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The evaluation of electrochemical sensing activity of hydrothermally derived PPy-MoS2-based nanocomposites subjected to 90 MeV C6+ ion beam with fluence ranging, 1.0 × 1010–1.0 × 1013 ions/cm2, is reported. Cross-linking, chain scissioning, and ion track formation could occur in the irradiated systems, as revealed from Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FE-SEM) studies. Electrochemical studies, viz., cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed in 0.1 M phosphate buffer solution (PBS) containing 5 mM K3[Fe(CN)6] as redox probe. High redox activity, lower charge transfer resistance (Rct = 490 Ω) and larger electroactive area (A = 0.4485 cm2) were obtained in case of the composite system irradiated with a fluence of 3.5 × 1011 ions/cm2. Immunosensor fabrication was executed via immobilization of mouse IgG over the pristine and post-irradiated electrodes. Afterwards, differential pulse voltammetry (DPV) was performed within the potential window − 0.2 to + 0.6 V (vs. Ag/AgCl) for the detection of specific analyte. Noticeably, the electrode system irradiated with a fluence of 3.5 × 1011 ions/cm2 is characterized by a lower limit of detection (LOD) of 0.203 nM and a higher sensitivity value of 10.0 µA mL ng−1 cm−2. The energetic particle irradiation at a modest fluence can offer beneficial effects to the PPy-MoS2-based nanohybrid system providing immense scope as advanced electrochemical biosensor. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS), with high sensitivity to a broad range of molecules, can detect molecular "fingerprints" in a complex substance and thereby offers a promising solution for noninvasive medical diagnostics and personal healthcare monitoring. The eventual realization of such applications relies on SERS substrates with dense and uniform hot spots, good chemical stability, and high mechanical durability. With these criteria in mind, we developed a flexible nanoporous SERS substrate via the in situ synthesis of gold nanostars (AuNSs) on an ion-track-etched polycarbonate membrane. The nanoporous SERS substrate can realize analyte enrichment and exhibit excellent Raman performance by taking the advantage of hot spots on AuNSs. The SERS substrate yields highly repeatable and uniform signals for analytes (e.g., methylene blue) over a wide concentration range from 10–4 to 10–13 M. The flexible SERS substrate even can work well after 2000 times bending and exhibit excellent stability for long-term use. It can be prepared on a large scale with a low-cost and simple fabrication process and can be used repeatedly after cleaning to reduce the use-cost further. On-body experiments prove that the sweat SERS substrate allows effective identification of sweat contents, such as lactic acid and uric acid (UA), and the monitoring of diet-induced variation in sweat UA. The potential of the wearable nanoporous SERS substrates in sweat analysis thus has been demonstrated, opening possibilities for autonomous and noninvasive medical health monitoring. [ABSTRACT FROM AUTHOR]

Deep sub-micron memory devices play a crucial role in space electronic applications due to their susceptibility to single-event upset and double-node upset types of soft errors. When a charged particle from space hit a scaled memory circuit, the critical charge of sensitive storage nodes drops, and a node upset happens across the storage nodes. This paper describes the soft error immune RHBD-14T SRAM cell (SEI-14T) for space and satellite applications. The SEI-14T memory cell consists of two latch circuits coupled in a self-recovering, state-restoring feedback manner. In addition, SEI-14T memory cell mitigate single event upset (SEU) in all sensitive nodes and a portion of double node upset. By considering the sensitive node area separation approach, the remaining upset pairs were recovered. To show the relative performance of the SEI-14T, the state-of-the-art of other radiation-resistant memory cells, such as the Quatro-10T, RHM-12T, RHD-12T, RSP-14T, RHPD-12T, RH-14T, EDP-12T, and QCCS-12T are considered. Compared to all other mentioned memory cells, SEI-14T has superior write stability, and greater read stability than all other memory cells. Furthermore, at 0.8 V supply voltage, SEI-14T minimizes 23%, 12.28% and 20.82% of read access time, write access time and static power consumption respectively compared to existing memory cells. Moreover, the critical charge of SEI-14T was $8.85\times / 6.56\times / 3.4\times / 5.75\times / 2.54\times / 2.47\times / 1.81\times / 1.63\times / 1.44\times $ times larger than 6T-SRAM/ Quatro-10T/ RHM-12T/ RHD-12T/ RSP-14T/ RHPD-12T/ RH-14T/ EDP-12T/ QCCS-12T memory cells.

This work reports molecular dynamics (MD) simulations of the formation of detailed ion track structures at the atomic scale in polymers. To simulate the initial chemical reactions and the subsequent thermal movement of polymer molecules, an adapted thermal spike model was implemented using a charge-implicit reactive force field potential. The MD simulation reproduces the physical–chemical process of ion track formation observed in the experiment, e.g., the bond breakage and creation, gas production and release, carbonization effect, and the relative radial density distributions, which are consistent with small angle X-ray scattering results of ion tracks in polyethylene terephthalate generated with 15.9 keV nm−1 Au and 10.9 keV nm−1 Xe ions, respectively. Based on the MD simulation, the ion tracks in polymers show a heavily-damaged core region with an inhomogeneous nanoporous structure, and a surrounding transition region with the mass density increasing gradually back to the same value as the pristine sample. [ABSTRACT FROM AUTHOR]

The aim of this experimental work was to investigate the influence of the ion beam charge state on damage production in nanomaterials. To achieve this, we employed Raman spectroscopy, atomic force microscopy, and transmission electron microscopy to investigate nanomaterials irradiated by a 23 MeV I beam. We found a significant influence of the ion charge state on damage production in monolayer graphene, but found no evidence of this effect in bilayer and trilayer graphene, nor in graphite. Furthermore, we found no evidence of this effect in CaF2 and SiO2 nanocrystals irradiated with the same ion beam. [ABSTRACT FROM AUTHOR]

This paper reports the electronic excitation and related energy transfer by swift (∼MeV/u) heavy ions on the basis of the Wave-Packet Model (WPM) in the extended version, by introducing the binding energy separation into energy transfer. This method makes it possible to estimate both the ionization component of the electronic stopping cross section and the ionization cross section (ICS) of an atom in the dielectric formalism under ion-impact and electron-impact. Applying the present theory to a superconducting material EuBa 2 Cu 3 O 7 (EBCO), it was found that the track diameter has a linear correlation with the primary ionization density more clearly than with the electronic stopping. This correlation is well described by a proposed model. The present analysis showed that the WPM method has a useful advantage to investigate the irradiation effect under swift heavy-ion impact. [ABSTRACT FROM AUTHOR]

The aim of this experimental work was to investigate the influence of the ion beam charge state on damage production in nanomaterials. To achieve this, we employed Raman spectroscopy, atomic force microscopy, and transmission electron microscopy to investigate nanomaterials irradiated by a 23 MeV I beam. We found a significant influence of the ion charge state on damage production in monolayer graphene, but found no evidence of this effect in bilayer and trilayer graphene, nor in graphite. Furthermore, we found no evidence of this effect in CaF2 and SiO2 nanocrystals irradiated with the same ion beam.

Quartz (SiO2) crystals possess intrinsic columnar pores perpendicular to (0001) surfaces, consisting of three- and six-membered ring (3MR and 6MR) structures of Si and O atoms. The diameters of the larger pores, i.e., 6 MRs, are ~0.49 nm, while the diameters of fullerene (C60) ions are 0.7 nm, i.e., larger than either type of the pores. Transmission electron microscopy observation evidenced approximately two times longer ion tracks in the channeling condition, i.e., 0° incidence to (0001) surface, than an off-channeling condition, i.e., 7° incidence in this case, under 6 MeV C60 ion injection. The track length at the 0° incidence decreases more steeply than that at the 7° incidence with decreasing the energy from 6 MeV to 1 MeV. Finally, the track lengths at the 0° and 7° incidences become comparable, i.e., the channeling-like effect disappears at 1 MeV irradiation. This study experimentally indicates that the channeling-like effect of C60 ions is induced in quartz crystals, while the sizes of the channels are smaller than the C60 ions.

ZnSe 2 O 5 nanocrystals with an orthorhombic structure were synthesized by electrochemical deposition into a-SiO 2 /n-Si ion track template formed by 200 MeV Xe ion irradiation with the fluence of 107 ions/cm2. The lattice parameters determined by the X-ray diffraction and calculated by the CRYSTAL computer program package are very close to each other. It was shown that ZnSe 2 O 5 has a direct band gap of 2.8 eV at the Γ-point. In addition, the calculated charge distribution and chemical bonds show that the crystal has an ion-covalent nature. The photoluminescence excited by photons at 300 nm has a low intensity arising mainly due to zinc and oxygen vacancies. [ABSTRACT FROM AUTHOR]

Nanochannel gating exists extensively in biological systems and has wide applications in nanofluidic studies. Magnetic control is non‐contact and penetrative compared to chemical or electrical gating. This work introduces the fabrication of magnetically gated single nanochannels by grafting superparamagnetic nanoparticles, via bridging of DNA single strands, onto the inner surface of the PET nanochannels which were prepared by single ion hit and ion track etching. The nanochannel showed sub‐second magnetic response with an ON/OFF ratio of 18 measured by ionic conductance under control with a permanent magnet. These magnetically gated single PET nanochannel are speficically advantageous for superficial drug‐delivery and non‐contact control in nanofluidic applications. [ABSTRACT FROM AUTHOR]

We present results of a systematic study of the morphology of etched ion tracks in amorphous SiO 2 using a combination of small angle X-ray scattering (SAXS) and scanning electron microscopy. We focus on the analysis of SAXS data obtained in grazing incidence (GISAXS) configuration from conical etched channels with a base radius of less than 50 nm. Swift heavy ion irradiation of 2 μm thick thermally grown SiO 2 layers with 185 MeV Au ions was conducted at the ANU Heavy Ion Accelerator Facility in Canberra, Australia. Low irradiation fluences of 109 ions per cm2 were chosen to minimize overlap of the etched structures. Irradiated samples were etched in aqueous hydrofluoric acid (HF) with concentrations of 5%, for etching times between 30 and 90 s. In grazing incidence configuration, we obtain good data quality from the very small cones, since the X-ray beam interacts with a greater proportion of the sample at the very low incidence angle compared with normal transmission mode. [ABSTRACT FROM AUTHOR]

• Detection thresholds of PET for B, C, N and O ions are determined using Radial Electron Fluence around Ion Tracks (REFIT). • Track response curve expressed by REFIT is compared to other physical parameters such as the stopping power, Z eff /β and REL. • Advantage for the use of REFIT is indicated. We try to establish a universal description for the response curve (i.e., relation between the track registration sensitivity and a physical parameters) of polyethylene terephthalate (PET) as a polymeric nuclear track detector. To do so, we adopt a newly developed physical concept Radial Electron Fluence around Ion Tracks (REFIT) using a Monte Carlo simulation in Geant4-DNA, which has been defined as the number of secondary electrons passing through a cylindrical surface that is co-axial to the ion path. We find 11% disagreement for the description of the detection thresholds, from which etch pits start their evolutions when the value of REFIT at a radius of 4.0 nm is used. However, compared to other physical parameters, the REFIT offers improved parameters for the detection thresholds of PET, such as the stopping power, Z eff /β and REL ω0=1000 eV. Finally, we discuss future issues affecting implementation of REFIT. [ABSTRACT FROM AUTHOR]

Gold and platinum nanoparticles of few-nm size were deposited on amorphous silicon nitride (a-SiN) films. These samples were irradiated with 380 MeV Au ions at grazing incident angles (θ i = 2°–5°) to a fluence of ∼1 × 1010 ions/cm2. The irradiated samples were observed using transmission electron microscopy (TEM). Ion tracks were clearly observed as long bright lines. Nanoparticles were found to be desorbed from long and narrow regions along the ion tracks. The surface temperature at the thermal spike produced by the ion impact was evaluated from the observed nanoparticle desorption. The observed temperature distribution is qualitatively explained by a one-dimensional two temperature model (1D-TTM) although there are some discrepancies which may be attributed to the surface effects which are not taken into account in 1D-TTM. [ABSTRACT FROM AUTHOR]

High energy ion irradiation is an important tool for nanoscale modification of materials. In the case of thin targets and 2D materials, which these energetic ions can pierce through, nanoscale modifications such as production of nanopores can open up pathways for new applications. However, materials modifications can be hindered because of subsequent energy release via electron emission. In this work, we follow energy dissipation after the impact of an energetic ion in thin graphite target using Geant4 code. Presented results show that significant amount of energy can be released from the target. Especially for thin targets and highest ion energies, almost 40% of deposited energy has been released. Therefore, retention of deposited energy can be significantly altered and this can profoundly affect ion track formation in thin targets. This finding could also have broader implications for radiation hardness of other nanomaterials such as nanowires and nanoparticles.

Both silicon and graphite are radiation hard materials with respect to swift heavy ions like fission fragments and cosmic rays. Recrystallisation is considered to be the main mechanism of prompt damage anneal in these two materials, resulting in negligible amounts of damage produced, even when exposed to high ion fluences. In this work we present evidence that these two materials could be susceptible to swift heavy ion irradiation effects even at low energies. In the case of silicon, ion channeling and electron microscopy measurements reveal significant recovery of pre-existing defects when exposed to a swift heavy ion beam. In the case of graphite, by using ion channeling, Raman spectroscopy and atomic force microscopy, we found that the surface of the material is more prone to irradiation damage than the bulk.

The influence of the charge state q on surface modifications induced by the impact of individual fast, heavy ions on muscovite mica was investigated. Beams of 593 MeV 197Auq+ with well-defined initial charge states over a relatively broad range of values (30 to 51) and at different irradiation geometries were used. At normal incidence, the impact features are rounded protrusions (hillocks) with ≳20 nm in diameter. At grazing angles, besides the hillocks, craters and elongated tails (up to 350 nm-long) extending along the direction of ion penetration are produced. It is shown that the impact features at normal incidence depend strongly on the initial charge state of the projectiles. This dependence is very weak at grazing angles as the ion reaches the equilibrium charge state closer to the surface. At normal ion incidence, the hillock volume scales with q3.3 ± 0.6. This dependence stems largely from the increase in the hillock height, as a weak dependence of the diameter was observed.

We report on the first observation of fine structure of latent tracks in rutile TiO 2 , which changes from cylinder to dumbbell-shape and then to sandglass-shape as a function of the ion path length. Moreover, the cone length of the track was found to be dependent on electronic energy loss. The results indicate that outflow of the thermal spike-induced molten phase produces the hillocks on surface and the void-rich zone near surface after epitaxial recrystallization due to material deficit, while at a deep depth, the lack of efficient outflow and recrystallization result in the absence of tracks. We propose that the various morphologies of tracks in rutile TiO 2 are a consequence of the molten phase outflow and recrystallization during rapid cooling down. [ABSTRACT FROM AUTHOR]

Abstract Ion track formation in amorphous SiO 2 was investigated using infrared spectroscopy. For comparison, one set of samples was also irradiated using 1.25 MeV gamma rays. An increase of 1044 cm−1 peak and decrease of 1078 cm−1 peak was observed in all cases. Experimental results were analysed using an analytical thermal spike model and non-standard model parameters were found. This finding is attributed to the amorphous structure of the material. Highlights • Damage kinetics in a-SiO 2 due to swift heavy ion and gamma ray irradiation was measured using infrared spectroscopy. • Ion track cross sections were compared to the predictions of the analytical thermal spike model. • Available literature data on ion tracks in a-SiO 2 was analysed using analytical thermal spike model. [ABSTRACT FROM AUTHOR]

Abstract We present a systematic study of the evolution of chemically etched ion tracks formed in thermally grown a-SiO 2 after irradiation with 1.1 GeV and 185 MeV Au ions. The irradiated material was subsequently etched with 2.5% hydrofluoric acid (HF) for different times yielding hollow conical shaped structures of various sizes. The characterisation of these structures was carried out by synchrotron-based small-angle X-ray scattering (SAXS) measurements, enabling the determination of the geometry and dimensions of the etched conical structures with sub-nanometre precision. The results indicate that the track etching behavior is influenced by the ion energy, and that at short etching times the latent track damage in the radial direction becomes significant. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ion track formation in polycarbonate is characterized by a damage zone of ∼2.5 nm radius with a density deficit of ∼5% • The stoichiometry of the damage track shows equal loss of C and O and increased H loss. • Annealing leads to track recovery by diffusion predominately from a track halo area of ∼5 nm radius. Abstract Ion tracks created in polycarbonate foils by irradiation with 2.2 GeV Au ions were characterized using a combination of small-angle x-ray and neutron scattering (SAXS/SANS) and Fourier transform infrared spectroscopy (FTIR). The ion tracks were found to consist of a cylindrical damage core with a radius of ∼2.5 ± 0.2 nm and a relative density approximately 5% below that of the pristine polycarbonate. Upon exposure to thermal annealing between 100 and 200 °C, the tracks were observed to double in size. Simultaneously, this led to a recovery in the density of the ion track, reaching a value just below that of the pristine polymer. A mechanism is proposed that explains this behavior by diffusion of radiolysis products/material flow into the under-dense track core from the surrounding region. Treatment of the tracks with UV radiation has shown no significant change in the track structure and size. [ABSTRACT FROM AUTHOR]

Latent ion tracks created by energetic heavy ions (12 MeV Ti to 946 MeV Au) in single crystal SrTiO 3 are investigated using Rutherford backscattering spectrometry and scanning transmission electron microscopy. The results demonstrate that pre-existing irradiation damage, introduced via elastic collision processes, interacts synergistically with the electronic energy deposition from energetic heavy ions to enhance formation of latent ion tracks. The average amorphous cross-section increases with the level of pre-damage and is linearly proportional to the electronic energy loss of the ions, with a slope dependent on the pre-damage level. For the highest energy ions (629 MeV Xe and 946 MeV Au), the tracks are continuous over the pre-damaged depth, but become discontinuous beyond the pre-damaged region. This work provides new understanding and insights on ion-solid interactions that significantly impact the interpretation of latent track formation processes, models of amorphization, and the fabrication of electro-ceramic devices. [ABSTRACT FROM AUTHOR]

In swift heavy ion track-based polymeric biosensor foils with incorporated enzymes one exploits the correlation between the analyte concentration and the sensor current, via the enrichment of charged enzymatic reaction products in the track’s confinement. Here we study the influence of the etched track radius on the biosensor’s efficiency. These sensors are analyte-specific only if both the track radii and the analyte concentration exceed certain threshold values of ∼15 nm and ∼10 −6  M (for glucose sensing), respectively. Below these limits the sensor signal stems un-specifically from any charge carrier. In its proper working regime, the inner track walls are smoothly covered by enzymes and the efficiency is practically radius independent. Theory shows that the measured current should be slightly sub-proportional to the analyte concentration; the measurements roughly reconfirm this. Narrower tracks (∼5–15 nm radius) with reduced enzyme coverage lead to decreasing efficiency. Tiny signals visible when the tracks are etched to effective radii between 0 and ∼5 nm are tentatively ascribed to enzymes bonded to surface-near nano-cracks in the polymer foil, resulting from its degradation due to aging, rather than to the tracks. Precondition for this study was the accurate determination of the etched track radii, which is possible only by a nanofluidic approach. This holds to some extent even for enzyme-covered tracks, though in this case most of the wall charges are compensated by enzyme bonding. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the feasibility of ion beam analysis techniques for monitoring swift heavy ion track formation. First, the use of the in situ Rutherford backscattering spectrometry in channeling mode to observe damage build-up in quartz SiO2 after MeV heavy ion irradiation is demonstrated. Second, new results of the in situ grazing incidence time-of-flight elastic recoil detection analysis used for monitoring the surface elemental composition during ion tracks formation in various materials are presented. Ion tracks were found on SrTiO3, quartz SiO2, a-SiO2, and muscovite mica surfaces by atomic force microscopy, but in contrast to our previous studies on GaN and TiO2, surface stoichiometry remained unchanged. Third, the usability of high resolution particle induced X-ray spectroscopy for observation of electronic dynamics during early stages of ion track formation is shown. [ABSTRACT FROM AUTHOR]

High-aspect ratio porous structures with controllable pore diameters and without a stiff substrate can be fabricated using the ion track technique. Atomic layer deposition is an ideal technique for depositing thin films and functional surfaces on complicated 3D structures due to the high conformality of the films. In this work, we studied Al 2 O 3 and TiO 2 films grown by ALD on pristine polyimide (Kapton HN) membranes as well as polyimide membranes etched in sodium hypochlorite (NaOCl) and boric acid (BO 3 ) solution by means of RBS, PIXE, SEM-EDX and helium ion microcopy (HIM). The focus was on the first ALD growth cycles. The areal density of Al 2 O 3 film in the 400 cycle sample was determined to be 51 ± 3 × 10 16 at./cm 2 , corresponding to the thickness of 55 ± 3 nm. Furthermore, the growth per cycle was 1.4 Å/cycle. The growth is highly linear from the first cycles. In the case of TiO 2 , the growth per cycle is clearly slower during the first 200 cycles but then it increases significantly. The growth rate based on RBS measurements is 0.24 Å/cycle from 3 to 200 cycles and then 0.6 Å/cycle between 200 and 400 cycles. The final areal density of TiO 2 film after 400 cycles is 148 ± 3 × 10 15 at./cm 2 which corresponds to the thickness of 17.4 ± 0.4 nm. The modification of the polyimide surface by etching prior to the deposition did not have an effect on the Al 2 O 3 and TiO 2 growth. [ABSTRACT FROM AUTHOR]