Tourism in Azores Islands: Persistence in the Monthly Arrivals

This study analyses the persistence in the international monthly arrivals to the Azores Islands using a model based on fractional integration and seasonal autoregressions. The estimated fractional differencing parameter gives an indication of the long run evolution of the series. We use both aggregate data and disaggregate monthly data by location of origin and island destination. The results show that the aggregate series corresponding to the total number of arrivals is a nonstationary I(d) process with d above 1, and the most persistent ones are those travelling to Säo Miguel, especially from Holland, Finland, Norway, Germany, Denmark and the UK.Monthly arrivals; Seasonal fractional integration; Persistence; Azores Islands.

A new approach to enantiopure β-endo-substituted azabicyclic proline analogues by base induced epimerization of a formyl derivative

13 pages, 6 schemes, 1 figure.The β-epimer of methyl (1S,2R,4R)-N-benzoyl-2-formyl-7-azabicyclo[2.2.1]heptane-1- carboxylate, (1S, 2S, 4R)-7, has been obtained by treatment of the exo-formyl derivative with triethylamine in methanol. The development of this epimerization procedure has further increased the already wide possibilities offered by our methodology and solves the problem of access to the endo derivatives that would result from the Diels–Alder reaction of Danishefsky’s diene and the C-4 unsaturated E-oxazolones, whose preparation frequently proves to be problematic.This work was carried out with the financial support of Ministerio de Ciencia y Tecnología and FEDER (project CTQ2004-5358) and Gobierno de Aragón (Grupo Consolidado E40).Peer reviewe

Structural reorganization in a hydrogen-bonded organic framework

Self-recognition of 3,3′,5,5′-azobenzenetetracarboxylic acid drives the formation of a grid-like anionic hydrogen-bonded framework with channels occupied by organic cations. This supramolecular solid is capable of reorganizing its connectivity in the presence of specific guests into a different crystalline architecture by sequential dissolution and recrystallization

Proton vs. neutron halo breakup

In this paper we show how effective parameters such as effective binding energies can be defined for a proton in the combined nuclear-Coulomb potential, including also the target potential, in the case in which the proton is bound in a nucleus which is partner of a nuclear reaction. Using such effective parameters the proton behaves similarly to a neutron. In this way some unexpected results obtained from dynamical calculations for reactions initiated by very weakly bound proton halo nuclei can be interpreted. Namely the fact that stripping dominates the nuclear breakup cross section which in turn dominates over the Coulomb breakup even when the target is heavy at medium to high incident energies. Our interpretation helps also clarifying why the existence and characteristics of a proton halo extracted from different types of data have sometimes appeared contradictory.Comment: 7 Latex pages, 3 table, 3 ps figures, to appear in Phys. Rev.

A Compressive Receding Horizon Approach for Smart Home Energy Management

UID/CEC/00326/2020Current increases in the demand for electricity require sustainable energy management measures and have promoted the adoption of clean and renewable sources, particularly at the residential building level. Active demand management is usually carried out through load shifting based on specific techniques, such as optimisation, heuristics, model-based predictive control and machine learning methodologies. This work addresses the problem of residential load scheduling via optimisation techniques. A compressive receding horizon strategy is proposed for week-ahead load shifting, and the selection is driven by traditional receding horizon and day-ahead allocation strategy misalignment, with weekly household appliance usage patterns. The proposed approach is compared with receding horizon and day-ahead scheduling techniques over 30 different weeks for a prototypical smart home with non-controllable demand, which is representative of a four-resident family and includes micro power generation and battery storage. The simulation results confirm the validity of the proposed strategy in the context of household appliance scheduling problems and show competitive electricity costs and resident discomfort performance compared to state-of-the-art approaches. Furthermore, the proposed compressive receding horizon strategy fully exploits weather and photovoltaic generation forecasts to promote self-consumption and grid demand stress reduction while providing environmental gains and financial benefits to the utility service and consumers, particularly in the case of simultaneously scheduling a huge number of households.publishersversionpublishe

A New Environmentally-Friendly Colorimetric Probe for Formaldehyde Gas Detection under Real Conditions

[EN] A new environmentally-friendly, simple, selective and sensitive probe for detecting formaldehyde, based on naturally-occurring compounds, through either colorimetric or fluorescence changes, is described. The probe is able to detect formaldehyde in both solution and the gas phase with limits of detection of 0.24 mM and 0.7 ppm, respectively. The probe has been tested to study formaldehyde emission in contaminated real atmospheres. The supported probe is easy to use and to dispose, and is safe and suitable as an individual chemodosimeter.This research was funded by the Spanish Government (projects MAT2015-64139-C4-4-R and AGL2015-70235-C2-2-R (MINECO/FEDER)) and the Generalitat Valenciana (project PROMETEOII/2014/047).Martínez-Aquino, C.; Costero, AM.; Gil Grau, S.; Gaviña, P. (2018). A New Environmentally-Friendly Colorimetric Probe for Formaldehyde Gas Detection under Real Conditions. Molecules. 23(10). https://doi.org/10.3390/molecules23102646S2310https://mcgroup.co.uk/news/20140627/formaldehyde-production-exceed-52-mln-tonnes.htmlGoris, J. A., Ang, S., & Navarro, C. (1998). Laboratory Safety: Minimizing the Toxic Effects of Formaldehyde. Laboratory Medicine, 29(1), 39-43. doi:10.1093/labmed/29.1.39Luo, W., Li, H., Zhang, Y., & Ang, C. Y. . (2001). Determination of formaldehyde in blood plasma by high-performance liquid chromatography with fluorescence detection. Journal of Chromatography B: Biomedical Sciences and Applications, 753(2), 253-257. doi:10.1016/s0378-4347(00)00552-1ROCHA, F., COELHO, L., LOPES, M., CARVALHO, L., FRACASSIDASILVA, J., DOLAGO, C., & GUTZ, I. (2008). Environmental formaldehyde analysis by active diffusive sampling with a bundle of polypropylene porous capillaries followed by capillary zone electrophoretic separation and contactless conductivity detection. Talanta, 76(2), 271-275. doi:10.1016/j.talanta.2008.02.037Korpan, Y. I., Gonchar, M. V., Sibirny, A. A., Martelet, C., El’skaya, A. V., Gibson, T. D., & Soldatkin, A. P. (2000). Development of highly selective and stable potentiometric sensors for formaldehyde determination. Biosensors and Bioelectronics, 15(1-2), 77-83. doi:10.1016/s0956-5663(00)00054-3Dong, S., & Dasgupta, P. K. (1986). Solubility of gaseous formaldehyde in liquid water and generation of trace standard gaseous formaldehyde. Environmental Science & Technology, 20(6), 637-640. doi:10.1021/es00148a016MITSUBAYASHI, K., NISHIO, G., SAWAI, M., SAITO, T., KUDO, H., SAITO, H., … MARTY, J. (2008). A bio-sniffer stick with FALDH (formaldehyde dehydrogenase) for convenient analysis of gaseous formaldehyde. Sensors and Actuators B: Chemical, 130(1), 32-37. doi:10.1016/j.snb.2007.07.086DEMKIV, O., SMUTOK, O., PARYZHAK, S., GAYDA, G., SULTANOV, Y., GUSCHIN, D., … GONCHAR, M. (2008). Reagentless amperometric formaldehyde-selective biosensors based on the recombinant yeast formaldehyde dehydrogenase. Talanta, 76(4), 837-846. doi:10.1016/j.talanta.2008.04.040Dennison, M. J., Hall, J. M., & Turner, A. P. F. (1996). Direct monitoring of formaldehyde vapour and detection of ethanol vapour using dehydrogenase-based biosensors. The Analyst, 121(12), 1769. doi:10.1039/an9962101769Wang, X., Si, Y., Mao, X., Li, Y., Yu, J., Wang, H., & Ding, B. (2013). Colorimetric sensor strips for formaldehyde assay utilizing fluoral-p decorated polyacrylonitrile nanofibrous membranes. The Analyst, 138(17), 5129. doi:10.1039/c3an00812fPinheiro, H. L. ., de Andrade, M. V., de Paula Pereira, P. A., & de Andrade, J. B. (2004). Spectrofluorimetric determination of formaldehyde in air after collection onto silica cartridges coated with Fluoral P. Microchemical Journal, 78(1), 15-20. doi:10.1016/j.microc.2004.02.017Antwi-Boampong, S., Peng, J. S., Carlan, J., & BelBruno, J. J. (2014). A Molecularly Imprinted Fluoral-P/Polyaniline Double Layer Sensor System for Selective Sensing of Formaldehyde. IEEE Sensors Journal, 14(5), 1490-1498. doi:10.1109/jsen.2014.2298872Xu, Z., Chen, J., Hu, L.-L., Tan, Y., Liu, S.-H., & Yin, J. (2017). Recent advances in formaldehyde-responsive fluorescent probes. Chinese Chemical Letters, 28(10), 1935-1942. doi:10.1016/j.cclet.2017.07.018Brewer, T. F., & Chang, C. J. (2015). An Aza-Cope Reactivity-Based Fluorescent Probe for Imaging Formaldehyde in Living Cells. Journal of the American Chemical Society, 137(34), 10886-10889. doi:10.1021/jacs.5b05340Roth, A., Li, H., Anorma, C., & Chan, J. (2015). A Reaction-Based Fluorescent Probe for Imaging of Formaldehyde in Living Cells. Journal of the American Chemical Society, 137(34), 10890-10893. doi:10.1021/jacs.5b05339Li, J.-B., Wang, Q.-Q., Yuan, L., Wu, Y.-X., Hu, X.-X., Zhang, X.-B., & Tan, W. (2016). A two-photon fluorescent probe for bio-imaging of formaldehyde in living cells and tissues. The Analyst, 141(11), 3395-3402. doi:10.1039/c6an00473cTang, Y., Kong, X., Xu, A., Dong, B., & Lin, W. (2016). Development of a Two-Photon Fluorescent Probe for Imaging of Endogenous Formaldehyde in Living Tissues. Angewandte Chemie International Edition, 55(10), 3356-3359. doi:10.1002/anie.201510373He, L., Yang, X., Liu, Y., Kong, X., & Lin, W. (2016). A ratiometric fluorescent formaldehyde probe for bioimaging applications. Chemical Communications, 52(21), 4029-4032. doi:10.1039/c5cc09796gSingha, S., Jun, Y. W., Bae, J., & Ahn, K. H. (2017). Ratiometric Imaging of Tissue by Two-Photon Microscopy: Observation of a High Level of Formaldehyde around Mouse Intestinal Crypts. Analytical Chemistry, 89(6), 3724-3731. doi:10.1021/acs.analchem.7b00044Song, H., Rajendiran, S., Kim, N., Jeong, S. K., Koo, E., Park, G., … Yoon, S. (2012). A tailor designed fluorescent ‘turn-on’ sensor of formaldehyde based on the BODIPY motif. Tetrahedron Letters, 53(37), 4913-4916. doi:10.1016/j.tetlet.2012.06.117Zhou, Y., Yan, J., Zhang, N., Li, D., Xiao, S., & Zheng, K. (2018). A ratiometric fluorescent probe for formaldehyde in aqueous solution, serum and air using aza-cope reaction. Sensors and Actuators B: Chemical, 258, 156-162. doi:10.1016/j.snb.2017.11.043Chaiendoo, K., Sooksin, S., Kulchat, S., Promarak, V., Tuntulani, T., & Ngeontae, W. (2018). A new formaldehyde sensor from silver nanoclusters modified Tollens’ reagent. Food Chemistry, 255, 41-48. doi:10.1016/j.foodchem.2018.02.030Fauzia, V., Nurlely, Imawan, C., Narayani, N. M. M. S., & Putri, A. E. (2018). A localized surface plasmon resonance enhanced dye-based biosensor for formaldehyde detection. Sensors and Actuators B: Chemical, 257, 1128-1133. doi:10.1016/j.snb.2017.11.031El Sayed, S., Pascual, L., Licchelli, M., Martínez-Máñez, R., Gil, S., Costero, A. M., & Sancenón, F. (2016). Chromogenic Detection of Aqueous Formaldehyde Using Functionalized Silica Nanoparticles. ACS Applied Materials & Interfaces, 8(23), 14318-14322. doi:10.1021/acsami.6b03224Li, Z., Xue, Z., Wu, Z., Han, J., & Han, S. (2011). Chromo-fluorogenic detection of aldehydes with a rhodamine based sensor featuring an intramolecular deoxylactam. Organic & Biomolecular Chemistry, 9(22), 7652. doi:10.1039/c1ob06448gGuglielmino, M., Allouch, A., Serra, C. A., & Calvé, S. L. (2017). Development of microfluidic analytical method for on-line gaseous Formaldehyde detection. Sensors and Actuators B: Chemical, 243, 963-970. doi:10.1016/j.snb.2016.11.093Xia, H., Hu, J., Tang, J., Xu, K., Hou, X., & Wu, P. (2016). A RGB-Type Quantum Dot-based Sensor Array for Sensitive Visual Detection of Trace Formaldehyde in Air. Scientific Reports, 6(1). doi:10.1038/srep36794Feng, L., Musto, C. J., & Suslick, K. S. (2010). A Simple and Highly Sensitive Colorimetric Detection Method for Gaseous Formaldehyde. Journal of the American Chemical Society, 132(12), 4046-4047. doi:10.1021/ja910366pGuo, X.-L., Chen, Y., Jiang, H.-L., Qiu, X.-B., & Yu, D.-L. (2018). Smartphone-Based Microfluidic Colorimetric Sensor for Gaseous Formaldehyde Determination with High Sensitivity and Selectivity. Sensors, 18(9), 3141. doi:10.3390/s18093141He, L., Yang, X., Ren, M., Kong, X., Liu, Y., & Lin, W. (2016). An ultra-fast illuminating fluorescent probe for monitoring formaldehyde in living cells, shiitake mushrooms, and indoors. Chemical Communications, 52(61), 9582-9585. doi:10.1039/c6cc04254fGangopadhyay, A., Maiti, K., Ali, S. S., Pramanik, A. K., Guria, U. N., Samanta, S. K., … Mahapatra, A. K. (2018). A PET based fluorescent chemosensor with real time application in monitoring formaldehyde emissions from plywood. Analytical Methods, 10(24), 2888-2894. doi:10.1039/c8ay00514aLin, Q., Fan, Y.-Q., Gong, G.-F., Mao, P.-P., Wang, J., Guan, X.-W., … Wei, T.-B. (2018). Ultrasensitive Detection of Formaldehyde in Gas and Solutions by a Catalyst Preplaced Sensor Based on a Pillar[5]arene Derivative. ACS Sustainable Chemistry & Engineering, 6(7), 8775-8781. doi:10.1021/acssuschemeng.8b01124Cox, E. D., & Cook, J. M. (1995). The Pictet-Spengler condensation: a new direction for an old reaction. Chemical Reviews, 95(6), 1797-1842. doi:10.1021/cr00038a004Jonsson, G., Launosalo, T., Salomaa, P., Walle, T., Sjöberg, B., Bunnenberg, E., … Records, R. (1966). Fluorescence Studies on Some 6,7-Substituted 3,4-Dihydroisoquinolines Formed from 3-Hydroxytyramine (Dopamine) and Formaldehyde. Acta Chemica Scandinavica, 20, 2755-2762. doi:10.3891/acta.chem.scand.20-2755BJÖRKLUND, A., EHINGER, B., & FALCK, B. (1968). A METHOD FOR DIFFERENTIATING DOPAMINE FROM NORADRENALINE IN TISSUE SECTIONS BY MICROSPECTROFLUOROMETRY. Journal of Histochemistry & Cytochemistry, 16(4), 263-270. doi:10.1177/16.4.263Stöckigt, J., Antonchick, A. P., Wu, F., & Waldmann, H. (2011). The Pictet-Spengler Reaction in Nature and in Organic Chemistry. Angewandte Chemie International Edition, 50(37), 8538-8564. doi:10.1002/anie.201008071Allou, L., El Maimouni, L., & Le Calvé, S. (2011). Henry’s law constant measurements for formaldehyde and benzaldehyde as a function of temperature and water composition. Atmospheric Environment, 45(17), 2991-2998. doi:10.1016/j.atmosenv.2010.05.04

Adaptive inverse analysis (AIA) applied and verified on various fiber reinforced concrete composites

During the past decades several inverse approaches have been developed to identify the stress-crack opening (σ−w) by means of indirect test methods, such as the notched three point bending-, wedge splitting-, and round panel testing. The aim is to establish reliable constitutive models for the tensile behavior of fiber reinforced concrete materials, suitable for structural design. Within this context, the adaptive inverse analysis (AIA) was recently developed to facilitate a fully general and automatized inverse analysis scheme, which is applicable in conjunction with analytical or finite element simulation of the experimental response. This paper presents a new formulation of the adaptive refinement criterion of the AIA method. The paper demonstrates that the refinement criterion of the nonlinear least square curve fitting process, is significantly improved by coupling the model error to the crack mouth opening and the crack opening displacement relationship. This enables an adaptive refinement of the σ−w model in the line segment with maximum model error, which entails significant improvement of the numerical efficiency of the AIA method without any loss of robustness. The improved method is applied on various fiber reinforced concrete composites and the results are benchmarked with the inverse analysis method suggested by the Japanese Concrete Institute (Method of test for fracture energy of concrete by use of notched beam, Japanese Concrete Institute Standard, Tokyo, 2003) and recently adopted in ISO 19044 (Test methods for fibre-reinforced cementitious composites—load-displacement curve using notched specimen, 2015). The benchmarking demonstrates that the AIA method, in contradiction to the JCI/ISO method, facilitates direct determination of the tensile strength and operational multi-linear σ−w models

Resorcinol Functionalized Gold Nanoparticles for Formaldehyde Colorimetric Detection

[EN] Gold nanoparticles functionalized with resorcinol moieties have been prepared and used for detecting formaldehyde both in solution and gas phases. The detection mechanism is based on the color change of the probe upon the aggregation of the nanoparticles induced by the polymerization of the resorcinol moieties in the presence of formaldehyde. A limit of detection of 0.5 ppm in solution has been determined. The probe can be deployed for the detection of formaldehyde emissions from composite wood boards.We thank the Spanish Government (projects MAT2015-64139-C4-4-R and AGL2015-70235-C2-2-R (MINECO/FEDER)) and the Generalitat Valenciana (project PROMETEOII/2014/047) for support.Martínez-Aquino, C.; Costero, AM.; Gil Grau, S.; Gaviña, P. (2019). Resorcinol Functionalized Gold Nanoparticles for Formaldehyde Colorimetric Detection. Nanomaterials. 9(2):1-9. https://doi.org/10.3390/nano9020302S1992Salthammer, T. (2013). Formaldehyde in the Ambient Atmosphere: From an Indoor Pollutant to an Outdoor Pollutant? Angewandte Chemie International Edition, 52(12), 3320-3327. doi:10.1002/anie.201205984Bruemmer, K. J., Brewer, T. F., & Chang, C. J. (2017). Fluorescent probes for imaging formaldehyde in biological systems. Current Opinion in Chemical Biology, 39, 17-23. doi:10.1016/j.cbpa.2017.04.010Lang, I., Bruckner, T., & Triebig, G. (2008). Formaldehyde and chemosensory irritation in humans: A controlled human exposure study. Regulatory Toxicology and Pharmacology, 50(1), 23-36. doi:10.1016/j.yrtph.2007.08.012IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Vol. 100F (2012). Chemical Agents and Related Occupations: Formaldehydehttps://monographs.iarc.fr/wp-content/uploads/2018/06/mono100F-29.pdfChung, P.-R., Tzeng, C.-T., Ke, M.-T., & Lee, C.-Y. (2013). Formaldehyde Gas Sensors: A Review. Sensors, 13(4), 4468-4484. doi:10.3390/s130404468Soman, A., Qiu, Y., & Chan Li, Q. (2008). HPLC-UV Method Development and Validation for the Determination of Low Level Formaldehyde in a Drug Substance. Journal of Chromatographic Science, 46(6), 461-465. doi:10.1093/chromsci/46.6.461Risholm-Sundman, M., Larsen, A., Vestin, E., & Weibull, A. (2007). Formaldehyde emission—Comparison of different standard methods. Atmospheric Environment, 41(15), 3193-3202. doi:10.1016/j.atmosenv.2006.10.079Kim, S., & Kim, H.-J. (2005). Comparison of standard methods and gas chromatography method in determination of formaldehyde emission from MDF bonded with formaldehyde-based resins. Bioresource Technology, 96(13), 1457-1464. doi:10.1016/j.biortech.2004.12.003Yeh, T.-S., Lin, T.-C., Chen, C.-C., & Wen, H.-M. (2013). Analysis of free and bound formaldehyde in squid and squid products by gas chromatography–mass spectrometry. Journal of Food and Drug Analysis, 21(2), 190-197. doi:10.1016/j.jfda.2013.05.010Toews, J., Rogalski, J. C., Clark, T. J., & Kast, J. (2008). Mass spectrometric identification of formaldehyde-induced peptide modifications under in vivo protein cross-linking conditions. Analytica Chimica Acta, 618(2), 168-183. doi:10.1016/j.aca.2008.04.049Zhou, X., Lee, S., Xu, Z., & Yoon, J. (2015). Recent Progress on the Development of Chemosensors for Gases. Chemical Reviews, 115(15), 7944-8000. doi:10.1021/cr500567rZhou, Y., Yan, J., Zhang, N., Li, D., Xiao, S., & Zheng, K. (2018). A ratiometric fluorescent probe for formaldehyde in aqueous solution, serum and air using aza-cope reaction. Sensors and Actuators B: Chemical, 258, 156-162. doi:10.1016/j.snb.2017.11.043Chaiendoo, K., Sooksin, S., Kulchat, S., Promarak, V., Tuntulani, T., & Ngeontae, W. (2018). A new formaldehyde sensor from silver nanoclusters modified Tollens’ reagent. Food Chemistry, 255, 41-48. doi:10.1016/j.foodchem.2018.02.030El Sayed, S., Pascual, L., Licchelli, M., Martínez-Máñez, R., Gil, S., Costero, A. M., & Sancenón, F. (2016). Chromogenic Detection of Aqueous Formaldehyde Using Functionalized Silica Nanoparticles. ACS Applied Materials & Interfaces, 8(23), 14318-14322. doi:10.1021/acsami.6b03224Martínez-Aquino, C., Costero, A., Gil, S., & Gaviña, P. (2018). A New Environmentally-Friendly Colorimetric Probe for Formaldehyde Gas Detection under Real Conditions. Molecules, 23(10), 2646. doi:10.3390/molecules23102646Guo, X.-L., Chen, Y., Jiang, H.-L., Qiu, X.-B., & Yu, D.-L. (2018). Smartphone-Based Microfluidic Colorimetric Sensor for Gaseous Formaldehyde Determination with High Sensitivity and Selectivity. Sensors, 18(9), 3141. doi:10.3390/s18093141Gangopadhyay, A., Maiti, K., Ali, S. S., Pramanik, A. K., Guria, U. N., Samanta, S. K., … Mahapatra, A. K. (2018). A PET based fluorescent chemosensor with real time application in monitoring formaldehyde emissions from plywood. Analytical Methods, 10(24), 2888-2894. doi:10.1039/c8ay00514aBi, A., Yang, S., Liu, M., Wang, X., Liao, W., & Zeng, W. (2017). Fluorescent probes and materials for detecting formaldehyde: from laboratory to indoor for environmental and health monitoring. RSC Advances, 7(58), 36421-36432. doi:10.1039/c7ra05651fSaha, K., Agasti, S. S., Kim, C., Li, X., & Rotello, V. M. (2012). Gold Nanoparticles in Chemical and Biological Sensing. Chemical Reviews, 112(5), 2739-2779. doi:10.1021/cr2001178Mayer, K. M., & Hafner, J. H. (2011). Localized Surface Plasmon Resonance Sensors. Chemical Reviews, 111(6), 3828-3857. doi:10.1021/cr100313vKong, B., Zhu, A., Luo, Y., Tian, Y., Yu, Y., & Shi, G. (2011). Sensitive and Selective Colorimetric Visualization of Cerebral Dopamine Based on Double Molecular Recognition. Angewandte Chemie International Edition, 50(8), 1837-1840. doi:10.1002/anie.201007071Ma, P., Liang, F., Wang, D., Yang, Q., Ding, Y., Yu, Y., … Wang, X. (2014). Ultrasensitive determination of formaldehyde in environmental waters and food samples after derivatization and using silver nanoparticle assisted SERS. Microchimica Acta, 182(3-4), 863-869. doi:10.1007/s00604-014-1400-9Wen, G., Liang, X., Liang, A., & Jiang, Z. (2015). Gold Nanorod Resonance Rayleigh Scattering-Energy Transfer Spectral Determination of Trace Formaldehyde with 4-Amino-3-Hydrazino-5-Mercap-1,2,4-Triazole. Plasmonics, 10(5), 1081-1088. doi:10.1007/s11468-015-9893-6Fauzia, V., Nurlely, Imawan, C., Narayani, N. M. M. S., & Putri, A. E. (2018). A localized surface plasmon resonance enhanced dye-based biosensor for formaldehyde detection. Sensors and Actuators B: Chemical, 257, 1128-1133. doi:10.1016/j.snb.2017.11.031Al-Muhtaseb, S. A., & Ritter, J. A. (2003). Preparation and Properties of Resorcinol-Formaldehyde Organic and Carbon Gels. Advanced Materials, 15(2), 101-114. doi:10.1002/adma.200390020Martí, A., Costero, A. M., Gaviña, P., & Parra, M. (2015). Selective colorimetric NO(g) detection based on the use of modified gold nanoparticles using click chemistry. Chemical Communications, 51(15), 3077-3079. doi:10.1039/c4cc10149aGodoy-Reyes, T. M., Llopis-Lorente, A., Costero, A. M., Sancenón, F., Gaviña, P., & Martínez-Máñez, R. (2018). Selective and sensitive colorimetric detection of the neurotransmitter serotonin based on the aggregation of bifunctionalised gold nanoparticles. Sensors and Actuators B: Chemical, 258, 829-835. doi:10.1016/j.snb.2017.11.181Lewicki, J. P., Fox, C. A., & Worsley, M. A. (2015). On the synthesis and structure of resorcinol-formaldehyde polymeric networks – Precursors to 3D-carbon macroassemblies. Polymer, 69, 45-51. doi:10.1016/j.polymer.2015.05.016Martí, A., Costero, A. M., Gaviña, P., Gil, S., Parra, M., Brotons-Gisbert, M., & Sánchez-Royo, J. F. (2013). Functionalized Gold Nanoparticles as an Approach to the Direct Colorimetric Detection of DCNP Nerve Agent Simulant. European Journal of Organic Chemistry, 2013(22), 4770-4779. doi:10.1002/ejoc.201300339Appendino, G., Minassi, A., Daddario, N., Bianchi, F., & Tron, G. C. (2002). Chemoselective Esterification of Phenolic Acids and Alcohols. Organic Letters, 4(22), 3839-3841. doi:10.1021/ol0266471Haiss, W., Thanh, N. T. K., Aveyard, J., & Fernig, D. G. (2007). Determination of Size and Concentration of Gold Nanoparticles from UV−Vis Spectra. Analytical Chemistry, 79(11), 4215-4221. doi:10.1021/ac0702084Liu, X., Atwater, M., Wang, J., & Huo, Q. (2007). Extinction coefficient of gold nanoparticles with different sizes and different capping ligands. Colloids and Surfaces B: Biointerfaces, 58(1), 3-7. doi:10.1016/j.colsurfb.2006.08.00

Diversity and hierarchy in supramolecular assemblies of triphenylalanine: from laminated helical ribbons to toroids

Microstructures from small phenylalanine-based peptides have attracted great attention lately because these compounds are considered to be a new class of tunable materials. In spite of the extensive studies on uncapped diphenylalanine and tetraphenylalanine peptides, studies on the self-assembly of uncapped triphenylananine (FFF) are very scarce and nonsystematic. In this work, we demonstrate that FFF assemblies can organize in a wide number of well-defined supramolecular structures, which include laminated helical-ribbons, leaflike dendrimers, doughnut-, needle-, and flower-shapes. These organizations are produced by the attractive or repulsive interactions between already formed assemblies and therefore can be controlled through the choice of solvents used as the incubation medium. Thus, the formation of the desired supramolecular structures is regulated through the protonation/deprotonation of the terminal groups, the polarity of the incubation medium, which affects both peptide···solvent interactions and the cavity solvation energy (i.e., solvent···solvent interactions), and the steric interactions between own assemblies that act as building blocks. Finally, the ß-sheet disposition in the latter structural motifs has been examined using both theoretical calculations and Fourier transform infrared spectroscopy. Results indicate that FFF molecules can adopt both parallel and antiparallel ß-sheets. However, the former one is the most energetically favored because of the formation of p–p stacking interactions between the aromatic rings of hydrogen-bonded strands.Preprin