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1. Cascade synthesis and optoelectronic applications of intermediate bandgap Cu3VSe4 nanosheets

   https://doi.org/10.1038/s41598-020-78649-9  

   Liu, Mimi ; Lai, Cheng-Yu ; Zhang, Meng ; Radu, Daniela R. ( December 2020 , Scientific Reports)

   Two-dimensional (2D) ternary materials recently generated interest in optoelectronics and energy-related applications, alongside their binary counterparts. To date, only a few naturally occurring layered 2D ternary materials have been explored. The plethora of benefits owed to reduced dimensionality prompted exploration of expanding non-layered ternary chalcogenides into the 2D realm. This work presents a templating method that uses 2D transition metal dichalcogenides as initiators to be converted into the corresponding ternary chalcogenide upon addition of copper, via a solution-phase synthesis, conducted in high boiling point solvents. The process starts with preparation of VSe₂nanosheets, which are next converted into Cu₃VSe₄sulvanite nanosheets (NSs) which retain the 2D geometry while presenting an X-ray diffraction pattern identical with the one for the bulk Cu₃VSe₄. Both the scanning electron microscopy and transmission microscopy electron microscopy show the presence of quasi-2D morphology. Recent studies of the sulfur-containing sulvanite Cu₃VS₄highlight the presence of an intermediate bandgap, associated with enhanced photovoltaic (PV) performance. The Cu₃VSe₄nanosheets reported herein exhibit multiple UV–Vis absorption peaks, related to the intermediate bandgaps similar to Cu₃VS₄and Cu₃VSe₄nanocrystals. To test the potential of Cu₃VSe₄NSs as an absorber for solar photovoltaic devices, Cu₃VSe₄NSs thin-films deposited on FTO were subjected to photoelectrochemical testing, showing p-type behavior and stable photocurrents of up to ~ 0.036 mA/cm². The photocurrent shows a ninefold increase in comparison to reported performance of Cu₃VSe₄nanocrystals. This proves that quasi-2D sulvanite nanosheets are amenable to thin-film deposition and could show superior PV performance in comparison to nanocrystal thin-films. The obtained electrical impedance spectroscopy signal of the Cu₃VSe₄ NSs-FTO based electrochemical cell fits an equivalent circuit with the circuit elements of solution resistance (R_s), charge-transfer resistance (R_ct), double-layer capacitance (C_dl), and Warburg impedance (W). The estimated charge transfer resistance value of 300 Ω cm²obtained from the Nyquist plot provides an insight into the rate of charge transfer on the electrode/electrolyte interface.

    

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2. Mixed Nanosphere Assemblies at a Liquid–Liquid Interface

   https://doi.org/10.1002/smll.202308560  

   Fink, Zachary ; Wu, Xuefei ; Kim, Paul Y. ; McGlasson, Alex ; Abdelsamie, Maged ; Emrick, Todd ; Sutter‐Fella, Carolin M. ; Ashby, Paul D. ; Helms, Brett A. ; Russell, Thomas P. ( November 2023 , Small)

   The in‐plane packing of gold (Au), polystyrene (PS), and silica (SiO₂) spherical nanoparticle (NP) mixtures at a water–oil interface is investigated in situ by UV–vis reflection spectroscopy. All NPs are functionalized with carboxylic acid such that they strongly interact with amine‐functionalized ligands dissolved in an immiscible oil phase at the fluid interface. This interaction markedly increases the binding energy of these nanoparticle surfactants (NPSs). The separation distance between the Au NPSs and Au surface coverage are measured by the maximum plasmonic wavelength (λ_max) and integrated intensities as the assemblies saturate for different concentrations of non‐plasmonic (PS/SiO₂) NPs. As the PS/SiO₂content increases, the time to reach intimate Au NP contact also increases, resulting from their hindered mobility. λ_maxchanges within the first few minutes of adsorption due to weak attractive inter‐NP forces. Additionally, a sharper peak in the reflection spectrum at NP saturation reveals tighter Au NP packing for assemblies with intermediate non‐plasmonic NP content. Grazing incidence small angle X‐ray scattering (GISAXS) and scanning electron microscopy (SEM) measurements confirm a decrease in Au NP domain size for mixtures with larger non‐plasmonic NP content. The results demonstrate a simple means to probe interfacial phase separation behavior using in situ spectroscopy as interfacial structures densify into jammed, phase‐separated NP films.

    

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3. Validation of Elemental and Isotopic Abundances in Late-M Spectral Types with the Benchmark HIP 55507 AB System

   https://doi.org/10.3847/1538-4357/ad1243  

   Xuan, Jerry W. ; Wang, Jason ; Finnerty, Luke ; Horstman, Katelyn ; Grimm, Simon ; Peck, Anne E. ; Nielsen, Eric ; Knutson, Heather A. ; Mawet, Dimitri ; Isaacson, Howard ; et al ( February 2024 , The Astrophysical Journal)

   M dwarfs are common host stars to exoplanets but often lack atmospheric abundance measurements. Late-M dwarfs are also good analogs to the youngest substellar companions, which share similarT_eff∼ 2300–2800 K. We present atmospheric analyses for the M7.5 companion HIP 55507 B and its K6V primary star with Keck/KPIC high-resolution (R∼ 35,000)K-band spectroscopy. First, by including KPIC relative radial velocities between the primary and secondary in the orbit fit, we improve the dynamical mass precision by 60% and find$M_B={88.0}_{-3.2}^{+3.4}{M}_{\mathrm{Jup}}$, putting HIP 55507 B above the stellar–substellar boundary. We also find that HIP 55507 B orbits its K6V primary star with$a={38}_{-3}^{+4}$au ande= 0.40 ± 0.04. From atmospheric retrievals of HIP 55507 B, we measure [C/H] = 0.24 ± 0.13, [O/H] = 0.15 ± 0.13, and C/O = 0.67 ± 0.04. Moreover, we strongly detect¹³CO (7.8σsignificance) and tentatively detect${\mathrm{H}}_2^{18}\mathrm{O}$(3.7σsignificance) in the companion’s atmosphere and measure${}^{12}\mathrm{CO}{/}^{13}\mathrm{CO}={98}_{-22}^{+28}$and${\mathrm{H}}_2^{16}\mathrm{O}/{\mathrm{H}}_2^{18}\mathrm{O}={240}_{-80}^{+145}$after accounting for systematic errors. From a simplified retrieval analysis of HIP 55507 A, we measure${}^{12}\mathrm{CO}{/}^{13}\mathrm{CO}={79}_{-16}^{+21}$and${\mathrm{C}}^{16}\mathrm{O}/{\mathrm{C}}^{18}\mathrm{O}={288}_{-70}^{+125}$for the primary star. These results demonstrate that HIP 55507 A and B have consistent¹²C/¹³C and¹⁶O/¹⁸O to the <1σlevel, as expected for a chemically homogeneous binary system. Given the similar flux ratios and separations between HIP 55507 AB and systems with young substellar companions, our results open the door to systematically measuring¹³CO and${\mathrm{H}}_2^{18}\mathrm{O}$abundances in the atmospheres of substellar or even planetary-mass companions with similar spectral types.

    

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4. Near-infrared Accretion Signatures from the Circumbinary Planetary-mass Companion Delorme 1 (AB)b*

   https://doi.org/10.3847/2041-8213/ac85ef  

   Betti, S. K. ; Follette, K. B. ; Ward-Duong, K. ; Aoyama, Y. ; Marleau, G. -D. ; Bary, J. ; Robinson, C. ; Janson, M. ; Balmer, W. ; Chauvin, G. ; et al ( August 2022 , The Astrophysical Journal Letters)

   Accretion signatures from bound brown dwarf and protoplanetary companions provide evidence for ongoing planet formation, and accreting substellar objects have enabled new avenues to study the astrophysical mechanisms controlling the formation and accretion processes. Delorme 1 (AB)b, a ∼30–45 Myr circumbinary planetary-mass companion, was recently discovered to exhibit strong Hαemission. This suggests ongoing accretion from a circumplanetary disk, somewhat surprising given canonical gas disk dispersal timescales of 5–10 Myr. Here, we present the first NIR detection of accretion from the companion in Paβ, Paγ, and Brγemission lines from SOAR/TripleSpec 4.1, confirming and further informing its accreting nature. The companion shows strong line emission, withL_line≈ 1–6 × 10⁻⁸L_⊙across lines and epochs, while the binary host system shows no NIR hydrogen line emission (L_line< 0.32–11 × 10⁻⁷L_⊙). Observed NIR hydrogen line ratios are more consistent with a planetary accretion shock than with local line excitation models commonly used to interpret stellar magnetospheric accretion. Using planetary accretion shock models, we derive mass accretion rate estimates of${\dot{M}}_{\mathrm{pla}}\sim 3$–4 × 10⁻⁸M_Jyr⁻¹, somewhat higher than expected under the standard star formation paradigm. Delorme 1 (AB)b’s high accretion rate is perhaps more consistent with formation via disk fragmentation. Delorme 1 (AB)b is the first protoplanet candidate with clear (signal-to-noise ratio ∼5) NIR hydrogen line emission.

    

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5. Wafer-scale synthesis of monolayer two-dimensional porphyrin polymers for hybrid superlattices

   https://doi.org/10.1126/science.aax9385  

   Zhong, Yu ; Cheng, Baorui ; Park, Chibeom ; Ray, Ariana ; Brown, Sarah ; Mujid, Fauzia ; Lee, Jae-Ung ; Zhou, Hua ; Suh, Joonki ; Lee, Kan-Heng ; et al ( December 2019 , Science)

   The large-scale synthesis of high-quality thin films with extensive tunability derived from molecular building blocks will advance the development of artificial solids with designed functionalities. We report the synthesis of two-dimensional (2D) porphyrin polymer films with wafer-scale homogeneity in the ultimate limit of monolayer thickness by growing films at a sharp pentane/water interface, which allows the fabrication of their hybrid superlattices. Laminar assembly polymerization of porphyrin monomers could form monolayers of metal-organic frameworks with Cu 2+ linkers or covalent organic frameworks with terephthalaldehyde linkers. Both the lattice structures and optical properties of these 2D films were directly controlled by the molecular monomers and polymerization chemistries. The 2D polymers were used to fabricate arrays of hybrid superlattices with molybdenum disulfide that could be used in electrical capacitors. 

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