effects
of vdW interactions in systems of industrial and tribological interest.
Here we simulated within the framework of density functional theory
(DFT) the adsorption of isooctane (2,2,4-trimethylpentane) and ethanol
on an Fe(100) surface, employing various exchange–correlation
functionals to take vdW forces into account. In particular, this paper
discusses the effect of vdW forces on the magnitude of adsorption
energies, equilibrium geometries, and their role in the binding mechanism.
According to our calculations, vdW interactions increase the adsorption
energies and reduce the equilibrium distances. Nevertheless, they
do not influence the spatial configuration of the adsorbed molecules.
Their effect on the electronic density is a nonisotropic, delocalized
accumulation of charge between the molecule and the slab. In conclusion,
vdW forces are essential for the adsorption of isooctane and ethanol
on a bcc Fe(100) surface.
organic semiconductor (MDMO-PPV) was used for testing a
modified version of a photoelectrochemical scanning droplet cell microscope
(PE-SDCM) adapted for use with nonaqueous electrolytes and containing
an optical fiber for localized illumination. The most attractive features
of the PE-SDCM are represented by the possibility of addressing small
areas on the investigated substrate and the need of small amounts
of electrolyte. A very small amount (ng) of the material under study
is sufficient for a complete electrochemical and photoelectrochemical
characterization due to the scanning capability of the cell. The electrochemical
behavior of the polymer was studied in detail using potentiostatic
and potentiodynamic investigations as well as electrochemical impedance
spectroscopy. Additionally, the photoelectrochemical properties were
investigated under illumination conditions, and the photocurrents
found were at least 3 orders of magnitude higher than the dark (background)
current, revealing the usefulness of this compact microcell for photovoltaic
hybrid thin films of CuSCN and rhodamine B (RB)
are electrochemically self-assembled (ESA) by cathodic electrolysis
in an ethanol/water mixture containing Cu2+, SCN–, and RB. By selecting the solvent, Cu2+/SCN– ratio, and the concentration of RB, we demonstrate several control
parameters in the film formation. High loading of RB into the film
has been achieved to reach a CuSCN:RB volume ratio of approximately
2:1. The RB solid could almost completely be extracted from the hybrid
film by soaking the film in dimethylacetamide (DMA), leading to a
large increase of the surface area. The crystallographic orientation
of the nanostructure with respect to the substrate can be controlled.
Efficient quenching of fluorescence of RB has been observed for the
CuSCN/RB hybrid film, implying hole injection from RB excited state
to CuSCN. Photoelectrochemical study on the porous crystalline CuSCN
obtained after the DMA treatment and sensitized with RB revealed sensitized
photocathodic action under visible light illumination, indicating
the potential usefulness of the porous CuSCN electrodes for construction
of tandem dye-sensitized solar cells.
In this paper, we developed a metal-enhanced fluorescence (MEF) substrate by modification of the commercially available surface enhanced Raman spectroscopy (SERS) substrate that may meet the reproducibility and sensitivity challenge of MEF. In spite of many studies and interest on MEF from a number of research groups, application to real-world situations and its commercial use remain challenging mainly due to the difficulties in fabricating reproducible MEF substrates. Specifically, one of the challenges is achieving a standardized MEF substrate for reproducible fluorescence intensity enhancement and/or changes in lifetime. The gold standard klarite substrates for SERS were coated with a thin layer of silver nanoparticles for MEF studies. To test the newly developed MEF substrates, a monolayer of streptavidin conjugated Alexa-647 was assembled on biotinylated-glass or MEF substrates. We observed over 50-fold increase in the fluorescence intensity from a monolayer of streptavidin conjugated Alexa-647 on the biotinylated MEF substrate compared to the same on glass substrate. A significant reduction in the lifetime and increased photostability of Alexa-647 on MEF substrate was observed. Fluorescence lifetime imaging was performed on the monolayer of dye assembled on the modified SERS substrates. We expect this study will serve as a platform to encourage the future use of a standardized MEF substrate for a plethora of sensing applications.
metal-enhanced fluorescence; fluorescence; SERS substrates; fluorescence lifetime imaging
plasmon modes in metallic nanostructures largely determine their optoelectronic
properties. Such plasmon modes can be manipulated by changing the
morphology of the nanoparticles or by bringing plasmonic nanoparticle
building blocks close to each other within organized assemblies. We
report the EELS mapping of such plasmon modes in pure Ag nanocubes,
Au@Ag core–shell nanocubes, and arrays of Au@Ag nanocubes.
We show that these arrays enable the creation of interesting plasmonic
structures starting from elementary building blocks. Special attention
will be dedicated to the plasmon modes in a triangular array formed
by three nanocubes. Because of hybridization, a combination of such
nanotriangles is shown to provide an antenna effect, resulting in
strong electrical field enhancement at the narrow gap between the
Unambiguous evidence for covalent sidewall functionalization of single-walled carbon nanotubes (SWCNTs) has been a difficult task, especially for nanomaterials in which slight differences in functionality structure produce significant changes in molecular characteristics. Nuclear magnetic resonance (NMR) spectroscopy provides clear information about the structural skeleton of molecules attached to SWCNTs. In order to establish the generality of proton NMR as an analytical technique for characterizing covalently functionalized SWCNTs, we have obtained and analyzed proton NMR data of SWCNT-substituted benzenes across a variety of para substituents. Trends obtained for differences in proton NMR chemical shifts and the impact of o-, p-, and m-directing effects of electrophilic aromatic substituents on phenyl groups covalently bonded to SWCNTs are discussed.
Chemical shift changes; SWCNT-substituted benzenes; p-substituted phenyl groups; electronic effects
We describe a novel method for creating luminescent lanthanide-containing nanoparticles in which the lanthanide cations are sensitized by the semiconductor nanoparticle’s electronic excitation. In contrast to previous strategies, this new approach creates such materials by addition of external salt to a solution of fully formed nanoparticles. We demonstrate this post-synthetic modification for the lanthanide luminescence sensitization of two visible emitting lanthanides (Ln), Tb3+ and Eu3+ ions, through ZnS nanoparticles in which the cations were added post-synthetically as external Ln(NO3)3·xH2O salt to solutions of ZnS nanoparticles. The post-synthetically treated ZnS nanoparticle systems display Tb3+ and Eu3+ luminescence intensities that are comparable to those of doped Zn(Ln)S nanoparticles, which we reported previously (J. Phys. Chem. A, 2011, 115, 4031–4041). A comparison with the synthetically doped systems is used to contrast the spatial distribution of the lanthanide ions, bulk versus surface localized. The post-synthetic strategy described in this work is fundamentally different from the synthetic incorporation (doping) approach and offers a rapid and less synthetically demanding protocol for Tb3+:ZnS and Eu3+:ZnS luminophores, thereby facilitating their use in a broad range of applications.
Trivalent Lanthanide; Luminescence; II–VI Nanoparticles; Post-synthetic strategy
Single- and double-strand breaks induced by soft X-rays (1.5 keV) and photo-emitted LEEs (0–30 eV) were measured in dry and humid thin films of plasmid DNA irradiated under different controllable levels of oxygen at standard ambient temperature and pressure (SATP). G values derived from these experiments shows that the presence of H2O and changing the atmosphere from N2 to O2, while keeping all other experimental parameters constant, increases the formation of DSBs by factors of 4.5 and 11.8 for X-rays and LEEs, respectively. Under an oxygenated environment in humid DNA films, the additional LEE-induced damage resulting from the combination of water and oxygen exhibits a supper-additive effect, which leads to the formation of DSBs with a G value almost 7 times higher than that obtained by X-ray photons. These results indicate that O2, H2O and LEEs effectively contribute synergistically to enhance the formation of DSBs.
PMID: 24976877 CAMSID: cams3763
radiation damage; single- and double- strand break; hydration level; oxygen fixation