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STEM education programs are often formulated with a "hands-on activities" focus across a wide array of topics from robotics to rockets to ecology. Traditionally, the impact of these programs is based on surveys of youth on program-specific experiences or the youths’ interest and impressions of science in general. In this manuscript, we offer a new approach to analyzing science programming design and youth participant impact. The conceptual framework discussed here concentrates on the organization and analysis of common learning activities and instructional strategies. We establish instrument validity and reliability through an analysis of validity threats and pilot study results. We conclude by using this instrument in an example analysis of a STEM education program.

Understanding electron–phonon interactions in metal-halide perovskites (MHPs) is critical for improving their performance in optoelectronic devices. Probing lattice vibrations with conventional spectroscopic methods, however, is challenging due to the sensitivity of MHPs to laser light, humidity, and temperature changes. Here we report low-frequency Raman spectra of the δ and γ phases, as well as mixed ion derivatives, of CsPbI3. These spectra were obtained by combining below-bandgap low-frequency Raman measurements using a 976 nm laser and nanoconfinement of crystals within inert scaffolds to stabilize the MHPs against temperature-induced polymorph transitions and humidity-induced degradation. Density functional theory calculations demonstrate that the main vibrational modes in the δ- and γ-CsPbI3 Raman spectra correspond to octahedral twisting and distortions. Effects of the A-site cation and halide on these vibrational modes were determined by analyzing low-frequency Raman spectra of CsPbIxBr3−x and MAyCs1−yPbI3. The Raman peak positions primarily depend on the lattice dimensions, regardless of the nature of the cations and anions, with lattice expansions causing a shift of the vibrational modes to lower frequencies.

The solution processing of optoelectronic active layers promises to usher in a new era of technologies, from rollable displays to smart textiles, but critical challenges remain in the processing of these materials. While solution-based deposition of these compounds, including organic small-molecules and polymers and metal–halide perovskites, is key to driving down manufacturing costs, the rapid, uncontrolled nature of solution processing invariably results in the formation of kinetically trapped films, with heterogeneities and defects spanning multiple length scales that degrade device performance. Given such finite time, usually on the order of seconds, for molecules to organize as solvent evaporates from the active layers, the use of nanoporous scaffolds to select for desired crystallization outcomes is a promising approach to addressing this critical issue. As the size of crystals decreases, their surface free energy plays an increasingly important role in dictating their morphology and structure. By c...

Reducing the size of metal halide perovskite crystals to the nanoscale has been demonstrated to stabilize high-performance metastable polymorphs at room temperature. Cesium lead iodide (CsPbI3), fo...

The realization of on-chip quantum networks ideally requires lossless interfaces between photons and solid-state quantum emitters. We propose and demonstrate on-chip arrays of metallo-dielectric antennas (MDA) that are tailored toward efficient and broadband light collection from individual embedded carbon nanotube quantum emitters by trapping air gaps on chip that form cavity modes. Scalable implementation is realized by employing polymer layer dry-transfer techniques that avoid solvent incompatibility issues, as well as a planar design that avoids solid-immersion lenses. Cryogenic measurements demonstrate 7-fold enhanced exciton intensity when compared to emitters located on bare wafers, corresponding to a light collection efficiency (LCE) up to 92% in the best case (average LCE of 69%) into a narrow output cone of ±15° that enables a priori fiber-to-chip butt coupling. The demonstrated MDA arrays are directly compatible with other quantum systems, particularly 2D materials, toward enabling efficient on...

Through a combination of rheological characterization and temperature-variable imaging methods, a novel gelation pathway in dilute solutions of a semiconducting polymer to achieve interconnected, crystalline networks with hierarchical porosity is reported. Upon rapid cooling, solutions of regioregular poly(3-hexylthiophene) (RR-P3HT) in ortho-dichlorobenzene formed thermoreversible gels. Temperature-variable confocal microscopy revealed cooling-induced structural rearrangement to progress through viscoelastic phase separation. The phase separation process arrested prematurely during the formation of micron-sized solvent-rich "holes" within the RR-P3HT matrix due to intrachain crystallization. Cryogen-based scanning electron microscopy of RR P3HT gels revealed the existence of an interfibrillar network exhibiting nano-sized pores. Remarkably, these networks formed to equal gel strengths when a third component, either small molecule phenyl C61 butyric acid methyl ester (PCBM) or non-crystallizing regiorandom (Rra)-P3HT, was added to the solution. Organic solar cells in which the active layers were deposited from phase-separated solutions displayed 45% higher efficiency compared to reference cells., 34 pages, 5 figures and 8 supplemental figures

Metal–halide perovskites are promising candidates to advance optoelectronic devices but are known to suffer from rapid material degradation. Here we demonstrate that nanoconfinement is an effective strategy for the long-term stabilization of metal–halide perovskite MAPbI3 crystals against humidity-induced degradation and temperature-induced polymorph transitions. Two-dimensional X-ray diffraction patterns of MAPbI3 films reveal an unprecedented air-stability of up to 594 days in non-chemically modified, non-passivated MAPbI3 films deposited on substrates imposing complete 2D confinement on the tens of nanometers length scale. Temperature-dependent X-ray diffraction analysis and optical spectroscopy further reveal the suppression of temperature-dependent phase transitions in nanoconfined MAPbI3 crystals. Most notably, the high-temperature cubic phase of MAPbI3, typically stable at temperatures above 327 K, remains present until a temperature of 170 K when the perovskite crystals are nanoconfined within the 100 nm diameter pores of anodized aluminum oxide templates. Photoluminescence mapping confirms that nanoconfined MAPbI3 crystals exhibit spatial uniformity on the tens of microns length scale, suggesting that nanoconfinement is an effective strategy for the formation of high-quality, stable MAPbI3 crystals across large areas.

Au nanorods (Au NRs) are promising candidates for sensing applications due to their tunable localized surface plasmon resonance wavelength. At temperatures above 250 °C, however, these structures are morphologically unstable and tend to evaporate. We herein report a novel refractory plasmonic nanocomposite system comprising Au NRs entrapped in anodized aluminum oxide (AAO) scaffolds that are stable up to 800 °C. Au NRs were synthesized in the cylindrical pores of sapphire-supported AAO via in situ electroless deposition on catalytic Au nanoparticles (Au NPs) anchored on the pore walls. The morphological characteristics and surface-enhanced Raman scattering (SERS) functionality of Au NRs before and after heat treatment were evaluated using SEM, XRD and Raman spectroscopy. Compared to unconfined Au NRs that evolved into spherical particles at temperatures below 250 °C and subsequently evaporated from the substrate surface, the morphology of Au NRs in AAO was preserved upon heat treatment at temperatures up to 800 °C. Furthermore, by tuning the AAO scaffolds thickness and pore diameter, the aspect ratio (AR) of the entrapped Au NRs was varied from 2.4 to 7.8. The SERS sensitivity of Au NRs in AAO was found to increase with decreasing AR when the incident light was parallel to the rod longitudinal axis, in close agreement with the calculated fourth power of the local electromagnetic field using the finite-difference time domain method.

This exploratory qualitative study investigated how doctoral students reported their personal and professional interaction experiences that they believed might facilitate or impede their academic pursuits in biomedical research. We collected 19 in-depth interviews with doctoral students in biomedical research from eight universities, and we based our qualitative analytic approach on the work of Miles and Huberman. The results indicated that among different sources and types of interaction, academic and emotional interactions from family and teachers in various stages essentially affected students’ persistence in the biomedical science field. In addition, co-mentorship among peers, departmental environment, and volunteer experiences were other essential factors. This study also found related experiences among women and underrepresented minority students that were important to their academic pursuit.

This study addresses the association between middle-school students' reported participation in science summer programmes and their reported expectation of a career in science and engineering. Data were collected on 1,580 students from eight middle schools in five states, applying an accelerated longitudinal design. Two consecutive cohorts were sampled over a two-year period time. Logistic regression analysis was used to examine the relationship between students' participation in science summer camps and their career interest in science and engineering while initial career interest and background information were considered. Results indicate that students who participated in science summer camps before or in the first year of the study, compared to students who did not, are significantly more likely to report science and engineering as their future career field in the second year of the study. It appears that students who once participated in science summer camps were more likely to later report a career i...

Do summer laboratory research apprenticeships during high school have an impact on entry to MD/PhD programs? This quantitative study (n= 236,432) examines the connection between laboratory research apprenticeship experience at the high school level and matriculation into one of the more rigorous educational programs for scientific research training., Do summer laboratory research apprenticeships during high school have an impact on entry into MD/PhD programs? Apart from the nearly decade-long span of time between high school and matriculation into an MD/PhD program, young people have many life-shaping experiences that presumably impact their education and career trajectories. This quantitative study (n = 236,432) examines the connection between early laboratory research apprenticeship experiences at the high school level and matriculation into one of the more rigorous educational programs for scientific research training. The span of time covered by this analysis reaches across more than a decade, examining the potential importance of research experiences during the precollege years in the educational trajectory of young people. Intertwined with this question on research experiences is a second major concern regarding diversity in the life sciences research corps. Diversity in this wide-ranging discipline refers specifically to the underrepresentation of Blacks/African Americans, Hispanics/Latino/as, and American Indians/Alaska Natives among the ranks of research scientists. Thus, this study includes analyses that specifically focus on research apprenticeships of Blacks/African Americans and Hispanics/Latino/as and their entrance into MD/PhD programs.