Strong Coupling of Two-Dimensional Excitons and Plasmonic Photonic Crystals: Microscopic Theory Reveals Triplet Spectra.

Monolayers of transition metal dichalcogenides (TMDCs) are direct-gap semiconductors with strong light-matter interactions featuring tightly bound excitons, while plasmonic crystals (PCs), consisting of metal nanoparticles that act as meta-atoms, exhibit collective plasmon modes and allow one to tailor electric fields on the nanoscale. Recent experiments show that TMDC-PC hybrids can reach the strong-coupling limit between excitons and plasmons, forming new quasiparticles, so-called plexcitons. To describe this coupling theoretically, we develop a self-consistent Maxwell-Bloch theory for TMDC-PC hybrid structures, which allows us to compute the scattered light in the near- and far-fields explicitly and provide guidance for experimental studies. One of the key findings of the developed theory is the necessity to differentiate between bright and originally momentum-dark excitons. Our calculations reveal a spectral splitting signature of strong coupling of more than 100 meV in gold-MoSe2 structures with 30 nm nanoparticles, manifesting in a hybridization of the plasmon mode with momentum-dark excitons into two effective plexcitonic bands. The semianalytical theory allows us to directly infer the characteristic asymmetric line shape of the hybrid spectra in the strong coupling regime from the energy distribution of the momentum-dark excitons. In addition to the hybridized states, we find a remaining excitonic mode with significantly smaller coupling to the plasmonic near-field, emitting directly into the far-field. Thus, hybrid spectra in the strong coupling regime can contain three emission peaks.

The Effect of Digital Mental Health Literacy Interventions on Mental Health: Systematic Review and Meta-Analysis.

BACKGROUND: Accelerated by technological advancements and the recent global pandemic, there is burgeoning interest in digital mental health literacy (DMHL) interventions that can positively affect mental health. However, existing work remains inconclusive regarding the effectiveness of DMHL interventions. OBJECTIVE: This systematic review and meta-analysis investigated the components and modes of DMHL interventions, their moderating factors, and their long-term impacts on mental health literacy and mental health. METHODS: We used a random-effects model to conduct meta-analyses and meta-regressions on moderating effects of DMHL interventions on mental health. RESULTS: Using 144 interventions with 206 effect sizes, we found a moderate effect of DMHL interventions in enhancing distal mental health outcomes (standardized mean difference=0.42, 95% CI -0.10 to 0.73; P<.001) and a large effect in increasing proximal mental health literacy outcomes (standardized mean difference=0.65, 95% CI 0.59-0.74; P<.001). Uptake of DMHL interventions was comparable with that of control conditions, and uptake of DMHL interventions did not moderate the effects on both proximal mental health literacy outcomes and distal mental health outcomes. DMHL interventions were as effective as face-to-face interventions and did not differ by platform type or dosage. DMHL plus interventions (DMHL psychoeducation coupled with other active treatment) produced large effects in bolstering mental health, were more effective than DMHL only interventions (self-help DMHL psychoeducation), and were comparable with non-DMHL interventions (treatment as usual). DMHL interventions demonstrated positive effects on mental health that were sustained over follow-up assessments and were most effective in enhancing the mental health of emerging and older adults. CONCLUSIONS: For theory building, our review and meta-analysis found that DMHL interventions are as effective as face-to-face interventions. DMHL interventions confer optimal effects on mental health when DMHL psychoeducation is combined with informal, nonprofessional active treatment components such as skills training and peer support, which demonstrate comparable effectiveness with that of treatment as usual (client-professional interactions and therapies). These effects, which did not differ by platform type or dosage, were sustained over time. Additionally, most DMHL interventions are found in Western cultural contexts, especially in high-income countries (Global North) such as Australia, the United States, and the United Kingdom, and limited research is conducted in low-income countries in Asia and in South American and African countries. Most of the DMHL studies did not report information on the racial or ethnic makeup of the samples. Future work on DMHL interventions that target racial or ethnic minority groups, particularly the design, adoption, and evaluation of the effects of culturally adaptive DMHL interventions on uptake and mental health functioning, is needed. Such evidence can drive the adoption and implementation of DMHL interventions at scale, which represents a key foundation for practice-changing impact in the provision of mental health resources for individuals and the community. TRIAL REGISTRATION: PROSPERO International Prospective Register of Systematic Reviews CRD42023363995; https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023363995.

Mother-child and father-child "serve and return" interactions at 9 months: Associations with children's language skills at 18 and 24 months.

Infants learn language through the back-and-forth interactions with their parents where they "serve" by uttering sounds, gesturing, or looking and parents "return" in prompt (i.e., close in time) and meaningful (i.e., semantically relevant to the object of interest) ways. In a sample of 9-month-old infants (n = 148) and their mothers and fathers (n = 296 parents) from ethnically and socioeconomically diverse backgrounds, we examined the associations between "serve and return" (SR) parent-child interactions and children's language skills at 18 and 24 months. We also examined the moderation effects between maternal and paternal SR interactions on language outcomes. SR interactions were transcribed and coded from videotaped parent-child toy play activities during home visits. We report three findings. First, mothers who provided more meaningful responses to their child's serves at 9 months had children with higher expressive language scores at 18 months. Second, fathers' prompt responses (i.e., within 3 s) at 9 months were associated with higher receptive language scores at 18 months, but their meaningful responses were negatively associated with receptive language scores at 24 months. Third, the negative association between fathers' meaningful responses and children's receptive language scores was reduced (compensated) when mothers' meaningful responses were high. Findings show that infants in ethnically and socioeconomically diverse families engage in frequent SR interactions with both mothers and fathers, who make unique contributions to infants' language development. We discuss implications for programs and policies that aim to promote early language development and reduce gaps in school readiness.

Synthesis of two-dimensional triazine covalent organic frameworks at ambient conditions to detect and remove water pollutants.

Synthesis of fully triazine frameworks (C3N3) by metal catalyzed reactions at high temperatures results in carbonized and less-defined structures. Moreover, metal impurities affect the physicochemical, optical and electrical properties of the synthesized frameworks, dramatically. In this work, two-dimensional C3N3 (2DC3N3) has been synthesized by in situ catalyst-free copolymerization of sodium cyanide and cyanuric chloride, as cheap and commercially available precursors, at ambient conditions on gram scale. Reaction between sodium cyanide and cyanuric chloride resulted in electron-poor polyfunctional intermediates, which converted to 2DC3N3 with several hundred micrometers lateral size at ambient conditions upon [2 + 2+2] cyclotrimerization. 2DC3N3 sheets, in bulk and individually, showed strong fluorescence with 63% quantum yield and sensitive to small objects such as dyes and metal ions. The sensitivity of 2DC3N3 emission to foreign objects was used to detect low concentration of water impurities. Due to the high negative surface charge (-37.7 mV) and dispersion in aqueous solutions, they demonstrated a high potential to remove positively charged dyes from water, exemplified by excellent removal efficiency (>99%) for methylene blue. Taking advantage of the straightforward production and strong interactions with dyes and metal ions, 2DC3N3 was integrated in filters and used for the fast detection and efficient removal of water impurities.

Consideration of Developmental Stage and the Debate on the Effects of Screens Use-Not All Things Are Created Equal.

This Viewpoint discusses the role of childhood developmental stage in research evaluating the effects of screen use among youth and its application to practice, policy, and the public.

Collective States in Molecular Monolayers on 2D Materials.

Collective excited states form in organic two-dimensional layers through Coulomb coupling of the molecular transition dipole moments. They manifest as characteristic strong and narrow peaks in the excitation and emission spectra that are shifted to lower energies compared with the monomer transition. We study experimentally and theoretically how robust the collective states are against homogeneous and inhomogeneous broadening, as well as spatial disorder that occurs in real molecular monolayers. Using a microscopic model for a two-dimensional dipole lattice in real space, we calculate the properties of collective states and their extinction spectra. We find that the collective states persist even for 1-10% random variation in the molecular position and in the transition frequency, with a peak position and integrated intensity similar to those for the perfectly ordered system. We measured the optical response of a monolayer of the perylene derivative MePTCDI on two-dimensional materials. On the wide-band-gap insulator hexagonal boron nitride, it shows strong emission from the collective state with a line width that is dominated by the inhomogeneous broadening of the molecular state. When the semimetal graphene is used as a substrate, however, the luminescence is completely quenched. By combining optical absorption, luminescence, and multiwavelength Raman scattering, we verify that the MePTCDI molecules form very similar collective monolayer states on hexagonal boron nitride and graphene substrates, but on graphene the line width is dominated by nonradiative excitation transfer from the molecules to the substrate. Our study highlights the transition from the localized molecular state of the monomer to a delocalized collective state in the two-dimensional molecular lattice that is entirely based on Coulomb coupling between optically active excitations of the electrons and molecular vibrations. The excellent properties of organic monolayers make them promising candidates for components of soft-matter optoelectronic devices.

Applying a family stress model to understand U.S. families' patterns of stress, media use, and child behavior during the COVID-19 pandemic.

The COVID-19 pandemic has greatly altered family life, and research among adults and families is finding increases in financial stress, mental health problems, screen time, parental conflict, and child behavior problems. Given these patterns, we sought to replicate these findings with a younger and largely non-white sample and consider how these constructs might relate to each other by using the Family Stress Model. From surveys of 247 predominately Latine mothers and fathers of children under 4 years in the U.S., we found that financial strain was related to children's media exposure and use, largely through impacts on parents' mental health and coparenting relationship. Interestingly, only use of television in the background and during mealtimes were associated with increases in children's behavior problems. Such findings better capture how stress may operate in a family system and offer a way to counsel parents about healthier media habits for children.

Caregivers' Experiences During the COVID-19 Pandemic and Their Children's Behavior.

The COVID-19 pandemic has financial and emotional impacts on families. We explored how caregivers' financial strain and mental health are associated with changes in their young children's behavior during the pandemic. We additionally considered whether having a sense of purpose moderated these associations. Caregivers (n = 300) in the emergency department of a children's hospital were surveyed anonymously about changes to their employment (e.g., reduced/increased hours and job loss), ability to pay for expenses and whether their child's behavior had changed. Aligned with the Family Stress Model, caregivers' financial strain was associated with poor mental health, inconsistent sleep routines, and changes in children's problematic and prosocial behaviors. A sense of purpose buffered some of these relationships. Families are differently affected by the pandemic and our findings underscore the need for supporting caregivers' mental health and connecting them with resources.

Radial Alignment of Carbon Nanotubes via Dead-End Filtration.

Dead-end filtration is a facile method to globally align single wall carbon nanotubes (SWCNTs) in large area films with a 2D order parameter, S2D , approaching unity. Uniaxial alignment has been achieved using pristine and hot-embossed membranes but more sophisticated geometries have yet to be investigated. In this work, three different patterns with radial symmetry and an area of 3.8 cm2 are created. Two of these patterns are replicated by the filtered SWCNTs and S2D values of ≈0.85 are obtained. Each of the radially aligned SWCNT films is characterized by scanning cross-polarized microscopy in reflectance and laser imaging in transmittance with linear, radial, and azimuthal polarized light fields. The former is used to define a novel indicator akin to the 2D order parameter using Malu's law, yielding 0.82 for the respective film. The films are then transferred to a flexible printed circuit board and terminal two-probe electrical measurements are conducted to explore the potential of those new alignment geometries.

Pregnant in a Pandemic: Connecting Perceptions of Uplifts and Hassles to Mental Health.

How women experience pregnancy as uplifting or a hassle is related to their mental and physical health and birth outcomes. Pregnancy during a pandemic introduces new hassles, but may offer benefits that could affect how women perceive their pregnancy. Surveying 118 ethnically and racially diverse pregnant women, we explore (1) women's traditional and pandemic-related pregnancy uplifts and hassles and (2) how these experiences of pregnancy relate to their feelings of loneliness, positivity, depression, and anxiety. Regressions show that women who experience more intense feelings of uplifts than hassles also feel more positive, less lonely, and have better mental health. Findings suggest that focusing on positive aspects of being pregnant, in general and during a pandemic, might be beneficial for pregnant women's mental health.

Observation of Multi-Directional Energy Transfer in a Hybrid Plasmonic-Excitonic Nanostructure.

Hybrid plasmonic devices involve a nanostructured metal supporting localized surface plasmons to amplify light-matter interaction, and a non-plasmonic material to functionalize charge excitations. Application-relevant epitaxial heterostructures, however, give rise to ballistic ultrafast dynamics that challenge the conventional semiclassical understanding of unidirectional nanometal-to-substrate energy transfer. Epitaxial Au nanoislands are studied on WSe2 with time- and angle-resolved photoemission spectroscopy and femtosecond electron diffraction: this combination of techniques resolves material, energy, and momentum of charge-carriers and phonons excited in the heterostructure. A strong non-linear plasmon-exciton interaction that transfers the energy of sub-bandgap photons very efficiently to the semiconductor is observed, leaving the metal cold until non-radiative exciton recombination heats the nanoparticles on hundreds of femtoseconds timescales. The results resolve a multi-directional energy exchange on timescales shorter than the electronic thermalization of the nanometal. Electron-phonon coupling and diffusive charge-transfer determine the subsequent energy flow. This complex dynamics opens perspectives for optoelectronic and photocatalytic applications, while providing a constraining experimental testbed for state-of-the-art modelling.

Plasmonic nanolaser based on a single oligomer.

We investigate the effect of manipulating the laser quality factor and the spectral properties of the gain medium on an oligomer-based plasmonic nanolaser. We develop different designs of the oligomer resonators, decreasing the lasing threshold and increasing the mode lifetime to improve the lasing efficiency. Based on the designs we are able to decrease the lasing threshold by a factor of ten. We discuss and show numerically the influence of the oligomer geometry, the lasing mode oscillation lifetime, and the photoluminescence peak linewidth of the gain medium on the lasing efficiency of the oligomer based plasmonic nanolaser.

Nanomechanical Spectroscopy of 2D Materials.

We introduce a nanomechanical platform for fast and sensitive measurements of the spectrally resolved optical dielectric function of 2D materials. At the heart of our approach is a suspended 2D material integrated into a high Q silicon nitride nanomechanical resonator illuminated by a wavelength-tunable laser source. From the heating-related frequency shift of the resonator as well as its optical reflection measured as a function of photon energy, we obtain the real and imaginary parts of the dielectric function. Our measurements are unaffected by substrate-related screening and do not require any assumptions on the underling optical constants. This fast (τrise ∼ 135 ns), sensitive (noise-equivalent power = 90⁣pW√Hz), and broadband (1.2-3.1 eV, extendable to UV-THz) method provides an attractive alternative to spectroscopic or ellipsometric characterization techniques.

Risks and Protective Factors of Hispanic Families and Their Young Children during the COVID-19 Pandemic.

This study examines the risk-related factors during the pandemic and protective factors that might reduce its effects on family functioning in a sample of 161 low-income Hispanic parents in the United States, recruited from an ongoing longitudinal intervention study. They were surveyed about family functioning six months into the pandemic. We focused on the associations between social (e.g., exposure to the virus) and economic (e.g., job loss) pandemic-related risks on parental stress, parenting, and children's socioemotional problems and skills, as well as the degree to which coparenting support, parents' positivity, economic support, and access to services and information mitigated (protected) the negative effects of these stressors on family functioning. We found that increases in economic risk were associated with more child competence skills, whereas increases in social risk were associated with less parental engagement. Positivity and economic support moderated the effects of economic risk on parental stress and engagement. These findings show that to intervene effectively with low-income Hispanic families, we need to strengthen and support the resources for coping with adversity.

Microscopic Understanding of Reaction Rates Observed in Plasmon Chemistry of Nanoparticle-Ligand Systems.

Surface-enhanced Raman scattering (SERS) is an effective and widely used technique to study chemical reactions induced or catalyzed by plasmonic substrates, since the experimental setup allows us to trigger and track the reaction simultaneously and identify the products. However, on substrates with plasmonic hotspots, the total signal mainly originates from these nanoscopic volumes with high reactivity and the information about the overall consumption remains obscure in SERS measurements. This has important implications; for example, the apparent reaction order in SERS measurements does not correlate with the real reaction order, whereas the apparent reaction rates are proportional to the real reaction rates as demonstrated by finite-difference time-domain (FDTD) simulations. We determined the electric field enhancement distribution of a gold nanoparticle (AuNP) monolayer and calculated the SERS intensities in light-driven reactions in an adsorbed self-assembled molecular monolayer on the AuNP surface. Accordingly, even if a high conversion is observed in SERS due to the high reactivity in the hotspots, most of the adsorbed molecules on the AuNP surface remain unreacted. The theoretical findings are compared with the hot-electron-induced dehalogenation of 4-bromothiophenol, indicating a time dependency of the hot-carrier concentration in plasmon-mediated reactions. To fit the kinetics of plasmon-mediated reactions in plasmonic hotspots, fractal-like kinetics are well suited to account for the inhomogeneity of reactive sites on the substrates, whereas also modified standard kinetics model allows equally well fits. The outcomes of this study are on the one hand essential to derive a mechanistic understanding of reactions on plasmonic substrates by SERS measurements and on the other hand to drive plasmonic reactions with high local precision and facilitate the engineering of chemistry on a nanoscale.

Challenging Parenting Behaviors in Ethnically Diverse Two-Parent Families in the United States: Association with Infants' Social Competence and Behavior Problems.

We used data from a sample of ethnically diverse first-time parents (N = 186) in the United States to examine differences between mothers' and fathers' challenging parenting behaviors (CPB) when infants were 9 months old as well as covariates of CPB. We also examined associations between CPB and infants' social competence and behavior problems when they were 12 months old. Results showed no differences between mothers and fathers in the level of CPB with their infants. Mothers with more depressive symptoms engaged in more CPB. Over and above the contributions of infants' gender and temperament and parents' education, mothers' and fathers' CPB was not associated with infants' social competence and behavior problems. This study expands our understanding of the universality of CPB and whether it is associated with social competence in ethnically diverse families.

Personalized Stress Monitoring using Wearable Sensors in Everyday Settings.

Since stress contributes to a broad range of mental and physical health problems, the objective assessment of stress is essential for behavioral and physiological studies. Although several studies have evaluated stress levels in controlled settings, objective stress assessment in everyday settings is still largely under-explored due to challenges arising from confounding contextual factors and limited adherence for self-reports. In this paper, we explore the objective prediction of stress levels in everyday settings based on heart rate (HR) and heart rate variability (HRV) captured via low-cost and easy-to-wear photoplethysmography (PPG) sensors that are widely available on newer smart wearable devices. We present a layered system architecture for personalized stress monitoring that supports a tunable collection of data samples for labeling, and present a method for selecting informative samples from the stream of real-time data for labeling. We captured the stress levels of fourteen volunteers through self-reported questionnaires over periods of between 1-3 months, and explored binary stress detection based on HR and HRV using Machine Learning methods. We observe promising preliminary results given that the dataset is collected in the challenging environments of everyday settings. The binary stress detector is fairly accurate and can detect stressful vs non-stressful samples with a macroF1 score of up to %76. Our study lays the groundwork for more sophisticated labeling strategies that generate context-aware, personalized models that will empower health professionals to provide personalized interventions.

Mental health concerns during the COVID-19 pandemic as revealed by helpline calls.

Mental health is an important component of public health, especially in times of crisis. However, monitoring public mental health is difficult because data are often patchy and low-frequency1-3. Here we complement established approaches by using data from helplines, which offer a real-time measure of 'revealed' distress and mental health concerns across a range of topics4-9. We collected data on 8 million calls from 19 countries, focusing on the COVID-19 crisis. Call volumes peaked six weeks after the initial outbreak, at 35% above pre-pandemic levels. The increase was driven mainly by fear (including fear of infection), loneliness and, later in the pandemic, concerns about physical health. Relationship issues, economic problems, violence and suicidal ideation, however, were less prevalent than before the pandemic. This pattern was apparent both during the first wave and during subsequent COVID-19 waves. Issues linked directly to the pandemic therefore seem to have replaced rather than exacerbated underlying anxieties. Conditional on infection rates, suicide-related calls increased when containment policies became more stringent and decreased when income support was extended. This implies that financial relief can allay the distress triggered by lockdown measures and illustrates the insights that can be gleaned from the statistical analysis of helpline data.

Family Functioning in the Time of COVID-19 Among Economically Vulnerable Families: Risks and Protective Factors.

The ongoing COVID-19 crisis has been particularly harmful to economically vulnerable families with young children. We surveyed 247 low-income mothers and fathers from 142 families in the United States about changes in their family life following the economic and social restrictions imposed by the pandemic. We examined the associations between pandemic-related risk factors such as economic stressors (e.g., loss of job) and social stressors (e.g., exposure to the virus) on family functioning (e.g., parents' mental health, parent engagement, and children's socioemotional behaviors) and the degree to which coparenting support and parents' positivity protected families from the negative effects of these stressors on their wellbeing. We found both positive and negative associations. Mothers and fathers who reported more economic stressors since the pandemic also observed that their children behaved more prosocially and that fathers experienced more mental health difficulties during the pandemic. Mothers and fathers who reported more social stressors reported that they were less engaged with their children and their children exhibited more behavior problems compared to before the pandemic. We also found that mothers and fathers who reported feeling more positive also reported feeling less depressed and stressed during the pandemic and observed that their children had more prosocial behaviors compared to before the pandemic. Compared to before the pandemic, mothers and fathers who reported a more supportive coparenting relationship also reported more parent engagement and observed more prosocial behaviors in their children. In terms of protective factors, high levels of parent positivity during the pandemic protected mothers (less mental health difficulties) whereas high levels of coparenting support protected fathers (less mental health difficulties) from the negative effects of economic stress on their mental health during the pandemic. These findings highlight family processes that could promote resilience in mothers and fathers in the face of pandemic-related economic and social stressors.