Multimodal Light-Harvesting Soft Hybrid Materials: Assisted Energy Transfer upon Thermally Reversible Gelation

Multimodal light-harvesting soft systems able to absorb UV-to-NIR radiations and convert into visible emissions have drawn much attention in the last years in order to explore new areas of application in energy, photonics, photocatalysis, sensors, and so forth. Here, we present a new hybrid system combining a supramolecular photonic gel of naphthalimidederived molecules self-assembled into fibers and upconverting NaYF4:Yb/Tm nanoparticles (UCNPs). The hybrid system presented here manipulates light reversibly as a result of an optical communication between the UCNPs and the photoactive gel network. Upon UV irradiation, the system shows the characteristic emission at 410 nm from the photoactive organomolecule. This emission is also activated upon 980 nm excitation thanks to an efficient energy transfer from the UCNPs to the fibrillary network. Interestingly, the intensity of this emission is thermally regulated during the reversible assembly or disassembly of the organogelator molecules, in such a way that gelator emission is only observed in the aggregated state. Additionally, the adsorption of the UCNPs with the supramolecular gel fibers enhances their emissive properties, a behavior ascribed to the isolation from solvent quenchers and surface defects, as well as an increased IR light scattering promoted by the fibrillary network. The reported system constitutes a unique case of a thermally regulated, reversible, dual UV and IR light-harvesting hybrid soft material

Pooled Time Series Modeling Reveals Smoking Habit Memory Pattern

Smoking is a habit that is hard to break because nicotine is highly addictive and smoking behavior is strongly linked to multiple daily activities and routines. Here, we explored the effect of gender, age, day of the week, and previous smoking on the number of cigarettes smoked on any given day. Data consisted of daily records of the number of cigarettes participants smoked over an average period of 84 days. The sample included smokers (36 men and 26 women), aged between 18 and 26 years, who smoked at least five cigarettes a day and had smoked for at least 2 years. A panel data analysis was performed by way of multilevel pooled time series modeling. Smoking on any given day was a function of the number of cigarettes smoked on the previous day, and 2, 7, 14, 21, 28, 35, 42, 49, and 56 days previously, and the day of the week. Neither gender nor age influenced this pattern, with no multilevel effects being detected, thus the behavior of all participants fitted the same smoking model. These novel findings show empirically that smoking behavior is governed by firmly established temporal dependence patterns and inform temporal parameters for the rational design of smoking cessation programs

A spectroscopic study to assess the photogeneration of singlet oxygen by graphene oxide

[EN] The photogeneration of singlet oxygen (O-1(2) ) during short irradiation times of graphene oxide (GO) is assessed under visible light with soft irradiation conditions either directly monitoring the phosphorescence emission of O-1(2) at ca. 1275 nm, or indirectly by means of the fluorescent probe 9, 10-anthracene diyl-bis(methylene)dimalonic acid (ABDA). Results obtained using both methodologies lead to the conclusion that O-1(2) generation is negligible under our experimental conditions. In the case of using ABDA very small emission changes were recorded, which could be attributed to other side reactions. Special care should be taken when using this spectroscopic probe to assess the generation of O-1(2), since ABDA and related probes based on the reactivity of the anthracene fluorophore can also detect electron transfer processes. This kind of approaches have been less explored in the field of Materials Science at the nanoscale, and we believe that the knowledge on the lack of generation of O-1(2) by irradiated GO is informative and useful, especially for the assessment of the environmental and biological toxicity of nanomaterials based on GO. (C) 2019 Elsevier B.V. All rights reserved.Ministerio de Economia y Competitividad of Spain (grant CTQ2015-71004-R) and Universitat Jaume I (grant P1.1B2015-76) are thanked for their financial support. C.F-L. thanks the Ministerio de Economia y Competitividad of Spain for a FPI fellowship. Technical support from SCIC of University Jaume I is acknowledged. The Instituto de Tecnologia Quimica (ITQ) thanks the support of the Severo Ochoa Program (SEV-2016-0683), and Consejo Superior de Investigaciones Cientificas (I-Link1063). We would like to thank Dr. Francisco Bosca for his technical assistance with the singlet oxygen emission measurements at the ITQ.Felip-León, C.; Puche Panadero, M.; Miravet, JF.; Galindo, F.; Feliz Rodriguez, M. (2019). A spectroscopic study to assess the photogeneration of singlet oxygen by graphene oxide. Materials Letters. 251:45-51. https://doi.org/10.1016/j.matlet.2019.05.001S455125

Insight into the esterase like activity demonstrated by an imidazole appended self-assembling hydrogelator

A low molecular weight hydrogelator with a covalently appended imidazole moiety is reported. Capable of percolating water in the pH range of 6 to 8, it proves to be an efficient catalyst upon self-assembly, showing Michaelis-Menten type kinetics. Activities at different pH values correlated with dramatic structural changes were observed. It can hydrolyse p-nitrophenyl acetate (pNPA) as well as inactivated esters, and l and d-phenylalanine methyl esters. The enhanced activity can be related to the conglomeration of catalytic groups upon aggregation resulting in their close proximity and the formation of hydrophobic pockets

Thermally regulated reversible formation of vesicle-like assemblies by hexaproline amphiphiles

Peptides composed of hexaproline and glutamic acid (P6E) or lysine (P6K) as C-terminal units show thermally promoted aggregation, affording vesicle-like assemblies upon heating to 80 ºC. The aggregation is analyzed by dynamic light scattering (DLS), with number averaged diameters of ca. 600 and 300 nm respectively for P6E and P6K. NMR studies reveal that upon heating the amount of NMR-visible species is reduced to ca. 50% and that an important conformational change is experienced by the molecules in solution. Circular dichroism (CD) shows that at 20º C the peptides present a polyproline II (PP-II) conformation which is disorganized upon heating. Scanning electron microscopy for samples which were fast frozen at 80 ºC reveals vesicle-like assemblies. Using pyrene as a fluorescence probe, a critical aggregation concentration of ca. 30 m was estimated for P6E while that of P6K was above 0.6 mM. The aggregation process is found to be fully reversible and could serve as a basis for development of stimuli responsive carriers

Photobehavior of the antipsychotic drug cyamemazine in a supramolecular gel protective environment

[EN] In this work, a molecular hydrogel made of gelator (S)-4-((3-methyl-1-(nonylamino)-1-oxobutan-2-yl)amino)-4-oxobutanoic acid (SVN) has been employed as soft container to modify the photochemical and photophysical behavior of the antipsychotic drug cyamemazine (CMZ). The interaction of CMZ with the gel network has been evidenced by fluorescence spectroscopy through a hypsochromic shift of the emission band (from lambda(max) = 521 nm in solution to lambda(max) = 511 nm in the gel) and an increase of the fluorescence lifetime (5.6 ns in PBS vs. 7.2 ns in the gel). In the laser flash photolysis experiments on CMZ/SVN systems, the CMZ triplet excited state ((3)CMZ*), monitored at lambda = 320 nm, has been more efficiently generated and became much longer-lived than in solution (2.7 mu s vs. 0.7 mu s); besides, photochemical ionization leading to the radical cation CMZ(+center dot) was disfavored. In the steady-state experiments, photooxidation of CMZ to afford the N,S-dioxide derivative CMZ-SONO has been retarded in the gel, which provides a more lipophilic and constrained microenvironment. Both the photophysical properties and the photoreactivity are in agreement with CMZ located in a less polar domain when entrapped in the supramolecular gel, as result of the interaction of the drug with the fibers of the supramolecular SVN gel.Financial support from the Spanish Government (CTQ2016-78875-P and CTQ2015-71004-R), the Generalitat Valenciana (PROMETEO/2017/075) and the European Union is gratefully acknowledged.Vendrell-Criado, V.; Angulo-Pachón, CA.; Miravet, JF.; Galindo, F.; Miranda Alonso, MÁ.; Jiménez Molero, MC. (2020). Photobehavior of the antipsychotic drug cyamemazine in a supramolecular gel protective environment. Journal of Photochemistry and Photobiology B Biology. 202:1-4. https://doi.org/10.1016/j.jphotobiol.2019.111686S14202Bourin, M., Dailly, E., & Hascöet, M. 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Selective and highly efficient dye scavenging by a pH-responsive molecular hydrogelator

A structurally simple low molecular weight hydrogelator derived from isophthalic acid forms robust pH-responsive hydrogels capable of highly efficient and selective dye adsorption

Broad-spectrum photo-antimicrobial polymers based on cationic polystyrene and Rose Bengal

New strategies to fight bacteria and fungi are necessary in view of the problem of iatrogenic and nosocomial infections combined with the growing threat of increased antimicrobial resistance. Recently, our group has prepared and described two new readily available materials based on the combination of Rose Bengal (singlet oxygen photosensitizer) and commercially available cationic polystyrene (macroporous resin Amberlite® IRA 900 or gel-type resin IRA 400). These materials showed high efficacy in the antimicrobial photodynamic inactivation (aPDI) of Pseudomonas aeruginosa. Here, we present the photobactericidal effect of these polymers against an extended group of pathogens like Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, and the opportunistic yeast Candida albicans using green light. The most interesting finding is that the studied materials are able to reduce the population of both Gram-positive and Gram-negative bacteria with good activity, although, for C. albicans, in a moderate manner. In view of the results achieved and especially considering the inexpensiveness of these two types of photoactive polymers, we believe that they could be used as the starting point for the development of coatings for self-disinfecting surfaces

HRMAS 1H NMR as a tool for the study of supramolecular gels

HRMAS 1H NMR is reported for the first time as a useful technique to gain insight into the dynamic properties of aggregates present in supramolecular gels. The study of several low molecular weight gelators with this technique in toluene and acetonitrile is described

Self-assembly of a peptide amphiphile: transition from nanotape fibrils to micelles

A thermal transition is observed in the peptide amphiphile C16-KTTKS (TFA salt) from nanotapes at 20 degrees C to micelles at higher temperature (the transition temperature depending on concentration). The formation of extended nanotapes by the acetate salt of this peptide amphiphile, which incorporates a pentapeptide from type I procollagen, has been studied previously [V. Castelletto et al., Chem. Commun., 2010, 46, 9185]. Here, proton NMR and SAXS provide evidence for the TFA salt spherical micelles at high temperature. The phase behavior, with a Krafft temperature separating insoluble aggregates (extended nanotapes) at low temperature from the high temperature micellar phase resembles that for conventional surfactants, however this has not previously been reported for peptide amphiphiles