Publications by authors named "Stephanie Reich"

68 Publications

The Protective Effects of Maternal and Paternal Factors on Children's Social Development.

Advers Resil Sci 2021 Jun 3;2(2):85-98. Epub 2021 Jul 3.

School of Education, University of California, Irvine.

The goal of this study is to examine associations among family and child protective factors, maternal and paternal levels of distress, and children's social competence in a sample of 156 ethnically and socioeconomically diverse first-time mothers, fathers, and their children, followed from 9 months to 30 months of age. Using multiple linear regression modeling, our results indicate that dyadic synchrony and children's positive temperament during infancy are significantly associated with fewer behavior problems and paternal optimism with high levels of social competence at 21 months (main effects). Father optimism and child positive temperament are only significantly related to higher levels of social competence and fewer behavioral problems, respectively, in the context of low levels of paternal distress (interaction effects). These results suggest that in our sample maternal dyadic synchrony operates in the same way across levels of maternal distress as it relates to children's behavior problems, with the exception of paternal optimism and children's positive temperament. Results also suggest that protective factors are different for mothers, fathers, and children.
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http://dx.doi.org/10.1007/s42844-021-00041-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8372823PMC
June 2021

Moiré-Induced Vibrational Coupling in Double-Walled Carbon Nanotubes.

Nano Lett 2021 Aug 9;21(16):6732-6739. Epub 2021 Aug 9.

Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.

Moiré patterns are additional, long-range periodicities in twisted crystalline bilayers. They are known to fundamentally change the electronic states of the layers, but similar effects on their mechanical and vibrational properties have not been discussed so far. Here we show that the moiré potential shifts the radial breathing mode in double-walled carbon nanotubes (DWCNTs). The change in frequency is expected to be proportional to the shift in optical transition energies, which are induced by the moiré patterns. To verify our model, we performed resonance Raman scattering on purified and sorted semiconducting DWCNTs. We find that the radial breathing mode shifts up to 14 cm higher in energy followed by displacement of optical transition energies of up to 200 meV to lower energies, in comparison to the single-walled tubes. We show how to identify the strong coupling condition in DWCNTs from their phonon frequencies and construct a Kataura plot to aid their future experimental assignment.
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http://dx.doi.org/10.1021/acs.nanolett.1c00295DOI Listing
August 2021

A Randomized Control Trial of Using Baby Books to Reduce New Mothers' Feelings of Stress and Depression.

Matern Child Health J 2021 Oct 30;25(10):1615-1625. Epub 2021 Jul 30.

University of California, Irvine, USA.

Objective: To determine whether embedding educational information about child development and optimal parenting practices from the Bright Futures Guidelines for Health Supervision into baby books can reduce women's depressive symptoms and parenting stress during the first 18 months of motherhood.

Methods: A sample of 167 low-income, primarily African-American, first-time mothers were randomized into three conditions while pregnant: an educational book group, a non-educational book group, or a no-book group. Depressive symptoms and parenting stress were assessed using two questionnaires during home visits when women were in their third trimester of pregnancy (baseline) and when their child was 2, 4, 6, 9, 12, and 18 months of age.

Results: Hierarchical Linear Models showed that women who received books with educational information shed depressive symptoms and parenting stress at a faster rate than women who received similar books without educational information and women who did not receive books.

Conclusions: These findings indicate that providing women with child development and parenting information via baby books can be an effective strategy for promoting new mothers' emotional wellbeing. Since feelings of sadness and stress are risky for both mothers and their infants, this easy to implement intervention holds great promise.
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http://dx.doi.org/10.1007/s10995-021-03200-9DOI Listing
October 2021

Anti-Stokes Raman Scattering of Single Carbyne Chains.

ACS Nano 2021 Jul 13. Epub 2021 Jul 13.

Photonics Laboratory, ETH Zürich, 8093 Zürich, Switzerland.

We investigate the anti-Stokes Raman scattering of single carbyne chains confined inside double-walled carbon nanotubes. Individual chains are identified using tip-enhanced Raman scattering (TERS) and heated by resonant excitation with varying laser powers. We study the temperature dependence of carbyne's Raman spectrum and quantify the laser-induced heating based on the anti-Stokes/Stokes ratio. Due to its molecular size and its large Raman cross section, carbyne holds great promise for local temperature monitoring, with potential applications ranging from nanoelectronics to biology.
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http://dx.doi.org/10.1021/acsnano.1c03893DOI Listing
July 2021

Kinetics and Mechanism of Plasmon-Driven Dehalogenation Reaction of Brominated Purine Nucleobases on Ag and Au.

ACS Catal 2021 Jul 23;11(13):8370-8381. Epub 2021 Jun 23.

Institute of Chemistry, Physical Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, 14476 Potsdam, Germany.

Plasmon-driven photocatalysis is an emerging and promising application of noble metal nanoparticles (NPs). An understanding of the fundamental aspects of plasmon interaction with molecules and factors controlling their reaction rate in a heterogeneous system is of high importance. Therefore, the dehalogenation kinetics of 8-bromoguanine (BrGua) and 8-bromoadenine (BrAde) on aggregated surfaces of silver (Ag) and gold (Au) NPs have been studied to understand the reaction kinetics and the underlying reaction mechanism prevalent in heterogeneous reaction systems induced by plasmons monitored by surface enhanced Raman scattering (SERS). We conclude that the time-average constant concentration of hot electrons and the time scale of dissociation of transient negative ions (TNI) are crucial in defining the reaction rate law based on a proposed kinetic model. An overall higher reaction rate of dehalogenation is observed on Ag compared with Au, which is explained by the favorable hot-hole scavenging by the reaction product and the byproduct. We therefore arrive at the conclusion that insufficient hole deactivation could retard the reaction rate significantly, marking itself as rate-determining step for the overall reaction. The wavelength dependency of the reaction rate normalized to absorbed optical power indicates the nonthermal nature of the plasmon-driven reaction. The study therefore lays a general approach toward understanding the kinetics and reaction mechanism of a plasmon-driven reaction in a heterogeneous system, and furthermore, it leads to a better understanding of the reactivity of brominated purine derivatives on Ag and Au, which could in the future be exploited, for example, in plasmon-assisted cancer therapy.
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http://dx.doi.org/10.1021/acscatal.1c01851DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8256422PMC
July 2021

The patterning toolbox FIB-o-mat: Exploiting the full potential of focused helium ions for nanofabrication.

Beilstein J Nanotechnol 2021 6;12:304-318. Epub 2021 Apr 6.

Corelab Correlative Microscopy and Spectroscopy, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.

Focused beams of helium ions are a powerful tool for high-fidelity machining with spatial precision below 5 nm. Achieving such a high patterning precision over large areas and for different materials in a reproducible manner, however, is not trivial. Here, we introduce the Python toolbox FIB-o-mat for automated pattern creation and optimization, providing full flexibility to accomplish demanding patterning tasks. FIB-o-mat offers high-level pattern creation, enabling high-fidelity large-area patterning and systematic variations in geometry and raster settings. It also offers low-level beam path creation, providing full control over the beam movement and including sophisticated optimization tools. Three applications showcasing the potential of He ion beam nanofabrication for two-dimensional material systems and devices using FIB-o-mat are presented.
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http://dx.doi.org/10.3762/bjnano.12.25DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8042487PMC
April 2021

Surface-Enhanced Raman Scattering and Surface-Enhanced Infrared Absorption by Plasmon Polaritons in Three-Dimensional Nanoparticle Supercrystals.

ACS Nano 2021 Mar 5;15(3):5523-5533. Epub 2021 Mar 5.

Department of Physics, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany.

Surface-enhanced vibrational spectroscopy strongly increases the cross section of Raman scattering and infrared absorption, overcoming the limited sensitivity and resolution of these two powerful analytic tools. While surface-enhanced setups with maximum enhancement have been studied widely in recent years, substrates with reproducible, uniform enhancement have received less attention although they are required in many applications. Here, we show that plasmonic supercrystals are an excellent platform for enhanced spectroscopy because they possess a high density of hotspots in the electric field. We describe the near field inside the supercrystal within the framework of plasmon polaritons that form due to strong light-matter interaction. From the polariton resonances we predict resonances in the far-field enhancement for Raman scattering and infrared absorption. We verify our predictions by measuring the vibrations of polystyrene molecules embedded in supercrystals of gold nanoparticles. The intensity of surface-enhanced Raman scattering is uniform within 10% across the crystal with a peak integrated enhancement of up to 300 and a peak hotspot enhancement of 10. The supercrystal polaritons induce pairs of incoming and outgoing resonances in the enhanced cross section as we demonstrate experimentally by measuring surface-enhanced Raman scattering with multiple laser wavelengths across the polariton resonance. The infrared absorption of polystyrene is likewise enhanced inside the supercrystals with a maximum enhancement of 400%. We show with a coupled oscillator model that the increase originates from the combined effects of hotspot formation and the excitation of standing polariton waves. Our work clearly relates the structural and optical properties of plasmonic supercrystals and shows that such crystals are excellent hosts and substrates for the uniform and predictable enhancement of vibrational spectra.
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http://dx.doi.org/10.1021/acsnano.1c00352DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7992191PMC
March 2021

Parents' Beliefs About the Benefits and Detriments of Mobile Screen Technologies for Their Young Children's Learning: A Focus on Diverse Latine Mothers and Fathers.

Front Psychol 2020 9;11:570712. Epub 2020 Oct 9.

School of Education, University of California, Irvine, Irvine, CA, United States.

Young children's use of mobile screens is increasing despite the American Academy of Pediatrics' recommendations to limit screen use. Research on TV has found that maternal beliefs about the effects of screens on children's learning and parental socioeconomic status influence children's media consumption. However, few studies have explored parents' beliefs about mobile screens and whether there are differences in beliefs by socioeconomic status, particularly within the largest ethnic minoritized group - Latines. Because Latines are a socioeconomically and linguistically heterogenous group, but are often represented by low-income mothers in research, it is important to understand whether there are socioeconomic and linguistic differences on how and why Latine mothers fathers permit their children to use mobile screens. This study used in-depth, semi-structured interviews to understand how and why Latine mothers (low-income = 10, middle-to-high income = 10) and fathers (low-income = 10, middle-to-high income = 10) permitted their children (0-4 years) to use mobile screens. Specifically, we discussed their beliefs about how mobile screens support and hinder their children's learning and how their children used them. Results from qualitative content analysis showed that mothers and fathers, across income, education levels, and language use, believed that they, as parents, were the key decision-makers in determining the extent to which mobile screens supported and hindered their young children's learning. They described mediation strategies of selecting appropriate content, setting time limits, and monitoring use, to ensure that their children primarily benefited from device use. However, two distinctions were noted. Parents with a high school diploma or beyond stressed the importance of co-using devices with their children. This was not mentioned by less formally educated parents. Additionally, low-income parents with diverse educational levels, mentioned the importance of continuously monitoring device use to avoid their children encountering inappropriate content. Findings can inform work seeking to promote optimal media habits among Latine families.
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http://dx.doi.org/10.3389/fpsyg.2020.570712DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7581903PMC
October 2020

Coping With Stress Through Texting: An Experimental Study.

J Adolesc Health 2021 03 12;68(3):565-571. Epub 2020 Aug 12.

Donald Bren School of Information and Computer Sciences, University of California, Irvine, California.

Purpose: Texting is used by many adolescents and has the potential to improve well-being, as youth can reach out for support immediately after experiencing a stressful situation. Many studies have examined whether texting is associated with well-being, but few have used experimental designs, preventing causal claims.

Methods: In this experimental study, 130 adolescents (M = 12.41) participated with a same-gender friend whom they texted regularly. Both adolescents completed a task that elicited stress and then engaged in one of the following randomly assigned activities: texting their friend, watching a video on a cellphone (passive-phone condition), or sitting quietly (no activity condition). Participants reported their mood and stress levels after the stress task and again after the activity. Heart rate variability was measured throughout.

Results: Participants who texted their friend reported higher moods (b = -.80, standard error [SE] = .24, p < .001, η = .09) and lower stress at the end of the study than those in the no activity condition (b = .51, SE = .25, p = .046, η = .04) and higher moods than adolescents in the passive-phone condition (b = -.74, SE = .25, p = .004, η = .08). No differences were noted between the passive-phone and no activity conditions. There were no differences in heart rate variability between the three conditions. The effects of texting on mood, self-reported stress, and heart rate variability did not differ by gender.

Conclusions: Both boys and girls may benefit from texting a friend after experiencing a stressful event.
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http://dx.doi.org/10.1016/j.jadohealth.2020.07.004DOI Listing
March 2021

Raman Scattering Cross Section of Confined Carbyne.

Nano Lett 2020 09 17;20(9):6750-6755. Epub 2020 Aug 17.

Department of Physics, Freie Universität Berlin, 14195 Berlin, Germany.

We experimentally quantify the Raman scattering from individual carbyne chains confined in double-walled carbon nanotubes. We find that the resonant differential Raman cross section of confined carbyne is on the order of 10 cm sr per atom, making it the strongest Raman scatterer ever reported.
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http://dx.doi.org/10.1021/acs.nanolett.0c02632DOI Listing
September 2020

Selective excitation of localized surface plasmons by structured light.

Opt Express 2020 Aug;28(16):24262-24274

We investigated the selective excitation of localized surface plasmons by structured light. We derive selection rules using group theory and propose a fitting integral to quantify the contribution of the eigenmodes to the absorption spectra. Based on the result we investigate three nano oligomers of different symmetry (trimer, quadrumer, and hexamer) in detail using finite-difference time-domain simulations. We show that by controlling the incident light polarization and phase pattern we are able to control the absorption and scattering spectra. Additionally, we demonstrate that the fitting between the incident light and the oligomer modes may favor a number of modes to oscillate. Dark modes produce strong changes in the absorption spectrum and bright modes in the scattering spectrum. The experimental precision (axial shift error) may be on the same order as the oligomer diameter making the orbital angular momentum selection rules robust enough for experimental observation.
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http://dx.doi.org/10.1364/OE.399225DOI Listing
August 2020

Structural order in plasmonic superlattices.

Nat Commun 2020 Jul 30;11(1):3821. Epub 2020 Jul 30.

Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, 20146, Hamburg, Germany.

The assembly of plasmonic nanoparticles into ordered 2D- and 3D-superlattices could pave the way towards new tailored materials for plasmonic sensing, photocatalysis and manipulation of light on the nanoscale. The properties of such materials strongly depend on their geometry, and accordingly straightforward protocols to obtain precise plasmonic superlattices are highly desirable. Here, we synthesize large areas of crystalline mono-, bi- and multilayers of gold nanoparticles >20 nm with a small number of defects. The superlattices can be described as hexagonal crystals with standard deviations of the lattice parameter below 1%. The periodic arrangement within the superlattices leads to new well-defined collective plasmon-polariton modes. The general level of achieved superlattice quality will be of benefit for a broad range of applications, ranging from fundamental studies of light-matter interaction to optical metamaterials and substrates for surface-enhanced spectroscopies.
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http://dx.doi.org/10.1038/s41467-020-17632-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7393164PMC
July 2020

Deep strong light-matter coupling in plasmonic nanoparticle crystals.

Nature 2020 07 29;583(7818):780-784. Epub 2020 Jul 29.

Department of Physics, Freie Universität Berlin, Berlin, Germany.

In the regime of deep strong light-matter coupling, the coupling strength exceeds the transition energies of the material, fundamentally changing its properties; for example, the ground state of the system contains virtual photons and the internal electromagnetic field gets redistributed by photon self-interaction. So far, no electronic excitation of a material has shown such strong coupling to free-space photons. Here we show that three-dimensional crystals of plasmonic nanoparticles can realize deep strong coupling under ambient conditions, if the particles are ten times larger than the interparticle gaps. The experimental Rabi frequencies (1.9 to 3.3 electronvolts) of face-centred cubic crystals of gold nanoparticles with diameters between 25 and 60 nanometres exceed their plasmon energy by up to 180 per cent. We show that the continuum of photons and plasmons hybridizes into polaritons that violate the rotating-wave approximation. The coupling leads to a breakdown of the Purcell effect-the increase of radiative damping through light-matter coupling-and increases the radiative polariton lifetime. The results indicate that metallic and semiconducting nanoparticles can be used as building blocks for an entire class of materials with extreme light-matter interaction, which will find application in nonlinear optics, the search for cooperative effects and ground states, polariton chemistry and quantum technology.
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http://dx.doi.org/10.1038/s41586-020-2508-1DOI Listing
July 2020

The Observed Quality of Caregiver-Child Interactions With and Without a Mobile Screen Device.

Acad Pediatr 2021 May-Jun;21(4):620-628. Epub 2020 Jul 14.

University of California (SM Reich and G Farkas), Irvine, Calif.

Objective: This study investigated how caregivers' mobile device use influenced the quality of their interactions with their children. The associations between quality of interactions and the type of activity (eg, typing/swiping, looking at screen), setting, caregiver-child proximity, and child behaviors were also examined.

Method: Researchers anonymously and systematically observed and coded the behavior of 98 caregiver-child dyads in public settings (eg, parks, food courts) during real-time, naturally occurring interactions using time sampling.

Results: Caregivers who used a mobile device for the entire observation engaged in less joint attention and were less responsive than caregivers who used the device some of the time. When looking at patterns within caregivers who used the device intermittently, the probability that they would engage in joint attention, initiate interactions with their child, talk, and display positive emotions was lower when they used a mobile device than when they did not. Child talking and positive affect were unrelated to caregiver device use. Activity type with the device, caregiver-child proximity and setting also related to interaction quality.

Conclusions: Caregiver device use was negatively associated with adult behaviors that are key components of high-quality caregiver-child interactions. Additionally, setting, activity type, and caregiver-child proximity are factors that should be considered because they relate to the quality of caregiver-child interactions in the context of mobile screen technologies.
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http://dx.doi.org/10.1016/j.acap.2020.07.012DOI Listing
July 2021

Resonant, Plasmonic Raman Enhancement of α-6T Molecules Encapsulated in Carbon Nanotubes.

J Phys Chem C Nanomater Interfaces 2019 Apr 2;123(16):10578-10585. Epub 2019 Apr 2.

Institut für Experimentalphysik, Freie Universität Berlin, Berlin 14195, Germany.

Surface-enhanced Raman scattering (SERS) and resonant Raman scattering are widely used techniques to enhance the Raman intensity of molecules and nanomaterials by several orders of magnitude. In SERS, typically, molecules are investigated and their intrinsic resonance is often ignored while discussing the plasmonic enhancement. Here, we study α-sexithiophenes encapsulated in carbon nanotubes placed in the center of a nanodimer. By dielectrophoretic deposition, we place the nanotubes precisely in the center of a plasmonic gold nanodimer and observe SERS enhancement from individual tube bundles. The encapsulated molecules are not subjected to chemical enhancement because of the protective character of the nanotube. Polarization-dependent Raman measurements confirm the alignment of the molecules within the carbon nanotubes (CNTs) and reveal the influence of the plasmonic near field on the molecule's Raman intensity. We investigate the encapsulated molecules in small CNT bundles with and without plasmonic enhancement and determine the molecular and plasmonic resonance by tuning the excitation wavelength. We observe a strong red shift of the maximum Raman intensity under plasmonic enhancement toward the plasmon resonance.
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http://dx.doi.org/10.1021/acs.jpcc.9b01600DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7011763PMC
April 2019

Dark plasmon modes for efficient hot electron generation in multilayers of gold nanoparticles.

J Chem Phys 2020 Feb;152(6):064710

Institute for Physical Chemistry, Universität Hamburg, Martin-Luther-King Platz 6, 20146 Hamburg, Germany.

The excitation of dark plasmons, i.e., coupled plasmon modes with a vanishing net dipole, is expected to favor Landau damping over radiative damping. Dark plasmon excitation might, therefore, lead to an increased absorption of energy within gold nanoparticles, resulting in a strong generation of hot electrons compared to the generation via bright plasmons. We performed transient-absorption spectroscopy on gold nanoparticle films to assess the initial electronic temperature before thermalization. We observe a significant increase in the electron-phonon coupling time when dark plasmon modes are excited in these films. The results indicate an efficient energy absorption due to the suppressed radiative decay of dark plasmon modes and a subsequent energy transformation into hot electrons.
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http://dx.doi.org/10.1063/1.5131696DOI Listing
February 2020

Understanding the Electron-Doping Mechanism in Potassium-Intercalated Single-Walled Carbon Nanotubes.

J Am Chem Soc 2020 Feb 22;142(5):2327-2337. Epub 2020 Jan 22.

Department of Chemistry and Pharmacy and Joint Institute of Advanced Materials and Processes (ZMP) , Friedrich-Alexander University of Erlangen-Nuremberg , Nikolaus-Fiebiger-Strasse 10 , 91058 Erlangen , Germany.

Single-walled carbon nanotubes (SWCNTs) can be doped with potassium, similar to graphite, leading to intercalation compounds. These binary systems exhibit a clear metallic character. However, the entire picture of how electron doping (e-doping) modifies the SWCNTs' vibrational spectra as a function of their diameter, chirality, and metallicity is still elusive. Herein, we present a detailed study of the intercalation and solid state reduction of metallic and semiconducting enriched HiPco SWCNTs. We performed a combined experimental and theoretical study of the evolution of their Raman response with potassium exposure, focusing specifically on their radial breathing mode (RBM). We found the charge donated from the potassium atoms occupies antibonding π orbitals of the SWCNTs, weakening their C-C bonds, and reducing the RBM frequency. This RBM downshift with increasing doping level is quasi-linear with a steplike behavior when the Fermi level crosses a van Hove singularity for semiconducting species. Moreover, this weakening of the C-C bonds is greater with decreasing curvature, or increasing diameter. Overall, this suggests the RBM downshift with e-doping is proportional to both the SWCNT's integrated density of states (DOS) ϱ(ε) and diameter . We have provided a precise and complete description of the complex electron doping mechanism in SWCNTs up to a charge density of -18 me/C, far beyond that achievable by standard gate voltage studies, not being the highest doping possible, but high enough to track the effects of doping in SWCNTs based on their excitation energy, diameter, band gap energy, chiral angle, and metallicity. This work is highly relevant to tuning the electronic properties of SWCNTs for applications in nanoelectronics, plasmonics, and thermoelectricity.
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http://dx.doi.org/10.1021/jacs.9b11370DOI Listing
February 2020

Few-Wall Carbon Nanotube Coils.

Nano Lett 2020 Feb 31;20(2):953-962. Epub 2019 Dec 31.

Department of Materials and Interfaces , Weizmann Institute of Science , Rehovot 7610001 , Israel.

While various electronic components based on carbon nanotubes (CNTs) have already been demonstrated, the realization of miniature electromagnetic coils based on CNTs remains a challenge. Coils made of single-wall CNTs with accessible ends for contacting have been recently demonstrated but were found unsuitable to act as electromagnetic coils because of electrical shorting between their turns. Coils made of a few-wall CNT could in principle allow an insulated flow of current and thus be potential candidates for realizing CNT-based electromagnetic coils. However, no such CNT structure has been produced so far. Here, we demonstrate the formation of few-wall CNT coils and characterize their structural, optical, vibrational, and electrical properties using experimental and computational tools. The coils are made of CNTs with 2, 3, or 4 walls. They have accessible ends for electrical contacts and low defect densities. The coil diameters are on the order of one micron, like those of single-wall CNT coils, despite the higher rigidity of few-wall CNTs. Coils with as many as 163 turns were found, with their turns organized in a rippled raft configuration. These coils are promising candidates for a variety of miniature devices based on electromagnetic coils, such as electromagnets, inductors, transformers, and motors. Being chirally and enantiomerically pure few-wall CNT bundles, they are also ideal for fundamental studies of interwall coupling and superconductivity in CNTs.
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http://dx.doi.org/10.1021/acs.nanolett.9b03977DOI Listing
February 2020

Photoswitchable single-walled carbon nanotubes for super-resolution microscopy in the near-infrared.

Sci Adv 2019 09 27;5(9):eaax1166. Epub 2019 Sep 27.

Université de Bordeaux, Laboratoire Photonique Numérique et Nanosciences, UMR 5298, F-33400 Talence, France.

The design of single-molecule photoswitchable emitters was the first milestone toward the advent of single-molecule localization microscopy, setting a new paradigm in the field of optical imaging. Several photoswitchable emitters have been developed, but they all fluoresce in the visible or far-red ranges, missing the desirable near-infrared window where biological tissues are most transparent. Moreover, photocontrol of individual emitters in the near-infrared would be highly desirable for elementary optical molecular switches or information storage elements since most communication data transfer protocols are established in this spectral range. Here, we introduce a type of hybrid nanomaterials consisting of single-wall carbon nanotubes covalently functionalized with photoswitching molecules that are used to control the intrinsic luminescence of the single nanotubes in the near-infrared (beyond 1 μm). Through the control of photoswitching, we demonstrate super-localization imaging of nanotubes unresolved by diffraction-limited microscopy.
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http://dx.doi.org/10.1126/sciadv.aax1166DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6868679PMC
September 2019

Separation of Specific Single-Enantiomer Single-Wall Carbon Nanotubes in the Large-Diameter Regime.

ACS Nano 2020 Jan 14;14(1):948-963. Epub 2020 Jan 14.

Institute of Nanotechnology , Karlsruhe Institute of Technology , Karlsruhe 76021 , Germany.

The enantiomer-level isolation of single-walled carbon nanotubes (SWCNTs) in high concentration and with high purity for nanotubes greater than 1.1 nm in diameter is demonstrated using a two-stage aqueous two-phase extraction (ATPE) technique. In total, five different nanotube species of ∼1.41 nm diameter are isolated, including both metallics and semiconductors. We characterize these populations by absorbance spectroscopy, circular dichroism spectroscopy, resonance Raman spectroscopy, and photoluminescence mapping, revealing and substantiating mod-dependent optical dependencies. Using knowledge of the competitive adsorption of surfactants to the SWCNTs that controls partitioning within the ATPE separation, we describe an advanced acid addition methodology that enables the fine control of the separation of these select nanotubes. Furthermore, we show that endohedral filling is a previously unrecognized but important factor to ensure a homogeneous starting material and further enhance the separation yield, with the best results for alkane-filled SWCNTs, followed by empty SWCNTs, with the intrinsic inhomogeneity of water-filled SWCNTs causing them to be worse for separations. Lastly, we demonstrate the potential use of these nanotubes in field-effect transistors.
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http://dx.doi.org/10.1021/acsnano.9b08244DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6994058PMC
January 2020

Pregnancy posting: exploring characteristics of social media posts around pregnancy and user engagement.

Mhealth 2019 8;5:46. Epub 2019 Oct 8.

School of Education, University of California Irvine, Irvine, CA, USA.

Background: Pregnant women use the Internet and social networking sites to meet a variety of pregnancy-related needs as well as to help make decisions regarding their pregnancy and/or parenting. Knowing more about the current landscape of social networking sites as it relates to pregnancy can inform future work that wants to leverage social media for education or support.

Methods: Across a 7-day period, we conducted a content analysis of 4 Facebook pregnancy-related groups and 4 Instagram pregnancy-related channels. The posts were coded based on the nature, content, and purpose of each post as well as the number of likes, shares, and comments for each. After establishing inter-rater reliability, univariate statistics were used to describe the nature, characteristics, and popularity of the posts for each group or channel. We then used logistic regressions to predict which characteristics were associated with being popular or unpopular with users.

Results: There were 288 eligible posts within the 7-day window. Only a small proportion of the large (182,000 to 2,527,712) amount of followers responded with likes or comments (comments: mean =0.02%, SD =0.04%; likes: mean =0.36%, SD =0.89%). Facebook posts tended to give more general pregnancy-related information or opportunities for personal sharing while Instagram posts often had emotional support themes or posts meant to make pregnancy relatable. Popular posts tended to try to make pregnancy more relatable (OR =4.21, P<0.01) or offer emotional support (OR =4.62, P<0.01), while unpopular posts tended to provide general pregnancy-related information (OR= 2.17, P<0.05).

Conclusions: In general, there were clear characteristics that differentiated the two social networking site posts that garner user attention or not. This can inform how to provide health information and social support via social media to maximize its influence. This work suggests which features are desirable for followers and can help those interested in leveraging Instagram and Facebook to provide pregnancy-related health information.
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http://dx.doi.org/10.21037/mhealth.2019.09.09DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6851430PMC
October 2019

Present and Future of Surface-Enhanced Raman Scattering.

ACS Nano 2020 01 8;14(1):28-117. Epub 2019 Oct 8.

Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences , Nanyang Technological University , 21 Nanyang Link , Singapore 637371 , Singapore.

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.
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http://dx.doi.org/10.1021/acsnano.9b04224DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6990571PMC
January 2020

Modeling Surface-Enhanced Spectroscopy With Perturbation Theory.

Front Chem 2019 16;7:470. Epub 2019 Jul 16.

Department of Physics, Freie Universität Berlin, Berlin, Germany.

Theoretical modeling of surface-enhanced Raman scattering (SERS) is of central importance for unraveling the interplay of underlying processes and a predictive design of SERS substrates. In this work we model the plasmonic enhancement mechanism of SERS with perturbation theory. We consider the excitation of plasmonic modes as an integral part of the Raman process and model SERS as higher-order Raman scattering. Additional resonances appear in the Raman cross section which correspond to the excitation of plasmons at the wavelengths of the incident and the Raman-scattered light. The analytic expression for the Raman cross section can be used to explain the outcome of resonance Raman measurements on SERS analytes as we demonstrate by comparison to experimental data. We also implement the theory to calculate the optical absorption cross section of plasmonic nanoparticles. From a comparison to experimental cross sections, we show that the coupling matrix elements need to be renormalized by a factor that accounts for the depolarization by the bound electrons and interband transitions in order to obtain the correct magnitude. With model calculations we demonstrate that interference of different scattering channels is key to understand the excitation energy dependence of the SERS enhancement for enhancement factors below 10.
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http://dx.doi.org/10.3389/fchem.2019.00470DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6660251PMC
July 2019

CONNECTION BETWEEN STRENGTH AND THERMAL CONDUCTIVITY OF METAL MATRIX COMPOSITES WITH UNIFORM DISTRIBUTION OF GRAPHITE FLAKES.

Int J Eng Sci 2019 Jun 4;139:70-82. Epub 2019 Apr 4.

Department of Mechanical and Aerospace Engineering, New Mexico State University Las Cruces, NM 88001, USA.

The paper focuses on the connection between thermal conductivity and overall strength of metal matrix composites on example of Al2024 and Mg-0.9Ca alloys reinforced with graphite flakes. We combine theoretical and experimental approaches to analyze the maximal stress concentration in such composites as a function of minimal distance between graphite flakes. The latter is linked to the volume fraction of the inhomogeneities, which governs overall thermal conductivity. Elimination of the volume fraction parameter leads to the explicit cross-property connection. This approach is possible if inhomogeneities in the material have the same shape and are uniformly distributed with no distinguishable clusters. The agreement between the theoretical predictions and experimental observations is very good.
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http://dx.doi.org/10.1016/j.ijengsci.2019.01.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7950997PMC
June 2019

Direct optical excitation of dark plasmons for hot electron generation.

Faraday Discuss 2019 05;214(0):159-173

Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.

An ideal plasmonic system for hot-electron generation allows the optical excitation of plasmons, limits radiation losses, exhibits strong non-radiative electron damping, and is made from scalable and cost-effective materials. Here we demonstrate the optical excitation of dark interlayer plasmons in bilayers of colloidal gold nanoparticles. This excitation is created by an antiparallel orientation of the dipole moments in the nanoparticle layers; it is expected to exhibit strongly reduced radiative damping. Despite the vanishing dipole moment, an incoming electromagnetic wave that is propagating normal to the surface will excite the dark mode due to field retardation. We observe a strong peak in the absorption spectrum of a colloidal gold bilayer (nanoparticle diameter = 46 nm); this peak is absent for a nanoparticle monolayer. The full width at half maximum of the dark mode is 230 meV for an ideal nanoparticle crystal and 320 meV for the structure produced by self-assembly out of solution. The position and width of the dark plasmon are efficiently tailored by the interparticle distance within the layer, nanoparticle size and layer number. We present time-resolved pump and probe experiments of hot-electron generation by bright and dark bilayer nanoparticle modes.
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http://dx.doi.org/10.1039/c8fd00149aDOI Listing
May 2019

Disparities in Caregivers' Experiences at the Dentist With Their Young Child.

Acad Pediatr 2019 Nov - Dec;19(8):969-977. Epub 2019 Mar 21.

School of Education (SM Reich, W Ochoa, A Gaona, Y Salcedo, and G Díaz).

Objective: To understand the experiences of diverse families when taking their young children to the dentist and to document their prevalence.

Methods: An exploratory sequential design was used. First, 4 focus groups (N = 33) comprised of low-income female caregivers of children under 6 years of age were conducted in English and Spanish. Discussions centered around facilitators and barriers to taking children to the dentist. Themes derived from the groups were then used to create a survey that was given to 1184 caregivers in English, Spanish, or Vietnamese.

Results: Thematic coding of focus groups found little support for typically reported barriers to pediatric oral health care utilization (eg, transportation, cost, knowledge); instead, caregivers reported negative experiences (eg, restraint, separation) as barriers. In the surveys, 66% of caregivers reported being separated from their children, 25% reported that their children were restrained (53.7% for cleanings), 26% of children were given sedating medication for cleanings, and 22% of the caregivers reported experiences that made them not want to return to the dentist. The prevalence of these experiences differed significantly among Latino, Asian, and Caucasian families and for annual incomes under or above $50,000.

Conclusions: Families with lower incomes and/or from ethnic and linguistic minority groups were more likely to report negative experiences at the dentist than higher income and Caucasian families. These data document the high prevalence of negative experiences and suggest ethnic, financial, and linguistic disparities in the quality of experiences. More research is needed on the role of dentists in facilitating or hindering oral health care utilization among diverse families.
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http://dx.doi.org/10.1016/j.acap.2019.03.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6828576PMC
August 2020

Separation of Small-Diameter Single-Walled Carbon Nanotubes in One to Three Steps with Aqueous Two-Phase Extraction.

ACS Nano 2019 Feb 28;13(2):2567-2578. Epub 2019 Jan 28.

Institute of Nanotechnology , Karlsruhe Institute of Technology , Karlsruhe 76344 , Germany.

An aqueous two-phase extraction (ATPE) technique capable of separating small-diameter single-walled carbon nanotubes in one, two, or at the most three steps is presented. Separation is performed in the well-studied two-phase system containing polyethylene glycol and dextran, but it is achieved without changing the global concentration or ratio of cosurfactants. Instead, the technique is reliant upon the different surfactant shell around each nanotube diameter at a fixed surfactant concentration. The methodology to obtain a single set of surfactant conditions is provided, and strategies to optimize these for other diameter regimes are discussed. In total, 11 different chiralities in the diameter range 0.69-0.91 nm are separated. These include semiconducting and both armchair and nonarmchair metallic nanotube species. Titration of cosurfactant suspensions reveal separation to be driven by the pH of the suspension with each ( n, m) species partitioning at a fixed pH. This allows for an ( n, m) separation approach to be presented that is as simple as pipetting known volumes of acid into the ATPE system.
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http://dx.doi.org/10.1021/acsnano.8b09579DOI Listing
February 2019

Fluorescent Polymer-Single-Walled Carbon Nanotube Complexes with Charged and Noncharged Dendronized Perylene Bisimides for Bioimaging Studies.

Small 2018 07 5;14(28):e1800796. Epub 2018 Jun 5.

Institute of Chemistry and Biochemistry, Freie Universität Berlin, 14195, Berlin, Germany.

Fluorescent nanomaterials are expected to revolutionize medical diagnostic, imaging, and therapeutic tools due to their superior optical and structural properties. Their inefficient water solubility, cell permeability, biodistribution, and high toxicity, however, limit the full potential of their application. To overcome these obstacles, a water-soluble, fluorescent, cytocompatible polymer-single-walled carbon nanotube (SWNT) complex is introduced for bioimaging applications. The supramolecular complex consists of an alkylated polymer conjugated with neutral hydroxylated or charged sulfated dendronized perylene bisimides (PBIs) and SWNTs as a general immobilization platform. The polymer backbone solubilizes the SWNTs, decorates them with fluorescent PBIs, and strongly improves their cytocompatibility by wrapping around the SWNT scaffold. In photophysical measurements and biological in vitro studies, sulfated complexes exhibit superior optical properties, cellular uptake, and intracellular staining over their hydroxylated analogs. A toxicity assay confirms the highly improved cytocompatibility of the polymer-wrapped SWNTs toward surfactant-solubilized SWNTs. In microscopy studies the complexes allow for the direct imaging of the SWNTs' cellular uptake via the PBI and SWNT emission using the 1st and 2nd optical window for bioimaging. These findings render the polymer-SWNT complexes with nanometer size, dual fluorescence, multiple charges, and high cytocompatibility as valuable systems for a broad range of fluorescence bioimaging studies.
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http://dx.doi.org/10.1002/smll.201800796DOI Listing
July 2018

"It's Just a Lot of Work": Adolescents' Self-Presentation Norms and Practices on Facebook and Instagram.

J Res Adolesc 2019 03 12;29(1):196-209. Epub 2018 Feb 12.

University of California, Irvine.

We explored adolescents' (12- to 18-year-olds; n = 51) awareness of their audience and subsequent self-presentation practices on Facebook and Instagram through focus group discussions. Findings suggest that teens, who are developmentally able to perceive a situation from the third-person perspective and who value peer approval, purposefully share content to appear interesting, well liked, and attractive. Some teens invested great effort into posting by these norms, even asking their friends to help; however, this was more common among girls. Older teens especially discussed taking the perspective of their audience when deciding what to post, which is consistent with the finding that perspective taking continues to develop throughout adolescence. These findings suggest that perspective taking skills and need for peer approval influence self-presentation online.
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http://dx.doi.org/10.1111/jora.12376DOI Listing
March 2019
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