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1. Control of Photopolymerization of BITh Thin Films with Plasmonic Metal/Dielectric Substrates

   L. Hesami, C. Yang ( September 2023 , IEEE)

   We studied effects of metal-dielectric substrates on photopolymerization of BITh monomer. We found that the rate of photopolymerization is getting higher if the monomer film is deposited on top of silver, gold, and lamellar structures. 

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2. 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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3. Observation of intensity dependent phase-separation in photoreactive monomer–nanoparticle formulations under non-uniform visible light irradiation

   https://doi.org/10.1039/D0SM00922A  

   Pathreeker, Shreyas ; Chen, Fu-Hao ; Biria, Saeid ; Hosein, Ian D. ( January 2020 , Soft Matter)

   We report observations of photopolymerization driven phase-separation in a mixture of a photo-reactive monomer and inorganic nanoparticles. The mixture is irradiated with visible light possessing a periodic intensity profile that elicits photopolymerization along the depth of the mixture, establishing a competition between photo-crosslinking and thermodynamically favorable phase-separating behavior inherent to the system. In situ Raman spectroscopy was used to monitor the polymerization reaction and morphology evolution, and reveals a key correlation between irradiation intensity and composite morphology extending the entire depth of the mixture, i.e. unhindered phase-separation at low irradiation intensity and arrested phase-separation at high irradiation intensity. 3D Raman volume mapping and energy dispersive X-ray mapping confirm that the intensity-dependent irradiation process dictates the extent of phase separation, enabling single-parameter control over phase evolution and subsequent composite morphology. These observations can potentially enable a single-step route to develop polymer–inorganic composite materials with tunable morphologies. 

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4. Spectroscopic investigations of electron and hole dynamics in MAPbBr 3 perovskite film and carrier extraction to PEDOT hole transport layer

   https://doi.org/10.1039/D1CP00658D  

   Niedzwiedzki, Dariusz M. ; Kouhnavard, Mojgan ; Diao, Yifan ; D'Arcy, Julio M. ; Biswas, Pratim ( June 2021 , Physical Chemistry Chemical Physics)

   null (Ed.)

   Organometallic halide perovskite (MAPPbBr 3 ), Rust-based Vapor Phase Polymerization (RVPP)-PEDOT hole transporting layers and (RVPP-PEDOT)/MAPPbBr 3 dual-layer, deposited on fluorine doped tin oxide glass were studied at room temperature using steady-state absorption, time-resolved photoluminescence imaging and femtosecond time-resolved absorption spectroscopy. Application of these techniques in conjunction with diverse excitation intensities allowed determination of various optoelectronic properties of the perovskite film and the time constant of the hole extraction process. Spectral reconstruction of the bandedge absorption spectrum using Elliot's formula enabled separation of the exciton band. The binding energy of the exciton was determined to be 19 meV and the bandgap energy of the perovskite film was 2.37 eV. Subsequent time-resolved photoluminescence studies of the perovskite film performed using a very weak excitation intensity followed by a global analysis of the data revealed monomolecular recombination dynamics of charge carriers occurring with an amplitude weighted lifetime of 3.2 ns. Femtosecond time-resolved transient absorption of the film performed after excitation intensity spanning a range of over two orders of magnitude enabled determining the rate constant of bimolecular recombination and was found to be 2.6 × 10 −10 cm 3 s −1 . Application of numerous high intensity excitations enabled observation of band filling effect and application of the Burstein–Moss model allowed to determine the reduced effective mass of photoexcited electron–hole pair in MAPPbBr 3 film to be 0.19 rest mass of the electron. Finally, application of transient absorption on RVPP-PEDOT/MAPPbBr 3 enabled determination of a 0.4 ps time constant for the MAPPbBr 3 -to-PEDOT hole extraction process. 

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5. Enlightening advances in polymer bioconjugate chemistry: light-based techniques for grafting to and from biomacromolecules

   https://doi.org/10.1039/d0sc01544j  

   Olson, Rebecca A. ; Korpusik, Angie B. ; Sumerlin, Brent S. ( May 2020 , Chemical Science)

   null (Ed.)

   Photochemistry has revolutionized the field of polymer–biomacromolecule conjugation. Ligation reactions necessitate biologically benign conditions, and photons have a significant energy advantage over what is available thermally at ambient temperature, allowing for rapid and unique reactivity. Photochemical reactions also afford many degrees of control, specifically, spatio-temporal control, light source tunability, and increased oxygen tolerance. Light-initiated polymerizations, in particular photo-atom-transfer radical polymerization (photo-ATRP) and photoinduced electron/energy transfer reversible addition–fragmentation chain transfer polymerization (PET-RAFT), have been used for grafting from proteins, DNA, and cells. Additionally, the spatio-temporal control inherent to light-mediated chemistry has been utilized for grafting biomolecules to hydrogel networks for many applications, such as 3-D cell culture. While photopolymerization has clear advantages, there are factors that require careful consideration in order to obtain optimal control. These factors include the photocatalyst system, light intensity, and wavelength. This Perspective aims to discuss recent advances of photochemistry for polymer biomacromolecule conjugation and potential considerations while tailoring these systems. 

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