Far-field, near-field and photothermal response of plasmonic twinned magnesium nanostructures.

Magnesium nanoparticles offer an alternative plasmonic platform capable of resonances across the ultraviolet, visible and near-infrared. Crystalline magnesium nanoparticles display twinning on the (101̄1), (101̄2), (101̄3), and (112̄1) planes leading to concave folded shapes named tents, chairs, tacos, and kites, respectively. We use the Wulff-based Crystal Creator tool to expand the range of Mg crystal shapes with twinning over the known Mg twin planes, i.e., (101̄x), x = 1, 2, 3 and (112̄y), y = 1, 2, 3, 4, and study the effects of relative facet expression on the resulting shapes. These shapes include both concave and convex structures, some of which have been experimentally observed. The resonant modes, far-field, and near-field optical responses of these unusual plasmonic shapes as well as their photothermal behaviour are reported, revealing the effects of folding angle and in-filling of the concave region. Significant differences exist between shapes, in particular regarding the maximum and average electric field enhancement. A maximum field enhancement (|E|/|E0|) of 184, comparable to that calculated for Au and Ag nanoparticles, was found at the tips of the (112̄4) kite. The presence of a 5 nm MgO shell is found to decrease the near-field enhancement by 67% to 90% depending on the shape, while it can increase the plasmon-induced temperature rise by up to 42%. Tip rounding on the otherwise sharp nanoparticle corners also significantly affects the maximum field enhancement. These results provide guidance for the design of enhancing and photothermal substrates for a variety of plasmonic applications across a wide spectral range.

Bimetallic copper palladium nanorods: plasmonic properties and palladium content effects.

Cu is an inexpensive alternative plasmonic metal with optical behaviour comparable to Au but with much poorer environmental stability. Alloying with a more stable metal can improve stability and add functionality, with potential effects on the plasmonic properties. Here we investigate the plasmonic behaviour of Cu nanorods and Cu-CuPd nanorods containing up to 46 mass percent Pd. Monochromated scanning transmission electron microscopy electron energy-loss spectroscopy first reveals the strong length dependence of multiple plasmonic modes in Cu nanorods, where the plasmon peaks redshift and narrow with increasing length. Next, we observe an increased damping (and increased linewidth) with increasing Pd content, accompanied by minimal frequency shift. These results are corroborated by and expanded upon with numerical simulations using the electron-driven discrete dipole approximation. This study indicates that adding Pd to nanostructures of Cu is a promising method to expand the scope of their plasmonic applications.

Seed-mediated synthesis of monodisperse plasmonic magnesium nanoparticles.

We reduce di-n-butylmagnesium with arene (naphthalene, biphenyl, phenanthrene) radical anions and dianions to obtain metallic, plasmonic Mg nanoparticles. Their size and shape depends on the dianion concentration and reduction potential. Based on these results, we demonstrate a seeded growth Mg nanoparticle synthesis and report homogeneous shapes with controllable monodisperse size distributions.

Plasmonic magnesium nanoparticles decorated with palladium catalyze thermal and light-driven hydrogenation of acetylene.

Bimetallic Pd-Mg nanoparticles were synthesized by partial galvanic replacement of plasmonic Mg nanoparticles, and their catalytic and photocatalytic properties in selective hydrogenation of acetylene have been investigated. Electron probe studies confirm that the Mg-Pd structures mainly consist of metallic Mg and sustain several localized plasmon resonances across a broad wavelength range. We demonstrate that, even without light excitation, the Pd-Mg nanostructures exhibit an excellent catalytic activity with selectivity to ethylene of 55% at 100% acetylene conversion achieved at 60 °C. With laser excitation at room temperature over a range of intensities and wavelengths, the initial reaction rate increased up to 40 times with respect to dark conditions and a 2-fold decrease of the apparent activation energy was observed. A significant wavelength-dependent change in hydrogenation kinetics strongly supports a catalytic behavior affected by plasmon excitation. This report of coupling between Mg's plasmonic and Pd's catalytic properties paves the way for sustainable catalytic structures for challenging, industrially relevant selective hydrogenation processes.

Synthesis of Controllable Cu Shells on Au Nanoparticles with Electrodeposition: A Systematic in Situ Single Particle Study.

Bimetallic Cu on Au nanoparticles with controllable morphology and optical properties were obtained via electrochemical synthesis. In particular, multilobed structures with good homogeneity were achieved through the optimization of experimental parameters such as deposition current, charge transfer, and metal ion concentration. A hyperspectral dark field scattering setup was used to characterize the electrodeposition on a single particle level, with changes in localized surface plasmon resonance frequency correlated with deposition charge transfer and amount of Cu deposited as determined by electron microscopy. This demonstrated the ability to tune morphology and spectra through electrochemical parameters alone. Time-resolved in situ measurements of single particle spectra were obtained, giving an insight into the kinetics of the deposition process. Nucleation of multiple cubes of Cu initially occurs preferentially on the tips of Au nanoparticles, before growing and coalescing to form a multilobed, lumpy shell. Modifying the surface of Au nanoparticles by plasma treatment resulted in thicker and more uniform Cu shells.

Opportunities and Challenges for Alternative Nanoplasmonic Metals: Magnesium and Beyond.

Materials that sustain localized surface plasmon resonances have a broad technology potential as attractive platforms for surface-enhanced spectroscopies, chemical and biological sensing, light-driven catalysis, hyperthermal cancer therapy, waveguides, and so on. Most plasmonic nanoparticles studied to date are composed of either Ag or Au, for which a vast array of synthetic approaches are available, leading to controllable size and shape. However, recently, alternative materials capable of generating plasmonically enhanced light-matter interactions have gained prominence, notably Cu, Al, In, and Mg. In this Perspective, we give an overview of the attributes of plasmonic nanostructures that lead to their potential use and how their performance is dictated by the choice of plasmonic material, emphasizing the similarities and differences between traditional and emerging plasmonic compositions. First, we discuss the materials limitation encapsulated by the dielectric function. Then, we evaluate how size and shape maneuver localized surface plasmon resonance (LSPR) energy and field distribution and address how this impacts applications. Next, biocompatibility, reactivity, and cost, all key differences underlying the potential of non-noble metals, are highlighted. We find that metals beyond Ag and Au are of competitive plasmonic quality. We argue that by thinking outside of the box, i.e., by looking at nonconventional materials such as Mg, one can broaden the frequency range and, more importantly, combine the plasmonic response with other properties essential for the implementation of plasmonic technologies.

Size Control in the Colloidal Synthesis of Plasmonic Magnesium Nanoparticles.

Nanoparticles of plasmonic materials can sustain oscillations of their free electron density, called localized surface plasmon resonances (LSPRs), giving them a broad range of potential applications. Mg is an earth-abundant plasmonic material attracting growing attention owing to its ability to sustain LSPRs across the ultraviolet, visible, and near-infrared wavelength range. Tuning the LSPR frequency of plasmonic nanoparticles requires precise control over their size and shape; for Mg, this control has previously been achieved using top-down fabrication or gas-phase methods, but these are slow and expensive. Here, we systematically probe the effects of reaction parameters on the nucleation and growth of Mg nanoparticles using a facile and inexpensive colloidal synthesis. Small NPs of 80 nm were synthesized using a low reaction time of 1 min and ∼100 nm NPs were synthesized by decreasing the overall reaction concentration, replacing the naphthalene electron carrier with biphenyl or using metal salt additives of FeCl3 or NiCl2 at longer reaction times of 17 h. Intermediate sizes up to 400 nm were further selected via the overall reaction concentration or using other metal salt additives with different reduction potentials. Significantly larger particles of over a micrometer were produced by reducing the reaction temperature and, thus, the nucleation rate. We showed that increasing the solvent coordination reduced Mg NP sizes, while scaling up the reaction reduced the mixing efficiency and produced larger NPs. Surprisingly, varying the relative amounts of Mg precursor and electron carrier had little impact on the final NP sizes. These results pave the way for the large-scale use of Mg as a low-cost and sustainable plasmonic material.

Improving the stability of plasmonic magnesium nanoparticles in aqueous media.

This work describes two different core-shell architectures based on Mg nanoparticles (NPs) synthesised in order to improve Mg's stability in aqueous solutions. The shell thickness in Mg-polydopamine NPs can be modulated from 5 to >50 nm by ending the polymerization at different times; the resulting structures stabilize the metallic, plasmonic core in water for well over an hour. Mg-silica NPs with shells ranging from 5 to 30 nm can also be prepared via a modified Stöber procedure and they retain optical properties in 5% water-in-isopropanol solutions. These new architectures allow Mg nanoplasmonics to be investigated as an alternative to Ag and Au in a broader range of experimental conditions for a rich variety of applications.

On the identification of twinning in body-centred cubic nanoparticles.

Many metals and alloys, including Fe and W, adopt body-centred cubic (BCC) crystal structures and nanoparticles of these metals are gaining significant scientific and industrial relevance. Twinning has a marked effect on catalytic activity, yet there is little evidence for or against the presence of twinning in BCC nanoparticles. Here, we explore the potential shapes of twinned BCC nanoparticles, and predict their electron microscopy and diffraction signatures. BCC single crystal and twinned shapes often appear similar and diffraction patterns along common, low-index zone axes are often indistinguishable, casting doubt on many claims of single crystallinity. We conclude by outlining how nanoparticles can be characterized to conclusively prove the presence or absence of twinning.

Tents, Chairs, Tacos, Kites, and Rods: Shapes and Plasmonic Properties of Singly Twinned Magnesium Nanoparticles.

Nanostructures of some metals can sustain light-driven electron oscillations called localized surface plasmon resonances, or LSPRs, that give rise to absorption, scattering, and local electric field enhancement. Their resonant frequency is dictated by the nanoparticle (NP) shape and size, fueling much research geared toward discovery and control of new structures. LSPR properties also depend on composition; traditional, rare, and expensive noble metals (Ag, Au) are increasingly eclipsed by earth-abundant alternatives, with Mg being an exciting candidate capable of sustaining resonances across the ultraviolet, visible, and near-infrared spectral ranges. Here, we report numerical predictions and experimental verifications of a set of shapes based on Mg NPs displaying various twinning patterns including (101̅1), (101̅2), (101̅3), and (112̅1), that create tent-, chair-, taco-, and kite-shaped NPs, respectively. These are strikingly different from what is obtained for typical plasmonic metals because Mg crystallizes in a hexagonal close packed structure, as opposed to the cubic Al, Cu, Ag, and Au. A numerical survey of the optical response of the various structures, as well as the effect of size and aspect ratio, reveals their rich array of resonances, which are supported by single-particle optical scattering experiments. Further, corresponding numerical and experimental studies of the near-field plasmon distribution via scanning transmission electron microscopy electron-energy loss spectroscopy unravels a mode nature and distribution that are unlike those of either hexagonal plates or cylindrical rods. These NPs, made from earth-abundant Mg, provide interesting ways to control light at the nanoscale across the ultraviolet, visible, and near-infrared spectral ranges.

When the Muses Strike: Creative Ideas of Physicists and Writers Routinely Occur During Mind Wandering.

How often are creative ideas generated during episodes of mind wandering, and do they differ from those generated while on task? In two studies ( N = 98, N = 87), professional writers and physicists reported on their most creative idea of the day, what they were thinking about and doing when it occurred, whether the idea felt like an "aha" moment, and the quality of the idea. Participants reported that one fifth of their most significant ideas of the day were formed during spontaneous task-independent mind wandering-operationalized here as (a) engaging in an activity other than working and (b) thinking about something unrelated to the generated idea. There were no differences between ratings of the creativity or importance of ideas that occurred during mind wandering and those that occurred on task. However, ideas that occurred during mind wandering were more likely to be associated with overcoming an impasse on a problem and to be experienced as "aha" moments, compared with ideas generated while on task.

Decoration of plasmonic Mg nanoparticles by partial galvanic replacement.

Plasmonic structures have attracted much interest in science and engineering disciplines, exploring a myriad of potential applications owing to their strong light-matter interactions. Recently, the plasmonic concentration of energy in subwavelength volumes has been used to initiate chemical reactions, for instance by combining plasmonic materials with catalytic metals. In this work, we demonstrate that plasmonic nanoparticles of earth-abundant Mg can undergo galvanic replacement in a nonaqueous solvent to produce decorated structures. This method yields bimetallic architectures where partially oxidized 200-300 nm Mg nanoplates and nanorods support many smaller Au, Ag, Pd, or Fe nanoparticles, with potential for a stepwise process introducing multiple decoration compositions on a single Mg particle. We investigated this mechanism by electron-beam imaging and local composition mapping with energy-dispersive X-ray spectroscopy as well as, at the ensemble level, by inductively coupled plasma mass spectrometry. High-resolution scanning transmission electron microscopy further supported the bimetallic nature of the particles and provided details of the interface geometry, which includes a Mg oxide separation layer between Mg and the other metal. Depending on the composition of the metallic decorations, strong plasmonic optical signals characteristic of plasmon resonances were observed in the bulk with ultraviolet-visible spectrometry and at the single particle level with darkfield scattering. These novel bimetallic and multimetallic designs open up an exciting array of applications where one or multiple plasmonic structures could interact in the near-field of earth-abundant Mg and couple with catalytic nanoparticles for applications in sensing and plasmon-assisted catalysis.

A preliminary investigation of attachment style and inflammation in African-American young adults.

Individuals' social experiences are associated with their mental health, physical health, and even mortality. Over the last 30 years, researchers have examined the ways in which these social experiences might be associated with chronic inflammation - a component underlying many of the chronic diseases of aging. Little research, however, has examined the role of adults' attachment style as a specific social component that might be associated with inflammation. In the present study, we utilized data from a sample of 59 African-American adults from the Maryland Adolescent Development in Context Study (MADICS) to examine the links between attachment avoidance and attachment anxiety and C-reactive protein (CRP) and interleukin (IL)-6. After controlling for demographic characteristics, body mass index, and depressive symptoms, attachment avoidance and anxiety were associated with IL-6 but not CRP. This study adds to the growing body of research identifying the wide range of social experiences associated with inflammation and further suggests that attachment relationship experiences may have implications for biological processes relevant to many chronic diseases of aging.

STARS experiential group intervention: a complex trauma treatment approach for survivors of human trafficking.

This is the abstract that was submitted online with the paper: Despite the fact that many survivors of human trafficking have experienced complex trauma, there are no established interventions designed to specifically address these impacts. Leaders in the field of complex trauma have advocated for the need for somatic approaches to intervention. This paper presents STARS Experiential Group treatment, the first structured bodybased group intervention that has been designed to address complex trauma in survivors of human trafficking. Three pilot groups were run in residential settings with adolescent and adult survivors of sex trafficking. Two adaptations were utilized, with one focusing on application of expressive arts modalities and the other incorporating theater games. Qualitative results, using thematic analysis, identified several themes related to challenges and potential benefits of these groups. Potential benefits of the STARS groups were found in the areas of Interpersonal Relationships, Regulation, and Self/ Identity, with fourteen sub-themes further describing positive impacts. Challenges within these areas are explored, to inform the development of group interventions for trafficking survivors. The results of this paper suggest that experiential, somatically-oriented group treatment shows promise as an important element of holistic intervention with trafficking survivors.

Treating adult survivors of childhood emotional abuse and neglect: A new framework.

This article provides the outline of a new framework for treating adult survivors of childhood emotional abuse and neglect. Component-based psychotherapy (CBP) is an evidence-informed model that bridges, synthesizes, and expands upon several existing schools, or theories, of treatment for adult survivors of traumatic stress. These include approaches to therapy that stem from more classic traditions in psychology, such as psychoanalysis, to more modern approaches including those informed by feminist thought. Moreover, CBP places particular emphasis on integration of key concepts from evidence-based treatment models developed in the past few decades predicated upon thinking and research on the effects of traumatic stress and processes of recovery for survivors. (PsycINFO Database Record

Perceptions of parental secure base support in African American adolescents and young adults: A preliminary study of predictive links to adult C-reactive protein.

Within the field of relationship science there is increasing interest in the connections between close relationships and physical health. In the present study, we examined whether adolescents' (~12 years old) and young adults' (~20 years old) perceptions of their parents as a secure base prospectively predict C-reactive protein (CRP), a commonly used marker of inflammatory activity, at age 32 in a well-characterized sample of African Americans. We utilized existing data collected as part of the Maryland Adolescent Development in Context Study (MADICS) to construct measures of perceptions of parental secure base support (SBS), general parental support, and peer support in early adolescence and early adulthood. In the present study, SBS was operationalized as the perceived ability to depend on parents in times of need. Fifty-nine African American MADICS participants who reported on perceived support in early adolescence and early adulthood participated in a follow-up home visit at age 32 during which serum CRP was measured via a blood draw. After controlling for inflammation-related confounds (e.g., tobacco use, body mass index), adolescents' perceptions of parental SBS, but not peer support or general parental support, predicted lower CRP values at age 32 (b = -.92, SE = .34, p < .05). None of the support variables in early adulthood predicted CRP at 32 years. This study adds to a growing literature on relationships and health-related outcomes and provides the first evidence for a link between parental SBS in adolescence and a marker of inflammatory activity in adulthood.

Profiles of distress in sheltered battered women: implications for intervention.

Heterogeneity in patterns of distress and psychological functioning was investigated using a person-oriented approach to data analysis in two diverse samples of battered women in shelters. In order to provide some empirically derived guidance to clinicians, scores on measures of depressive symptoms as well as state and trait anxiety were cluster analyzed. A four-cluster solution provided the best fit for both samples of women, and despite the demographic differences in the women, generally similar clusters were found in both samples. One cluster contained women with minimal distress; another, those who were mildly anxious; in a third cluster, the women were moderately to highly depressed and anxious; and in a fourth cluster, the women were reporting severe levels of distress. Implications for treatment include the importance of providing individually tailored interventions for the women, based on differential combinations of depression and anxiety, especially for women whose distress levels are in the high and severe ranges of distress.

Mediators of suicidal ideation within a sheltered sample of raped and battered women.

The relationship between suicide attempts and the experience of intimate partner physical violence has been examined in recent literature. The present study extended this literature by examining the relationship between intimate partner rape and suicidal ideation in a sheltered sample of battered women. Fifty women were recruited from a regional shelter setting for battered women in a Midwestern city in the United States. Fifty-eight percent had experienced intimate partner rape. More than one-third of the sample confirmed experiencing suicidal ideation at least "some of the time" within the past week. Experiencing intimate partner rape was significantly associated with suicidal ideation and symptoms of post-traumatic stress disorder (PTSD) and depression. Tests of mediation revealed that both PTSD and depressive symptoms mediated the relationship between intimate partner rape and suicidal ideation.

A randomized clinical trial of eye movement desensitization and reprocessing (EMDR), fluoxetine, and pill placebo in the treatment of posttraumatic stress disorder: treatment effects and long-term maintenance.

OBJECTIVE: The relative short-term efficacy and long-term benefits of pharmacologic versus psychotherapeutic interventions have not been studied for posttraumatic stress disorder (PTSD). This study compared the efficacy of a selective serotonin reup-take inhibitor (SSRI), fluoxetine, with a psychotherapeutic treatment, eye movement desensitization and reprocessing (EMDR), and pill placebo and measured maintenance of treatment gains at 6-month follow-up. METHOD: Eighty-eight PTSD subjects diagnosed according to DSM-IV criteria were randomly assigned to EMDR, fluoxetine, or pill placebo. They received 8 weeks of treatment and were assessed by blind raters posttreatment and at 6-month follow-up. The primary outcome measure was the Clinician-Administered PTSD Scale, DSM-IV version, and the secondary outcome measure was the Beck Depression Inventory-II. The study ran from July 2000 through July 2003. RESULTS: The psychotherapy intervention was more successful than pharmacotherapy in achieving sustained reductions in PTSD and depression symptoms, but this benefit accrued primarily for adult-onset trauma survivors. At 6-month follow-up, 75.0% of adult-onset versus 33.3% of child-onset trauma subjects receiving EMDR achieved asymptomatic end-state functioning compared with none in the fluoxetine group. For most childhood-onset trauma patients, neither treatment produced complete symptom remission. CONCLUSIONS: This study supports the efficacy of brief EMDR treatment to produce substantial and sustained reduction of PTSD and depression in most victims of adult-onset trauma. It suggests a role for SSRIs as a reliable first-line intervention to achieve moderate symptom relief for adult victims of childhood-onset trauma. Future research should assess the impact of lengthier intervention, combination treatments, and treatment sequencing on the resolution of PTSD in adults with childhood-onset trauma.