Chemical Education Today
Reports from Other Journals
Research Advances by Angela King
Nano Scrub Brushes for Renaissance Masterpieces
1. Carretti, Emiliano; Giorgi, Rodorico; Berti, Debora; Baglioni, Piero. Oil-in-Water Nanocontainers as Low Environmental Impact Cleaning Tools for Works of Art: Two Case Studies. Langmuir 2007, 23, 6396–6403. 2. Bonini, Massimo; Lenz, Sebastian; Giorgi, Rodorico; Baglioni, Piero. Nanomagnetic Sponges for the Cleaning of Works of Art. Langmuir 2007, 17, 8681–8685. 3. Research Advances has published additional applications of chemistry in art. See J. Chem. Educ. 2006, 83, 1738–1742.
Photo by P. Baglioni.
Figure 1. Vechietta’s fresco in Santa Maria della Sacala, Siena, Italy. SEM micrograph of a microsample showing a thick layer of polymer before (A) and after (B) the application of a microemulsion. Reprinted with permission from Langmuir 2007, 23, 6396–6403. Copyright 2007 American Chemical Society.
More Information
Photo by P. Baglioni.
Scientists in Italy are reporting development and use on Renaissance masterpieces of a simple, less-expensive method for the world’s most delicate cleanups—on precious paintings and other works of art. The method uses oil-in-water nanocontainers to restore artwork dulled by the centuries-old buildup of grime and damaged from floods and failed past attempts at preservation involving acrylic and vinyl polymers. In pioneering work, Piero Baglioni and colleagues at the University of Florence describe tiny droplets of cleaning agents suspended in water to form microemulsions. The team used p-xylene as the non-polar phase due to its noted ability to dissolve acrylic polymers, and form either nonionic or mixed ionic/ nonionic (alkyl polyglycosides, APG) microemulsions in water. These nanocontainers have several advantages over traditional methods, which may involve the use of pure organic solvents. The microemulsions have a milder cleaning action, for instance, so are less likely to damage fragile surfaces. In addition, they use up to 95% less organic solvent and have less environmental impact than traditional cleaning methods. “These innovative systems are very attractive for the low amount of organic solvent… and the very efficient and mild impact of the cleaning procedure on the fragile painted surfaces,” the report states. Frescoes are particularly hard to clean, as conventional solvents can remove polymeric material on the surface but fail to penetrate and cleanse the porous fresco structure. APG, polymeric acetals of fatty acids and glucose, have been known since the late 1800s and have good surface active properties and are very biodegradable. However, an economically-feasible way to synthesize them was only developed at the close of the 20th century. Researchers report on successful use of the technology in actual restorations, including a Renaissance painting that had been degraded by application of a polyacrylate coating during a previous restoration attempt and removing tar-like deposits
from a fresco in Florence that was damaged during the 1996 flooding of the Arno River. Another recent report by Baglioni (Figures 1 and 2) discusses the synthesis and characterization of functionalized magnetic nanoparticles associated with gels. These “nanosponges” have been used in combination with oil-in-water microemulsions in the field of cultural heritage.
Figure 2. The effects of the nanocontainer treatment can be seen by looking at photos of the same fresco region taken before (above) and after (below) treatment.
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Chemical Education Today
Reports from Other Journals 4. This Journal has published many articles on the chemistry of art. For a recent article, see Uffelman, E. S. Teaching Science in Art. J. Chem. Educ. 2007, 84, 1617–1624; also Kafetzopoulos, C.; Spyrellis, N.; Lymperopoulou-Karaliota, A. The Chemistry of Art and the Art of Chemistry. J. Chem. Educ. 2006, 83, 1484. 5. A general discussion of chemistry’s role in art restoration can be found online at http:// pubs.acs.org/cen/coverstory/7931/7931art.html (accessed Aug 2007).
Particle Emissions from Laser Printers Might Pose Health Concern Indoor air quality (IAQ) is affected not only by outdoor pollutants, but also by fibers, particles, organic vapors, and inorganic gases released by indoor air pollution sources. Poor IAQ has previously been linked to an increase in health complaints. Printers are a possible source of indoor air pollution, releasing volatile organic compounds, ozone, and particulate
emissions. Certain laser printers used in offices and homes release tiny particles of toner-like material into the air that people can inhale deep into lungs where the particles may pose a health hazard, scientists are reporting. Lidia Morawska and colleagues in Australia classified 17 out of 62 printers in the study as “high particle emitters” because they released such elevated quantities of particles, which the researchers believe to be toner, the ultrafine powder used instead of ink in laser printers to form text and images.
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Reports from Other Journals One of the printers released particles into an experimental chamber at a rate comparable to the particle emissions from cigarette smoking, the report stated. Thirty-seven of the 62 printers, on the other hand, released no particles that diminished air quality; six released only low levels, and two medium levels. All printers were monitored in an open office, and the researchers recorded data on three laser printers in an experimental chamber. The study included popular models in the U. S. and Australia sold internationally under the Canon, HP Color Laserjet, Ricoh, and Toshiba brand names. Most of the printer-generated particles detected were ultrafine, Morawska said, explaining that such contaminants are easily inhaled into the smallest passageways of the lungs where they could pose “a significant health threat”. Previous studies have focused on emissions of volatile organic compounds, ozone, and toner particles from office printers and copiers. However, the research left broad gaps in scientific understanding of particle emissions and airborne concentrations of particles, the report noted. The study included three steps. Researchers first monitored office and outdoor particle number concentrations for more than 48 hours. They then measured the particle number concentrations in the vicinity of all printers in the building. Finally, they used an experimental chamber to measure particle concentrations and emission rates from three different printers. The experimental chamber was ~1 m3 with an air flow rate during experiments of 2.3 l/min. Inlet and outlets ports and HEPA filters allowed the introduction of particle-free air and the collection of analytical samples. A condensation particle counter (CPC) was used for continuous real-time measurements of total concentrations of particles in the range of 0.007–3 μm in the office. A scanning mobility particle sizer (SMPS) was used to measure submicrometer particle number concentrations and size distributions both outdoors and in the experimental chamber. (See Figure 3.) Morawska and colleagues, who are with the Queensland University of Technology in Brisbane, initially were not trying to close that knowledge gap. “It wasn’t an area that we consciously decided to study,” Morawska said in an interview. “We came across it by chance. Initially we were studying the efficiency of ventilation systems to protect office settings from outdoor air pollutants. We soon realized that we were seeing air pollution originating indoors, from laser printers.” The study found that indoor particle levels in the office air increased fivefold during work hours due to printer use. Printers emitted more particles when operating with new toner cartridges, and when printing graphics and images that require greater quantities of toner. Funded by Queensland Department of Public Works and The Cooperative Research Centre for Construction Innovation, the report includes a list of the brands and models in the study classified by concentration of particles emitted. As a result of the study, the scientists are calling on government officials to consider regulating emission levels from laser printers. “By all means, this is an important indoor source of pollution,” Morawska said. “There should be regulations.”
The health effects from inhaled ultrafine particles depend on particle composition, but the results can range from respiratory irritation to more severe illnesses, such as cardiovascular problems or cancer, Morawska said. “Even very small concentrations can be related to health hazards,” she said. “Where the concentrations are significantly elevated means there is potentially a considerable hazard.” Larger particles also could be unhealthy without reaching the deepest parts of the lung. “Because they are larger,” Morawska added, “they contain more mass and can carry more toxins into the body. No matter how you look at it, there could be problems.” Morawska said that more research on the health effects of inhaling printer-generated particles is needed. As a first step to lower risk, people should ensure that rooms in offices or houses are well ventilated to allow airborne particles to disperse. More Information 1. He, Congrong; Morawska, Lidia; Taplin, Len. Particle Emission Characteristics of Office Printers. Environ. Sci. Technol. 2007, 41, 6039–6045. 2. This Journal has published an apparatus for measuring air pollution in schools. See Rockwell, Dean M.; Hansen, Tony. Inventory Control: Sampling and Analyzing Air Pollution: An Apparatus Suitable for Use in Schools. J. Chem. Educ. 1994, 71, 318. 3. Additional discussion of this paper is available online at http:// www.brisbanetimes.com.au/articles/2007/07/31/1185647880054.html and http://pubs.acs.org/subscribe/journals/esthag-w/2007/aug/science/ nl_printers.html (both sites accessed Aug 2007).
Advance Promises New Era in Recycling of Plastics In an advance toward a new era in recycling of plastics, scientists in Japan are reporting development of a process that breaks certain plastics down into their original chemical ingredients, which can be reused to make new, high-quality plastic. That approach fostered recycling of beverage cans, scrap steel, and glass containers, which are melted to produce aluminum, steel, and glass. However, no process has emerged to depolymerize the long chains of molecules that make up millions of pounds of polymer, or plastic, materials that are trashed each year. Instead, recycling of certain plastics involves melting and reforming into plastic that is less pure than the original. Akio Kamimura and Shigehiro Yamamoto recently reported invention of an efficient new method to depolymerize polyamide plastics—which include nylon and Kevlar. The technology, still at the laboratory-scale stage, does not require costly pressure chambers, extreme temperatures, or high energy inputs. Rather, it uses ordinary laboratory glassware. The method relies on ionic liquids, liquids that contain only ions (atoms or molecules with an electric charge) and are powerful solvents. Ionic liquids are nonvolatile and stable at high temperatures, characteristics that make them ideal solvents for depolymerization. Researchers used an ionic liquid that changed nylon-6 into its monomer, captrolactam (Figure 4). The best
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Figure 4. Scientists in Japan have developed a method that utilizes ionic liquids to efficiently depolymerize polyamides. Reprinted with permission from Org. Lett. 2007, 9, 2533. Copyright 2007 American Chemical Society.
Figure 5. Comparison of NMR spectra of PP13 TFSI after being reused five times for the depolymerization reaction at various temperatures. Reprinted with permission from Org. Lett. 2007, 9, 2533. Copyright 2007 American Chemical Society.
results were obtained by using DMAP as a catalyst with the ionic liquid PP13 TFSI, N-methyl-N-propylpiperidinium bis(trifluoromethansulfonyl)imide, as the solvent, and heating to 300 °C for six hours. The product could be isolated through distillation by use of a Kugelrohr apparatus under reduced pressure. Product purity was assessed with GC/ MS. The scientists also determined that the ionic liquid solvent could be recycled at least five times. NMR monitoring demonstrated that the ionic liquid underwent no decomposition during reaction (Figure 5).
“This is the first example of the use of ionic liquids for effective depolymerization of polymeric materials and will open a new field in ionic liquid chemistry as well as plastic recycling,” the report states. More Information 1. Kamimura, Akio; Yamamoto, Shigehiro. An Efficient Method to Depolymerize Polyamide Plastics: A New Use of Ionic Liquids. Org. Lett. 2007, 9, 2533. 2. Additional discussion of this paper is available online at http://www.sciencenews. org/articles/20070707/fob1.asp (accessed Aug 2007).
3. Many resources on polymers and materials are available online at http://library. stanford.edu/depts/swain/hosted/ncw/2005/ materials.html (accessed Aug 2007). 4. This Journal has published many activities regarding polymer science. For examples, see J. Chem. Educ. 2006, 83, 1428; 2006, 83, 1531; 2006, 83, 439; and 2006, 83, 443.
Angela G. King is Senior Lecturer in Chemistry at Wake Forest University, P.O. Box 7486, Winston-Salem, NC 27109;
[email protected].
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