The Israel Chemist and Chemical Engineer ICE Issue 8 · November 2021 · Kislev 5782 https://doi.org/10.51167/ice00000 The Israel Chemical Society הימיכל תילארשיה הרבחה The Israel Chemical Society (ICS: www.chemistry.org.il)
? GC – Analyzer , או GC/MS , או GC אתם צריכים תוכלו להשיג הכל ספקטרו ישראלאצלנו ב (ניתן לראות הדגמה בארץ) 1 2 3 4 GC/MS ו- GC במגוון קונפיגורציות, עם כל מגוון הגלאים הקיימים בשוק. מגוון אנלייזרים מוכנים לעבודה, על פי דרישות הלקוח: .Chromatec Crystal 9000 GC מבוססי › קונפיגורציה מוכנה היישר מהמפעל, כולל כל האינג’קטורים, › , הקולונות ושאר האביזרים. Valves הגלאים, ה- בדיקת השיטות ו-ולידציה טרם השחרור מהמפעל. › תוכנה ידידותית המאפשרת שליטה על › כל חלקי המערכת, כולל אביזרי צד שלישי. תמיכה אפליקטבית מלאה. › ניתן להזמין אנלייזרים שונים: אנלייזרים מבוססים על שיטות בינלאומיות: › ...EN ,ISO ,ASTM אנלייזרים ייחודיים בהתאם לשיטות › המפותחות אצל היצרן, ועוברות ולידציה. אנלייזרים המפותחים על פי דרישות ספציפיות › ואפליקציות של הלקוח לאנליזות רוטיניות. וגמישות מירבית R&D פתרונות הן בהנדסת החומרה (להתאמה לדרישות הלקוח) והן בהנדסת התוכנה (לשליטה, בקרה, דיאגנוסטיקה, עיבוד תוצאות, דוחו”ת ועוד). לפרטים: ד”ר גל אופנהים, ספקטרו ישראל [email protected] אימייל: 054-2424557 ,03-9693014 טלפון: http://www.spectro.co.il/ | https://www.chromatec-instruments.com/
3 The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 Table of Contents Editorials 4 Letter from the Editor Arlene D. Wilson-Gordon 5 Letter from President of ICS Ehud Keinan Scientific Articles 6 Laser-guided printing Hagay Shpaisman 12 Separating the “players” from the “spectators” in operando spectroscopy of catalysis Charlotte Vogt History of Chemistry Article 18 Sidney Loeb and the origins of pressure retarded osmosis Bob Weintraub Profile 22 Interviewwith Avi Domb Arlene D. Wilson-Gordon Reports 25 Women in science Rachel Mamlok-Naaman 31 The 2021 ICS prize ceremony: July 1, 2021, The Open University, Ra’anana, Israel Ehud Keinan
4 Letter from the Editor Dear Readers, The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 Welcome to the eighth issue of the Israel Chemist and Engineer (ICE) online magazine, a publication of the Israel Chemical Society (ICS). We hope you will find the magazine interesting and will be inspired to contribute to future issues. We have two scientific articles on novel topics, one by Hagay Shpaisman of Bar-Ilan entitled “Laser-guided printing” and one by Charlotte Vogt of the Technion entitled “Separating the ‘players’ from the ‘spectators’ in operando spectroscopy of catalysis”. Bob Weintraub continues to inform us about the history of science, this time with an article entitled “Sidney Loeb and the origins of pressure retarded osmosis”. Rachel Mamlok-Naaman of the Weizmann Institute, the recipient of the 2020 IUPAC award for distinguished women in chemistry or chemical engineering, has contributed an article on “Women in science”. I had the pleasure of interviewing Avi Domb of the Hebrew University for this issue of the ICE. Avi is currently serving as the Chief Scientist of the Israel Ministry of Innovation, Science and Technology, yet another peak in his colorful and varied career. Finally, the indomitable ICS President Ehud Keinan presents a report of the 2021 ICS prize ceremony that was held in July 2021 at the Open University campus in Ra’anana in lieu of the 2021 ICS annual meeting that had to be cancelled due to the covid-19 epidemic. If you have suggestions for future editions, comments on the current issue, or would like to contribute an article, please contact me at [email protected]. Arlene D. Wilson-Gordon Professor Emerita Chemistry Department, Bar-Ilan University ICE Editor
The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 5 Letter from President of ICS Dear Colleagues, Although the Covid-19 pandemic with its consequences will continue affecting every aspect of our life, it seems that we have crossed the worst phase, and have gradually resumed all the professional and personal activities of pre-Covid times. We had to skip the 2021 Meeting, but we kept our traditional award ceremony and held it at the Open University campus on July 1, 2021 (see my report in this issue). The 86th ICS Annual Meeting, initially scheduled for February 2021, will take place on February 22-23, 2022. I expect high attendance because many ICS members and students are eager to meet physically rather than virtually, resume beneficial networking, and exchange their ideas and recent discoveries. Profs. Charles Diesendruck and Saar Rahav of the Technion’s Schulich Faculty of Chemistry will chair the meeting. I look forward to seeing many of you at this gathering. The establishment of the ACS Chapter in Israel marks a significant advance for our Society. On November 18, 2021, we celebrated the Chapter’s inauguration at the Open University campus in Ra’anana. Many ACS members attended the event with their spouses. They participated in an informal discussion on the Chapter’s goals and plans, such as ICS– ACS joint membership, research funding opportunities, ACS–ICS joint symposia at the ACS National Meetings, binational collaboration, and exchange programs of scientists, graduate students, and even high-school pupils. We also discussed the preparations for the elections of the Chapter’s officers - President, Secretary-General, and Treasurer. In my introductory comments, I explained that the ACS is the largest and most influential chemical society worldwide. Founded in 1876 (just 57 years before the establishment of the ICS), the ACS has become a truly international organization with 20% of its 155,000 members residing outside the USA. The 25 international chapters add to a remarkable array of 33 technical divisions and 186 local sections. At the end of the evening, Prof. Dan Shechtman of the Technion, who received the 1999 Wolf Prize in Physics, and the 2011 Nobel Prize in Chemistry for discovering quasiperiodic crystals, lectured on “American and Israeli Wolf Prize Laureates, and their scientific achievements.” As youmay know, the International Union of Pure and Applied Chemistry (IUPAC) has recently elected me to become the Union’s 41st President. It is the second time in the 103-year history of IUPAC that the Union has an Israeli President. The first was Prof. Joshua Jortner, who served as the 28th President (1998-1999). I feel honored to continue his legacy. My service as Editor-in-Chief of the Israel Journal of Chemistry (IJC), the ICS’s Official Journal, continues to be a source of great satisfaction. The newly released Impact Factor (IF) for 2020-2021 is 3.333, representing a 43.7% increase from last year. Even more impressive is the IJC Total Citations of 3520, representing a 28.40% increase from last year. It is remarkable that within just one decade since we started our collaboration with Wiley-VCH, the IF increased from 0.380 to 3.333, and citations went up from 883 to 3520. The credit for these achievements goes to many of you who served as Guest Editors of topical issues or contributed highly cited articles. Please get in touch with me directly for any new ideas concerning future topics that deserve to be highlighted by our journal. Finally, I am delighted to see this ICE magazine developing under Editor-in-Chief, Prof. Arlene Wi lson-Gordon. I encourage you to contribute an article to the ICE on any topic you like, including popular science, history of science, report on an event, opinions, etc. Please, don’t hesitate to contact Arlene or me on these matters. Enjoy your reading, Ehud Keinan President, the Israel Chemical Society
6 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 Upper left, clockwise: Ehud Greenberg, Dr. Nina Armon, Dr. Eitan Edri and Ornit Nagler-Avramovitz are PhD students (Nina and Eitan have graduated) in the lab of Prof. Shpaisman. Dr. Yuval Elias is the scientific editor of the Chemistry Department at Bar-Ilan University. Hagay Shpaisman is an associate professor at Bar-Ilan University and leads the laboratory of directed material assembly, devising and developing new methods for bottom-up assembly. Abstract: Laser-guided assembly of microstructures where materials are patterned into 2D/3D structures with (sub) micron resolution and less waste than standard top-downmethods has many applications includingmicroelectronics, sensors, andmedical devices. Liquids allow a simple setup andmay be easily handled and recycled. However, this simplicity conceals various underlyingmechanisms that cannot be identified by simply observing the initial or final materials. Furthermore, this field is of interest to chemists, physicists, and chemical/material engineers where each group is focused on different aspects of the deposition process, sometimes leading to confusion regarding the overall mechanism. Here we offer a methodical short overview where mechanisms are divided according to the material source – preformed or locally synthesized, and then by the driving force. Various methods are compared, and advantages and limitations are discussed. Finally, we illuminate various future directions for advancing this exciting field. Laser-guided printing Ehud Greenberg,a,b Nina Armon,a,b Eitan Edri,a,b Ornit Nagler-Avramovitz,a,b Yuval Eliasa and Hagay Shpaismana,b* aDepartment of Chemistry and bInstitute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 5290002, Israel *Email: [email protected] 1. Introduction Formation of patterns is important for many applications including medicine, robot ics, electronics, and food production. Structures produced by bottom-up approaches, in two dimensions as well as in three-dimensional additive manufacturing (AM), may be more complex and incur less waste than traditional methods. The microscale is particularly important for electronic, optoelectronic, photonic, electromechanical and medical devices, as well as for various sensors. Moreover, personalized macro-scaled products such as implants and drugs often have micro-sized features, which play an important role. Highly precise optical manipulation of light offers outstanding resolution, while printing at high speeds is achieved by rapid steering of the laser. A large variety of materials including metals, oxides, alloys, polymers, and biological cells have been assembled by laser-based methods. Techniques based on liquids are desirable as they allow simple setups, easy handling, excellent resolution, and recycling with minimum waste. Focusing on assembly based on lasers in liquid environments, the common setup (Figure 1) encompasses severa l mechanisms. Variants combine different principles of operation. Different mechanisms, operation modes and material characteristics are therefore easy to miss. Whereas reviews on printing with lasers deal primarily with preformed materials, local synthesis is mentioned mainly in reviews that survey a wide range of methods, such as those composed by Elder  and Ngo  and coworkers. Specific material families have also been reviewed, e.g. metal microstructures by Hirt and coworkers . Here, we offer a short overview that presents both preformed material deposition and in situ synthesis. We refer the interested readers to our recent indepth progress report . Methods are divided by the driving https://doi.org/10.51167/ice00008
7 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 force leading to material deposition, and mechanisms are explained. Table 1 briefly summarizes various methods in terms of the mechanism and key aspects. Printing method Mechanism Materials Maximum speed Feature size Comments Photothermal Local heating by laser – temperature gradient: I) ion separation – local electric field, supports movement of charged particles towards heated area and/or II) particles carried by liquid (bulk) motion towards focal point. Metals, polymers, organic molecules ~1 µm/s 300 nm – 200 μm Reconfigurable printing was demonstrated. Microbubble assisted Local heating increases the vapor pressure until a micro-bubble is formed. Convective flows, capillary forces carry particles towards base of micro-bubble where some are pinned. Metals, polymers, organic molecules 10 mm/s ~510 nm – 50 µm I) Laser modulation forms continuous patterns. II) 3D particle-covered hollow spherical structures were shown. Optical forces Optical forces due to photon momentum conservation (particle >> λ) or electrostatics (size << λ) used to either: I) optically trap and deposit materials at desired locations on the substrate, or II) push toward the substrate (scattering force). Metals, polymers, organic molecules, living cells particle every 5 s Individual objects (mostly) deposited selectively nanometers to micrometers I) Minimal inter-particle distance – 60-150 nm. II) Fixation by gel and electrophoresis. Single photon reactions Polymerization by photons with enough energy to excite electron from ground to higher state close to liquid surface (poor selectivity in z-direction). Layered approach forms 3D polymeric microstructures. Photocurable resins 4000 mm/s 5–70 µm Available commercially. Multi photon reactions Non-linear process – at least two photons required to excite electron, promoting chemical reaction. High energy pulsed lasers polymerize/reduce metal ions. Laser energy tuned to produce sub-diffractionlimit features. 3D microstructures by multi-photon reactions (freely moving focal point). Photocurable resins, metals 0.9 mm/s 65 nm – 5 µm Commercially available. Thermally driven reactions Occur upon heating due to laser light absorption, increasing probability to overcome activation barrier and promote electron transfer. Oxides, metals, polymers, organic molecules, alloys, compounds (molecular) 10 mm/s ~0.7–500 µm Multi layered (2.5D) and simple 3D microstructures were demonstrated. Table 1. Brief comparison of printing methods. Adapted with permission . Copyright 2021, Wiley-VCH.
8 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 Figure 1. Common setup for laser guided printing from a liquid medium. Laser focused on the liquid forms 2D/3D microstructures by moving relative to a substrate carrying liquid. The various deposition mechanisms are represented by a question mark. Reproduced with permission  . Copyright 2021, Wiley-VCH. 2. Directed assembly of preformed materials Focused laser illumination can assemble preformed materials at the focal spot owing to thermal and/or optical force. 2.1. Thermal force Photo-therma l heat ing moves par t icles mainly by thermophoretic motion and convective flow. Micro-bubble assisted printing is a special case where the motion is convective, and particles are pinned to the microbubble base. 2.1.1. Photo-thermal printing Thermophoresis — particle motion due to a thermal gradient — proceeds mainly by an opto-thermoelectric mechanism. Local heating leads to a temperature gradient and ion separation according to the Soret coefficient. The consequential local electric field results in movement of charged particles towards (or away from) the heated area (Figure 2a, right). Photo-thermal printing may alternatively proceed by a mechanism in which the liquid motion carries particles. Local heating of the liquid can produce variations in pressure, density and surface tension. The density tends to decrease with temperature, as most solvents expand, resulting in flow driven by buoyancy, gradients in pressure, and local Figure 2. Methods of printing from a liquid according to material origin – preformed/synthesized locally. Preformed assembly methods are divided according to forces that affect material movement towards the focal spot. Local synthesis methods are divided according to the photon absorption mechanism. Reproduced with permission . Copyright 2021, Wiley-VCH.
9 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 convection. With heat, the surface tension becomes lower, and the flow proceeds according to Marangoni convection. Drag forces act on the particles, which move along streamlines of the liquid (Figure 2a, left). While material accumulation following heating by optothermal means has been shown quite commonly, few researchers demonstrated assembly on substrates in a permanent manner. Such permanent fixing of dispersed materials may be achieved by making the continuous phase solid (e.g., hydrogel) by depletion forces or Van der Waals interactions. 2.1.2. Micro-bubble assisted printing A beamproduced by a continuous wave (CW) laser is absorbed by the particles or by a substrate that absorbs light. Due to the resultant heating, the pressure of the vapor increases until a microbubble is formed . Focusing the laser close to the interface of the liquid and the substrate produces a gradient in temperature, such that the part of the microbubble closer to the substrate is hotter. This produces gradients in surface tension and density, which lead to convection currents (natural and Marangoni, respectively) that carry the particles, along with capillary forces. Some of the particles are pinned at the interface between the three phases (gas, liquid and solid) and show typical spherical deposition around the contact area of the bubble/substrate (Figure 2b) [7,8]. By moving the sample or the laser, the micro-bubble can propagate by depinning the bubble/liquid/substrate interface. Particles are deposited around the new location of the bubble, and micro-structures can be printed by repeating this process. Continuous patterns may be formed by laser modulations that enable improved control over the microbubble’s size and prevent its pinning to the deposited material . 2.2. Optical forces Optical tweezers (OTs) are the best known method that uses optical forces to manipulate particles [9–14]. When the particle size is considerably greater than the wavelength of the laser (Mie regime), a force is generated in accordance with momentum conservation of absorbed, reflected or refracted photons. If the refractive index is higher than that of the medium, the force will pull/push it towards the most intense gradient. Nanoparticles (NPs) much smaller than the wavelength (Rayleigh regime) experience an electrostatic force due to different polarizability with respect to the medium. NPs with higher polarizability have a dipole moment that arises from the light’s electric field, and advance along the intensity gradients toward the focal point. Axial/radial components are parallel/perpendicular to the beam direction. Materials trapped with OTs may be micro-printed on substrates (Figure 2c) by movement of the trap with respect to the substrate. Interestingly, optical forces allow microprinting even without optical trapping. Material can be pushed towards the substrate using the component along the axis (e.g., for particles that are highly scattering). In either case (trapping/pushing), Van der Waals interactions can bind particles with the substrate. Particles may be permanently set on the substrate also by local thermal heating, gelation, electrophoretic deposition, and ultraviolet (UV) triggering. 3. Local directed synthesis Beyond particle/cell assembly, lasers allow localized synthesis from liquid/dissolved precursors. Advantages include greater stability and avoidance of preparation steps or stabilizers that can have a negative impact on the properties of the deposited material. Complex systems can be formed more easily, for example alloys, which are difficult to produce frommaterials that are preformed. 3.1. Single-photon reactions When a single photon excites an electron, thereby promoting a chemical reaction, photo-polymerization may occur in which laser irradiation polymerizes liquid or dissolved monomers. For liquids, reactions of single photons arise from laser illumination (mainly in the UV range) where photons can excite electrons (Figure 2d). The resin includes liquid molecules with a variety of functions – building blocks (monomers/cross linkers) and photo-sensitizers, which absorb light and transfer energy to photo-initiators, forming reactive species (e.g., radicals/cations) that initiate polymerization. These functions can be obtained in molecules of different type, or in separate parts of molecules of the same type. The desired 2Dmicro-structure is formed by steering the laser on a (thin) layer of the resin. Repeated scanning with an additional thin layer produces a 3D polymeric microstructure. The need for such layered 3D printing arises from the limited depth of penetration and selectivity in the perpendicular direction (along the z-axis). This technology is used commercially in many systems for a variety of applications. 3.2. Multi-photon reactions Non-l inear mult i-photon processes where elect ron excitation requires more than one photon (and a chemical reaction is promoted) proceed with rather low probability, as nearly simultaneous absorption is needed to initiate the process, requiring high energy pulsed lasers. The multiphoton absorption mechanism is used mainly for photopolymerization and reduction of metal ions. Usually, the liquid is transparent to the wavelength, obviating the need to add layers of thin liquid resin for 3D formation (required for single photon reactions). The substrate is moved relative
10 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 to the focal point, and 2D/3D structures are produced inside the liquid resin bulk (Figure 2e). In this non-linear process with threshold effect, the laser energy can be tuned to produce sub-diffraction-limit features. Multi-photon and single photon polymerizations require similar components (see Section 3.1): building blocks and photo-sensitizers/initiators. Multi-photon reduction requires electron acceptors (metal ions) and photo-reducing agents. The reduction process was suggested to form NPs and structures of metal by nucleation, growth, and aggregation. Commercial units are available for high-resolution polymeric 3D printing (e.g., by Nanoscribe and Microlight3D) and are used for various applications. 3.3. Thermally driven reactions When heat is generated by absorption of the laser, there is a greater probability that the reaction activation barrier will be overcome and electron transfer promoted (Figure 2f). It was suggested by Lachish-Zalait et al.  that initiation of the deposition process requires adsorption to the substrate of very small amounts of precipitate, which absorb laser radiation and undergo thermal decomposition. Metals as well as oxidized metals are produced from precursor solutions that consist mostly of metal ions, which have an activation energy that is higher than that of the photons. The reaction is sometimes faster than expected due to the local rise in temperature, explained by the gradient in temperature between the spot of the laser and the medium; the resultant convection flows provide a steady supply of precursors. Minimal diameters of microstructures (circular deposition) and linewidths are ~0.7–500 µm. Recent studies suggested a major role for microbubbles [17,18] attributed to gradients that lead (see Section 2.1.2) to convection currents; in combination with capillary flow and liquid evaporation around the microbubble. These currents were thought to increase ion concentration and even lead to supersaturation. Due to the higher temperatures and concentrations, material is deposited around the threephase (liquid/gas/solid) contact interface. Greenberg et al.  showed deposition at the interface of NPs that were formed in liquid (along with materials that were synthesized locally). Laser modulation prevents pinning of the bubble to the deposited material and improves control over its size. 4. Discussion Due to the similarity between the various methods, the differences in underlying mechanism, operation, and characteristics of the printed material can easily be missed. There is no “perfect” method. Figure 3 reveals that certain applications require a specific method. For example optical forces, while inferior in terms of speed, are the only method that allows particles to be placed in close proximity (60 nm apart) and living cells to be manipulated. Reactions of single photons offer the greatest speed but are limited to printing of polymers. Methods that enable microfabrication of various materials are advantageous, as flexibility in material choice allows better compatibility for diverse applications. Some methods demonstrated deposition of various materials. Directed assembly of preformedmetals, polymers and organic materials can be expanded to deposit NP dispersions of other materials. Another advantage of such deposition is exceptional control over size and shape of particles forming the microstructure, as specific properties can be chosen. Local synthesis is obviously not applicable to living cells. Various applications benefit from minimal feature size. Photo-thermal, micro-bubble assisted, multi photon and thermally driven printing all achieve sub-micron feature size, while single-photon reactions are limited to microns. While diffraction is considered a limiting barrier, features with a smaller size of tens of nm were achieved by reactions with multiple photons due to non-linear processes. The size range provided by one laser passage is significant for applications that require a feature size much larger than the minimal value. Repeated printing with a small feature size not only requires significant time but may also provide subpar quality due to boundaries between adjacent features. Diverse feature size is also required for connection of macro-sized objects to micro and sub-microstructures. Figure 3. (a) Various aspects of laser-based printing from liquids – green (excellent), yellow (mediocre), red (poor). (b) Printing methods applicable for various material families and (c) linewidths. (d) Abbreviations. Reproduced with permission . Copyright 2021, Wiley-VCH.
11 The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 Scientific Article 5. Conclusion & outlook Laser-based printing from liquids appear promising for various applications. It is simple, uses materials that allow easy handling and efficient recycling, and allows versatility, high resolution, and printing of arbitrary structures on various substrates. Traditional methods for fabrication such as inkjet printing, selective laser sintering (SLS) and lithography may be combined with laser-based methods. Laser-guided printing offers a number of advantages, and may complement or replace top-down approaches. Printing of micro-structures with single/multi-photon polymerization is highly developed and commercially mature. However, it is limited to polymers; for other materials, appropriate methods are needed. Commercialization requires scaling up, e.g. printing in parallel with separate beams, or increasing velocity. Limits of printing velocity and feature size should be studied theoretically and experimentally. Methods currently limited to 2D assemblies require additional research to allow 3D microstructures. Micro-sized structures are envisioned not only within macro-sized objects, but also as standalone objects, e.g. for medical usage. For such micro-objects (e.g., devices and robots) materials need to be assembled with different functionalities. Microprinting of materials with “smart” properties (e.g. shape-memory polymers) and tailored composites are essential. By comparing the various mechanisms, this overview will hopefully illuminate the different methods and lead to future developments. References 1. B. Elder, R. Neupane, E. Tokita, U. Ghosh, S. Hales and Y. L. Kong, Adv. Mater., 2020, 32, 1907142. 2. T. D. Ngo, A. Kashani, G. Imbalzano, K. T. Q. Nguyen and D. Hui, Compos. B Engin., 2018, 143, 172–196. 3. L. Hirt, A. Reiser, R. Spolenak and T. Zambelli, Adv. Mater., 2017, 29, 1604211. 4. N. Armon, E. Greenberg, E. Edri, O. Nagler-Avramovitz, Y. Elias and H. Shpaisman, Adv. Funct. Mater., 2021, 31, 2008547. 5. E. Edri, N. Armon, E. Greenberg, S. Moshe-Tsurel, D. Lubotzky, T. Salzillo, I. Perelshtein, M. Tkachev, O. Girshevitz and H. Shpaisman, ACS Appl. Mater. Interfaces, 2021, 13, 36416–36425. 6. Y. Xie and C. Zhao, Nanoscale, 2017, 9, 6622–6631. 7. N. Armon, E. Greenberg, M. Layani, Y. S. Rosen, S. Magdassi and H. Shpaisman, ACS Appl. Mater. & Interfaces, 2017, 9, 44214–44221. 8. S. Fujii, K. Kanaizuka, S. Toyabe, K. Kobayashi, E. Muneyuki and M. Haga, Langmuir, 2011, 27, 8605–8610. 9. I. Jacob, E. Edri, E. Lasnoy, S. Piperno and H. Shpaisman, Soft Matter, 2017, 13, 706–710. 10. C. Hosokawa, H. Yoshikawa and H. Masuhara, Phy. Rev. E, 2005, 72, 21408. 11. E. Lasnoy, O. Wagner, E. Edri and H. Shpaisman, Lab Chip, 2019, 19, 3543–3551. 12. D. G. Grier, Nature, 2003, 424, 810–816. 13. Y. Roichman and D. G. Grier, Complex Light and Optical Forces. Vol. 6483. International Society for Optics and Photonics, 2007, pp. 64830F-64830F–5. 14. S.-H. Lee and D. G. Grier, Opt. Express, 2007, 15, 1505–1512. 15. H. Wang, S. Liu, Y.-L. Zhang, J.-N. Wang, L. Wang, H. Xia, Q.-D. Chen, H. Ding and H.-B. Sun, Sci. Technol. Adv. Mater., 2015, 16, 024805. 16. A. Lachish-Zalait, D. Zbaida, E. Klein and M. Elbaum, Adv. Funct. Mater., 2001, 11, 218–223. 17. E. Greenberg, N. Armon, O. Kapon, M. Ben-Ishai and H. Shpaisman, Adv. Mater. Interfaces, 2019, 1900541. 18. S. Fujii, R. Fukano, Y. Hayami, H. Ozawa, E. Muneyuki, N. Kitamura and M. Haga, ACS Appl. Mater. Interfaces, 2017, 9, 8413–8419.
12 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 Charlotte Vogt received her PhDwith Greatest Distinction fromUtrecht University in the Netherlands in 2020, working with Professor Bert Weckhuysen. In 2021, she was listed on Forbes’ ‘30 under 30’ list and in the same year she started her own research group as Assistant Professor at the Technion Institute for Technology in Israel. Her group focuses on the development of novel tools for deep fundamental understanding of catalytic processes at work. Separating the “players” from the “spectators” in operando spectroscopy of catalysis Charlotte Vogt Schulich Faculty of Chemistry, Technion, Israel Institute of Technology, Technion City, Haifa 32000, Israel Email: [email protected] Abstract Surface processes at complex material interfaces are important for many different applications, most notably heterogeneous catalysis. Approximately 90% of chemical processes - and thus nearly all manmade things - include at least one catalytic step. Studying relevant surface processes allows us to rationally design new or better catalysts andmaterials but it is difficult to do so under relevant conditions of temperature, pressure, andmaterial complexity. In this article, I discuss an experimental approach borrowed from lock-in amplifiers, equipment often found in physics laboratories, which can overcome many of these challenges. In this way, we can study details of catalytic reactions under highly relevant conditions with the aim to generate the next generation of fundamental insights into surface processes. 1. Studying catalysts at work 1.1 The complexity of catalyst systems A surface or an interface defines a boundary between a material and its surrounding environment. At an atomic level, surface atoms have a different chemical environment from those in the bulk of the material; they have fewer nearest neighbors. As such, surface atoms exhibit higher chemical reactivity, and this general property makes them very useful in a large variety of chemical and biological processes. To increase the available surface per unit weight of material, it is common practice to finely divide the material whose surface properties are desired, thereby forming e.g., nanoparticles which are often supported on high-surface area (metal oxide) supports. Another commonly used form of (high-surface area) catalysts are zeolites, which act as solid Brønsted acids. Supported nanoparticular catalysts and zeolites by far make up the largest fraction (in terms of catalyst weight, product weight, and also economic value) of processes that are applied industrially. Such materials are used and studied throughout industry and academia, for example in catalysis, but also in materials science, across energy storage applications, and so forth, due to their high chemical reactivity and stability . During catalytic processes, molecular adsorbates at the surface affect the surface, geometric, and electronic structure of the catalysts, particularly so at the high temperatures and pressures which are often relevant to actual applications (for example, the Haber-Bosch process occurs above 350 °C and at pressures of over 200-300 bar) . Our current understanding of such fundamental changes to relevant catalysts at operating temperatures and pressures is lacking; there are so-called temperature-, pressure- and material complexity gaps . One of the reasons that so much is still unknown is that it is inherently difficult to study processes at surfaces under relevant conditions. For a catalytic system that is in interaction https://doi.org/10.51167/ice00009
13 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 with adsorbates, depending on the mode of operation, spectroscopic signals are generally of low relative intensity. This holds true both for surface-sensitive spectroscopies, and bulk techniques. Figure 1 shows some applications and limitations of commonly applied spectroscopic techniques, X-ray absorption spectroscopy (XAS) and infrared (IR) spectroscopy, to study catalytic reactions. Firstly so, they are limited because the exposed surface-fractions of the metals that comprise nanoparticles are often in the singledigit percentile, as is the fraction of Brønsted acid sites of a zeolite. For example, an 8 nm Ni nanoparticle consists of approximately 25,000 atoms , of which approximately 0.1 are surface atoms. Secondly, spectral information is often heavily clouded by the least active species  as different types of sites, or surface fractions, have different interactions with adsorbates. Furthermore, of the relatively small fraction of exposed surface, an even smaller fraction does the actual job . In practice, this means that the majority of the signals in a spectroscopic measurement come from the molecules that are the most stable (i.e., the least reactive), instead of the molecules that are undergoing reaction or, in other words, “spectator species” mask active species. Thirdly, surfaces and in particular nanoparticles are structurally highly dynamic under the elevated temperatures and pressures at which they are often applied, and particularly when exposed to adsorbates or reactants . To summarize, our fundamental knowledge of the interaction of adsorbates with nanoparticles is lacking due to: 1. Small spectroscopic signal changes in noisy environments 2. Broad and convoluted signals 3. Adsorbate-sur face systems change dynamica l ly, particularly so as a result of the processes under study. 1.2 Past and present approaches For these reasons, an overwhelming majority of studies in the literature have oversimplified the systems under study, for example, by using single crystal facets, studied under ultra-high vacuum conditions (an approach that is termed surface science) [3, 7-11]. These approaches have yielded many of the important insights on which we currently build our understanding. However, in recent years it has become increasingly apparent that adsorbates and surfaces have completely different physical parameters, such as surface stability, mobility of species, surface coverages, and surface energies, at relevant conditions of pressure and temperature [3, 12, 13]. Several surface-science groups around the world are attempting to close this gap by performing surface-science experiments at less high-vacuum conditions, approaching “ambient” pressures [13–15]. However, many of these approaches still make use of model surfaces rather than the supported nanoparticles that are used in applications, and these measurements are generally performed in a static manner. When a static measurement is performed on a surface that is in chemical and physical equilibrium, much information is lost as to how this equilibrium was reached. That is, for a given reaction intermediate to cover a surface, often several sequential elementary reaction steps have occurred on the time scale of milliseconds to seconds, each of which affect the surface and subsequent steps [1, 16]. Notable approaches to studymodel surfaces at conditionsmore relevant to applications are, for example, high-pressure scanning tunneling microscopy (STM) of model hydrodesulfurization catalysts working together with an industrial partner [17, 18]. The same group is working on integrating STM and Figure 1. Two ensemble (bulk) spectroscopy types (X-ray absorption spectroscopy, and infrared absorption spectroscopy) which can be applied at high pressures and temperatures, and at high temporal resolution and their limitations in the field of study.
14 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 atomic force microscopy (AFM) in a single microscope, applicable at high pressures. Furthermore, static microspectroscopy measurements have been performed in gaseous environments with spatial resolutions of down to 20–30 nm . Notable efforts from catalysis company Haldor Topsøe include a focus on advancing high-resolution transmission electron microscopy (HR-TEM) for heterogeneous catalysis applications [20, 21]. Nevertheless, these approaches still often study model materials, such as single crystal slabs, rather than industrial catalysts, which contain mesopores, micropores and even nanopores, and are combinations of several different materials, including for example promotors. Furthermore, while temperature may be (slightly) increased, pressure is disregarded, or vice versa. The operando spectroscopy approach is an approach that is gaining more and more traction after its introduction approximately 20 years ago , particularly due to these considerations. The operando spectroscopy approach is to study a catalyst at work, under reaction conditions, and while quantifying the products in order to ensure relevance. Nevertheless, this approach is plagued (at least) by the problems 1–3 listed above. 2. Modulated excitation spectroscopy 2.1 Principles and background A possible way to overcome these limitations is by taking the working principle of lock-in amplifiers. Lock-in amplifiers are among the most widely used general tools in physics and engineering labs, generally used to measure the amplitude and phase of an oscillating electrical system or, more specifically, to extract a very small electronic measurement signal from e.g., the utility frequency of -50-60 MHz by use of a known carrier-wave frequency. The working principle is to take the input signal along with the unwanted noise, combine it with a known reference signal and put this through a frequency mixer, after which the desired frequency is filtered out using an adjustable low-pass filter. This entire principle of mixing, and filtering is called phase-sensitive detection (PSD) . This phase-sensitive detection follows the following equation [24-28]: (1) with A, the original signal as a function of energy E and time t, ФPSD the modulation phase angle, k the harmonic (k = 1, fundamental harmonic), and T = 1/ω as the demodulation period, see also Figure 2. Steps have been made to combine the methodology with relevant systems in simple heterogeneous catalytic systems, most notably by spectroscopists at the Swiss Light Source, such as Ferri and Nachtegaal [27,29]. The “phase-sensitive” phrasing stems from the principle that (aside from any component which has a different frequency than the reference signal) any out-of-phase component which has the same frequency as the reference signal is attenuated, which can mathematically be explained by the functional orthogonality of sine functions. That is, if you multiply a sine with a cosine function it is attenuated. As Fourier’s theorem states that any function can be described as the sum of sine and cosine functions, one might expect the cosine to also appear in Eq. 1. However, by the addition of the phase shift and phase angle components to Eq. 1 this Fourier property can be simulated manually and therefore manipulated. 2.2 Uses and examples in catalysis One might deduce from the explanation of the lock-in amplifier that the addition of a known reference signal to a noisy system allows for the demodulation of very small signal fractions (see point 1 in Section 1.1 above). Let the signal in this case be the convoluted spectroscopic signal from a catalytically active supported Pt nanoparticle system, and the known reference signal be a periodic excitation of this system with alternating gas pulses; O2 and CO. The frequency of the external stimulation ω and the demodulation phase angle Φk PSD (which in practice is an arbitrary input) are applied leading to the attenuation of all components of the original signal that do not follow ω , such as the contribution of “spectator” signal (the spectral species which are present but do not partake in the reaction). For example, upon the examination of this hypothetical Pt system with hard-X-rays, we can cancel the signal from inorganic atoms that comprise the bulk of the Pt nanoparticles (in the case that they do not respond to the external gas stimulation) or, by using infrared spectroscopy, we can distinguish between vibrations from active and inactive organic catalytic intermediates thereby elucidating side reactions from the main active reaction pathways (see, for example, Figure 3). Figure 2. A scheme showing the principle behind modulated-excitation spectroscopy.
15 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 One might imagine the difficulty in applying an exact squarewave function of gas pulses, yet as stated above this approach to demodulation still holds valid due to Fourier’s theorem stating that any arbitrary function can be described by an arbitrary combination of sine and cosine functions. In essence, phase-sensitive detection is a Fourier transformation, with the addition of phase sensitivity to reduce noise. Some benefits of such analysis have already been proven by the study of basic systems such as the reversible oxidation of noble metals , where the sensitivity of such detection was greatly enhanced. In the case of the application of such spectroscopies to the complex and demanding systems that are relevant to catalysis, it may have some additional benefits. For example, after demodulation, for every phase angle one obtains one demodulated spectrum, and for every higher harmonic we obtain another demodulated spectrum. In principle one should be able to use the phase angle and higher harmonic as a descriptor for the kinetic behavior of the spectral signal under investigation, as the degree of attenuation is dependent on the phase offset with respect to the initial pulse onset and harmonicity. Via simulation of spectroscopic data, it was shown that transient species possessing fast kinetics are enhanced relative to those possessing slower kinetics in the fundamental harmonic . As such, by examining higher harmonics one should – in principle – be able to distinguish species with faster kinetics from those with slower. 2.3 Perspective The past two decades have seen significant improvements in the application of spectroscopic techniques such as infrared and UV-Vis spectroscopy, or X-ray absorption spectroscopy to study catalysis at work, an approach that is termed operando spectroscopy. Nevertheless, with traditional application of such spectroscopic techniques it can be very difficult to determine the most relevant information (active sites, active reaction intermediates, active phases, and even dynamic changes) due to the high degree of complexity of the catalystreactant matrix e.g., in terms of pressure, temperature, and material complexity. Advances in the combination of spectroscopic techniques with increasingly higher time resolution, along with e.g., operando spectroscopic reactors, digital valve control and a posteriori data analysis, offer novel overall approaches to study catalytic reactions at work. In this article some examples have been given of achievable results. In our new research group at the Technion these, and several other approaches, will be developed and applied with the overall goal of obtaining novel fundamental insights into catalytic processes and driving the discovery time of new catalysts and materials down significantly. References 1. J. A. Dumesic, G. W. Huber, M. Boudart, in Handbook of Heterogeneous Catalysis, ed. G. Ertl, H. KnÖzinger, F. Schüth, J. Weitkamp, Wiley-VCH, Weinheim, 2nd edn., 2008, 1445-1462. 2. H. F. Rase, Handbook of Commercial Catalysts - Heterogeneous Catalysts, CRC Press, Boca Raton, 2000. 3. G. A. Somorjai and K. McCrea, Appl. Catal. A Gen., 2001, 222, 3–18. 4. C. Vogt, E. Groeneveld, G. Kamsma, M. Nachtegaal, L. Lu, C. J. Kiely, P. H. Berben, F. Meirer and B. M. Weckhuysen, Nat. Catal., 2018, 1, 127–134. 5. S. Bordiga, E. Groppo, G. Agostini, J. A. Van Bokhoven and C. Lamberti, Chem. Rev., 2013, 113, 1736–1850. 6. H. S. Taylor, Proc. R. Soc., 1925, 108, 105–111. 7. G. A. Somorjai, A. M. Contreras, M. Montano and R. M. Rioux, Proc. Natl. Acad. Sci., 2006, 103, 10577–10583. 8. J. Wolff, A. G. Papathanasiou, I. G. Kevrekidis, H. H. Rotermund and G. Ertl, Science, 2001, 294, 134–137. 9. G. Ertl, Angew. Chem. Int. Ed., 2008, 47, 3524–3535. 10. G. Kleinle, V. Penka, R. J. Behm, G. Ertl and W. Moritz, Phys. Rev. Lett., 1987, 58, 148–151. 11. G. A. Somorjai, Catal. Letters, 1992, 12, 17–34. Figure 3. Schematic example of possible results with modulated excitation type experimentation. FT-IR spectra before and after demodulation, and the separation of active and spectator species. Top half of figure is reproduced with permission from reference .
16 Scientific Article The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 12. J. Qian, Q. An, A. Fortunelli, R. J. Nielsen and W. A. Goddard, J. Am. Chem. Soc., 2018, 140, 6288–6297. 13. B. Eren, D. Zherebetskyy, L. L. Patera, C. H. Wu, H. Bluhm, C. Africh, L.-W. Wang, G. A. Somorjai and M. Salmeron, Science, 2016, 351, 475–478. 14. F. Tao, S. Dag, L.-W. Wang, Z. Liu, D. R. Butcher, H. Bluhm, M. Salmeron and G. A. Somorjai, Science, 2010, 327, 850–853. 15. C. Heine, B. A. J. Lechner, H. Bluhm and M. Salmeron, J. Am. Chem. Soc., 2016, 138, 13246–13252. 16. J. A. Dumesic, G. W. Huber, M. Boudart, in Handbook of Heterogeneous Catalysis, ed. G. Ertl, H. KnÖzinger, F. Schüth, J. Weitkamp, Wiley-VCH, Weinheim, 2nd edn., 2008. 17. R. V. Mom, J. N. Louwen, J. W. M. Frenken and I. M. N. Groot, Nat. Commun., 2019, 10, 2546. 18. J. W. M. Frenken and I. M. N. Groot, MRS Bull., 2017, 42, 834– 841. 19. C. Y. Wu, W. J. Wolf, Y. Levartovsky, H. A. Bechtel, M. C. Martin, F. D. Toste and E. Gross, Nature, 2017, 541, 511–515. 20. T. W. Hansen, J. B. Wagner, P. L. Hansen, S. Dahl, H. Topsøe and C. J. H. Jacobsen, Science, 2001, 294, 1508–1510. 21. J. B. Wagner, P. L. Hansen, A. M. Molenbroek, H. Topsøe, B. S. Clausen and S. Helveg, J. Phys. Chem. B, 2003, 107, 7753–7758. 22. B. M. Weckhuysen, Chem. Commun., 2002, 97–110. 23. Principles of lock-in detection and the state of the art, 2016, Zurich Instruments. 24. R. Kopelent, J. A. Van Bokhoven, J. Szlachetko, J. Edebeli, C. Paun, M. Nachtegaal and O. V. Safonova, Angew. Chem. Int. Ed., 2015, 54, 8728–8731. 25. B. Mutz, A. Gänzler, M. Nachtegaal, O. M ller, R. Frahm, W. Kleist and J.-D. Grunwaldt, Catalysts, 2017, 7, 279. 26. V. Marchionni, D. Ferri, O. Kröcher and A. Wokaun, Anal. Chem., 2017, 89, 5801–5809. 27. D. Ferri, M. S. Kumar, R. Wirz, A. Eyssler, O. Korsak, P. Hug, A. Weidenkaffa and M. A. Newton, Phys. Chem. Chem. Phys. PCCP, 2010, 12, 5634–5646. 28. P. M ller and I. Hermans, Ind. Eng. Chem. Res., 2017, 56, 1123– 1136. 29. C. F. J. König, J. A. Van Bokhoven, T. J. Schildhauer and M. Nachtegaal, J. Phys. Chem. C, 2012, 116, 19857–19866. 30. G. L. Chiarello and D. Ferri, Phys. Chem. Chem. Phys., 2015, 17, 10579–10591. 31. C. Vogt, E. B. Sterk, M. Monai, J. Palle, B. Zijlstra, E. Groeneveld, P. H. Berben, J. M. Boereboom, E. J. M. Hensen, F. Meirer, I. A. W. Filot and B. M. Weckhuysen, Nat. Commun, 2019, 10, 5330.
17 The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782
18 The Israel Chemist and Chemical Engineer Issue 8 · November 2021 · Kislev 5782 History of Chemistry Articles BobWeintraub was born in Brooklyn, New York andmade aliyah in 1975 to Beer Sheva, where he remained. He earned the PhD in Physical Chemistry from MIT and the Diploma in Library Science from the Hebrew University of Jerusalem. He held positions in scientific and technical librarianship in industry, hospital and academic institutions. He is now retired. He has an interest in the history of chemistry. Sidney Loeb and the origins of pressure retarded osmosis Bob Weintraub POB 5979, Beer-Sheva 8415901 Email: [email protected] Abstract In 1973, Sidney Loeb invented the process for generating power that he called Pressure Retarded Osmosis (PRO). PRO was invented under the Israeli government program of applied research for the utilization of arid climates, local raw materials and natural resources. From 2003 to 2013, a major attempt was made to develop PRO into a commercially viable power source but the project was not successful. Advances in membrane and other technologies have now led to renewed interest in its commercialization. The origins of PRO and personal recollections of the author are presented. Introduction Prof. Sidney Loeb (1917-2008) came to Beer-Sheva in 1967 to teach reverse osmosis (RO) technology at the Negev Institutes for AridZone Research, later part of the Ben-GurionUniversity of the Negev (BGU). Loeb is best known as the co-inventor in 1964, together with S. Sourirajan, of practical reverse osmosis, the most important method of water desalination . Later, he made aliya, accepting a position at the newly established BGU. I have previously reported on this period as it relates to Loeb’s work in Israel on RO. The interested reader is referred to that article Chemistry in Israel, December 2001, (8), p 8-9. In 1973, Loeb invented the process for generating power that he called pressure retarded osmosis, or PRO, at Ben-Gurion University of the Negev. The concept of producing power from the mixing of fresh and salt water was first suggested by R. E. Pattle in 1954 . Loeb invented a process to harvest this energy source. Sid and I were close friends and we would discuss the invention. In the mid-1970’s we both worked at the same research center of Ben-Gurion University. I joined the center in 1975 during the time that research on PRO was being carried out. I saw how that unique research environment combined with Sid’s experience on related systems and, most importantly, his engineering genius, all came together in PRO (see Figure 1). The invention met the primary goal of the institute, applied research for the utilization of arid climates, local raw materials and natural resources, to the benefit of both Israel and of other arid areas. https://doi.org/10.51167/ice00010www.digipage.co.il