Insights into the structure and Ion transport of pectin-[BMIM][PF6] electrolytes

We investigate the effect of pectin on the structure and ion transport properties of the room-temperature ionic liquid electrolyte 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) using molecular dynamics simulations. We find that pectin induces intriguing structural changes in the electrolyte that disrupt large ionic aggregates and promote the formation of smaller ionic clusters, which is a promising finding for ionic conductivity. Due to pectin in [BMIM][PF6] electrolytes, the diffusion coefficient of cations and anions is observed to decrease by a factor of four for a loading of 25 wt. % of pectin in [BMIM][PF6] electrolyte. A strong correlation between the ionic diffusivities (D) and ion-pair relaxation timescales (τc) is observed such that D ∼ τc−0.75 for cations and D ∼ τc−0.82 for anions. The relaxation timescale exponents indicate that the ion transport mechanisms in pectin-[BMIM][PF6] electrolytes are slightly distinct from those found in neat [BMIM][PF6] electrolytes (⁠⁠). Since pectin marginally affects ionic diffusivities at the gain of smaller ionic aggregates and viscosity, our results suggest that pectin-ionic liquid electrolytes offer improved properties for battery applications, including ionic conductivity, mechanical stability, and biodegradability

Donor-acceptor stacking arrangements in bulk and thin-film high-mobility conjugated polymers characterized using molecular modelling and MAS and surface-enhanced solid-state NMR spectroscopy

Conjugated polymers show promising properties as cheap, sustainable and solution-processable semiconductors. A key challenge in the development of these materials is to determine the polymer chain structure, conformation and packing in both the bulk polymer and in thin films typically used in devices. However, many characterisation techniques are unable to provide atomic-level structural information owing to the presence of disorder. Here, we use molecular modelling, magic-angle spinning (MAS) and dynamic nuclear polarisation surface-enhanced NMR spectroscopy (DNP SENS) to characterise the polymer backbone group conformations and packing arrangement in the high-mobility donor-acceptor copolymer diketopyrrolo-pyrrole-dithienylthieno[3,2-b] thiophene (DPP-DTT). Using conventional H-1 and C-13 solid-state MAS NMR coupled with density functional theory calculations and molecular dynamics simulations, we find that the bulk polymer adopts a highly planar backbone conformation with a laterally-shifted donor-on-acceptor stacking arrangement. DNP SENS enables acquisition of C-13 NMR data for polymer films, where sensitivity is limiting owing to small sample volumes. The DNP signal enhancement enables a two-dimensional H-1-C-13 HETCOR spectrum to be recorded for a drop-cast polymer film, and a C-13 CPMAS NMR spectrum to be recorded for a spin-coated thin-film with a thickness of only 400 nm. The results show that the same planar backbone structure and intermolecular stacking arrangement is preserved in the films following solution processing and annealing, thereby rationalizing the favourable device properties of DPP-DTT, and providing a protocol for the study of other thin film materials

Active Packaging for Strawberry and Coriander: A Natural Extract Impregnated Paper

Active packaging is considered as a sustainable solution to overcome postharvest losses of fresh produce. In the present study, a paper-based antimicrobial packaging approach was developed using a bioactive extract matrix from citrus leaves and fenugreek seeds, which possess antimicrobial and antioxidant properties. This matrix was impregnated into kraft paper, referred to as the “freshness keeper”. To assess the presence of the matrix extract, the impregnated paper was characterized through GC-MS analysis, FTIR, and SEM. The antimicrobial and antioxidant activities of the active solution were assessed, demonstrating effectiveness against various spoilage organisms, with activity ranging from 13 mm to 15 mm. Analysis using GC-MS identified volatile compounds with antimicrobial properties. Coriander leaves and strawberries were used as a proof of concept for shelf life under different storage conditions (22–24 and 2–4 °C). Physicochemical properties, such as % weight loss, chlorophyll content, color value, total aerobic plate count, pH, and total soluble solids (TSS), as well as sensory analysis, were evaluated to understand the shelf life. The synergistic effect of the matrix had a significant impact on maintaining physiochemical properties, sensory quality, and microbiological load of coriander and strawberries. The results of this study demonstrate that the freshness keeper is an effective approach for preserving the quality and freshness of coriander for up to 5 days at 22–24 °C and 25 days at 2–4 °C, as well as strawberries for 3–4 days at 22–24 °C. In contrast, control samples spoil in 2 days at 22–24 °C and 14 days at 2–4 °C for coriander and 2 days at 22–24 °C for strawberries. In addition, no flavor migration from the product was detected. Thus, the developed freshness keeper can play a vital role in reducing postharvest losses of fresh produce

Comparision of Heat Exchangers for Indirect Evaporative Cooling: Review

In this paper the study of the different types of heat exchangers used in indirect evaporative cooling system is carried out based on its performance parameters and the material used. The performance of IEC is mainly depending on the type of heat exchanger used. For this purpose, different types of HX with their performance parameters, design aspects, material used for it has been studied at different environmental conditions. From this we understand the importance of HX performance in overall IEC system and also which HX is much better than among the different types of heat exchangers available. This paper aims on the comparison of different heat exchanger used in indirect evaporative cooling for sufficient cooling comfort;reduce environmental impact and lower energy consumption in future

Solid-State Dynamic Nuclear Polarization at 9.4 and 18.8 T from 100 K to Room Temperature

We thank Lenaic Leroux for technical help.International audienceEfficient dynamic nuclear polarization (DNP) in solids, which enables very high sensitivity NMR experiments, is currently limited to temperatures of around 100 K and below. Here we show how by choosing an adequate solvent, 1H cross effect DNP enhancements of over 80 can be obtained at 240 K. To achieve this we use the biradical TEKPol dissolved in a glassy phase of ortho-terphenyl (OTP). We study the solvent DNP enhancement of both TEKPol and BDPA in OTP in the range from 100 to 300 K at 9.4 and 18.8 T. Surprisingly, we find that the DNP enhancement decreases only relatively slowly for temperatures below the glass transition of OTP (Tg = 243 K), and 1H enhancements around 15–20 at ambient temperature can be observed. We use this to monitor molecular dynamic transitions in the pharmaceutically relevant solids Ambroxol and Ibuprofen

Dynamic Nuclear Polarization Efficiency Increased by Very Fast Magic Angle Spinning

International audienceDynamic Nuclear Polarization has recently emerged as a tool to enhance the sensitivity of solid-state NMR experiments. However, so far high enhancements (>100) are limited to relatively low magnetic fields, and DNP at fields higher than 9.4 T significantly drops in efficiency. Here we report solid-state Overhauser effect DNP enhancements of over 100 at 18.8 T. This is achieved through the unexpected discovery that enhancements increase rapidly with increasing magic angle spinning rates. The measurements are made using 1,3-bisdiphenylene-2-phenylallyl (BDPA) dissolved in ortho-terphenyl (OTP) at 40 kHz MAS. We introduce a source-sink diffusion model for polarization transfer which is capable of explaining the experimental observations. The advantage of this approach is demonstrated on mesoporous alumina with the acquisition of well-resolved DNP surface enhanced 27Al CP spectra

Dynamic nuclear polarization at 40 kHz magic angle spinning

International audienceDNP-enhanced solid-state NMR spectroscopy under magic angle spinning (MAS) is rapidly developing into a powerful analytical tool to investigate the structure of a wide range of solid materials, because it provides unsurpassed sensitivity gains. Most developments and applications of DNP MAS NMR were so far reported at moderate spinning frequencies (up to 14 kHz using 3.2 mm rotors). Here, using a 1.3 mm MAS DNP probe operating at 18.8 T and ∼100 K, we show that signal amplification factors can be increased by up to a factor two when using smaller volume rotors as compared to 3.2 mm rotors, and report enhancements of around 60 over a range of sample spinning rates from 10 to 40 kHz. Spinning at 40 kHz is also shown to increase 29Si coherence lifetimes by a factor three as compared to 10 kHz, substantially increasing sensitivity in CPMG type experiments. The contribution of quenching effects to the overall sensitivity gain at very fast MAS is evaluated, and applications are reported on a functionalised mesostructured organic–inorganic material