1,721,008 research outputs found
Design and characterization of new materials for the assembly of micro and nano-devices: the gateway toward improved and novel applications in medicinal, life, and environmental sciences
No full textBiochar-Derived Persistent Free Radicals: A Plethora of Environmental Applications in a Light and Shadows Scenario
No full textBiochar (BC) is a carbonaceous material obtained by pyrolysis at 200–1000 °C in the limited presence of O2 from different vegetable and animal biomass feedstocks. BC has demonstrated great potential, mainly in environmental applications, due to its high sorption ability and persistent free radicals (PFRs) content. These characteristics enable BC to carry out the direct and PFRs-mediated removal/degradation of environmental organic and inorganic contaminants. The types of PFRs that are possibly present in BC depend mainly on the pyrolysis temperature and the kind of pristine biomass. Since they can also cause ecological and human damage, a systematic evaluation of the environmental behavior, risks, or management techniques of BC-derived PFRs is urgent. PFRs generally consist of a mixture of carbon- and oxygen-centered radicals and of oxygenated carbon-centered radicals, depending on the pyrolytic conditions. Here, to promote the more productive and beneficial use of BC and the related PFRs and to stimulate further studies to make them environmentally safer and less hazardous to humans, we have first reviewed the most common methods used to produce BC, its main environmental applications, and the primary mechanisms by which BC remove xenobiotics, as well as the reported mechanisms for PFR formation in BC. Secondly, we have discussed the environmental migration and transformation of PFRs; we have reported the main PFR-mediated application of BC to degrade inorganic and organic pollutants, the potential correlated environmental risks, and the possible strategies to limit them
Bamboo-Based Biochar: A Still Too Little-Studied Black Gold and Its Current Applications
No full textBiochar (BC), also referred to as “black gold”, is a carbon heterogeneous material rich in aromatic systems and minerals, preparable by the thermal decomposition of vegetable and animal biomasses in controlled conditions and with clean technology. Due to its adsorption ability and presence of persistent free radicals (PFRs), BC has demonstrated, among other uses, great potential in the removal of environmental organic and inorganic xenobiotics. Bamboo is an evergreen perennial flowering plant characterized by a short five-year growth period, fast harvesting, and large production in many tropical and subtropical countries worldwide, thus representing an attractive, low-cost, eco-friendly, and renewable bioresource for producing BC. Due to their large surface area and increased porosity, the pyrolyzed derivatives of bamboo, including bamboo biochar (BBC) or activated BBC (ABBC), are considered great bio-adsorbent materials for removing heavy metals, as well as organic and inorganic contaminants from wastewater and soil, thus improving plant growth and production yield. Nowadays, the increasing technological applications of BBC and ABBC also include their employment as energy sources, to catalyze chemical reactions, to develop thermoelectrical devices, as 3D solar vapor-generation devices for water desalination, and as efficient photothermal-conversion devices. Anyway, although it has great potential as an alternative biomass to wood to produce BC, thus paving the way for new bio- and circular economy solutions, the study of bamboo-derived biomasses is still in its infancy. In this context, the main scope of this review was to support an increasing production of BBC and ABBC and to stimulate further studies about their possible applications, thus enlarging the current knowledge about these materials and allowing their more rational, safer, and optimized application. To this end, after having provided background concerning BC, its production methods, and its main applications, we have reviewed and discussed the main studies on BBC and ABBC and their applications reported in recent years
Nanocellulose Application for Metal Adsorption and Its Effect on Nanofiber Thermal Behavior
No full textCarboxylate (TCNF) and sulfonated (SCNC) cellulose nanofibers were synthesized and used as adsorbents for metallic cations in aqueous solutions: Na+ and Hg2+ (SCNC); Mg2+ and Hg2+ (TCNF). ICP-OES analysis of the liquid phase revealed metal removal efficiencies at room temperature of 89.3% (Hg2+) and 100% (Mg2+) for TCNF, 35.2% (Hg2+) and 63.3% (Na+) for SCNC after 3 h of contact. Interestingly, the nanofibers exhibited a distinct thermal degradation profile (characterized by two main events) compared to that of cellulose, suggesting that their nanostructured morphology and surface functionalization may enhance thermal instability. Additionally, the presence of metals at its surface notably altered the thermal degradation kinetics, as observed for mercury and magnesium in TCNF. Finally, the results for SCNC strongly suggest that the mechanism for thermal degradation can also change, as observed for mercury and sodium, expressed through the appearance of a new DTG peak located around 300 degrees C
THE CONTROL OF THE CHOLESTERIC PITCH BY SOME AZO PHOTOCHEMICAL CHIRAL SWITCHES
No full textA few chiral azo compounds, which undergo reversible photochemical switching, are presented. Of these, the most interesting contain the binaphthyl moiety and belong to the C-2 (derivatives 1 and 2) or C-1 symmetry group (derivatives 3 and 4). These binaphthyl compounds display intense CD and high values. Photochemical switching has profound effects on both the CD and values of these compounds; in the case of compound 3, the sign of beta changes upon isomerisation. Compound 2 has, to our knowledge, the highest P of the switches reported in the literature and also seems the most interesting owing to its fast response to photochemical stimuli. Nematic phases can be transformed into cholesteric phases with reflection bands in the visible region by doping with reasonable amounts of 1 and 2. The reflection colours can be changed reversibly by photoisomerisation of the switches. Thermal reversion of the colourless UV photostationary state to the green isomeric EE state or to intermediate coloured states is temperature dependent. This can allow the thermal history of a sample to be traced
A monolithic 5-(pyrrolidin-2-yl)tetrazole flow microreactor for the asymmetric aldol reaction in water–ethanol solvent
No full textAn (S)-5-(pyrrolidin-2-yl)-1H-tetrazole organocatalyst has been prepared in the form of a monolithic column through the radical copolymerization of a styryl-functionalized pyrrolidinyl-tetrazole derivative, sty- rene and divinylbenzene in the presence of porogens (dodecanol and toluene). The activity of the mono- lithic pyrrolidinyl-tetrazole organocatalyst (triturated polymer) has been initially tested under batch condi- tions using the asymmetric aldol reaction of cyclohexanone and p-nitrobenzaldehyde as the benchmark. A prerequisite of the study has been the utilization of the eco-friendly water–ethanol mixture as the solvent. After having established the high efficiency and recyclability of the catalyst under these conditions, the effect of the flow regime has been evaluated by fabricating the corresponding monolithic microreactor (pressure-resistant stainless steel column). It has been demonstrated by a brief substrate scope study that the flow regime contributes to preserve the activity of the pyrrolidinyl-tetrazole catalyst over time (5 days on stream) with an almost twofold increase in productivity moving from batch to flow conditions. An added value of the flow procedure has been the optimization of a suitable 2D instrumental setup for simultaneous flow reaction and online flow-injection analysis
REVERSIBLE INTERCONVERSION BETWEEN A SUPRAMOLECULAR POLYMER AND A DISCRETE OCTAMERIC SPECIES FROM A GUANOSINE DERIVATIVE BY DYNAMIC CATION BINDING AND RELEASE
No full textThe tunable interconversion between two highly ordered supramolecular motifs (G-quartet K+-templated column and G-ribbon) of a lipophilic guanosine derivative fueled by cation complexation and release in a cryptand [2.2.2] containing guanosine solution is reported. The process is controlled by the sequential addition of acid and base
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
New chemical and electric bamboo-based biomaterial: a new insight into advanced functional material
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