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1دورية أكاديمية
المصدر: Frontiers in Chemistry, Vol 8 (2020)
مصطلحات موضوعية: fluorescence, molecular switches, photochemistry, molecular logic gates, boron dipyrromethene, protonation, Chemistry, QD1-999
الوصف: Molecules that respond to input stimulations to produce detectable outputs can be exploited to mimic Boolean logic operators and reproduce basic arithmetic functions. We have designed a two-state fluorescent probe with tunable emission wavelength for the construction of a molecular logic gate with reconfigurable single– or dual–output capability. The system is based on a BODIPY skeleton coupled with 4-(dimethylamino)benzaldehyde. The behavior of the molecular logic gate can be easily investigated in solution with fluorescence spectroscopy, and the optical readout (fluorescence) can be monitored in one (green) or two (green and red) channels. Depending on the solvent of choice, single INHIBIT or dual INHIBIT/IMPLY logic functions can be achieved using chemical inputs (acid and base). Reconfiguration from single– to dual–output is thus made possible by operating the system in acetonitrile (single output) or toluene (dual output), respectively. The logic gate can be switched by manipulating the fluorescence emission via protonation or deprotonation, even when immobilized onto a glass substrate. At the solid state, the resulting output can be stored for extended periods of time. This feature provides two added benefits: (i) memory function and (ii) “set/reset” capability of the logic gate. Our design thus provides a proof-of-concept interface between the molecular and electronic domains.
وصف الملف: electronic resource
العلاقة: https://www.frontiersin.org/article/10.3389/fchem.2020.00470/fullTest; https://doaj.org/toc/2296-2646Test
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2دورية أكاديمية
المؤلفون: Gregory K. Hodgson, Stefania Impellizzeri, Juan C. Scaiano
مصطلحات موضوعية: Nanoparticle synthesis, properties and applications, organic chemistry, Pechmann Reaction, catalysis, Single molecule fluorescence microscopy
الوصف: Photochemically prepared samarium oxide nanoparticles (Sm2O3NP) efficiently catalyze the formation of coumarin 153 via the Pechmann trans-esterification and condensation process. The formation of the fluorescent coumarin allowed the catalytic process to be monitored in real time at the single molecule level using Total Internal Reflection Fluorescence Microscopy (TIRFM). Benchtop experiments conducted in parallel demonstrated that the observed catalysis occurred in solution rather than by pure heterogeneous catalysis and is due to a mobile population of small Sm2O3NP released from a polydisperse original sample containing larger particles. TIRFM provided unique insights by demonstrating that catalysis by these smaller colloidal particles is in fact a surface process, while the larger particles are merely suppliers of the small catalytic nanostructures. We refer to this behaviour as a semi-heterogeneous catalytic system. This work showcases the opportunity that single molecule fluorescence techniques can offer in terms of understanding and ultimately improving benchtop and scaled-up synthesis. This specific example highlights the general applicability of this approach to the study of widely-utilized chemical reactions and lays the groundwork for researchers to adopt similar strategies in other systems.
الإتاحة: https://doi.org/10.32920/26018245.v1Test
https://figshare.com/articles/journal_contribution/Dye_Synthesis_in_the_Pechmann_Reaction_Catalytic_Behaviour_of_Samarium_Oxide_Nanoparticles_Studied_Using_Single_Molecule_Fluorescence_Microscopy/26018245Test -
3دورية أكاديمية
المؤلفون: Stefania Impellizzeri, Sabrina Simoncelli, Chiara Fasciani, M. Luisa Marín, Geniece L. Hallett-Tapley, Gregory K. Hodgson, Juan C. Scaiano
مصطلحات موضوعية: Organic chemistry, n.e.c, heterogeneous acid catalysts, condensation, catalysts, total internal reflection fluorescence microscopy
الوصف: Solid niobium oxides (Nb2O5· n H2O) and niobium phosphate were used as heterogeneous acid catalysts to promote the condensation between a switchable oxazine and a fluorescent coumarin in an aprotic solvent. The catalysts were found to promote the generation of an active methylene from the enamine-based portion of the oxazine, which was followed by a nucleophilic attack on the aldehyde functionality of the coumarin reagent. In the resulting system, the emission of the conjugated fluorophore can be observed at 670 nm and, thus, the processes occurring at the catalyst surface can be monitored in real time by total internal reflection fluorescence microscopy (TIRFM).
الإتاحة: https://doi.org/10.32920/26018239.v1Test
https://figshare.com/articles/journal_contribution/Mechanistic_Insights_into_the_Nb2O5_and_Niobium_Phosphate_Catalyzed_In_Situ_Condensation_of_a_Fluorescent_Halochromic_Assembly/26018239Test -
4دورية أكاديمية
مصطلحات موضوعية: Nanoparticle synthesis, properties and applications, organic chemistry, Novel Samarium Oxide Nanoparticles, Brønsted Acid
الوصف: Samarium oxide nanoparticles (Sm2O3NP) were prepared photochemically for the first time. Characterization shows spherical, polydisperse Sm2O3NP stabilized by 4-HEBA, a substituted benzoic acid. The Sm2O3NP also possess Brønsted acidity. This new material may prove to be a potent heterogeneous acid catalyst.
الإتاحة: https://doi.org/10.32920/26018242.v1Test
https://figshare.com/articles/journal_contribution/Photochemical_Synthesis_and_Characterization_of_Novel_Samarium_Oxide_Nanoparticles_Toward_a_Heterogeneous_Br_nsted_Acid_Catalyst/26018242Test -
5دورية أكاديمية
المؤلفون: M. Luisa Marín, Geniece L. Hallett-Tapley, Stefania Impellizzeri, Chiara Fasciani, Sabrina Simoncelli, José Carlos Netto-Ferreira, Juan C. Scaiano
مصطلحات موضوعية: Nanoparticle synthesis, properties and applications, organic chemistry, catalysis, nanoparticles, Niobium Oxide
الوصف: Several forms of niobium oxide were prepared, including nanostructured mesoporous materials, and their acidity properties were comprehensively investigated and compared with commercially available materials. The composites were characterized by a variety of techniques, including XRD, TEM, N2 adsorption and Hammett acid indicator studies. The acidity of the niobium oxide derivatives was also investigated by the ability of the materials to successfully promote the halochromic ring-opening of an oxazine-coumarin probe that was specifically designed for use in fluorescence imaging studies. The ring-opening reaction was easily monitored using UV-visible, fluorescence and NMR spectroscopy. Single molecule microscopy was employed to gain a more in-depth understanding of the niobium oxide acid catalysis pathway. Using this technique, the rate of niobium oxide mediated protonation was estimated to be 1.8 × 10−13 mol m−2 s−1. Single molecule analysis was also used to obtain a detailed map of Brønsted acid sites on the niobium oxide surface. The active sites, located by multiple blinking events, do not seem to be localized on any area of the material, but rather randomly distributed throughout the solid state surface. As the reaction proceeds, the sites with the highest acidity and accessibility are gradually consumed, making the next tier of acid sites available for reaction. The phenomenon was more closely characterized by using time lapsed reactivity maps.
الإتاحة: https://doi.org/10.32920/26018233.v1Test
https://figshare.com/articles/journal_contribution/Synthesis_Acid_Properties_and_Catalysis_by_Niobium_Oxide_Nanostructured_Materials/26018233Test -
6دورية أكاديمية
مصطلحات موضوعية: Nanoparticle synthesis, properties and applications, organic chemistry, nanocatalysts, click reactions, Single-Molecule Spectroscopy
الوصف: Colloidal or heterogeneous nanocatalysts can improve the range and diversity of Cu(I)-catalysed click reactions and facilitate catalyst separation and reuse. Catalysis by metal nanoparticles raises the question as to whether heterogeneous catalysts may cause homogeneous catalysis through metal ion leaching, since the catalytic process could be mediated by the particle, or by metal ions released from it. The question is critical as unwanted homogeneous processes could offset the benefits of heterogeneous catalysis. Here, we combine standard bench scale techniques with single-molecule spectroscopy to monitor single catalytic events in real time and demonstrate that click catalysis occurs directly at the surface of copper nanoparticles; this general approach could be implemented in other systems. We use ‘from the mole to the molecule’ to describe this emerging idea in which mole scale reactions can be optimized through an intimate understanding of the catalytic process at the single-molecule—single catalytic nanoparticle level.
الإتاحة: https://doi.org/10.32920/26018236.v1Test
https://figshare.com/articles/journal_contribution/Copper_Nanoparticle_Heterogeneous_Catalytic_Click_Cycloaddition_Confirmed_by_Single-Molecule_Spectroscopy/26018236Test -
7دورية أكاديمية
المؤلفون: Matteo Amelia, Tommaso Avellini, Simone Monaco, Stefania Impellizzeri, Ibrahim Yildiz, Françisco M. Raymo, Alberto Credi
مصطلحات موضوعية: Nanoparticle synthesis, properties and applications, electrochemistry, electron transfer, nanoparticles, redox potentials, voltammetry
الوصف: Semiconductor quantum dots (QDs) are inorganic nanoparticles which, because of their unique size-dependent electronic properties, are of high potential interest for the construction of functional nanodevices. Photoinduced electron transfer is a versatile mechanism used to implement light-induced functionalities in multicomponent (supra)molecular assemblies. Indeed, QDs can be employed as active components in new generations of these systems. The rational design of the latter, however, requires prior knowledge of the photo-physical properties and redox potentials of the nanocrystals. Here we discuss the results of recent systematic electrochemical investigations aimed at understanding the structural factors that regulate the redox properties of CdSe core and CdSe–ZnS core–shell QDs.
الإتاحة: https://doi.org/10.32920/26018092.v1Test
https://figshare.com/articles/journal_contribution/Redox_properties_of_CdSe_and_CdSe_ZnS_quantum_dots_in_solution/26018092Test -
8دورية أكاديمية
مصطلحات موضوعية: Organic chemistry, n.e.c, optical writing, nanoparticles administration time, fluorescence
الوصف: We designed a hybrid nanoparticle–molecular system composed of silver nanostructures (AgNP) and a fluorogenic boron dipyrromethene (BODIPY) that can be selectively activated by UVA or UVC light in the presence of an appropriate photoacid generator (PAG). Light irradiation of the PAG encourages the release of p -toluenesulfonic, triflic or hydrobromic acid, any of which facilitate optical ‘writing’ by promoting the formation of a fluorescent species. Metal-enhanced fluorescence (MEF) by AgNP was achieved through rational design of the nano–molecular system in accordance with the principles of radiative decay engineering. In addition to increasing signal to noise, AgNP permitted shorter reaction times and low irradiance – all of which have important implications for applications of fluorescence activation in portable fluorescence patterning, bioimaging and super-resolution microscopy. Single molecule fluorescence microscopy provided unique insights into the MEF mechanism which were hidden by ensemble-averaged measurements, demonstrating that single molecule ‘reading’ is a valuable tool for characterizing particle–molecule interactions such as those responsible for the relative contributions of increased excitation and plasmophoric emission toward overall MEF. This work represents a step forward in the contemporary design of synergistic nano–molecular systems, and showcases the advantage of fusion between classic spectroscopic techniques and single molecule methods in terms of improved quantitative understanding of fluorophore–nanoparticle interactions, and how these interactions can be exploited to the fullest extent possible.
الإتاحة: https://doi.org/10.32920/26018050.v1Test
https://figshare.com/articles/journal_contribution/Optical_writing_and_single_molecule_reading_of_photoactivatable_and_silver_nanoparticle-enhanced_fluorescence/26018050Test -
9دورية أكاديمية
مصطلحات موضوعية: Organic chemistry, n.e.c, INHIBIT, IMPLICATION, molecular logic
الوصف: Molecules that respond to input stimulations to produce detectable outputs can be exploited to mimic Boolean logic operators and reproduce basic arithmetic functions. We have designed a two-state fluorescent probe with tunable emission wavelength for the construction of a molecular logic gate with reconfigurable single– or dual–output capability. The system is based on a BODIPY skeleton coupled with 4-(dimethylamino)benzaldehyde. The behavior of the molecular logic gate can be easily investigated in solution with fluorescence spectroscopy, and the optical readout (fluorescence) can be monitored in one (green) or two (green and red) channels. Depending on the solvent of choice, single INHIBIT or dual INHIBIT/IMPLY logic functions can be achieved using chemical inputs (acid and base). Reconfiguration from single– to dual–output is thus made possible by operating the system in acetonitrile (single output) or toluene (dual output), respectively. The logic gate can be switched by manipulating the fluorescence emission via protonation or deprotonation, even when immobilized onto a glass substrate. At the solid state, the resulting output can be stored for extended periods of time. This feature provides two added benefits: (i) memory function and (ii) “set/reset” capability of the logic gate. Our design thus provides a proof-of-concept interface between the molecular and electronic domains.
الإتاحة: https://doi.org/10.32920/26015899.v1Test
https://figshare.com/articles/journal_contribution/A_Reconfigurable_Dual-Output_INHIBIT_and_IMPLICATION_Molecular_Logic_Gate/26015899Test -
10دورية أكاديمية
المؤلفون: Derek Isrow, Musa Ahmadi, Stefania Impellizzeri, Burjor Captain
مصطلحات موضوعية: Organic chemistry, n.e.c, nickel-tin dimer, chemistry
الوصف: Ni(COD)2 reacts with But3SnH and CNBut at room temperature to afford the trigonal bipyramidal complex Ni(SnBut3)2(CNBut)3, 3 . Exposing a solution of 3 to CO gas results in ligand exchange generating the pale yellow complex, Ni(SnBut3)2(CNBut)2(CO), 4 . In the presence of light, a Ni-Sn bond in 4 is cleaved converting two equivalents of compound 4 into the deep purple nickel-tin dimer, [Ni(SnBut3)(CNBut)2(CO)]2, 5 . The reaction is believed to proceed through radical mechanisms.
الإتاحة: https://doi.org/10.32920/26015893.v1Test
https://figshare.com/articles/journal_contribution/Photochemical_synthesis_and_radical_generation_of_the_nickel-tin_dimer_Ni_SnBut3_CNBut_2_CO_2/26015893Test
النص الكامل