Suchergebnisse

Unmanned aerial vehicles (UAV, aka drones) are being used for mapping macro-litter in the environment. As drone images require a manual processing task for detecting marine litter, it is of interest to evaluate the accuracy of non-expert citizen science operators (CSO) in performing this task. Students from Italian secondary schools (in this work, the CSO) were invited to identify, mark, and classify stranded litter items on a UAV orthophoto collected on an Italian beach. A specific training program and working tools were developed for the aim. The comparison with the standard in situ visual census survey returned a general underestimation (50%) of items. However, marine litter bulk categorisation was fairly in agreement with the in situ survey, especially for sources classification. The concordance level among CSO ranged between 60% and 91%, depending on the item properties considered (type, material, and colour). As the assessment accuracy was in line with previous works developed by experts, remote detection of marine litter on UAV images can be improved through citizen science programs, upon an appropriate training plan and provision of specific tools. ; This paper is part of NAUTILOS project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 101000825. This work was supported by the Portuguese Foundation for Science and Technology (FCT) and by the European Regional Development Fund (FEDER) through COMPETE 2020, Operational Program for Competitiveness and Internationalization (POCI) in the framework of UIDB/ 00308/2020 and the research project UAS4Litter (PTDC/EAM-REM/30324/2017). ; Published ; 3349 ; 7SR AMBIENTE – Servizi e ricerca per la società ; JCR Journal

Nano-graphene oxide (nano-GO) is a new class of carbon based materials being proposed for biomedical applications due to its small size, intrinsic optical properties, large specific surface area, and easy to functionalize. To fully exploit nano-GO properties, a reproducible method for its production is of utmost importance. Herein we report, the study of the sequential fracture of GO sheets onto nano-GO with controllable lateral width, by a simple, and reproducible method based on a mechanism that we describe as a confined hot spot atomic fragmentation/reduction of GO promoted by ultrasonication. The chemical and structural changes on GO structure during the breakage were monitored by XPS, FTIR, Raman and HRTEM. We found that GO sheets starts breaking from the defects region and in a second phase through the disruption of carbon bonds while still maintaining crystalline carbon domains. The breaking of GO is accompanied by its own reduction, essentially by the elimination of carboxylic and carbonyl functional groups. Photoluminescence and photothermal studies using this nano-GO are also presented highlighting the potential of this nanomaterial as a unique imaging/therapy platform. ; Gil Gonçalves thanks the Fundação para a Ciência e Tecnologia (FCT) for the PostDoc grant (SFRH/BDP/84419/2012). A de Andres thanks MINECO (MAT2012-37276-C03-01) project. M Vila thanks the FCT for the 2013 investigator grant. We would like to thank Fundação para a Ciência e a Tecnologia (FCT, Portugal), the European Union, QREN, FEDER, COMPETE, for funding the TEMA Research Unit (PEst-C/QUI/UI0062/2013). The authors acknowledge the SUDOE and ERDF within the Territorial Cooperation Programme IVB funding through the project CarbonInspired 2.0 (Grant Agreement SOE4/P1/E793). ; Peer reviewed

Carbon dots are an emerging family of zero-dimensional nanocarbons behaving as tunable light harvesters and photoactivated charge donors. Coupling them to carbon nanotubes, which are well-known electron acceptors with excellent charge transport capabilities, is very promising for several applications. Here, we first devised a route to achieve the stable electrostatic binding of carbon dots to multi- or single-walled carbon nanotubes, as confirmed by several experimental observations. The photoluminescence of carbon dots is strongly quenched when they contact either semiconductive or conductive nanotubes, indicating a strong electronic coupling to both. Theoretical simulations predict a favorable energy level alignment within these complexes, suggesting a photoinduced electron transfer from dots to nanotubes, which is a process of high functional interest. Femtosecond transient absorption confirms indeed an ultrafast (<100 fs) electron transfer independent of nanotubes being conductive or semiconductive in nature, followed by a much slower back electron transfer (≈60 ps) from the nanotube to the carbon dots. The high degree of charge separation and delocalization achieved in these nanohybrids entails significant photocatalytic properties, as we demonstrate by the reduction of silver ions in solution. The results are very promising in view of using these "all-carbon" nanohybrids as efficient light harvesters for applications in artificial photocatalysis and photosynthesis. ; A.S. was supported by the "L'Oréal Italia Per le Donne e la Scienza" Program (17th edition). A.S. and F.M. thank the Italian Ministry of University and Research (MUR) for project PRIN2017 "CANDL2", grant number 2017W75RAE. G.G. thanks the Portuguese Science Foundation (FCT) for Programme Stimulus of Scientific EmploymentIndividual Support (CEECIND/01913/2017). We acknowledge funding received by the Karlsruhe Nano Micro Facility (KNMF)− proposal ID 2019-021025715. ; With funding from the Spanish government through the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019-000917-S). ; Peer reviewed

Carbon nanodots (Cdots) are now emerging as promising nonlinear fluorophores for applications in biological environments. A thorough and systematic approach to the two-photon induced emission of Cdots that could provide design guidelines to control their nonlinear emission properties is still missing. In this work, we address the nonlinear optical spectroscopy of Cdots prepared by controlled chemical cutting of graphene oxide (GO). The two-photon absorption in the 700–1000 nm region and the corresponding emission spectrum are carefully investigated. The highest two-photon absorption cross-section estimated was 130 GM at 720 nm. This value is comparable with the one reported for graphene nanoribbons with push–pull architecture. The emission spectrum depends on the excitation mode. At the same excitation energy, nonlinear excitation results in excitation-wavelength independent emission, while upon linear excitation the emission is excitation-wavelength dependent. The biphotonic interaction seems to be selective towards sp2 clusters bearing electron donor and acceptor groups found in push–pull architectures. Both linear and nonlinear emission can be understood based on the existence of isolated sp2 clusters involved in π–π stacking interactions with clusters in adjacent layers. ; The authors are grateful to Fundação para a Ciência e Tecnologia (FCT, Portugal), European Union, QREN, FEDER and COMPETE for funding the QOPNA, TEMA, and CQFM research unit (project Pest-C/QUI/UI0062/2013, UID/EMS/ 00481/2013 and UID/NAN/50024/2013). FCT is acknowledged for the Post-Doctoral grants of C. I. M. S., S. N. P and I. F. A. M., and for supporting the individual work contract of E. M., I. B. and P. A. A. P. M. within the Investigador FCT program (SFRH/BPD/105478/2014, SFRH/BPD/92409/2013, SFRH/BPD/ 75782/2011, IF/00759/2013, IF/00582/2015 and IF/00917/ 2013). G. G. gratefully acknowledges the funding by European Commission under individual fellowship Marie SklodowskaCurie (NANOTER, Grant Agreement 708351). ; Peer reviewed