The quest to provide clean water to the entire population has led to a tremendous boost in the development of environmental nanotechnology. Toward this end, micro/nanomotors are emerging as ...attractive tools to improve the removal of various pollutants. The micro/nanomotors either are designed with functional materials in their structure or are modified to target pollutants. The active motion of these motors improves the mixing and mass transfer, greatly enhancing the rate of various remediation processes. Their motion can also be used as an indicator of the presence of a pollutant for sensing purposes. In this Perspective, we discuss different chemical aspects of micromotors mediated environmental cleanup and sensing strategies along with their scalability, reuse, and cost associated challenges.
Heavy metal contamination in water is a serious risk to the public health and other life forms on earth. Current research in nanotechnology is developing new nanosystems and nanomaterials for the ...fast and efficient removal of pollutants and heavy metals from water. Here, we report graphene oxide-based microbots (GOx-microbots) as active self-propelled systems for the capture, transfer, and removal of a heavy metal (i.e., lead) and its subsequent recovery for recycling purposes. Microbots’ structure consists of nanosized multilayers of graphene oxide, nickel, and platinum, providing different functionalities. The outer layer of graphene oxide captures lead on the surface, and the inner layer of platinum functions as the engine decomposing hydrogen peroxide fuel for self-propulsion, while the middle layer of nickel enables external magnetic control of the microbots. Mobile GOx-microbots remove lead 10 times more efficiently than nonmotile GOx-microbots, cleaning water from 1000 ppb down to below 50 ppb in 60 min. Furthermore, after chemical detachment of lead from the surface of GOx-microbots, the microbots can be reused. Finally, we demonstrate the magnetic control of the GOx-microbots inside a microfluidic system as a proof-of-concept for automatic microbots-based system to remove and recover heavy metals.
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► Visual detection based gold and silver nanoparticles aggregation. ► Functionalized and non-functionalized nanoparticles. ► High selectivity and sensitivity. ► No complex ...instrumentation is required/chemical creativity for analyte detection.
Localized surface plasmon resonance (LSPR) is one of the most remarkable features of gold nanoparticles (Au NPs) and silver nanoparticles (Ag NPs). Due to these inherent optical properties, colloidal solutions of Au and Ag NPs have high extinction coefficients and different colour in the visible region of the spectrum when they are well-spaced in comparison with when they are aggregated. Therefore, a well-designed chemical interaction between the analyte and NPs surroundings leads to a change of colour (red to blue for Au NPs and yellow to brown for Ag NPs from well-spaced to aggregated ones, respectively) allowing the visual detection of the target analyte.
These approaches have exhibited an excellent analytical performance with high sensitivities due to the strong LSPR and excellent selectivity strategically driven by the interaction analyte-NPs surroundings involving mainly electrostatic and hydrogen bond interactions as well as donor–acceptor chemical reactions, among others. In addition, this kind of colorimetric assays has received considerable attention in the analytical field because of their simplicity and low cost since they do not require any expensive or complex instrumentation. As a consequence of this, detection of molecules with a high significance in the bio-medical, clinical, food safety and environmental fields including DNA, proteins and a wide spectrum of organic molecules as well as inorganic ions have been impressively reported in the most relevant literature using these assays.
This timely review offers a rational vision of the main achievements yielded in the relevant literature according to this exciting and creative analytical field.
Water contamination from industrial and anthropogenic activities is nowadays a major issue in many countries worldwide. To address this problem, efficient water treatment technologies are required. ...Recent efforts have focused on the development of self-propelled micromotors that provide enhanced micromixing and mass transfer by the transportation of reactive species, resulting in higher decontamination rates. However, a real application of these micromotors is still limited due to the high cost associated to their fabrication process. Here, we present Fe2O3-decorated SiO2/MnO2 microjets for the simultaneous removal of industrial organic pollutants and heavy metals present in wastewater. These microjets were synthesized by low-cost and scalable methods. They exhibit an average speed of 485 ± 32 μm s–1 (∼28 body length per s) at 7% H2O2, which is the highest reported for MnO2-based tubular micromotors. Furthermore, the photocatalytic and adsorbent properties of the microjets enable the efficient degradation of organic pollutants, such as tetracycline and rhodamine B under visible light irradiation, as well as the removal of heavy metal ions, such as Cd2+ and Pb2+.
Biofilm colonies are typically resistant to general antibiotic treatment and require targeted methods for their removal. One of these methods includes the use of nanoparticles as carriers for ...antibiotic delivery, where they randomly circulate in fluid until they make contact with the infected areas. However, the required proximity of the particles to the biofilm results in only moderate efficacy. We demonstrate here that the nonpathogenic magnetotactic bacteria Magnetosopirrillum gryphiswalense (MSR-1) can be integrated with drug-loaded mesoporous silica microtubes to build controllable microswimmers (biohybrids) capable of antibiotic delivery to target an infectious biofilm. Applying external magnetic guidance capability and swimming power of the MSR-1 cells, the biohybrids are directed to and forcefully pushed into matured Escherichia coli (E. coli) biofilms. Release of the antibiotic, ciprofloxacin, is triggered by the acidic microenvironment of the biofilm, ensuring an efficient drug delivery system. The results reveal the capabilities of a nonpathogenic bacteria species to target and dismantle harmful biofilms, indicating biohybrid systems have great potential for antibiofilm applications.
The COVID-19 pandemic caused several changes in the teaching-learning process, as it abruptly replaced the conventional classes into online classes despite social distancing requirements. Such ...changes may be associated with several mental health problems and negatively affect the quality of life and academic performance of university students. We performed a cluster analysis in a large sample of Brazilian undergraduate students, considering sociodemographic data, physical activity frequency, study areas, Burnout Syndrome (BS), Quality of Life (QoL) and perception of online learning (OL) during COVID-19 pandemic. Seven hundred and three students (between 17 and 62 years, from 67 higher education institutions) participated in the study. We identified three different profiles of students regarding psychological aspects and OL perception. The first profile, called as the 'Low QoL' group was composed of younger students, mainly females, with higher frequency of psychological disorders (as evidenced by the self-report of depression and/or anxiety), in addition to higher Burnout scores, lower QoL and worse OL perception. The second profile called 'Intermediate QoL' comprised participants with an average age of 45 years, with a greater number of men, married, with kids and working in addition to studying. They presented better OL scores than the 'Low QoL' group. The third profile called 'Better QoL' comprised students with higher scores in all domains of QoL and better OL perception, with greater frequency of physical activity and lower BS scores. Students from Health courses showed higher scores for general QoL, and also for the psychological and environmental domains in relation to the other areas. Besides, students of the Exact Sciences courses showed higher scores on all OL perception items in comparison to the other courses. Our results provide insights regarding the mental health profile of undergraduate students, allowing educational managers to outline specific coping strategies to assist students during the pandemic.
•Nanoparticles and antioxidants: chemistry for assessing antioxidant capacity.•Synthesis of nanoparticles for evaluating total antioxidant capacity.•Chemistry on nanoparticles for selective detection ...of target antioxidants.
The current review describes the creative use of metallic nanoparticles (mostly gold and silver) and quantum dots as novel tools for reliable assessment of antioxidant activity in food and biological samples. Since evaluation of antioxidant capacity is a complex issue, these nanomaterials emerge as novel, simple and inexpensive tools in the field, becoming not only a valuable alternative to classical approaches but also a complementary one.
From 2008 to date, basically, single‐cross microchip electrophoresis (ME) design has been used for food analysis with electrochemicaland laser‐induced fluorescencedetection being the most ...commonprinciples coupled. In the last 4 years, the main outlines were: (i) the exploration of new analytes such as heavy metals, nitrite, micotoxins, microorganisms, and allergens; (ii) the development of electrokinetic microfluidic (bio‐) sensors into microchip format for the detection of toxins; and interestingly (iii) although sample preparation is still performed off‐chip, an important increase in works dealing with complicated food samples has been clearly noticed. Although microchip technology based on electrokinetics is emerging from important fields such as authentication of foods, detection of frauds, toxics, and allergens; the marriage between micro‐ and nanotechnologies and total integration approaches has not reached the expected impact in the field but it is still a great promise for the development of ME of new generations for food analysis.
The first example of a self‐propelled tubular motor that releases an enzyme for the efficient biocatalytic degradation of chemical pollutants is demonstrated. How the motors are self‐propelled by the ...Marangoni effect, involving simultaneous release of SDS surfactant and the enzyme remediation agent (laccase) in the polluted sample, is illustrated. The movement induces fluid convection and leads to the rapid dispersion of laccase into the contaminated solution and to a dramatically accelerated biocatalytic decontamination process. The greatly improved degradation efficiency, compared to quiescent solutions containing excess levels of the free enzyme, is illustrated for the efficient biocatalytic degradation of phenolic and azo‐type pollutants. The high efficiency of the motor‐based decontamination approach makes it extremely attractive for a wide‐range of remediation processes in the environmental, defense and public health fields.
Keep the motor running: Catalytic degradation of pollutants by enzyme‐releasing motors is reported. The first example of a self‐propelled tubular motor that releases an enzyme in a controlled fashion for the efficient biocatalytic degradation of chemical pollutants is described (see figure).
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•Self-propelled micromotors made of cobalt ferrite (CFO micromotors), that function as the catalyst for both self-propulsion and Fenton-like reaction were prepared.•Synthesis of CFO ...micromotors is noble metal free and does not require the use of special equipment, making it facile and cost-effective.•Presence of a surfactant is not required for self-propelled of CFO micromotors.•The CFO micromotors are proved as an efficient tool for antibiotic removal and can be easily recovered from the system using external magnets.
Self-propelled micromotors have previously shown to enhance pollutant removal compared to non-motile nano-micro particles. However, these systems are expensive, difficult to scale-up and require surfactant for efficient work. Efficient and inexpensive micromotors are desirable for their practical applications in water treatment technologies. We describe cobalt-ferrite based micromotors (CFO micromotors) fabricated by a facile and scalable synthesis, that produce hydroxyl radicals via Fenton-like reaction and take advantage of oxygen gas generated during this reaction for self-propulsion. Once the reaction is complete, the CFO micromotors can be easily separated and collected due to their magnetic nature. The CFO micromotors are demonstrated for highly efficient advanced oxidative removal of tetracycline antibiotic from the water. Furthermore, the effects of different concentrations of micromotors and hydrogen peroxide on the antibiotic degradation were studied, as well as the generation of the highly reactive hydroxyl radicals responsible for the oxidation reaction.
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