Precise local control of liquid crystal pretilt on polymer layers by focused ion beam nanopatterning

• Maxim V. Gorkunov,
• Irina V. Kasyanova,
• Vladimir V. Artemov,
• Alena V. Mamonova and
• Serguei P. Palto

Beilstein J. Nanotechnol. 2019, 10, 1691–1697, doi:10.3762/bjnano.10.164

• through the LC layer. Due to the LC birefringence, they acquire different optical paths: for the x-polarized state, and for the y-polarized state. For a relatively weak birefringence Δn = ne − no, we can write the measured phase retardation approximately as which is formally x-dependent. Substituting

Magnetic segregation effect in liquid crystals doped with carbon nanotubes

• Danil A. Petrov,
• Pavel K. Skokov,
• Alexander N. Zakhlevnykh and
• Dmitriy V. Makarov

Beilstein J. Nanotechnol. 2019, 10, 1464–1474, doi:10.3762/bjnano.10.145

• distortions in the orientational structure, the refractive index of the ordinary ray no remains unchanged, and the refractive index of the extraordinary ray ne will decrease and approach the value of no. Above the Fréedericksz transition the value of the effective refractive index neff depending on the angle

• the optical phase lag, in Equation 24 we change from integration over the coordinate ζ to integration over the angle φ using Equation 10, then Equation 24 can be written as Here, δ0 = 2πL(ne − no)/λ is the phase lag in the absence of a magnetic field, and the notation is introduced. In Equation 25

• passing through the NLC cell with a CNT impurity. For calculations we use the values of the refractive index of the liquid crystal 5CB (no = 1.53, ne = 1.71 for λ = 632.8 nm [45]), on the basis of which NLC–CNT mixtures can be prepared [24][32][50]. From Figure 7 it can be seen that in the initial planar

Molecular attachment to a microscope tip: inelastic tunneling, Kondo screening, and thermopower

• Rouzhaji Tuerhong,
• Mauro Boero and
• Jean-Pierre Bucher

Beilstein J. Nanotechnol. 2019, 10, 1243–1250, doi:10.3762/bjnano.10.124

• tunneling microscope (Modified Createc LT-STM) equipped with a vector magnetic field of 1 T. As described in [21], the Au(111) single crystal was cleaned by repeated cycles of Ne+ ion bombardment followed by thermal annealing at 800 K. The MnPc molecules were evaporated from an Al2O3 crucible heated by

Correlation of surface-enhanced Raman scattering (SERS) with the surface density of gold nanoparticles: evaluation of the critical number of SERS tags for a detectable signal

• Vincenzo Amendola

Beilstein J. Nanotechnol. 2019, 10, 1016–1023, doi:10.3762/bjnano.10.102

• micro-Raman instrument (CCD detector with 100 mm slits) on the TEM grids containing the AuNTs and using the 633 nm line of a He–Ne laser. The laser power at the entrance pupil of the microscope objective was 0.85 mW, corresponding to 0.65 mW at the output of the microscope objective (measured with a

Nanoscale optical and structural characterisation of silk

• Meguya Ryu,
• Reo Honda,
• Adrian Cernescu,
• Arturas Vailionis,
• Armandas Balčytis,
• Jitraporn Vongsvivut,
• Jing-Liang Li,
• Denver P. Linklater,
• Elena P. Ivanova,
• Vygantas Mizeikis,
• Mark J. Tobin,
• Junko Morikawa and
• Saulius Juodkazis

Beilstein J. Nanotechnol. 2019, 10, 922–929, doi:10.3762/bjnano.10.93

• (LC) retarder, which was inserted with its slow-axis perpendicular to the orientation of the silk fiber (see inset in Figure 3b). Using such a geometry, it is possible to compensate for the birefringence of the silk fibers, Δn ≡ ne − no > 0, with a phase delay imparted by the LC retarder. When the

An efficient electrode material for high performance solid-state hybrid supercapacitors based on a Cu/CuO/porous carbon nanofiber/TiO₂ hybrid composite

• Mamta Sham Lal,
• Thirugnanam Lavanya and
• Sundara Ramaprabhu

Beilstein J. Nanotechnol. 2019, 10, 781–793, doi:10.3762/bjnano.10.78

• and a transmission electron microscope (JEOL JEM 2100) operating at 200 kV. The crystalline structure was identified using a Rigaku Rintz Ultima X-ray diffraction unit. Raman spectra were analyzed by a LabRAM HP 800 UV with a 632 nm He–Ne laser as the excitation source in the range of 100–3000 cm−1 at

Site-controlled formation of single Si nanocrystals in a buried SiO₂ matrix using ion beam mixing

• Xiaomo Xu,
• Thomas Prüfer,
• Daniel Wolf,
• Hans-Jürgen Engelmann,
• Lothar Bischoff,
• René Hübner,
• Karl-Heinz Heinig,
• Wolfhard Möller,
• Stefan Facsko,
• Johannes von Borany and
• Gregor Hlawacek

Beilstein J. Nanotechnol. 2018, 9, 2883–2892, doi:10.3762/bjnano.9.267

• + or Ne+ ion beam mixing of Si into a buried SiO2 layer followed by thermally activated phase separation. Binary collision approximation and kinetic Monte Carlo methods are conducted to gain atomistic insight into the influence of relevant experimental parameters on the Si NC formation process. Energy

• -filtered transmission electron microscopy is performed to obtain quantitative values on the Si NC size and distribution in dependence of the layer stack geometry, ion fluence and thermal budget. Employing a focused Ne+ beam from a helium ion microscope, we demonstrate site-controlled self-assembly of

• single Si NCs. Line irradiation with a fluence of 3000 Ne+/nm2 and a line width of 4 nm leads to the formation of a chain of Si NCs, and a single NC with 2.2 nm diameter is subsequently isolated and visualized in a few nanometer thin lamella prepared by a focused ion beam (FIB). The Si NC is centered

Contactless photomagnetoelectric investigations of 2D semiconductors

• Marian Nowak,
• Marcin Jesionek,
• Barbara Solecka,
• Piotr Szperlich,
• Piotr Duka and
• Anna Starczewska

Beilstein J. Nanotechnol. 2018, 9, 2741–2749, doi:10.3762/bjnano.9.256

• occasional holes and cracks. The presence of single-layer graphene was confirmed by Raman spectroscopy using an NTEGRA Spectra (NT-NDT) device with a wavelength of 532 nm. The carrier mobility μe = 1256(25) cm2V−1s−1 and sheet carrier concentration ne = 4.65(6)·1016 m−2 in the graphene were determined using

• concentration (μe = 1256(25) cm2V−1s−1 and ne = 4.65(6)·1016 m−2 determined using Van der Pauw method). It should be underlined that one of the most important properties of graphene [33][34][35] and other 2D materials [2][36][37][38][39][40][41] is the strong electric field effect which leads to

Enhancement of X-ray emission from nanocolloidal gold suspensions under double-pulse excitation

• Wei-Hung Hsu,
• Frances Camille P. Masim,
• Armandas Balčytis,
• Hsin-Hui Huang,
• Tetsu Yonezawa,
• Aleksandr A. Kuchmizhak,
• Saulius Juodkazis and
• Koji Hatanaka

Beilstein J. Nanotechnol. 2018, 9, 2609–2617, doi:10.3762/bjnano.9.242

• permittivity of material, ν is the electron–ion collision rate, ω is the optical cyclic frequency at the wavelength of excitation, ne,a,cr are the electron, atom and critical densities, respectively. The imaginary part of the permittivity is given by: The threshold fluence for water to reach the ENZ state can

• plasma frequency ωp when the electron density, ne, is known. For instance, for gold ne = 5.9 × 1022 cm−3. The refractive index under ENZ conditions can be calculated as with use of Equation 2: Then AENZ = 4κ/[(κ + 1)2 + κ2] and the fluence threshold for the ENZ state is (Equation 3): with Δg = 6.2 eV

• calculated from the force F = Δp/Δt where the momentum in a medium of refractive index n of a laser pulse with energy E is p = nE/c[46]. When a light pulse of power P traverses from a low refractive index (n0 = 1, air) into a medium with larger refractive index (n1 = 1.33, water), momentum is gained and the

Pattern generation for direct-write three-dimensional nanoscale structures via focused electron beam induced deposition

• Lukas Keller and
• Michael Huth

Beilstein J. Nanotechnol. 2018, 9, 2581–2598, doi:10.3762/bjnano.9.240

• variable keeps track of the number of deposition events ne necessary to write the edge. ne represents the upper limit of variable ie that monitors the writing progress for the edge. The value for ne follows from the length of the edge le divided by the value of sF. Equation 2 provides an overview of the

• calibration experiment at a similar height z3D,i ≈ ζ would compensate for the reduced precursor coverage effect because ne = le/sF. Now we have For the set of values {(hi+1 − hi)/(z3D,i+1 − z3D,i)} vs the heights {z3D,i} obtained from the calibration experiment we perform a polynomial fit and obtain n ≤ 3

Self-assembled quasi-hexagonal arrays of gold nanoparticles with small gaps for surface-enhanced Raman spectroscopy

• Emre Gürdal,
• Simon Dickreuter,
• Fatima Noureddine,
• Pascal Bieschke,
• Dieter P. Kern and
• Monika Fleischer

Beilstein J. Nanotechnol. 2018, 9, 1977–1985, doi:10.3762/bjnano.9.188

• measured in a confocal Raman spectrometer (LabRam HR 800, Horia JobinYvon) using a 632.8 nm He–Ne-laser with a laser power of 50 mW and a 50× objective. The laser aperture was set to 1000 µm, the slit size to 200 µm and the grating had 1800 lines/mm, resulting in a spectral resolution of ≈2 cm−1. For all

Defect formation in multiwalled carbon nanotubes under low-energy He and Ne ion irradiation

• Santhana Eswara,
• Jean-Nicolas Audinot,
• Brahime El Adib,
• Maël Guennou,
• Tom Wirtz and
• Patrick Philipp

Beilstein J. Nanotechnol. 2018, 9, 1951–1963, doi:10.3762/bjnano.9.186

• Department, Luxembourg Institute of Science and Technology, 41 rue du Brill, L-4422 Belvaux, Luxembourg 10.3762/bjnano.9.186 Abstract The mechanical, structural, electronic and magnetic properties of carbon nanotubes can be modified by electron or ion irradiation. In this work we used 25 keV He+ and Ne+ ion

• thickness and ion species, the sputter yield is significantly higher for the bottom than the top side. For He+ and Ne+ irradiation, damage formation evolves differently, with a change in the trend of the ratio of D to G peak in the Raman spectra being observed for He+ but not for Ne+. This can be attributed

• -resolution imaging tool [32][33]. A He+ or Ne+ ion beam can be used to irradiated the samples with an impact energy in the range of 5 to 30 keV, either for imaging or nano-machining [34][35], or for doing both simultaneously [33]. For instance, the HIM has already been used for the imaging of graphene flakes

SO₂ gas adsorption on carbon nanomaterials: a comparative study

• Deepu J. Babu,
• Divya Puthusseri,
• Frank G. Kühl,
• Sherif Okeil,
• Michael Bruns,
• Manfred Hampe and
• Jörg J. Schneider

Beilstein J. Nanotechnol. 2018, 9, 1782–1792, doi:10.3762/bjnano.9.169

• carried out at 900 °C by passing ethene (200 sccm), hydrogen (800 sccm), argon (1200 sccm) and ppm-scale quantities of water vapor together for 15 min. Characterization techniques Raman measurements were performed using a Horiba Jobin Yvon, model HR 800 LabRAM high-resolution microscope using a He–Ne

Interaction-tailored organization of large-area colloidal assemblies

• Silvia Rizzato,
• Elisabetta Primiceri,
• Anna Grazia Monteduro,
• Adriano Colombelli,
• Angelo Leo,
• Maria Grazia Manera,
• Roberto Rella and
• Giuseppe Maruccio

Beilstein J. Nanotechnol. 2018, 9, 1582–1593, doi:10.3762/bjnano.9.150

• properties of cobalt nanoholes were investigated by the magneto-optical Kerr effect technique in longitudinal configuration. The samples were placed between the poles of a GMW 3470 electromagnet, where the magnetic field intensity was measured by a Group3 Teslameter probe. A He–Ne laser beam (wavelength 633

Optical near-field mapping of plasmonic nanostructures prepared by nanosphere lithography

• Gitanjali Kolhatkar,
• Alexandre Merlen,
• Jiawei Zhang,
• Chahinez Dab,
• Gregory Q. Wallace,
• François Lagugné-Labarthet and
• Andreas Ruediger

Beilstein J. Nanotechnol. 2018, 9, 1536–1543, doi:10.3762/bjnano.9.144

• Nanofinder 30 Raman spectrometer and a thermoelectrically cooled CCD detector. A TEM00 cw He–Ne laser (632.8 nm) and a cw solid-state Cobolt 04-01 series laser (532.1 nm) were used as the excitation sources. A 0.7 N.A. Mitutoyo MPlan Apo 100× objective placed under a 65° inclination was used to focus the

Facile chemical routes to mesoporous silver substrates for SERS analysis

• Elina A. Tastekova,
• Alexander Y. Polyakov,
• Anastasia E. Goldt,
• Alexander V. Sidorov,
• Alexandra A. Oshmyanskaya,
• Irina V. Sukhorukova,
• Dmitry V. Shtansky,
• Wolgang Grünert and
• Anastasia V. Grigorieva

Beilstein J. Nanotechnol. 2018, 9, 880–889, doi:10.3762/bjnano.9.82

• , it changed drastically. These values are lower than the EF of 109 reported for 10−9–10−12 M aliquots of crystalline violet deposited on mesoporous silver mesocrystals enhanced with a 633 nm He–Ne laser [23]. Concerning the mp-Ag/Ag slides, the corresponding SERS spectra of R6G (Figure 4c) showed a

Perfusion double-channel micropipette probes for oxygen flux mapping with single-cell resolution

• Yang Gao,
• Bin Li,
• Riju Singhal,
• Adam Fontecchio,
• Ben Pelleg,
• Zulfiya Orynbayeva,
• Yury Gogotsi and
• Gary Friedman

Beilstein J. Nanotechnol. 2018, 9, 850–860, doi:10.3762/bjnano.9.79

• Era Pump Systems, Inc., Dual-NE-1000) was used to supply suction. To study the effects of perfusion flow on molecular diffusion around the tip of the theta pipette, the pipette tip was immersed at a 5° angle to the substrate into a large drop of water (0.3 mL) placed on a microscope slide, while

Dynamic behavior of nematic liquid crystal mixtures with quantum dots in electric fields

• Emil Petrescu,
• Cristina Cirtoaje and
• Octavian Danila

Beilstein J. Nanotechnol. 2018, 9, 399–406, doi:10.3762/bjnano.9.39

• parallel with the field direction. During this reorientation process, the refractive index of the sample also changes: where no and ne are, respectively, the ordinary and extraordinary refractive indexes and θ is the angle between the direction of the light and ne. Between the extraordinary and ordinary

• orientation trying to align with the field. A He–Ne laser beam crossed the sample through the windows of the holder and the emergent signal was recorded with a Thor Lab photovoltaic cell. Two crossed polarizers at 45° were placed on both sides of the sample to obtain equal intensities for ordinary and

Temperature-tunable lasing from dye-doped chiral microdroplets encapsulated in a thin polymeric film

• Gia Petriashvili,
• Mauro Daniel Luigi Bruno,
• Maria Penelope De Santo and
• Riccardo Barberi

Beilstein J. Nanotechnol. 2018, 9, 379–383, doi:10.3762/bjnano.9.37

• symmetry of the molecules, the periodicity of the structure is half the helix pitch, p. When light propagates along the helical axes, it will experience Bragg reflection at λ0 = np, where λ0 is the wavelength of the maximum reflection and n is the average of the refractive indices defined as: n = (ne + no

• )/2, where ne and no are the extraordinary and ordinary refraction indices, respectively. As a consequence, a whole range of wavelengths does not propagate inside the material and it is indicated as photonic band gap (PBG). The full width at half maximum of the PBG equals to Δλ = pΔn, where Δn = ne

Photocatalytic and adsorption properties of TiO₂-pillared montmorillonite obtained by hydrothermally activated intercalation of titanium polyhydroxo complexes

• Mikhail F. Butman,
• Nikolay L. Ovchinnikov,
• Nikita S. Karasev,
• Nataliya E. Kochkina,
• Alexander V. Agafonov and
• Alexandr V. Vinogradov

Beilstein J. Nanotechnol. 2018, 9, 364–378, doi:10.3762/bjnano.9.36

• dilution of the solution. Figure 15 shows the results of particle size analysis for the intercalation solution using the laser beam dynamic scattering method (analyzer Zetasizer Nano ZS «Malvern Instruments Ltd», He–Ne laser with a wavelength of 633 nm and a recording angle of 173°). The particle size

Dynamic behavior of a nematic liquid crystal with added carbon nanotubes in an electric field

• Emil Petrescu and
• Cristina Cirtoaje

Beilstein J. Nanotechnol. 2018, 9, 233–241, doi:10.3762/bjnano.9.25

• applied field, deviating by an angle θ from their initial direction (Figure 1). This deviation reaches its maximum value (θm) after a time period called the relaxation time. Consequently, the refractive index of the cell is also changing: where no and ne are the ordinary and extraordinary refractive

• were slowly cooled down to 29 °C in a holder placed inside a Mettler Toledo stage. The terminals of the holder were connected to a HIOKI RLC power source from which a 10 kHz ac voltage was applied. A 632.8 He–Ne laser sent a beam through the sample placed between two crossed polarizers (Figure 5). A

Electrical properties of a liquid crystal dispersed in an electrospun cellulose acetate network

• Doina Manaila Maximean,
• Octavian Danila,
• Pedro L. Almeida and
• Constantin Paul Ganea

Beilstein J. Nanotechnol. 2018, 9, 155–163, doi:10.3762/bjnano.9.18

• . A He–Ne laser beam (wavelength 623.8 nm) passes through the sample, which is modulated by an ac voltage provided by a function generator–amplifier system. The laser beam is detected by a high-speed photodiode with adjustable gain (Thorlabs). The electrical signal generated by the photodiode was

Co-reductive fabrication of carbon nanodots with high quantum yield for bioimaging of bacteria

• Jiajun Wang,
• Xia Liu,
• Gesmi Milcovich,
• Tzu-Yu Chen,
• Edel Durack,
• Sarah Mallen,
• Yongming Ruan,
• Xuexiang Weng and
• Sarah P. Hudson

Beilstein J. Nanotechnol. 2018, 9, 137–145, doi:10.3762/bjnano.9.16

• Bruker D8 Advance device with a graphite monochromatized Cu Kα radiation source (λ = 1.54056 Å). XRD diagrams were recorded from 10° to 60° with a step size of 0.02° at 3° min−1. Raman measurements were performed with a Renishaw RM1000 confocal microscope and a He–Ne laser (633 nm, 10 mW). The laser beam

Nematic liquid crystal alignment on subwavelength metal gratings

• Irina V. Kasyanova,
• Artur R. Geivandov,
• Vladimir V. Artemov,
• Maxim V. Gorkunov and
• Serguei P. Palto

Beilstein J. Nanotechnol. 2018, 9, 42–47, doi:10.3762/bjnano.9.6

• plates was insured with teflon spacers and was measured to be 5.7 ± 0.5 μm. The cell is filled with Merck E7 LC material (no = 1.527, ne = 1.751 at a wavelength of 546 nm and temperature T = 25.0 °C [11]). Results and Discussion We performed visual observations of the cell under polarized light. In

• transverse magnetic (TM) modes are due to the optical anisotropy of the LC: the TM mode is polarized along the grating wavevector (and across the slits), thus, it deals with the ordinary refractive index, no, whereas the orthogonal TE mode interacts with the extraordinary refractive index, ne. Based on the

• = 5.1 ± 0.05 μm. The inaccuracy is defined by spectral dispersion of the ordinary refractive index. Then the effective extraordinary index can be found from the TE spectrum maximum: ne = LTE/2dlocal = 1.73 ± 0.01. Given the inaccuracy, the found value of the effective extraordinary index is very close

Study of the vertically aligned in-plane switching liquid crystal mode in microscale periodic electric fields

• Artur R. Geivandov,
• Mikhail I. Barnik,
• Irina V. Kasyanova and
• Serguei P. Palto

Beilstein J. Nanotechnol. 2018, 9, 11–19, doi:10.3762/bjnano.9.2

• -coated onto the inner substrates surfaces and baked at 90 °C for 30 min. The LC cells were filled at room temperature using the following LC mixtures: 1) Merck E7 LC material (ne = 1.7462, Δn = 0.2246 at λ = 589 nm, 20 °C; ε|| = 19.0 (at f = 1 kHz), Δε = +13.8, γ = 0.19 Pa·s at 20 °C, K1 = 11.1 pN, K2

• = 9.0 pN, K3 = 17.1 pN) [12], and 2) Merck ZLI1957/5 LC material (ne = 1.6240, Δn = 0.1213 at λ = 589 nm, 20 °C; ε|| = 8.0 (at f = 1 kHz), Δε = +4.5, γ = 0.105 Pa·s at 20 °C, K1 =14 pN, K2 = 7 pN, K3 = 16 pN) [13]. Electrooptical measurements were performed under a polarizing microscope Olympus CX31PF