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2-Methyl-3-buten-2-ol (MBO232) is a biogenic volatile organic compound (BVOC), and has a large percentage of emission into the atmosphere. The vacuum ultraviolet (VUV) photochemistry of BVOCs is of great importance for atmospheric chemistry. Studies have been carried out on several BVOCs but have not extended to MBO232. In the present report, the photoionization and dissociation processes of MBO232 in the energy range of 8.0–15.0 eV have been studied by tunable VUV synchrotron radiation coupled with a time-of-flight mass spectrometer. By measuring the photoionization spectra, the adiabatic ionization energy (AIE) of MBO232 and the appearance energies (AEs) of the eight identified fragment ions (i.e., C4H7O+, C3H7O+, C5H9+, C3H6O+, CH3CO+, CH3O+, C4H5+, and C3H5+) were determined. High-level quantum chemistry calculations suggest that there are 3 direct channels and 5 indirect channels via transition states and intermediates accountable for these fragments. Among the reaction channels, the direct elimination of CH3 is the most dominant channel and produces the resonance-stabilized radical cation. Most interestingly, our results show that the CH3 selectively migrates towards the cation, which leads to the different indirect channels. The CH3 migration is a rare process in the dissociative photoionization of metal-free organic molecules. We explain the process by molecular orbital calculations and electron localization function analysis and explore the non-conventional dissociation channels via the CH3 roaming mechanism. We further perform kinetics analysis using RRKM theory for the channels of interest. The activation barrier, and rate constants are analyzed for the branching fractions of the products. These results provide important implications for the VUV photochemistry of BVOCs in the atmosphere. [ABSTRACT FROM AUTHOR]

Two novel copolymer donors based on one-dimensional (1D)–two-dimensional (2D) asymmetrical benzodithiophene (BDT) units (BDTPH-H and BDTPH-OR) and 2,3-diphenyl-5,8-di(thiophen-2-yl)quinoxaline (DTQx) were synthesized and compared with one-dimensional or two-dimensional symmetric BDT unit based photovoltaic polymers. Both asymmetrical polymers exhibited promising photovoltaic performance compared with 1D and 2D symmetric BDT polymers. The power conversion efficiency (PCE) of PBDTPH-DTQx based polymer solar cells is 5.6%, with balanced VOC = 0.7 V, JSC = 11.89 mA cm−2 and FF = 67.3%, which is almost the highest PCE compared with similar BDT unit and fluorine-free substituted DTQx based polymer. What is more, PBDTPH-DTQx shows better performance than PBDTPHO-DTQx due to the single phenyl making DTQx more planar and with better π–π stacking than alkoxy phenyl. These findings demonstrate that the 1D–2D asymmetrical BDT units are also applicable to poor planarity fluorine-free substituted quinoxaline acceptor system. [ABSTRACT FROM AUTHOR]

To study which strategy (extending side chain π-conjugation with single-bonded or fused aromatic rings) is more effective in improving the photovoltaic properties of benzodithiophene (BDT)-based polymers, naphthyl (NP) and biphenyl (BP) units were introduced to the BDT core as conjugated side chains. Two polymers PBDTNP-DTBO and PBDTBP-DTBO based on NP or BP-substituted BDT and 5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]oxadiazole (DTBO) were designed. These two polymers only exhibited small differences in the chemical structure, but great differences in photovoltaic performance. PBDTNP-DTBO showed a high power conversion efficiency (PCE) of 8.79%, with an open-circuit voltage (Voc) of 0.82 V, a short-circuit current density (Jsc) of 14.34 mA cm−2, and a fill factor (FF) of 74.73%, while PBDTBP-DTBO only showed a maximum PCE of 6.69%, with a Voc of 0.75 V, a Jsc of 13.55 mA cm−2, and a FF of 65.86%. Hence, extending the side chain π-conjugation system of a BDT-based polymer with naphthyl is a more effective method to enhance the photovoltaic properties. [ABSTRACT FROM AUTHOR]

The conformational change of the polymer backbone has an obvious influence on the blended film morphology and the photovoltaic properties. A planar polymer backbone can provide strong intermolecular interaction, but excessive self-aggregation usually disadvantages a favorable film morphology. Here, a dithienothiophene (DTT) unit and a terthiophene (T3) unit were introduced to construct a pair of new conjugated polymers, PDTT-DTBT and PT3-DTBT, respectively, to investigate the correlation between the conformation of the polymer backbone and the photovoltaic properties. The highly planar structure of the DTT unit made PDTT-DTBT exhibit a stronger molecular aggregation than PT3-DTBT. Compared to the DTT unit, the T3 unit changed the molecular structure from fused thiophenes to linked ones, which relaxed the rigidity of the polymer backbone and reduced the degree of polymer self-aggregation, and a more suitable blended film morphology was formed. Due to the weaker electron-donating ability of the DTT unit, PDTT-DTBT/PC71BM-based devices showed a higher open circuit voltage (Voc) of 0.75 V, and a power conversion efficiency (PCE) of 8.01% was obtained with a short-circuit current (Jsc) of 14.85 mA cm−2 and a filled factor (FF) of 71.62%. This PCE value was slightly higher than for PT3-DTBT/PC71BM-based devices, which exhibited a PCE of 7.68% (along with a Voc of 0.66 V, a Jsc of 16.62 mA cm−2 and a FF of 69.69%). [ABSTRACT FROM AUTHOR]

A novel monomer alkoxybiphenyl-substituted benzodithiophene (BDTBP) was synthesized and used as the donor to construct a donor–acceptor copolymer PBDTBP–DTffBT with 4,7-di(4-(2-ethylhexyl)-2-thienyl)-5,6-difluoro-2,1,3-benzothiadiazole (DTffBT) as the acceptor unit. Compared with the corresponding polymer PBDTP–DTffBT based on alkoxyphenyl-substituted BDT, PBDTBP–DTffBT exhibits a red-shifted UV-vis absorption spectra due to its extended π-conjugation structure. The maximum power conversion efficiency (PCE) of PBDTBP–DTffBT based polymer solar cells (PSCs) is 6.70% with Voc = 0.85 V, Jsc = 12.72 mA cm−2 and FF = 62.14%, and the hole mobility is 3.45 × 10−4 cm2 V−1 s−1 while the maximum PCE of PSCs based on PBDTP–DTffBT is only 4.91% and the hole mobility is 1.70 × 10−5 cm2 V−1 s−1. These findings demonstrate that BDTBP unit is a promising building block for constructing a copolymer with high hole mobility, and extending the π-conjugation length on the alkoxyphenyl-substituted BDT is helpful to improve the photovoltaic properties. [ABSTRACT FROM AUTHOR]

Dopant-free poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4,5-b′]dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thieno[3,4-b] thiophene)-2,6-diyl] (PBDTTT-C) polymer is used as hole transporting material (HTM) in electron transporting material (ETM) free planar perovskite solar cells (PSCs). The devices with a PBDTTT-C HTM show higher power conversion efficiency (PCE = 9.95%) than the devices with a P3HT HTM (PCE = 6.17%) with enhanced short circuit current density (Jsc), open circuit voltage (Voc) and fill factor (FF) in a simple device configuration (ITO/CH3NH3PbI3/PBDTTT-C/MoO3/Ag), due to the suitable energy level, better carrier mobility and lower interfacial charge recombination. [ABSTRACT FROM AUTHOR]

Uniform α-Fe2O3 quasi-cubes with high-index facets exposed were synthesized in a controlled manner through a simple hydrothermal method using Mg2+ ions as structure-directing agents. The as-prepared α-Fe2O3 quasi-cubes are bound by (012), (10−2), and (1−12) facets with an edge length of about 200 nm and a dihedral angle of 86°. In the reaction system, the Mg2+ ions would undertake the role of structure and surface director, adsorb to the α-Fe2O3 high energy surface and induce the α-Fe2O3 nanoparticles to grow into quasi-cubic nanocrystals bound by high-index facets. Magnetic measurements testify that the quasi-cubes display surface-dependent magnetic behavior. The α-Fe2O3 quasi-cubes have a splitting between the FC curve and the ZFC curve from the highest experimental temperature to the lowest temperature and no Morin transformation occurs, indicating that they would be under defect ferromagnetic control both at room temperature and low temperature. [ABSTRACT FROM AUTHOR]

In this study, porous Co3O4 nanospheres were controllably synthesized by applying metal Cu2+ ions as structure-inducing agents. The growth of the Co3O4 nanostructures was induced by the metal ions without the addition of any surfactants. The porous Co3O4 nanospheres were composed of nanosheets. When used as electrode materials in a supercapacitor, the porous Co3O4 nanospheres exhibited a much better capacity of 246.7 F g−1 than commercial Co3O4 powder at a current density of 0.5 A g−1, maintaining 86% of the initial capacity at a current density of 1 A g−1 after 500 cycles. Such high performance can be attributed to the desirable morphology. The results manifest that porous Co3O4 nanospheres composed of nanosheets are promising electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

2-Methyl-3-buten-2-ol (MBO232) is a biogenic volatile organic compound (BVOC), and has a large percentage of emission into the atmosphere. The vacuum ultraviolet (VUV) photochemistry of BVOCs is of great importance for atmospheric chemistry. Studies have been carried out on several BVOCs but have not extended to MBO232. In the present report, the photoionization and dissociation processes of MBO232 in the energy range of 8.0-15.0 eV have been studied by tunable VUV synchrotron radiation coupled with a time-of-flight mass spectrometer. By measuring the photoionization spectra, the adiabatic ionization energy (AIE) of MBO232 and the appearance energies (AEs) of the eight identified fragment ions (i.e., C4H7O+, C3H7O+, C5H9+, C3H6O+, CH3CO+, CH3O+, C4H5+, and C3H5+) were determined. High-level quantum chemistry calculations suggest that there are 3 direct channels and 5 indirect channels via transition states and intermediates accountable for these fragments. Among the reaction channels, the direct elimination of CH3 is the most dominant channel and produces the resonance-stabilized radical cation. Most interestingly, our results show that the CH3 selectively migrates towards the cation, which leads to the different indirect channels. The CH3 migration is a rare process in the dissociative photoionization of metal-free organic molecules. We explain the process by molecular orbital calculations and electron localization function analysis and explore the non-conventional dissociation channels via the CH3 roaming mechanism. We further perform kinetics analysis using RRKM theory for the channels of interest. The activation barrier, and rate constants are analyzed for the branching fractions of the products. These results provide important implications for the VUV photochemistry of BVOCs in the atmosphere.