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Heightening Awareness for Graduate Students of the Potential Impacts of Nanomaterials on Human Health and the Environment Using a Theoretical−Practical Approach Nathalie F. S. de Melo,† Leonardo F. Fraceto,§ and Renato Grillo*,‡ †

São Leopoldo Mandic Institute and Research Center, Laboratory of Immunology and Molecular Biology, 13045-755, Campinas, SP, Brazil § São Paulo State University (UNESP), Institute of Science and Technology, 18087-180, Sorocaba, SP, Brazil ‡ São Paulo State University (UNESP), Department of Physics and Chemistry, School of Engineering, 15385-000, Ilha Solteira, SP, Brazil S Supporting Information *

ABSTRACT: Rapid growth in nanoscience and nanotechnology in recent years has been accompanied by studies of the toxicity and potential impacts of nanomaterials on human health and the environment, but less has been done concerning education in this area. There is therefore a need for courses that address this theme at universities worldwide, in order to improve the training of students, stimulate research in this area, and make information available to the wider population. The present work proposes a model for a theoretical and practical course for graduate students, introducing basic concepts of nanotechnology, methods for the characterization of nanomaterials, environmental applications, and potential toxic effects of nanomaterials in the environment. The course includes five theoretical and practical topics: (i) nanomaterials characterization, (ii) practical approaches, (iii) environmental applications, (iv) nanomaterials toxicity, and (v) integrated studies. These are designed to provide the students with a clear understanding of nanoscience and nanotechnology, addressing the main aspects of toxicity of nanomaterials, their correlations with physicochemical properties, and potential solutions for environmental problems. The teaching model was delivered to Master’s and Ph.D. students in a graduate program in Brazil, with highly satisfactory results. KEYWORDS: Environmental Chemistry, Nanotechnology, Graduate Education/Research, Interdisciplinary/Multidisciplinary, Hands-On Learning/Manipulatives, Laboratory Instruction



INTRODUCTON

It is important to develop courses that integrate nanotechnology concepts, methods for the characterization of nanomaterials, environmental applications, and the possible toxicity of these materials and their effects in the environment. The students should be able to develop critical abilities regarding the technology and disseminate information to the wider society, as well as be able to handle nanomaterials safely. Here, we present a proposal for a theoretical and practical course on nanotechnology and the environment, aimed at graduate students. The course was delivered to 15 students of the Postgraduate Program in Environmental Sciences of São Paulo State University (UNESP) in Sorocaba (Brazil).

Nanoscience and nanotechnology (N&N) has developed rapidly in recent years, with structures smaller than 1000 nm being used in many different areas. In the agricultural and environmental sectors, N&N is employed in processes for pollutant remediation1−4 (such as the use of zerovalent Fe to degrade pollutants present in groundwater3), production of new materials for water treatment,5 nanosensors for the detection of organic compounds6 or pathogens,7 and new tools for agricultural applications.8−18 Novel nanotechnological products constantly appear on the market, and consequently, there is growing concern about the toxicity and potential impacts of these nanomaterials toward human health and the environment.19−22 These issues, together with the complexity and multidisciplinarity of nanotechnology,23 have led to the introduction of undergraduate and graduate courses in this area at universities worldwide.24−26 There is a need for the training of students in N&N in order to provide the qualified workforce required in academia and to meet the current and future demands of industry.25,27 © XXXX American Chemical Society and Division of Chemical Education, Inc.



COURSE STRUCTURE

The course structure was designed to be simple and dynamic, enabling graduate students to progress through stages using previously established concepts. Received: February 1, 2017 Revised: July 24, 2017

A

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Figure 1. Basic structure of the Nanotechnology and Environment course comprising five main topics: nanomaterials characterization; environmental applications; nanomaterials toxicity; practical approaches; and integrated studies.

Table 1. Chronogram of the Course, with Suggested Workloads for the Different Topicsa Workloadb 2h

2h 4h

First Day Presentation of the course Introduction to Nanotechnology Interval Nanomaterial Characterization Techniques I Interval Practical classes P1, P2, P3

Second Day Nanomaterial Characterization Techniques II Interval Environmental Applications I Interval Practical classes P1, P2, P3

Third Day

Fourth Day

Environmental Applications II Interval Nanotoxicology I Interval Practical classes P1, P2, P3

Nanotoxicology II Interval Seminars Interval Seminars and evaluation

a

P1, Synthesis of polymeric nanoparticles and evaluation of active agent encapsulation efficiency; P2, Synthesis and characterization of metal nanoparticles; P3, Characterization of nanoparticles by DLS, NTA, and AFM. bThe workload is only a suggestion and can be altered as required.

The course was then divided into five different topics, comprising the characterization of nanomaterials, practical approaches, environmental applications, toxicity aspects, and integrated studies, as shown in Figure 1. This structural organization of the course was intended to deepen the knowledge of the student about each topic in an integrated way. A suggested program for the course is shown in Table 1. The course was designed to be delivered in a condensed form, using a chronogram of 8 h per day for 4 consecutive days. Nonetheless, the same structure could be employed for longer periods, if required, only maintaining the ratios of the times allocated to the different tasks.

First, as teachers of this course, we made a brief personal introduction (career, background, etc.), and after this the students made a presentation in which they expressed their motivations and expectations for the course, as well as their backgrounds in nanotechnology and environment. Second, a brief introduction was provided to the main concepts in nanoscience and nanotechnology, with discussion of current developments, providing the participants with a clear and concise overview of the theme. Topics related to the size and type of nanomaterials, their fate and toxicity in the environment and in humans, regulatory procedures, and examples of products already commercially available were some of the issues considered at this stage. B

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Table 2. Techniques for the Characterization of Nanomaterials Discussed in the Course, Including the Analytical Principles, the Main Applications, and Some Limitations Technique

Measurement Principle

Main Applications

DLS ZP

Light scattering and Brownian motion Electrophoretic mobility

Size and polydispersity index Surface charge

NTA

Light scattering and Brownian motion

OM

Interaction of light with the material

Size, polydispersity index, and particle concentration Detection of aggregates (stability)

SEM TEM

Interaction of electrons with the material Interaction of electrons with the material

Size and morphology Size, morphology, and crystallinity

AFM UV−vis

Scanning of the surface with a probe (cantilever) Interaction of light with the material

VSM

Detection of the magnetization of a nanomaterial based on Faraday’s law of induction Combination of alternating magnetic fields and magnetic nanoparticles as heating agents Elution of a nanomaterial based on a field applied to a fluid suspension

Surface morphology Size and colloidal stability of plasmonic nanoparticles Measurement of magnetic moment and determination of magnetic behavior Measurement of the heating rates of magnetic nanomaterials in animals Separation of nanomaterials in complex matrices

MH FFF

Limitations Requires a low analyte concentration Ionic strength can interfere in the analysis Low analyte concentrations Low magnification (up to ∼2000 times) Conductive or metal-coated samples Electron beams may damage biological samples Requires a vibration-free environment Requires previous calibration Low sensitivity compared with other similar methods Small sample holder Expensive equipment and requirement for specialist operator

Figure 2. Representation of the practical classes: (A) Development of modified release systems employing polymeric nanoparticles; (B) Synthesis of metal nanoparticles with plasmonic and magnetic properties; (C) Characterization of nanoparticles using DLS, NTA, and AFM techniques.

Nanomaterials Characterization

course. The techniques discussed in this topic are shown in Table 2, together with their main applications and limitations.

This topic consisted of lectures intended to inform the students of the principles of the various analytical techniques used to characterize nanomaterials. This step was very important, as it provided the tools necessary for understanding articles and concepts that would be introduced during the remainder of the

Practical Sessions

The practical classes were structured so that the students could experience the preparation and characterization of different sizes and types of nanomaterials, using the synthesis of organic C

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Figure 3. Metal nanoparticles synthesized by the students: A) Silver nanoparticles, showing the color of the suspensions at different stages of the synthesis and the corresponding plasmonic absorption bands measured by UV−vis spectroscopy; B) Preparation of the magnetic nanoparticles and their attraction to a magnet in a static magnetic field (0.2 T).

Figure 4. Examples of the results of the DLS, NTA, and AFM characterizations of the polymeric nanoparticles prepared by the students.

tripolyphosphate (CS-TPP) nanospheres. The herbicide atrazine (ATZ) was associated with the PLA nanospheres and nanocapsules as a model active ingredient, and the encapsulation efficiency of the herbicide in each system was determined using high-performance liquid chromatography (HPLC). The encapsulation efficiency was ∼68% for PLA nanospheres and ∼80% for PLA nanocapsules. Detailed descriptions of the pesticide release systems can be found in our earlier publications.9,29−35 The full methodology used to prepare the materials and determine the encapsulation efficiencies can be found in the Supporting Information. Practical Class B: Synthesis and Characterization of Metal Nanoparticles. In this class, the students synthesized metal nanoparticles (MNPs) using iron oxide and silver nitrate as precursors, in order to obtain nanoparticles with magnetic and plasmonic properties, respectively. Both types of MNPs were synthesized by a simple and rapid procedure (described in the Supporting Information). The students characterized the plasmonic nanoparticles by UV−vis spectrophotometry, and the magnetic properties of the nanoparticles were observed by positioning a magnet near the nanoformulation (Figure 3). Several previous studies have described the synthesis of these nanoparticles,36,37 as well their environmental and human health applications.38−40 Practical Class C: Characterization of the Nanoparticles by DLS, NTA, and AFM. In this class, the students were able to determine the size distribution, polydispersity

and inorganic nanoparticles as well as different synthesis routes (such as nanoprecipitation, electrostatic interaction, and the sol−gel process). This topic included the preparation of nanoparticles that have different applications and physicochemical properties, such as the modified release of active ingredients, and plasmonic and magnetic effects. The practical classes were structured into three sessions, denoted A (synthesis of polymeric nanoparticles), B (synthesis of metal nanoparticles), and C (characterization of nanoparticles by DLS, NTA, and AFM). The students were allocated to the groups, and after completion of each session, the groups proceeded (clockwise) to the next session, until all the students had participated in the three sessions. A schematic representation of the procedure is provided in Figure 2. A description of each practical class is given below. Practical Class A: Synthesis of Polymeric Nanoparticles and Evaluation of Active Ingredient Encapsulation Efficiency. In this class, the students synthesized three types of polymeric nanoparticles (NPs) that are widely used in modified release systems for various bioactive molecules.9,28 These NPs could be defined as nanospheres (composed of a solid polymeric matrix) and nanocapsules (composed of a polymeric shell surrounding an oily nucleus), with both having the ability to associate with bioactive compounds.28 The nanoprecipitation technique was used to prepare nanocapsules and nanospheres of poly(D,L-lactide) (PLA), while the ionotropic gelation method was used to prepare chitosan/ D

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Table 3. Examples of Articles Used by the Students for Discussion of the Environmental Applications of Nanomaterials Particles

Characterization Methodsa

Characterization Results

Feo NPs

TEM, XRD, XPS, BET

∼50 nm; surface area: 14.8 m2 g−1

Feo NPs

SEM/EDS, XRD

∼65 nm

Au, Ag, and ZnO NPs

DLS, TEM

CNT with Fe2O3 NPs

DLS, ZP, TGA, XRD, BET, TEM, FE/SEM

Feo coated NPs

Other work

Au NP: 51.7 nm; −55 mV ZnO NP: 32.4 nm; + 10.4 mV (increase of ZP as a function of increasing CaCl2) NP: 1−5 nm CNT: 20−40 nm FeO NP: 50−80 nm Coated: 400−500 nm

MnO2 NPs (+CMC) (−CMC)

HPLC, AAS, TEM, DLS, ion chromatography

Applications

Refs 41

Better results, compared to a traditional system (Fe electrodes); DQO −66.15% Controlling the transport and fate of NPs

42

Removal of oil in water

Efficient

44

Removal of decabromodiphenyl from soil Degradation of estradiol in soil and water

Efficient removal and lower phytotoxicity

45

Potential use in situ

46

Assisting transport in sand columns

∼39.5 nm (+CMC) Size distribution: 0.8 nm

Main Environmental Results After addition of the NPs, there was a significant reduction of Pu and U

Treatment of water contaminated with Pu and U Treatment of alcoholic effluent

43

a TEM: transmission electron microscopy; XRD: X-ray powder diffraction; XPS: X-ray photoelectron spectroscopy; SEM: scanning electron microscopy; SEM/EDS: scanning electron microscopy with X-ray microanalysis; DLS: dynamic light scattering; ZP: zeta potential; TGA: thermogravimetric analysis; BET: Brunauer−Emmett−Teller; FE/SEM: field emission scanning electron microscopy; HPLC: high-performance liquid chromatography; AAS: atomic absorption spectroscopy; VSM: vibrating sample magnetometer.

environmental applications of nanomaterials, as well as to identify the characterization techniques and interpret the results presented.

index, zeta potential, particle concentration, and morphology of the polymeric and inorganic nanoparticles, using the techniques of dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), and atomic force microscopy (AFM), as shown in the Figure 4. In addition, the students learned how to interpret the data and participated in in-depth discussions about these techniques and possible interferences and limitations. All the parameters of these analyses can be found in the Supporting Information. The overall goal of the practical sessions was to provide the participants with the opportunity to synthesize different types of nanoparticles (polymeric, magnetic, and plasmonic), and to understand basic aspects of some of the techniques used for nanoparticle characterization (DLS, NTA, and AFM). The students were also able to prepare a carrier system for a bioactive compound (the herbicide atrazine) and evaluate the encapsulation efficiency using high-performance liquid chromatography. The practical classes therefore consolidated the theory introduced earlier in the course. It should be noted that all the waste material generated in the practical sessions was correctly disposed of.

Toxicity of Nanomaterials

The approach adopted in this topic was theoretical classes concerning aspects of the toxicity of nanomaterials. The first issue considered was the potential problems that could arise from the use of nanotechnology, such as the different types of waste generated, the behavior and fate of nanomaterials in the environment, their biological implications,47 and the use of toxicology as a tool to evaluate the potential toxicity of nanomaterials.48,49 Subsequently, the importance of characterization of these materials was discussed. The literature contains much information about the toxicity of nanoparticles, although there are no standardized procedures for the assessment of toxicity and there are insufficient characterization data available, making it difficult to compare results.50 This topic also included methods for measuring the toxicity of nanomaterials, such as in vitro and in vivo tests, as well as risk assessment (Table 4). Finally, discussion among the students was used to encourage a critical view of the toxicological aspects of nanomaterials. These issues were important for enabling the participants to understand and evaluate the potential toxicity of nanomaterials during the integration stage of the course.

Environmental Applications

In this topic, the students were divided into groups of four and were provided with articles published in environmental journals (for example: Water Research, Journal of Environmental Management, Journal of Hazardous Materials, Chemical Engineering Journal, and Journal of Environmental Chemical Engineering). The aim was to read the articles and identify items that had been addressed earlier in the course, such as (a) the type of nanoparticle synthesized or used, (b) the characterization methods, (c) the results obtained, and (d) environmental applications. The student then summarized this information on a blackboard and presented the results to the other members of the group, followed by a discussion of each article. Examples of some of the articles used are provided in Table 3. The purpose of this activity was to provide the students with information concerning recent work on the

Integrated Study

In the preceding stages of the course, the students learned important aspects of nanotechnology, characterization methods, environmental applications, and potential toxic effects of nanomaterials. In this stage, the students were again split into groups, with each group being given selected articles published in the journal Environmental Science & Technology. The aim was to set up a workshop attended by the other participants, using all the knowledge acquired throughout the course and identifying the positive and negative aspects of the articles. Afterward, all the other participants had to comment on and discuss the work presented, in a collective evaluation of the E

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Table 4. Examples of in Vitro and in Vivo Tests Most Widely Used for the Toxicological Evaluation of Nanomaterials Type of Test In vitro

Assaysa MTT WTS-1, MTS, XTT LDH Live/dead Neutral Red TUNEL

In vivo

Vibrio f ischeri (bacteria) Daphnia magna (microcrustacean) Danio rerio (f ish) Xenopus laevis (f rog) Allium cepa (onion)

understand the information published in scientific articles. To this end, during the course the students were encouraged to develop their critical abilities with respect to the topic of environmental nanotechnology. At the end of the course, it could be seen that they had been able to develop such abilities and that with this course they fulfilled their initial motivations and expectations. In the final sessions, the students participated in seminars designed to demonstrate the knowledge acquired during the earlier stages, revealing a good depth of understanding during the discussions concerning the themes of the seminars. After the course, they had therefore acquired the necessary conditions to understand and discuss themes related to environmental nanotechnology. Hence, the main outcomes of the course were knowledge of the following topics: • Definitions used in nanotechnology; • Theory and practice of nanomaterial characterization methods; • Aspects of nanomaterial toxicity and its relation to physicochemical properties; • Applications of nanotechnology in helping to resolve environmental problems; • Positive and negative effects of the use of nanotechnology in the environment. During the final evaluation, the 15 students who participated in this course were able to engage in dynamic discussion with the teachers concerning the structure of the course and the knowledge acquired during its implementation. At this time, the teachers could evaluate whether the students had understood all the content of the course, as well as the impact of the course for each student. It should be noted that due to the nature of the course structure, evaluations were not made in the form of tests, but rather by means of discussions and qualitative analysis of the degree of assimilation of the course content. Table 6 lists some of the main aspects of the course impacts described by the students for each topic. In addition, concerning evaluation of the course, the students were unanimous in stating that they had greatly enjoyed the course, and in their explanations described their reasons for such an opinion. Among the main aspects that caused the students to evaluate the course as positive, the following can be highlighted: (i) contextualized structure of the topic concerning nanotechnology and the environment; (ii) integration between theory and practice; (iii) the level of the course, which ranged from introductory material to in-depth discussion of issues in the environmental area, together with their current status; and (iv) the dynamic approach of the lecturers. In addition, the students greatly enjoyed the final seminars, where during the presentations made by the groups, discussions were held concerning the main advances and limitations of the reported studies, always providing context by linking these with the theoretical and practical training provided throughout the course. At the end of the process, the students were highly

Parameters Dye reduction (mitochondrial activity) Dye reduction (plasma membrane activity) LDH enzyme release after cell lysis Green (live cells) or red (dead cells) color Uptake and accumulation of dye in liposomes Detection of DNA fragments (apoptosis) Loss of fluorescence Reproduction, loss of mobility, death Malformation, death Malformation Mutagenicity

a

Cell proliferation reagent (MTT, WTS-1, MTS, XTT); Lactate dehydrogenase (LDH); Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL).

topic in question. Some of the articles selected for use in the seminars are listed in Table 5. After completion of the seminars, a discussion was held with the participants about the course structure, teaching methods, and whether the course met the expectations of the students, as well as its strengths and weaknesses. The students generally agreed that courses adopting the methodology used here were more interesting and improved the acquisition of knowledge in a given area. They also highlighted the greater involvement of the participants in the various activities, which improved the exchange of knowledge and contributed to the success of the learning process. Students Learning Outcomes

The course students received an integrated training that included theoretical nanotechnology concepts together with related direct practical classes. During the first edition of the course, the audience (15 students) was composed of Master’s and PhD students with different intended careers (environmental engineering, biotechnology, biology, chemistry, pharmacy, etc.). As an outcome of the course, it was anticipated that the students would be able to understand the principles of nanotechnology and its importance in the environmental area. It was also expected that they would acquire a background in the preparation and characterization of nanomaterials, understanding the inherent difficulties and limitations of the different methodologies. In addition, an intention of the course was that contact of the students with research in the area of nanotechnology would provide them with the critical ability to

Table 5. Articles Used in the Seminars for the Purpose of Consolidating the Knowledge Acquired during the Course Article Title

Type of Nanomaterial

Bioaccumulation and Toxicity of CuO Nanoparticles by a Freshwater Invertebrate after Waterborne and Dietborne Exposures Evidence of Translocation and Physiological Impacts of Foliar Applied CeO2 Nanoparticles on Cucumber (Cucumis sativus) Plants Fate of Ag-NPs in Sewage Sludge after Application on Agricultural Soils F

Copper oxide nanoparticles Cerium dioxide nanoparticles Silver nanoparticles

Environment Studied

Refs

Aquatic

51

Terrestrial

52

Terrestrial

53

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Table 6. Skills Acquired by the Students for Each Topic of the Course Topic Characterization of nanomaterials

Practical approaches

Environmental applications Toxicity aspects

Integrated studies

Skills • Nanomaterials can be characterized using different techniques and methods. • A nanomaterial must be characterized in various ways in order to determine a broad range of properties. • The development of new equipment and techniques that offer greater precision and accuracy is required for the characterization of nanomaterials under environmental conditions. • Nanoparticles can be prepared in the laboratory using simple techniques and apparatus. • Nanomaterials can present different physicochemical properties (for example, plasmonic and magnetic effects). • Nanomaterials can be used as carrier systems for biological compounds and can be functionalized in various ways for use in different applications (in the areas of health, agriculture, and food, etc.). • There are many possible types of nanomaterials and potential environmental applications. • Nanomaterials can contribute to the emergence of new tools for environmental management and conservation. • Despite their benefits, evaluation is required of the toxicity of nanomaterials in different environments (water, soil, and air). • Each nanomaterial possesses individual characteristics and therefore needs to be characterized, including evaluation of toxicity, prior to its use. For example, many types of silver nanoparticles exhibit biological activity, but the synthesis routes may be different, leading to completely different physicochemical characteristics, so it is impossible to make generalizations. • Regulatory aspects are extremely important for the development of this technology. • The complexity of nanotechnology and its environmental applications demands highly qualified professionals in distinct areas, in order to ensure that each can contribute the maximum amount of knowledge for the resolution of problems, as well as to ensure that this new technology does not lead to problems for human health and the environment.

enthusiastic about the topic of environmental nanotechnology, with many of them showing interest in using such technology in their Master’s and Ph.D. studies. Furthermore, the students appreciated the critical perspective that was adopted throughout the course, especially the toxicity aspects of nanomaterials allied to the development of nanomaterials with the potential for use in environmental applications. One issue requiring attention and improvement was that the students felt that the course could be extended. This was discussed among the lecturers, who suggested that the course should be implemented in different modules and that changes and/or extensions could be included in future versions.

consecutive days, with 8 h on each day. However, in order to avoid being too tiring, and to ensure that all the topics are properly understood, the course could be structured for delivery at different times and/or on different days during consecutive weeks. Future versions of the course could include the following modifications: (i) selection of other topics that were not covered in the papers discussed in the seminars; (ii) identification of other interesting topics, such as occupational health, the interactions of nanomaterials with plants and microorganisms, and the perception of the consumer in relation to nanotechnology, among other issues; (iii) from the perspective of the practical sessions, consideration could be given to the development of new types of nanoparticulate systems, as well as the use of different materials and characterization methodologies (such as TEM and SEM, among others), although this would depend on the available laboratory facilities; (iv) alteration of the number of hours per day, and days per week, according to the audience. Other modifications could be implemented in order to provide wider dissemination of information concerning the topic of environmental nanotechnology, hence contributing to the development of science in this area.

Final Remarks

The course developed here used a simple participatory theoretical and practical format that enabled the students to understand, discuss, and consolidate knowledge on the emerging topic of environmental nanotechnology. The methodology adopted fulfilled the need to integrate nanotechnology concepts, nanomaterial characterization techniques, and environmental applications, addressing the issues of toxicity of nanomaterials and their impacts in the environment. It should be noted that the course could be adapted for use with undergraduate students, although a number of modifications would be necessary due to the characteristics of this educational level. Such adaptations include a greater emphasis of teachers on indicating the different areas of application of nanotechnology, as well as greater attention to describing the fundamental concepts, necessary for understanding the course. In addition, the number of students should not be very high, due to the nature of the practical classes and the equipment required for the nanomaterial characterizations. The implementation of such an undergraduate course should be considered extremely important and should be encouraged in order to stimulate the interest of the students in this area of science. A further consideration is that for both postgraduate and undergraduate courses, the students should be from different career areas, enabling contributions from different perspectives. Another important point to highlight concerns the structure of the course. In its current form, it was delivered over four



ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available on the ACS Publications website at DOI: 10.1021/acs.jchemed.7b00087.



Laboratory experimental practical sessions A, B, and C. (PDF, DOCX)

AUTHOR INFORMATION

Corresponding Author

*Department of Physics and Chemistry, School of Engineering, São Paulo State University (UNESP). Avenida Brasil, n° 56, Centro, CEP: 15385-000, Ilha Solteira, SP, Brazil. Tel.: +55 18 3743 1074; E-mail: [email protected]/renato.grillo@ ymail.com. G

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ORCID

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Leonardo F. Fraceto: 0000-0002-2827-2038 Renato Grillo: 0000-0002-0284-5782 Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENTS The authors would like to express their gratitude to the Postgraduate Program in Environmental Sciences of São Paulo State University (UNESP), as well as to the course participants and to J. L. Oliveira for assistance with the AFM analysis. The authors also thank the Brazilian National Council for Scientific Research (CNPq) and the São Paulo State Research Foundation (FAPESP).



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DOI: 10.1021/acs.jchemed.7b00087 J. Chem. Educ. XXXX, XXX, XXX−XXX