Moderate Conversion Research Articles

Improvement of photoluminescence efficiency and photoelectricity performances of InP quantum dots through the passivation of surface defects

At present, InP quantum dot-sensitized solar cells (QDSSCs) still show moderate power conversion efficiency (PCE), because of charge recombination on the surface defects. Herein, we report a method to reduce the surface defects of InP quantum dots by Ga-doped and ZnS shell coating, which improves the performance of InP QDSSCs. Simultaneous enhancement of photoluminescence (PL) and photo-electricity performance of Ga doped InP (Ga:InP) quantum dots (QDs), Ga:InP/ZnS core/shell QDs were achieved. The maximum PL quantum yield of Ga:InP QDs and Ga:InP/ZnS QDs reached 14.9% and 76%, respectively. The maximum PCE value of Ga:InP and Ga:InP/ZnS QDSSCs reached 3.0% and 4.5% under 1 sun illumination (AM 1.5 G, 100 mW/cm2), respectively. The J-V curve revealed that Ga doping and ZnS shell coating reduced the surface recombination and increased the cell efficiency and stability. These results provided a new approach to obtaining quantum dot materials with high luminescence properties or good solar cell performances.

Enhancing rhamnolipid production via immobilized Pseudomonas stutzeri lipase: A comparative study

Rhamnolipids (RLs) are widely studied biosurfactants with significant industrial potential in cosmetics, pharmaceuticals, and bioremediation due to their excellent surface activity, emulsifying properties and bioactive characteristics. However, high production costs impede their mass production. This study investigates the immobilization of Pseudomonas stutzeri lipase (PSL) on various supports to enhance RL synthesis efficiency, focusing on yield and regioselectivity in the enzymatic synthesis of 4-O-lauroylrhamnose by the transesterification of rhamnose with vinyl laurate. Three immobilization methods were compared: covalent binding, adsorption on Celite, and adsorption on hydrophobic supports. The immobilization efficiency varied depending on the method used, with the lowest observed for adsorption on Celite (56 %), followed by covalent immobilization on Sepabeads (EC-EP/S 78 % and EC-EP/L 70 %), and the highest for adsorption on hydrophobic supports (83–97 %, with EC-OD being the best at 97 %). For the enzymatic synthesis of 4-O-lauroylrhamnose, covalent immobilization on Sepabeads™ EC-EP yielded low conversions due to restricted conformational freedom of the enzyme. Celite® 545 adsorption resulted in moderate conversion rates, limited by the electrostatic interactions restricting enzyme activity. The most promising results were obtained with hydrophobic supports, particularly Purolite® ECR8806F, achieving nearly complete conversion and maintaining high regioselectivity at the 4-position of rhamnose in both THF and the green solvent 2-methyltetrahydrofuran (2-MeTHF). The study highlights the critical role of support hydrophobicity and active surface area in the immobilized enzyme performance. PSL immobilized on Purolite® ECR8806F demonstrated significant potential for sustainable RLs production, showing excellent reusability, stability and productivity across multiple reaction cycles. This study presents a significant advancement in RLs production by optimizing PSL immobilization and reaction conditions, facilitating the way for more cost-effective and sustainable industrial applications.

Highly efficient Y3-xBaxAl5-xSixO12:Cr3+ near-infrared phosphor for plant growth

Near-infrared (NIR) phosphors enhance the growth of plants due to their superior penetration. However, relatively high thermal quenching and low quantum efficiency restrict the development of NIR phosphors. In this study, Y3-xBaxAl5-xSixO12:Cr3+ phosphors (YBAS:Cr3+) with varying concentrations of Ba2+-Si4+ and Cr3+ were studied. The results demonstrate high-purity phases are obtained with doping Ba2+-Si4+ and Cr3+. The Ba2+-Si4+ doping enhances crystallinity and near-spherical particles are synthesized. The theoretical calculations indicate a significant reduction in bandgap with doping Ba2+-Si4+, resulting in impurity levels appearing in the valence band region. The state density calculation shows that the band formation is contributed by all elements. The optimal Ba2+-Si4+ doping concentration is 0.05 mol and the Cr3+ doping content is 0.09 mol. The critical distance (R c ) is 16.62 Å. Dipole–dipole interactions and radiation reabsorptions are main concentration quenching mechanisms. Lattice distortions occur with the introduction of Ba2+-Si4+ and the value (D r ) is 0.052. The YBAS:0.09Cr3+ phosphor shows a crystal field strength with a Dq/B value of 2.76. The phosphor exhibits a high quantum efficiency (73.42%), superior thermal quenching resistance (∼70% initial intensity at 150°C), and a suitable fluorescence lifetime (130.04 µs). A near-infrared pc-LED with YBAS:0.09Cr3+ phosphor displays a high output power of 167.12 mW and a moderate conversion efficiency of 3.82%.

Development of a local wall concentration model for the design of single pass tangential flow filtration (SPTFF) systems with viral vector surrogates

Recent advances in the use of viral vectors for gene therapy has created a need for efficient downstream processing of these novel therapeutics. Single-pass tangential flow filtration (SPTFF) can potentially improve final product quality via reductions in shear, and it can increase manufacturing productivity via simple implementation into continuous/intensified processes. This study investigated the impact of variations in pressure and flow rate along the length of the membrane on overall SPTFF performance. Constant-flux filtration experiments at feed fluxes from 14 to 420 L/m2/h (Reynolds numbers <20) were performed using Pellicon® 3 TFF cassettes with fluorescent nanoparticles as model viral vectors. The location of nanoparticle accumulation shifted towards the filter outlet at high conversion and was also a function of the permeate flow configuration. These phenomena were explained using a newly developed concentration polarization model that predicts the distribution in local wall concentration over the length of the membrane. The model accurately captured the observed nanoparticle accumulation trends, including the effects of the permeate flow profile (co-current, divergent, or convergent flow) on nanoparticle accumulation within the SPTFF module. Nanoparticle accumulation at moderate conversion was more uniform using convergent flow, but nanoparticle accumulation at 80 % conversion (5x concentration factor) can be minimized using a divergent flow configuration. The local wall concentration model was also used to evaluate the critical flux by assuming that fouling occurs when the nanoparticle concentration at any point along the membrane surface exceeds 15 % by volume. These results provide important insights for the design and operation of SPTFF technology for inline concentration of viral vectors.

Ni2+ activated broadband near-infrared II germanate phosphor for pc-LED applications

The broadband near-infrared (NIR) pc-LED is considered as a new generation of light source for substance measurements based on NIR spectroscopy. The most studied Cr3+ doped broadband NIR phosphors emit in the near-infrared I region. However, there is a demand for broadband near-infrared II solid-state light sources for expanding the variety of detected substances. Herein, Ni2+ activated NIR II Mg14Ge5O24 phosphor is synthesized by high-temperature solid-state method. The phosphor shows a asymmetric broad NIR emission band peaked at 1420 nm, that is assigned to the 3T2(3F)→3A2(3F) transition of Ni2+. It is observed that the asymmetric emission band is contributed from two Ni2+ centers, Ni2+(I) and Ni2+(II), occupying Ge4+ site with the emission peaked at 1313 nm and Mg2+ site with the emission peaked at 1435 nm, respectively. It is found that the addition of Ti4+ and B3+ can significantly change the intensity ratio of the two Ni2+ centers and enhance the overall emission intensity. Moreover, the addition of Mn4+ results in only Ni2+(II) emission. The origin of the unique features mentioned above is discussed. The temperature dependence of the NIR emissions is also studied. Finally a broadband NIR II pc-LED with a moderate electro-optical conversion efficiency of 1.4 % is fabricated based on a 400 nm LED chip. The results indicate that the modified Mg14Ge5O24:Ni2+ is a potential broadband NIR II phosphor for pc-LED applications.

The impact of CBDC on a deposit-dependent banking system

We examine implications of a central bank digital currency (CBDC) for banks using business models particularly dependent on customer deposits. Employing unique customer data hand-collected from German savings and cooperative banks, we generate conversion rates for deposits into a CBDC. Even at moderate conversion rates, most banks would have experienced funding problems and lost profits if a CBDC had been introduced in most years from 2000 onward. Our results are relevant for commercial banks, contributing to better assessments of the impact of CBDCs on liquidity and profitability and help central banks to identify implementation costs for banks within historical and hypothetical interest rate environments.

Enhancing CO and H2 Production in Propane Dry Reforming in Excess of CO2.

This study focuses on addressing the challenges in the dry reforming of propane, a process historically marked by low syngas yields and only moderate conversions of CO2 and propane. The primary objective was to enhance CO2 utilization and boost the selectivity of syngas (CO and H2) production using titania-based catalysts. For synthesizing these catalysts, an impregnation method was employed with subsequent characterization through X-ray diffraction (XRD), N2 adsorption-desorption, ammonia temperature-programmed desorption (TPD), and hydrogen temperature-programmed reduction (TPR). The titania-based catalysts generally possess weak acidic strength, with each catalyst displaying a unique reduction profile. The dry reforming process using these catalysts resulted in varying levels of propane conversion, with V/Ti, Ir/Ti, Al/Ti, and Zr/Ti catalysts showing distinct efficiencies. Notably, the Ir/Ti and V/Ti oxide catalysts achieved the lowest selectivity for generating intermediate byproducts such as methane, ethane, ethylene, and propylene while successfully promoting higher syngas CO and H2 production alongside stable propane conversion. When exposed to excess CO2, each catalyst consumed differing amounts of CO2 molecules. Particularly, the Ir/Ti and V/Ti oxide catalysts demonstrated enhanced activity in promoting CO2 reactions with intermediate radical species, facilitating carbon-carbon (C-C) bond dissociation and leading to increased syngas production. This study offers valuable insights into the potential of titania-based catalysts in improving the efficiency and selectivity of propane dry reforming processes for blue hydrogen.

Study on Improving Electrochemical Machining Performances through Energy Conversion of Electrolyte Fluid

Electrochemical machining (ECM) is regarded as a promising and cost-effective manufacturing method for difficult-to-cut materials with complex shapes and structures. The flow-field state of machining gaps is considered a key factor affecting machining performance in ECM engineering practice and has been widely studied. However, little attention has been given to the fluid energy of electrolytes during the ECM process. This study mainly focuses on the influence of the conversion between dynamic and static pressure energy of electrolyte fluid on ECM performance. The simulation results show that by changing the degree of convergence of the electrolyte outlet, the dynamic and static pressure energy of the electrolyte can be effectively adjusted, and increased static pressure energy can be obtained by sacrificing dynamic pressure energy. The experimental results show that electrolyte energy conversion can achieve better surface quality and material removal rate (MRR). However, excessive sacrifice of fluid dynamic pressure energy will also worsen the ECM performance. By combining MRR and Ra, moderate fluid energy conversion can achieve better machining performance, with a degree of convergence of around 50%–70%. The experimental results also show that moderate energy conversion of the electrolyte fluid can improve the utilization efficiency of electrical energy in the ECM process. This may be because the static pressure of the electrolyte can effectively compress the volume of gas products and reduce the electrical resistivity of the machining gap. These conclusions can provide some useful assistance for ECM engineering practice.

Minor Changes in Response Modules Leading to a "U-Shaped" Conversion Rate of Docetaxel Prodrug Nanoassemblies.

The prodrug-based nanoassemblies offer an alternative to settle the deficiencies of traditional chemotherapy drugs. In this nanosystem, prodrugs typically comprise drug modules, modification modules, and response modules. The response modules are crucial for facilitating the accurate conversion of prodrugs at specific sites. In this work, we opted for differentiated disulfide bonds as response modules to construct docetaxel (DTX) prodrug nanoassemblies. Interestingly, a subtle change in response modules leads to a "U-shaped" conversion rate of DTX-prodrug nanoassemblies. Prodrug nanoassemblies with the least carbon numbers between the disulfide bond and ester bond (PDONα) offered the fastest conversion rate, resulting in powerful treatment outcomes with some unavoidable toxic effects. PDONβ, with more carbon numbers, possessed a slow conversion rate and poor antitumor efficacy but good tolerance. With most carbon numbers in PDONγ, it demonstrated a moderate conversion rate and antitumor effect but induced a risk of lethality. Our study explored the function of response modules and highlighted their importance in prodrug development.

In Situ Formed Amorphous Bismuth Sulfide Cathodes with a Self-Controlled Conversion Storage Mechanism for High Performance Hybrid Ion Batteries.

Conversion-type electrodes offer a promising multielectron transfer alternative to intercalation hosts with potentially high-capacity release in batteries. However, the poor cycle stability severely hinders their application, especially in aqueous multivalence-ion systems, which can fundamentally impute to anisotropic ion diffusion channel collapse in pristine crystals and irreversible bond fracture during repeated conversion. Here, an amorphous bismuth sulfide (a-BS) formed in situ with unprecedentedly self-controlled moderate conversion Cu2+ storage is proposed to comprehensively regulate the isotropic ion diffusion channels and highly reversible bond evolution. Operando synchrotron X-ray diffraction and substantive verification tests reveal that the total destruction of the Bi─S bond and unsustainable deep alloying are fully restrained. The amorphous structure with robust ion diffusion channels, unique self-controlled moderate conversion, and high electrical conductivity discharge products synergistically boosts the capacity (326.7 mAh g-1 at 1 A g-1 ), rate performance (194.5 mAh g-1 at 10 A g-1 ), and long-lifespan stability (over 8000 cycles with a decay rate of only 0.02 ‰ per cycle). Moreover, the a-BS Cu2+ ‖Zn2+ hybrid ion battery can well supply a stable energy density of 238.6Wh kg-1 at 9760W kg-1 . The intrinsically high-stability conversion mechanism explored on amorphous electrodes provides a new opportunity for advanced aqueous storage.

Functionalized Electron‐Rich Pyridines as Initiators for the Epoxy Homopolymerization

AbstractA simple and modular dialkylation of two electron‐rich pyridine derivatives, namely 4‐aminopyridine or 1,2,3,4‐tetrahydropyrido[3,4‐b]pyrazine, is achieved by aza‐Michael reactions with electron‐poor olefins (ethyl acrylate and acrylonitrile). Reducing the ester groups in the ethyl acrylate‐derived compounds yielded the corresponding hydroxyl‐containing derivatives. Subsequently, homopolymerization of phenyl glycidyl ether as well as an epoxy‐alcohol polyaddition are catalyzed using the introduced compounds. As a reference catalyst, 4‐dimethylaminopyridine is used. It is found that in all cases an irreversible termination of the polymerization at temperatures above 100 °C occurred. The decomposition is particularly rapid in the case of pyridine derivatives containing hydroxyl groups. In contrast, at a constant temperature of 100 °C, the latter compounds gave the fastest phenyl glycidyl ether homopolymerization and high conversions are found for all electron‐rich pyridine derivatives. However, testing the catalysts at high alcohol concentrations at temperatures higher than 100 °C resulted in similarly moderate conversions in all cases.

Influence of Bifunctional PtZn/SiO&lt;sub&gt;2&lt;/sub&gt; and H-ZSM-5 Catalyst on the Rates and Selectivity of Propene Aromatization

Previous studies on the conversion of olefins to aromatics with bifunctional Ga- or Zn-ZSM-5 catalysts have concluded that benzene, toluene, and xylenes (BTX) yields are significantly higher than for ZSM-5 alone. These results were attributed to the higher aromatic dehydrogenation rate of Ga or Zn. In this study, a highly active, bifunctional PtZn/SiO&lt;sub&gt;2&lt;/sub&gt; (1.3 wt% Pt, 2.6 wt% Zn) with H-ZSM-5 (Si/Al = 40) catalyst is investigated for propene aromatization at 723 K and 823 K. At low to moderate propene conversions, in addition to BTX, small alkanes and olefins are produced. Many of these may also be converted to aromatics at higher propene conversion while others are not, for example, methane, ethane and propane. When compared at equivalent space velocity or propene conversion, the bifunctional catalyst has a much higher selectivity to aromatics than ZSM-5; however, when compared at equivalent conversion of all reactive intermediates, the bifunctional catalyst exhibits very similar BTX selectivity. At 723 K, for ZSM-5 the primary non-reactive by-products are propane and butane; while, for the bifunctional catalyst the major non-reactive product is propane. At 823 K, both ZSM-5 and the bifunctional catalyst convert propane and butane to aromatics increasing the aromatic yields, and the by-products are methane and ethane.

Importance of Process Variables and Their Optimization for Oxidative Coupling of Methane (OCM).

Oxidative coupling of methane (OCM) is a promising process for converting natural gas into high-value chemicals such as ethane and ethylene. The process, however, requires important improvements for commercialization. The foremost is increasing the process selectivity to C2 (C2H4 + C2H6) at moderate to high levels of methane conversion. These developments are often addressed at the catalyst level. However, optimization of process conditions can lead to very important improvements. In this study, a high-throughput screening (HTS) instrument was utilized for La2O3/CeO2 (3.3 mol % Ce) to generate a parametric data set within the temperature range of 600-800 °C, CH4/O2 ratio between 3 and 13, pressure between 1 and 10 bar, and catalyst loading between 5 and 20 mg leading to space-time between 40 and 172 s. Statistical design of experiments (DoE) was applied to gain insights into the effect of operating parameters and to determine the optimal operating conditions for maximum production of ethane and ethylene. Rate-of-production analysis was used to shed light on the elementary reactions involved in different operating conditions. The data obtained from HTS experiments established quadratic equations relating the studied process variables and output responses. The quadratic equations can be used to predict and optimize the OCM process. The results demonstrated that the CH4/O2 ratio and operating temperatures are key for controlling the process performance. Operating at higher temperatures with high CH4/O2 ratios increased the selectivity to C2 and minimized COx (CO + CO2) at moderate conversion levels. In addition to process optimization, DoE results also allowed the flexibility of manipulating the performance of OCM reaction products. A C2 selectivity of 61% and a methane conversion of 18% were found to be optimum at 800 °C, a CH4/O2 ratio of 7, and a pressure of 1 bar.

A Pathway for Aldol Additions Catalyzed by l-Hydroxyproline-Peptides via a β-Hydroxyketone Hemiaminal Intermediate

While the use of l-proline-derived peptides has been proven similarly successful with respect to enantioselectivity, the physico-chemical and conformational properties of these organocatalysts are not fully compatible with transition state and intermediate structures previously suggested for l-proline catalysis. l-Proline or l-4-hydroxyproline catalysis is assumed to involve proton transfers mediated by the carboxylic acid group, whereas a similar mechanism is unlikely for peptides, which lack a proton donor. Herein, we prepared an array of hydroxyproline-based dipeptides through amide coupling of Boc-protected cis- or trans-4-l-hydroxyproline (cis- or trans-4-Hyp) to benzylated glycine (Gly-OBn) and l-valine (l-Val-OBn) and used these dipeptides as catalysts for a model aldol reaction. Despite the lack of a proton donor in the catalytic site, we observed good stereoselectivities for the R-configured aldol product both with dipeptides formed from cis- or trans-4-Hyp at moderate conversions after 24 h. To explain this conundrum, we modeled reaction cycles for aldol additions in the presence of cis-4-Hyp, trans-4-Hyp, and cis- and trans-configured 4-Hyp-peptides as catalysts by calculation of free energies of conformers of intermediates and transition states at the density functional theory level (B3LYP/6-31G(d), DMSO PCM as solvent model). While a catalytic cycle as previously suggested with l-proline is also plausible for cis- or trans-4-Hyp, with the peptides, the energy barrier of the first reaction step would be too high to allow conversions at room temperature. Calculations on modeled transition states suggest an alternative pathway that would explain the experimental results: here, the catalytic cycle is entered by the acetone self-adduct 4-hydroxy-4-methylpentan-2-one, which forms spontaneously to a small extent in the presence of a base, leading to considerably reduced calculated free energy levels of transition states of reaction steps that are considered rate-determining.

Microwave-assisted catalytic transfer hydrogenolysis of lignin-derived aromatic ethers over Ru/C

Cleavage of aromatic ether bonds through hydrogenolysis is one of the most promising routes for depolymerisation and transformation of lignin into value-added chemicals. Herein, we investigate the catalytic transfer hydrogenolysis (CTH) of benzyl phenyl ether (BPE), as a model molecule of α-O-4 lignin linkages, over commercial Ru/C under microwave irradiation using 2-propanol as H-donor. By tuning the reaction parameters, such as time, temperature and catalyst amount, BPE was fully converted, at 150 °C in 5 min of irradiation, with a related aromatics selectivity of 92%. Phenylethylphenyl ether (PPE), and diphenyl ether (DPE), as a models of β-O-4 and 4-O-5 linkages, respectively, were also considered to this scope and under optimized reaction conditions, >99% and 72% conversion, respectively, were achieved with >89% aromatics selectivity. Remarkably, catalytic tests with moderate conversions clearly showed that the cleavage of etheric C-O bond was the primary step under CTH conditions, while the hydrogenations of the aromatic rings take place in a subsequent step. Overall, the screening of the reaction parameters was crucial to avoid the hydrogenation of aromatic rings. No less significant was the Ru/C stability, which has been recycled at least six times without any noticeable activity loss.

High Conductivity, Semiconducting, and Metallic PEDOT:PSS Electrode for All-Plastic Solar Cells.

Plastic electrodes are desirable for the rapid development of flexible organic electronics. In this article, a plastic electrode has been prepared by employing traditional conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and plastic substrate polyethersulfone (PES). The completed electrode (Denote as HC-PEDOT:PSS) treated by 80% concentrated sulfuric acid (H2SO4) possesses a high electrical conductivity of over 2673 S/cm and a high transmittance of over 90% at 550 nm. The high conductivity is attributed to the regular arrangement of PEDOT molecules, which has been proved by the X-ray diffraction characterization. Temperature-dependent conductivity measurement reveals that the HC-PEDOT:PSS possesses both semiconducting and metallic properties. The binding force and effects between the PEDOT and PEI are investigated in detail. All plastic solar cells with a classical device structure of PES/HC-PEDOT:PSS/PEI/P3HT:ICBA/EG-PEDOT:PSS show a PCE of 4.05%. The ITO-free device with a structure of Glass/HC-PEDOT:PSS/Al4083/PM6:Y6/PDINO/Ag delivers an open-circuit voltage (VOC) of 0.81 V, short-circuit current (JSC ) of 23.5 mA/cm2, fill factor (FF) of 0.67 and a moderate power conversion efficiency (PCE) of 12.8%. The above results demonstrate the HC-PEDOT:PSS electrode is a promising candidate for all-plastic solar cells and ITO-free organic solar cells.

Functional bagasse: As a versatile catalyst for henry reaction and additive-free cycloaddition of CO2

A facile synthetic route thrived for the synthesis of a multifunctional solid base catalyst. The amine-functionalized bagasse was synthesized by anchoring the ethylenediamine on the bagasse. Then, the functionalized bagasse was further converted to quaternary ammonium functionalized bagasse. From elemental composition, the nitrogen content of sugarcane bagasse was increased after post-functionalization and confirms the successful functionalization of amine functionality. The FT-IR analysis reveals the formation the functionalization of amine group on the secondary hydroxyl group of bagasse. Further, the formation of quaternary ammonium salt on the bagasse was supported by the XPS analysis and with the binding energy value at 401.75 eV, which corroborates the formation of C-N+ bond. The acid-base titration exhibited 0.328 mmol/g of basicity on the amine-functionalized sugarcane bagasse. The inexpensive amine-functionalized bagasse was used for the condensation of nitromethane with various bio-derived carbonyl compounds. The amine-functionalized bagasse gave complete conversion of aldehydes with 80–90% yield of desired β-nitroalkenes. The amine-functionalized catalyst manifested good recyclability up to four cycles. Further, the quaternary ammonium functionalized bagasse is used for the synthesis of cyclic carbonates from epoxides without adding any external additives (metal, co-catalyst, and solvents). The quaternary ammonium functionalized bagasse showed moderate conversion of epoxides (20–61%) with good selectivity of desired cyclic carbonates.

Proposal for Deep-UV Emission from a Near-Infrared AlN/GaN-Based Quantum Cascade Device Using Multiple Photon Up-Conversion

We propose the use of an n-doped periodic AlN/GaN quantum cascade structure for the optical up-conversion of multiple near-infrared (near-IR) photons into deep-ultraviolet (deep-UV) radiation. Without applying an external bias voltage, the active region of such a device will (similar to an un-biased quantum cascade laser) resemble a sawtooth-shaped inter-subband structure. A carefully adjusted bias voltage then converts this sawtooth pattern into a ‘quantum-stair’. Illumination with λ = 1.55 µm radiation results in photon absorption thereby lifting electrons from the ground state of each main well into the first excited state. Three additional GaN quantum wells per period then provide by LO-phonon-assisted tunneling a diagonal transfer of these electrons towards the ground level of the neighboring period. From there, the next near-infrared (near-IR) photon absorption, electron excitation, and partial relaxation takes place. After 12 such absorption, transfer, and relaxation processes, the excited electrons have gained a sufficiently high amount of energy to undergo in the final AlN-based p-type contact layer an electron-hole band-to-band recombination. By employing this procedure, multiple near-IR photons will be up-converted to produce deep-UV radiation. Since for a wavelength of 1.55 µm very powerful near-IR pump lasers are readily available, such an up-conversion device will (even at a moderate overall conversion efficiency) potentially result in an equal or even higher output power than the one of an AlN-based p-n-junction light-emitting diode. The proposed structures are therefore very interesting for applications such as ultra-high-resolution photolithography or printing, water purification, medical equipment disinfection, white light generation, or the automotive industry.

Perylene diimide-based non-fullerene acceptors with A-D-A'-D-A architecture for organic solar cells.

The vinylene-bridged helical PDI dimer (PDI2) has been an alternative PDI building blocks for non-fullerene acceptor (NFAs). However, the development of PDI2 derivatives still lag behind, and most of PDI2 derivatives based organic solar cells (OSCs) only achieved a moderate power conversion efficiencies (PCE) of less than 8%. In this contribution, an acceptor-donor-acceptor-donor-acceptor (A-D-A'-D-A) architecture was introduced to facilitate the improvement of photovoltaic properties. Two acceptors named diIDTIC-PDI2 and diFIDTIC-PDI2 were designed and synthesized, in which a PDI2 moiety flanked with two indacenodithiophene (IDT) units was employed as the D-A'-D core and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC) or fluorinated IC (IC2F) acted as terminal groups, respectively. The photovoltaic performances of these two acceptors were explored using PM1 as the electron donor. Compared to diIDTIC-PDI2, the fluorinated diFIDTIC-PDI2 based OSCs obtained enhanced photovoltaic performance with the best PCE of 9.77%, a VOC of 0.957 V, JSC of 13.58 mA cm-2 and FF of 75.1%. These results illustrate that engineering terminal groups is a robust strategy of enhancing the efficiency of PDI based acceptors with A-D-A'-D-A architecture.

Rapid Ring-Opening Polymerization of γ-Butyrolactone toward High-Molecular-Weight Poly (γ-butyrolactone) by an Organophosphazene Base and Bisurea Binary Catalyst.

The low temperature condition, long reaction time and associated high energy inputs involved in the polymerization process still hampered the scalable production of poly(γ-butyrolactone) (PγBL) via ring-opening polymerization (ROP) of low strained γBL due to its unfavorable thermodynamics. In this contribution, we presented the rapid ROP of γBL using a bisurea in combination with an organophosphazene base as the binary catalyst. Well-defined PγBL samples with various terminal groups were prepared by using different alcohol initiators. The bisurea as a co-catalyst exhibited much higher catalytic activity even compared to the most active monourea in previous report as supported by the kinetic experiments. A moderate monomer conversion of 61% was achieved within 10 mins, producing high-molecular-weight PγBL with Mn up to 37.5 kDa and good mechanical properties. The short polymerization time considerably reduced the energy cost for the ROP of γBL conducted at low temperature condition. This study may clear away obstacles for the scalable production and practical applications for PγBL.