ChemRxiv : the preprint server for chemistry最新文献

{"title":"Preventing bulky cation diffusion in lead halide perovskite solar cells","authors":"C. Perini, Esteban Rojas-Gatjens, Magdalena Rovello, A. C. Castro Mendez, Juanita Hidalgo, Y. An, Ruipeng Li, Carlos Silva-Acuña, Juan‐Pablo Correa‐Baena","doi":"10.33774/chemrxiv-2021-197pf","DOIUrl":"https://doi.org/10.33774/chemrxiv-2021-197pf","url":null,"abstract":"The impact on device stability of the bulky cation-modified interfaces in halide perovskite solar cells is not well-understood. We demonstrate the thermal instability of the bulky cation interface layers used in some of the highest performing solar cells to date. X-ray photoelectron spectroscopy and synchrotron-based grazing incidence X-ray scattering measurements reveal significant changes under thermal stress in the chemical composition and structure at the surface of these films. The changes impact charge carrier dynamics and device operation, as shown in transient photoluminescence, excitation correlation spectroscopy, and solar cells. The type of cation used for passivation affects the extent of these changes, where long carbon chains provide more stable interfaces and thus longer durability (more than 1000 hrs at 55ºC). Such findings highlight that annealing the treated interfaces before characterization is critical to enable reliable reporting of performances and to drive the selection between different cations.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47086300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A New Formula Assignment Algorithm for the Deuterium Labeled Ultrahigh-Resolution Mass Spectrometry: Implications to the Formation Mechanism of Halogenated Disinfection Byproducts","authors":"Qing-Long Fu, M. Fujii, Akari Watanabe, Eunsang Kwon","doi":"10.33774/chemrxiv-2021-cjw3m","DOIUrl":"https://doi.org/10.33774/chemrxiv-2021-cjw3m","url":null,"abstract":"The ultrahigh-resolution mass spectrometry (UHR-MS) coupled with isotope labeling is of increasing attentions in elucidating the transform mechanisms of dissolved organic matter (DOM). However, there is a paucity of automated formula assignment algorithm applicable to halogenated disinfection byproducts (Xn-DBPs), particurally for iodinated organic compounds, and deuterated DOM . Herein, for the first time, we have developed a novel formula assignment algorithm based on deuterium-labeled UHR-MS, namely FTMSDeu, and the algorithm was applied to determine precursor molecules of Xn-DBPs and evaluate the relative contribution of electrophilic addition and electrophilic substitution reactions in Xn-DBPs formation according to the hydrogen/deuterium exchange of DOM molecules. Furthermore, tandem mass spectrometry with homologous-based network analysis was employed to validate the formula assignment accuracy (41%) of FTMSDeu for iodinated disinfection byproducts (In-DBPs). And the remaining In-DBPs compounds were assigned with the empirical rule of minimum number of non-oxygen heteratoms. The electrophilic substitution accounted for 82%-98%, 71%-89%, and 43%-45% of Xn-DBPs formation for Xn-DBPs containing chlorine, bromine, and iodine, respectively, manifesting the dominant role of electrophilic substitution in chlorine disinfection under conditions of low bromine and iodine concentrations. The absence of presumed Xn-DBPs precursors in some treatments in this study also suggests that Xn-DBPs formation include secondary reactions (e.g., oxidation, hydrolysis) in addition to electrophilic addition and/or substitution of halogens. These findings highlight the significance of isotopically labeled UHR-MS techniques in revealing the transformation of DOM in natural and engineered systems.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44468993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bias corrections for speciated and source-resolved PM2.5 chemical transport model simulations using a geographically weighted regression","authors":"Carlos Hernandez, K. Skyllakou, Pablo Garcia Rivera, Brian T. Dinkelacker, J. Marshall, A. Pope, Allen Robinson, S. Pandis, P. Adams","doi":"10.33774/CHEMRXIV-2021-H71P5","DOIUrl":"https://doi.org/10.33774/CHEMRXIV-2021-H71P5","url":null,"abstract":"The ability to provide speciated and source-resolved PM2.5 estimates make chemical transport models a potentially valuable tool for exposure assessments. However, epidemiological studies often require unbiased estimates, which can be challenging for chemical transport models. We use geographically weighted regression to predict and correct the bias in source-resolved PM2.5 species (elemental carbon, organic aerosol, ammonium, nitrate, and sulfate) across the continental U.S. for 2001 and 2010. The regression models are trained using speciated ground-level monitors from the CSN and IMPROVE networks. A 10-fold cross-validation shows minimal bias across all simulated PM2.5 species (0 – 3%) and improved agreement with ground-level monitors (R2 = 0.53 – 0.97). Corrections also improve the agreement between simulated and observed species mixtures on a fractional basis. The source-resolved exposure estimates developed in this study are suitable for use in health analyses of PM2.5 toxicity.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42451902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanistic Insights into Formic Acid Dehydrogenation and Carbon dioxide Amidation Using Electrophilic Ru(II)-Complexes","authors":"Rahul Kumar","doi":"10.33774/chemrxiv-2021-dr9br","DOIUrl":"https://doi.org/10.33774/chemrxiv-2021-dr9br","url":null,"abstract":"The [RuCl(dppe)2][OTf] (1) complex dehydrogenates formic acid under ambient conditions and results in the formation of trans-[Ru(η2-H2)Cl(dppe)2][OTf] (2) and trans-[Ru(η2-H2)H(dppe)2][OTf] (3) complexes. Addition of sodium formate to this reaction mixture increased the rate of formic acid dehydrogenation and complex 3 was obtained as the final product. Furthermore, complex 1 dehydrogenates formic acid catalytically in the presence of Hunig base. After several catalytic cycles, quantitative amounts of H2 and CO2 were produced at 298 K. The proposed formate bound intermediates cis-[2-Ru(HCO2)(dppe)2] were too unstable to be observable (or isolable), however, an analogous cis-[Ru(2-CF3CO2)(dppe)2][OTf] complex (6) was synthesized and characterized. This complex also dehydrogenates formic acid and led to the formation of complex 3. Based on NMR spectroscopic studies and other related chemical reactions, a plausible mechanism for formic acid dehydrogenation using complex 1 has been proposed. Moreover, 13C NMR spectral data on transfer hydrogenation of CO2 using complex 1 in presence of tert-butyl amine-borane (TBAB) as a secondary hydrogen source resulted in the amidation of CO2 to tert-butyl formamide.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42508344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Employing artificial neural networks to find reaction coordinates and pathways for self-assembly","authors":"Jörn H Appeldorn, Simon Lemcke, T. Speck, A. Nikoubashman","doi":"10.33774/chemrxiv-2021-9t07w","DOIUrl":"https://doi.org/10.33774/chemrxiv-2021-9t07w","url":null,"abstract":"Capturing the autonomous self-assembly of molecular building blocks in computer simulations is a persistent challenge, requiring to model complex interactions and to access long time scales. Advanced sampling methods allow to bridge these time scales but typically require to construct accurate low-dimensional representations of the transition pathways. In this work, we demonstrate for the self-assembly of two single-stranded DNA fragments into a ring-like structure how autoencoder architectures based on unsupervised neural networks can be employed to reliably expose transition pathways and to provide a suitable low-dimensional representation. The assembly occurs as a two-step process through two distinct half-bound states, which are correctly identified by the neural net. We exploit this latent space representation to construct a Markov state model for predicting the four molecular conformations and transition rates. Our work opens up new avenues for the computational modeling of multi-step and hierarchical self-assembly, which has proven challenging so far.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43878844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deep learning for industrial processes: Forecasting amine emissions from a carbon capture plant","authors":"K. Jablonka, C. Charalambous, E. Sanchez Fernandez, G. Wiechers, P. Moser, Juliana Monteiro, B. Smit, S. Garcia","doi":"10.33774/chemrxiv-2021-322h5","DOIUrl":"https://doi.org/10.33774/chemrxiv-2021-322h5","url":null,"abstract":"One of the main environmental impacts of amine-based carbon capture processes is the emission of the solvent and degradation products into the atmosphere. To mimic the mounting importance of intermittent operations of power plants we performed a stress test in which we measured the amine emissions from a pilot plant that has been in operation using a mixture of amines (CESAR1) in a slipstream from a coal-fired power plant. Understanding how changes in the operation far from the steady-state of the plant affect the emissions is key to designing emission mitigation strategies. However, conventional process modelling techniques struggle to capture the full dynamic, multivariate, and non-linear nature of this data. In this work, we report how a data-intensive approach can be used to learn the mapping between process and emissions from data. The resulting model can forecast the emissions, can be used to analyse the data and also perform in silico stress tests. By doing so, we reveal that emission mitigation strategies that work well for single component solvents (e.g. monoethanolamine) need to be revised for a mixture of solvents such as CESAR1. We expect that the combination of large amounts of data with flexible learning algorithms will impact the way we design and operate industrial processes, as we can now harvest information at conditions where conventional approaches fail.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49140381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metal-organic frameworks induce hypergolic ignition of bulk metals","authors":"H. Titi, J. Marrett, Olivier Jobin, C. Mottillo, Blaine G Fiss, Audrey Moores, É. Robert, R. Rogers, T. Friščić","doi":"10.33774/chemrxiv-2021-f4dh4","DOIUrl":"https://doi.org/10.33774/chemrxiv-2021-f4dh4","url":null,"abstract":"We demonstrate the unprecedented ability to induce hypergolic behavior, i.e. rapid and spontaneous ignition upon contact with an oxidizer, in non-hypergolic metal fuels by blending them with hypergolic metal-organic frameworks (HMOFs). Using magnesium, aluminum or zinc metal as the fuel, we demonstrate materials with ignition delays (IDs) below 50 ms, and calculated specific impulse (Isp) in the 220-250 s range. These parameters are comparable to those of toxic and carcinogenic hydrazine-based hypergols conventionally used in aerospace technologies, suggesting a route to develop cleaner, safer propulsion systems.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45905829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of a Bruker timsTOF Pro for Native Mass Spectrometry","authors":"Erin M. Panczyk, Dalton T. Snyder, Fanny C. Liu, Yu-Fu Lin, M. Ridgeway, Melvin A Park, C. Bleiholder, V. Wysocki","doi":"10.33774/chemrxiv-2021-qr78t","DOIUrl":"https://doi.org/10.33774/chemrxiv-2021-qr78t","url":null,"abstract":"Mass spectrometry-based assays in structural biology studies typically measure either intact or digested proteins. Traditionally, there are different mass spectrometers dedicated for such measurements: those focused on the rapid analysis of small molecules, such as digested peptides, and those designed for high mass intact analysis. The Bruker timsTOF Pro mass spectrometer (ion mobility-quadrupole-time of flight platform, IM-Q-TOF), has become widely utilized for the analysis of small molecules in the fields of proteomics and metabolomics, with ion mobility spectrometry offering an additional stage of ion separation coupled to liquid chromatography. While this instrument has proven capabilities for small molecule analysis, the ability to perform high-quality native mass spectrometry of intact protein complexes remains largely uninvestigated. Here, we evaluate this IM-Q-TOF platform for the analysis of intact proteins and non-covalently bound protein complexes as small as 12 kDa (cytochrome c) and as large as 801 kDa (GroEL), utilizing the full range of ion mobility, MS, and MS/MS (in-source cleanup and collision cell CID) experiments available on this platform. In-source activation and collision cell CID were found to be robust capabilities for both small and large complexes. Nonetheless, the TIMS analyzer was soft enough to preserve protein-ligand interactions between 1,3-benzenedisulfonamide and carbonic anhydrase. TIMS-CID was performed on the protein complexes streptavidin (53 kDa), avidin (68 kDa) and cholera toxin B (CTB, 58 kDa). Pyruvate kinase and GroEL were beyond the trapping capabilities of the commercial TIMS analyzer. Although quadrupole selection is limited to m/z 3000 by the manufacturer, ions of significantly higher m/z can be transmitted and studied. The present results show that the commercially available Bruker IM-Q-TOF platform can be used for both omics and native mass spectrometry applications; however, modifications to the commercial RF drivers for the TIMS analyzer and quadrupole will be required if protein complexes greater than a few tens of kDa are of interest.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47696088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Facile Transformation of Amino acids into 1,4-dihydropyridines and their Crystallographic Analysis","authors":"A. Adak, Puneeth Koppal","doi":"10.33774/chemrxiv-2021-vpvqq","DOIUrl":"https://doi.org/10.33774/chemrxiv-2021-vpvqq","url":null,"abstract":"A facile transformation of amino acids into substituted 1,4-dihydropyridines (1,4-DHP) is reported. The natural amino acids were converted into gamma-amino beta-keto esters and used for the synthesis of substituted 1,4-dihydropyridines from the Hantzsch reaction. Using amino acids as starting materials, a variety of dihydropyridine derivatives have been synthesized and isolated in good yields. This method is found to be efficient and compatible with various amino acid side-chains and amine protecting groups. Results reported here suggested that amino acids can be used to synthesize highly versatile heterocyclic 1,4-dihydropyridine derivatives, without using any catalyst.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44037229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mono-alkyl Phosphinic Acids as Ligands in Nanocrystal Synthesis","authors":"Evert Dhaene, P. Smet, Klaartje De Buysser, J. De Roo","doi":"10.33774/chemrxiv-2021-0hw9k","DOIUrl":"https://doi.org/10.33774/chemrxiv-2021-0hw9k","url":null,"abstract":"Surfactants play a crucial role in the synthesis of colloidal nanocrystals. Nevertheless, only a handful molecules are currently used, oleic acid being the most typical example. Here, we show that mono-alkyl phosphinic acids are an interesting surfactant class with a reactivity that is intermediate between carboxylic acids and phosphonic acids. We first present the synthesis of n-hexyl, 2-ethylhexyl, n-tetradecyl, n-octadecyl, and oleyl phosphinic acid. These compounds are suitable surfactants during high-temperature nanocrystal synthesis (240-300°C). In contrast to phosphonic acids, they do not form poly anhydride gels. Consequently, CdSe quantum dots synthesized with octadecylphosphinic acid are conveniently purified, and are free from background scattering in UV-Vis. The CdSe nanocrystals have a very low polydispersity and a photoluminescence quantum yield up to 18%, without additional shell. Furthermore, we could synthesize CdSe and CdS nanorods using phosphinic acid ligands and found a remarkable purity (i.e. without tetrapod impurities). We conclude that the reactivity towards TOP-S and TOP-Se precursors decreases in the series: cadmium carboxylate > cadmium phosphinate > cadmium phosphonate. By introducing a third and intermediate class of surfactants, we enhance the versatility of surfactant-assisted syntheses.","PeriodicalId":72565,"journal":{"name":"ChemRxiv : the preprint server for chemistry","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46385753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}