Browsing by Author "Tavares, Pedro B."
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- Core-shell nanocomposites prepared by hierarchical co-assembly: the role of the carbon shell in catalytic wet peroxide oxidation processesPublication . Ribeiro, Rui; Silva, Adrián; Tavares, Pedro B.; Figueiredo, José; Faria, Joaquim; Gomes, HelderThe diffraction pattern of Fe3O4 (not shown) confirmed the presence of only one phase, corresponding to magnetite with a lattice parameter a = 8.357 Å and a crystallite size of 16.6 ± 0.2 nm. The diffraction pattern of MGNC (not shown) confirmed the presence of a graphitic phase, in addition to the metal phase, suggesting that Fe3O4 nanoparticles were successfully encapsulated within a graphitic structure during the synthesis of MGNC. The core-shell structure of MGNC is unequivocally demonstrated in the TEM micrograph shown in Fig. 1b. Characterization of the MGNC textural and surface chemical properties revealed: (i) stability up to 400 oC under oxidizing atmosphere; (ii) 27.3 wt.% of ashes (corresponding to the mass fraction of Fe3O4); (iii) a micro-mesoporous structure with a fairly well developed specific surface area (SBET = 330 m2 g-1); and (iv) neutral character (pHPZC = 7.1). In addition, the magnetic nature of MGNC (Fig. 2) is an additional advantage for possible implementation of in situ magnetic separation systems for catalyst recovery.
- Development and characterization of magnetic nanoparticles for theranostic applicationsPublication . Rodrigues, Raquel Oliveira; Bañobre-López, Manuel; Gallo, Juan; Tavares, Pedro B.; Lima, Rui A.; Silva, Adrián; Gomes, HelderMagnetic nanoparticles (MNPs), especially iron oxide nanoparticles, have attracted much attention in the last decades due to their remarkable physicochemical and magnetic properties. These properties coupled with their low toxicological effects, make MNPs ideal for biomedical applications1. In addition, chemical functionalization with specific biocompatible targeting molecules provides them with the ability to selectively attach to cells or tissues.
- Haemocompatibility of iron oxide nanoparticles synthesized for theranostic applications: a high-sensitivity microfluidic toolPublication . Rodrigues, Raquel Oliveira; Bañobre-López, Manuel; Gallo, Juan; Tavares, Pedro B.; Silva, Adrián; Lima, Rui A.; Gomes, HelderThe poor heating efficiency of the most reported magnetic nanoparticles (MNPs), allied to the lack of comprehensive biocompatibility and haemodynamic studies, hampers the spread of multifunctional nanoparticles as the next generation of therapeutic bio-agents in medicine. The present work reports the synthesis and characterization, with special focus on biological/toxicological compatibility, of superparamagnetic nanoparticles with diameter around 18 nm, suitable for theranostic applications (i.e. simultaneous diagnosis and therapy of cancer). Envisioning more insights into the complex nanoparticle-red blood cells (RBCs) membrane interaction, the deformability of the human RBCs in contact with magnetic nanoparticles (MNPs) was assessed for the first time with a microfluidic extensional approach, and used as an indicator of haematological disorders in comparison with a conventional haematological test, i.e. the haemolysis analysis. Microfluidic results highlight the potential of this microfluidic tool over traditional haemolysis analysis, by detecting small increments in the rigidity of the blood cells, when traditional haemotoxicology analysis showed no significant alteration (haemolysis rates lower than 2 %). The detected rigidity has been predicted to be due to the wrapping of small MNPs by the bilayer membrane of the RBCs, which is directly related to MNPs size, shape and composition. The proposed microfluidic tool adds a new dimension into the field of nanomedicine, allowing to be applied as a highsensitivity technique capable of bringing a better understanding of the biological impact of nanoparticles developed for clinical applications.
- Hybrid magnetic graphitic nanocomposites for catalytic wet peroxide oxidation applicationsPublication . Ribeiro, Rui; Silva, Adrián; Tavares, Pedro B.; Figueiredo, José; Faria, Joaquim; Gomes, HelderFe3O4, with a lattice parameter a = 8.357 Å and average particle size of 12.5 ± 3.6 nm, was successfullyencapsulated within a graphitic structure by a hierarchical co-assembly approach, followed by thermalannealing. The resulting material was denoted as MGNC—magnetic graphitic nanocomposite. MGNC pos-sesses average core size of 109 ± 35 nm (mainly composed by agglomerates of magnetic nanoparticles),stability up to 400◦C under oxidizing atmosphere, a micro-mesoporous structure with a fairly developedspecific surface area (SBET= 330 m2g−1) and neutral character (pHPZC= 7.1).Catalytic wet peroxide oxidation (CWPO) experiments performed with a 4-nitrophenol (4-NP)/Fe3O4mass ratio fixed at 36.6, allowed to achieve high efficiency of catalyst usage throughout the wide range of4-NP concentration considered (200 mg L−1–5 g L−1). The inclusion of Fe3O4nanoparticles in a graphiticstructure during the synthesis of MGNC was found to (i) enhance the catalytic activity in CWPO whencompared to Fe3O4, due to increased adsorptive interactions between the surface of the catalyst andthe pollutant molecules, while (ii) strongly limiting the leaching of Fe species from Fe3O4to the treatedwater, due to the confinement effect caused by the carbon shell.As a result of these effects, unprecedented pollutant mass removals were obtained − rangingfrom 5000 mg g−1h−1, when the CWPO process is performed with [4-NP]0= 200 mg L−1at pH = 3, to1250 mg g−1h−1, when [4-NP]0= 5 g L−1. High efficiency of H2O2consumption is obtained when MGNC isapplied in the CWPO of 4-NP solutions at pH = 3, with TOC removals per unit of H2O2decomposed ( H2O2)in the range 64–100%. In addition, the MGNC catalyst is also active at pH = 6; in this case a pollutant massremoval of 2090 mg g−1h−1was obtained.Although MGNC partially deactivates through successive reusability cycles, the pollutant mass removalobtained at the end of the fourth cycle is still very high when 200 mg L−14-NP solutions are considered(4808 mg g−1h−1, representing only a ca. 4% decrease when compared to the first cycle). A higher deac-tivation of the MGNC catalyst is observed when 5 g L−14-NP solutions are employed. Nevertheless, thepollutant mass removal obtained at the end of the third cycle is still high (551 mg g−1h−1).
- Hybrid magnetic graphitic nanocomposites towards catalytic wet peroxide oxidation of the liquid effluent from a mechanical biological treatment plant for municipal solid wastePublication . Ribeiro, Rui; Rodrigues, Raquel Oliveira; Silva, Adrián; Tavares, Pedro B.; Carvalho, Ana Maria; Figueiredo, José; Faria, Joaquim; Gomes, HelderMagnetite, nickel and cobalt ferrites were prepared and encapsulated within graphitic shells, resulting in three hybrid magnetic graphitic nanocomposites. Screening experiments with a 4-nitrophenol aqueous model system (5 g L −1 ) allowed to select the best performing catalyst, which was object of additional studies with the liquid effluent resulting from a mechanical biological treatment plant for municipal solid waste. Due to its high content in bicarbonates (14350 mg L −1 ) and chlorides (2833 mg L −1 ), controlling the initial pH was a crucial step to maximize the performance of the catalytic wet peroxide oxidation (CWPO) treatment. The catalyst load was 0.5 g L −1 , a very low dosage when compared to the high chemical oxygen demand (COD) of the effluent − 9206 mg L −1 . At the optimum operating pH (i.e., pH = 6), ca. 95% of the aromaticity was converted and ca. 55% of COD and total organic carbon (TOC) of the liquid effluent was removed. The biodegradability of the liquid effluent was enhanced during the treatment by CWPO, as reflected by the 2-fold increase of the five-day biochemical oxygen demand (BOD 5 ) to COD ratio (BOD 5 /COD), namely from 0.21 (indicating non-biodegradability) to 0.42 (suggesting biodegradability of the treated wastewater). In addition, the treated water revealed no toxicity against selected bacteria. Lastly, a magnetic separation system was designed for in-situ catalyst recovery after the CWPO reaction stage. The high catalyst stability was demonstrated through five reaction/separation sequential experiments in the same vessel with consecutive catalyst reuse.
- Multiple manipulators path planning using double A∗Publication . Tavares, Pedro B.; Lima, José; Costa, Pedro; Moreira, António Paulo G. M.Streamlining automated processes is currently undertaken by developing optimization methods and algorithms for robotic manipulators. This paper aims to present a new approach to improve streamlining of automatic processes. This new approach allows for multiple robotic manipulators commonly found in the industrial environment to handle different scenarios, thus providing a high-flexibility solution to automated processes. Design/methodology/approach - The developed system is based on a spatial discretization methodology capable of describing the surrounding environment of the robot, followed by a novel path-planning algorithm. Gazebo was the simulation engine chosen, and the robotic manipulator used was the Universal Robot 5 (UR5). The proposed system was tested using the premises of two robotic challenges: EuRoC and Amazon Picking Challenge. Findings - The developed system was able to identify and describe the influence of each joint in the Cartesian space, and it was possible to control multiple robotic manipulators safely regardless of any obstacles in a given scene. Practical implications - This new system was tested in both real and simulated environments, and data collected showed that this new system performed well in real-life scenarios, such as EuRoC and Amazon Picking Challenge. Originality/value - The new proposed approach can be valuable in the robotics field with applications in various industrial scenarios, as it provides a flexible solution for multiple robotic manipulator path and motion planning.
- A new microfluidic methodology to assess the haemocompatibility of magnetic nanoparticles designed for theranostic applicationsPublication . Rodrigues, Raquel Oliveira; Bañobre-López, Manuel; Gallo, Juan; Tavares, Pedro B.; Silva, Adrián; Gomes, Helder; Lima, Rui A.The remarkable physicochemical properties of magnetic nanoparticles (MNPs) at the nanoscale have boosted the development of new and promising strategies for the simultaneous diagnosis and treatment of diseases, particularly in cancer therapy Ð the so-called theranostic applications (1). In these strategies, the intrinsic superparamagnetic properties of MNPs have been exploited to gain access into multifunctional systems able to simultaneously perform as enhanced magnetic resonance imaging (MRI) contrast agents, efficient nanocarriers for drug delivery and nanoheaters in magnetic hyperthermia based therapy (2), among others.
- Thermal infrared image processing to assess heat generated by magnetic nanoparticles for hyperthermia applicationsPublication . Rodrigues, Raquel Oliveira; Gomes, Helder; Lima, Rui A.; Silva, Adrián; Rodrigues, Pedro João; Tavares, Pedro B.; Tavares, João Manuel R.S.Magnetic fluid hyperthermia (MFH) is considered a promising therapeutic technique for the treatment of cancer cells, in which magnetic nanoparticles (MNPs) with superparamagnetic behavior generate mild-temperatures under an AC magnetic field to selectively destroy the abnormal cancer cells, in detriment of the healthy ones. However, the poor heating efficiency of most NMPs and the imprecise experimental determination of the temperature field during the treatment, are two of the majors drawbacks for its clinical advance. Thus, in this work, different MNPs were developed and tested under an AC magnetic field (~1.10 kA/m and 200 kHz), and the heat generated by them was assessed by an infrared camera. The resulting thermal images were processed in MATLAB after the thermographic calibration of the infrared camera. The results show the potential to use this thermal technique for the improvement and advance of MFH as a clinical therapy.