Categoriearchief: Elders gepubliceerd

Process Nano-Technology

Appeared earlier in TG magazine 6 of 2003.

At first glance, the title may seem a contradictio in términis because for nano-technology the relevant length scale is the nanometer – one billionth of a meter or the length of a row of 10 hydrogen atoms laid side by side – whereas for process technology the relevant length scale is meters or beyond. It is exactly this discrepancy of more than nine orders of magnitude in length scales that allows the new direction in chemical process technology that will be discussed below: in essence another way of Nature Inspired Chemical Engineering (NICE), or even better, Nature Inspired Colloidal Systems (NICS), as a new direction for our Colloid Science group.


“It is a staggeringly small world that is below,” said the famous physicist Richard Feynman in his 1959 speech about nano-technology There’s Plenty of Room at the Bottom [1]. “In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction”. Indeed, 40 years after, nano-technologists have come quite far and it is not easy to cover all the contributions that have been made. Surely nano-tubes come to mind as well as molecular motors, but also improvements in sub-micron lithography fall within the realm of nano-technology. A specific definition of this new field is however not so easily given. A generic definition would involve a characteristic length scale of about one na­no­meter. Quite unlike their wont, physicists do not bother too much about a definition and name nano-technology whatever lets them (i) Get essentially every atom in the right place; (ii) Make almost any structure consistent with the laws of physics that one can specify in molecular detail; (iii) Have manufacturing costs not greatly exceeding the cost of the required raw material and energy. Two main concepts associated with nano-technology are positional assembly and self-replication. The first concept implies an interest in molecular robotics. i.e. robotic devices that are molecular both in their size and precision. Self-replication on the other hand is of course required to scale up the production of the materials.

Contemporary chemical processes are crude at the molecular level moving around atoms in bulk quantities. It is the Law of Large Numbers that governs them and our main control mechanisms involve bulk properties such as flow rates and temperature. Process technology indeed does look like a giant’s attempt to make an origami butterfly. But surely, this is not the whole story about chemical process technology. There are many processes that make use of colloidal systems such as emulsions and particulate dispersions. Examples are easily found in the food or paint industry. For the relevant characteristic length scale one usually takes the dimension of the particles that constitute colloidal systems. This yields length scales in the range from tenths of nanometers up to hundreds of micrometers.

Interfacial Engineering

Fig. 1:    Schematic representation of the principle of charge stabilization. The diffuse double layer around the colloidal particles consists of co-ions (closed) and counter-ions (open). Upon closer approach the bare charge of the particles becomes less screened.

Most, if not all, properties of the colloidal systems derive from the interface between the dispersed phase and the continuous phase. The essential task of the interface is to keep the two phases separated and is commonly known as colloidal stabilization; see e.g. [2,3]. There are basically two different methods to achieve colloidal stability. One method involves dissociated groups at the interface that render electrical charge to the interface and the particle as a whole. Since equally charged objects repel each other, this charge prevents particles from aggregating or coalescing. The counter ions and added salt ions will, however, accumulate close to the interface in what is called the diffuse double layer, see figure 1. They do so in such a way as to diminish the effect of the charge over larger distances; a phenomenon called screening. The associated DLVO-theory is due to Derjaguin, Landau, Verwey and Overbeek. The multitude of contributions to this subject by Dutch colloid scientists is reflected by the two last names mentioned in the acronym DLVO by which this theory is known. The Debye length measures the thickness of the electrical double layer that, depending on ionic strength, varies from several tenths of nanometers down to less than a nanometer. The other method is called steric stabilization and, despite its frequent use in industrial processes, much less is formally known on its mechanism of which the essence is depicted in figure 2. The adsorbed or chemically grafted polymer chains prevent close encounters of colloidal particles. A (too) simple argument for the repulsion lies in the gain of the free energy of mixing when the polymer chains of neighboring particles are overlapping. The thickness of an adsorbed or grafted polymer layer can be varied at will. Since its function is to shield the omnipresent Van der Waals attraction between the colloidal particles, a thickness of a few nanometers is sufficient.

Fig. 2 Schematic representation of the principle of steric stabilization. Upon closer approach the polymer chains would mix which is entropically unfavorable.

The characteristic size of the colloidal interface is in the nanometer regime. And there is quite some of it! In a system with the rather modest fill factor of 10% consisting of colloidal particles of a typical size of one micrometer there is about 300 m2 of interfacial area per liter. Interfacial Engineering, a word coined by Stokes and Evans [3] as an alternative to the rather old fashioned name of colloid and interface science, therefore certainly belongs to the nano-technologies!

A classical example where interfacial engineering plays a dominant role on an industrial scale is emulsion polymerization for the preparation of polymer particles (latex) by radical polymerization. The dispersed phase is initially formed by the monomers. A small amount of monomers, in equilibrium with the dispersed monomer, is dissolved in the continuous phase. The initiator, also in the continuous water phase, starts the polymerization by penetrating through the particle surfactant membranes. Some initiator may encounter monomer in the continuous phase and start polymerization there, but at some point the growing molecules become insoluble and form surfactant coated polymer particles themselves. Excess heat is easily removed through the continuous water phase. Depletion of monomer terminates the reactions. The process is fully controlled by the interface and by the surfactant molecules that constitute the interface. Moreover, even at quite significant volume fractions the viscosity if the dispersion is quite low which renders processing extremely simple. Modern developments include the use of spherical and bicontinuous micro emulsions for polymer and inorganic particle templating.

Controlled Release and Separation

A multitude of present day products, such as high quality paper or water borne paints, are made by sophisticated use of interfacial engineering. In all these products and processes the interface plays the simple role of separating two phases, albeit a given level of permeability to certain constituents is programmed. Recently, new functions have been introduced and one has made interfaces that are responsive to their environment in a predetermined manner. An example is the potion containing cod liver oil, which of old is fed to young children in winter to supplement their vitamin A and D intake. In wintertime there is less sunlight and hence the body production of these vitamins is low, for instance causing rachitis.  Few children are fond of this potion in its classical form. The present form is in fact an emulsion where the yellow oil is dispersed in an orange juice. Due to the interface, the badly tasting oil will not free in the mouth. Upon digestion, the interfacial membranes in the emulsion are destroyed and the cod liver oil can release the vitamin in the intestines.

Nowadays, many pharmaceuticals make use of this principle of controlled release. However, when controlled release is one way to govern a process, then controlled separation would be another. The exposure of an absorbent when exterior conditions are fitting is also a technique and it is already used as a means to catch poisonous molecules before these can permeate into the blood circulation.

Nano-structured Interfaces

Much more control would be attainable if it were possible to integrate more functions in the interfaces. Such nano-structured interfaces could respond to changes in their environment in a predetermined manner, much in the same way as the simple examples given above. More interestingly, these nano-devices could also be made to respond to external signals brought about by magnetic fields or light. Imagine for instance two solutions con­tai­ning strong reagents. Simply mixing them would yield incomplete reaction and uncontrolled heat production. These may become well mixed, without reacting, when one component is dispersed in impermeable colloidally sized capsules. At some stage in the process, where mixing is deemed sufficient, the permeability of the capsules is increased proportional to an external signal. The reaction will now run in a controlled manner under optimal conditions. This maybe sounds too fantastic, but one way to achieve this would be to make the capsules of a material that can be selectively modified by the action of microwaves or ultra­violet light.

Fig. 3 Synthesis of a nano-capsule by sequential adsorption of counter charged polyelectrolyte layers and subsequent removal of the core particle.

What is needed to turn this fantasy into reality is first of all methods to make nano-structured interfaces. Currently, there are quite some promising developments in that direction. One such development uses layer-by-layer deposition of alternately cationic and anionic polyelectrolyte layers on a core particle. The core particle can be a polymer particle itself, or a metal or inorganic particle, see fig. 3. The result is a multilayer core-shell particle with predetermined surface properties. In an extension of the technique, one removes the core particle after which the shell remains of which the permeability can be tuned by external means. Another development involves the adsorption of nano-sized particles onto the surface of a colloidal particle, see fig. 4. Under the right conditions, capillarity forces the nano-particles to fully cover the colloidal particle. Extensions of this technique involve the fusion of the nano-particles after which a core-shell particle with specific properties is created. Another extension is, just as with the polyelectrolyte coated particles, the removal of the core after which a so-called colloidosome is created. The size of the shell particles depends on the size of the initiating core particle. These above examples deal with so-called self-assembling systems but of course direct synthesis constitutes another possibility.

Fig. 4: Synthesis of nano-structured colloids by adsorption of anano-particle monolayer. Subsequent removal of the core particleleaves a capsule (top right), and fusion of the adsorbed monolayerresults in a coreshell particle (bottom right).

The way nano-structured interfaces are made already suggests methods to control them. The multilayer polyelectrolyte capsules can be controlled by pH or ionic strength whereas the colloidosomes are quite insensitive to these variables. Other methods to induce a particular response in nano-structured interfaces require the incorporation of, for instance, inorganic particles or more complicated structures. Some macromolecules such as present in biological cells could also introduce useful functions. In this sense, nano-structured interfaces are not new at all as Nature has designed its systems likewise.

Control of processes by means of nano-structured interfaces can be based on two complementary approaches: (i) extreme control, an internal stabilization by coupling rate phenomena to the environmental variables such as concentrations; and (ii) process control, by using the functions of the interfaces either as sensors, as actuators, or both. The dynamics of the system will be completely different from what is presently known. It will for instance not be possible to treat the system as a continuum and it will be necessary to find ways of including nano-devi­ces that are acting almost at the molecular level into a complete system description. It poses a serious challenge to process engineers to devise new models to perform process nano-control. Certainly, there is the potential of more powerful process control with the added degrees of freedom provided by the nano-structured interfaces.


Nano-structured interfaces also provide a new pathway to design and operate processes in a sustainable manner according to a philosophy of closed material cycles and maximum energy efficiency. At first glance, there is the disadvantage of introducing components into the product that were used to build the nano-structured interfaces. It might contaminate the product and it may even pose a hazard. In terms of mass, the amount of these materials is quite low and in many cases the end product often comes in dispersed form anyway. The cost involved in making the nano-structured interfaces should be recovered by the added value to the products.

However, the nano-structured interfaces can actually be used to advantage. Firstly, one may contain toxic or otherwise harmful reagents in impermeable capsules so as to transfer the material in a safe and efficient way towards the relevant process step. Secondly, one might conceive the possibility of capturing selectively some products in capsules so as to separate them efficiently from the environment. Essentially, once a process is properly designed, sustainability can be achieved at any level.

More fantasy

Once the way to make nano-structured is known, many more tasks may become feasible. Some of those derive back to controlled release and separation between continuous and dispersed phase. And there is no limit to the number of dispersed phases. It is easy to conceive multiphase systems where exchange between phases is controlled by internal or external means. But the interface can act as a scavenger itself. In order to achieve that, we can dress the interface with molecular entities, in essence nano-devices, that complex specific molecular species such as contaminations. Recently, new molecules have been designed that allow the control over complexation by means of light. In one conformation the molecule is able to complex a metal ion and in the other not. Transition between these two conformers is affected by light.

An interesting possibility is to design nano-structured interfaces in such a way that they could also be used to bring molecules in the right proximity to synthesize special molecules, so as to produce for instance straight alkanes from methane without producing syngas. This would require more accurate positioning of groups within the interface. With present day polymerisation methods that are used to make for instance block copolymers this might become reality as well. Extending this idea, nano-devices could act as catalysts themselves or allow the external control of the action of catalysts. And similarly nano-devices could be used to control the number of crystallization nucleation sites and maybe even crystal shape and maximum size comes to mind.


The ideas presented above, of which some are actively being researched, constitute a new challenge to chemical process technology. It is in fact a combination of old and new science because colloidal stability will remain an issue, in particular when interfaces are changing their function. The challenge to good old colloid science is to rejuvenate with the newly available nano-possibilities while treasuring its scientific standards with respect to colloidal stability.

Let’s now come back to what the physicists believed nano-technology would allow them to do and see whether the above discussed process nano-technology. The first issue was “Getting essentially every atom in the right place”. Surely this is an easier job with fluids than with the solid state, but nano-structured interfaces indeed can do just that. But chemists can go further, as it is within their capabilities to synthesize new molecules. The second issue was “Making almost any structure consistent with the laws of physics that one can specify in molecular detail”. The relevant physical laws are those of quantum mechanics. Even though in principle these laws are known, their predictive power in chemistry is rather limited. In actual fact, chemists often devise methods that seem to lure quantum chemistry. Finally, the third issue was “Have manufacturing costs not greatly exceeding the cost of the required raw material and energy”. As argued before, the cost involved in making and using nano-structured interfaces should at least balance with the added value of the resulting products. In addition, legislation may make the difference, as was the case for water borne paints. The necessity to produce a solvent-free product made manufacturers introduce dispersions of binder and pigment despite their intrinsically higher cost. In conclusion, there is no contradictio in términis.


  • Feynman RP, see
  • Frens G, Cahiers Fysische Chemie, Delft University Press 2001.
  • Stokes RJ and Evans DF, Fundamentals of Interfacial Engineering, Jossey-Bass 1996.


Voorwoord bij TG almanak 106 in 2006.

Beste TG’ers en belangstellenden,

Het is een indrukwekkende traditie, de “Almanak van het Technologisch Gezelschap”. Nummer 106 alweer. Gefeliciteerd daarmee.

Als we ervan uitgaan dat elk jaar een nieuwe almanak is verschenen, dan zou in 1901 de eerste almanak zijn uitgegeven. Dat is precies het jaar waarin Jacobus Henricus van ’t Hoff, als eerste, de Nobelprijs voor de scheikunde kreeg. Voordat het zover was heeft van ’t Hoff een behoorlijk moeilijke tijd gehad. Terwijl hij uit alle macht op zoek was naar een fatsoenlijke aanstelling publiceerde hij het pamflet waarin hij voorstelde om moleculen niet als 2-dimensio­nale maar als 3-dimensionale objecten te zien. Daarmee kon hij allerlei tot dan toe onverklaarbare feiten verklaren, zoals het verschil in optische activiteit van glucose en fructose. Het was een gewaagd stuk en het ontlokte de organisch chemicus Kolbe een cynisch essay getiteld “de tekenen der tijden II” dat in mei 1877 werd gepubliceerd. Daarin betichtte hij van ’t Hoff er van “Pegasus” beklommen te hebben voor een gewaagde tocht door het “chemische Parnassus” vanwaar het hem toescheen dat atomen gerangschikt zijn in ruimtelijke structuren. Kolbe was van mening dat wetenschappers zich tot de feiten moesten beperken en betoogde dat het niet alleen onwetenschappelijk maar ook schadelijk is voor wetenschappers om de fantasie de vrije loop te laten. Dat kwam hard aan!

Maar van ’t Hoff sloeg keihard terug met een flitsende inaugurele rede in 1878 waarin hij betoogde dat fantasie en wetenschap niet zonder elkaar kunnen. Bij elke wetenschappelijke handeling is er

  • de keuze van wat en wanneer waar te nemen;
  • de keuze om de experimentele onderzoeksomstandigheden te veranderen;
  • het uitvinden van nieuwe onderzoeksmethoden;
  • de herkenning van onverwachte patronen in waarnemingen;
  • het uitvinden van een hypothese om de waarnemingen te verklaren

Einstein verwoordde het veel krachtiger “Verbeelding is belangrijker dan Kennis”.

Voor technologen, uw gezelschap dus, is verbeelding minstens zo belangrijk als kennis: creativiteit noemen we dat nu. De PublicatCie die deze almanak heeft samengesteld had daar zeker niet te kort aan, u zult het zien als u er in bladert. Het thema wordt geïntroduceerd  als “iets dat aandacht trekt, met weerlicht en discolicht. Vanzelfsprekend moet bij deze presentatie ook de aandacht worden getrokken voor het thema; dat doen we zo …

Jacobus Hendrikus van ‘t Hoff

Eerder verschenen in TG-Magazine 17-1 van oktober 2013.

J.H. van ‘t Hoff door Marian Nugteren (201 3)

De “Procestechnologie” heeft J.H. van ‘t Hoff als icoon verkozen, maar waarom eigenlijk? Van ’t Hoff staat bekend als de eerste – en bovendien de eerste Nederlandse – Nobelprijswinnaar in de Chemie. Hij is het meest bekend voor zijn uitwerking van de consequenties van een drie-dimen-sionale structuur van moleculen. Zijn verdere werk betrof reactiekinetiek en colligatieve verschijnselen zoals de osmotische druk. Onderwerpen die weliswaar dichter bij de procestechnologie staan dan de moleculaire structuur, maar toch niet het hart ervan vormen. De “Procestechnologie” zelf noemt als belangrijkste feit dat van ’t Hoff in Delft heeft gestudeerd maar als dat de enige reden is dan is dat wel een erg gezochte.

Is de keuze dan niet terecht geweest? Niets is minder waar! Er is een hele goede reden waarom juist van ’t Hoff gekozen zou moeten worden. Van ’t Hoff kwam immers tot het voorstellen van een driedimensionale molecuulstructuur doordat hij er achter kwam dat moleculen met precies dezelfde atoomgetallen toch verschillende fysische eigenschappen hadden en op basis daarvan
gescheiden konden worden. Hij zelf werkte het voorbeeld van melkzuur uit, waarvan een links- en een rechtsdraaiende variant
bestaan. En scheiding, dat is de kern van de procestechnologie. Wat dat betreft is het uiterst toepasselijk dat wij Nederlanders spreken van scheikunde voor wat in andere landen als chemie wordt betiteld. De andere bijdragen van van ’t Hoff, aan de reactiekinetiek en de colligatieve verschijnselen, komen daarmee ook beter tot hun recht.

En er is nog meer! Nadat van ’t Hoff zijn voorstel had gepubliceerd werd dat door de zittende chemici veroordeeld als fantasie. De organisch chemicus Kolbe schreef “Er hat es bequemer erachtet, den Pegasus (offenbar der Thierartzneischule entlehnt) zu besteigen, und zu verkünden, wie ihm auf dem durch kühnen Flug erklommenen chemischen Parnas die Atomen im Weltenraume gelagert erschienen sind …”. Op al die aantijgingen heeft van ’t Hoff niet gereageerd. Allengs raakte zijn voorstel meer geaccepteerd en in 1878 aanvaardde hij het ambt van hoogleraar in Amsterdam. In de inaugurele rede die hij toen uitsprak reageerde hij voor de eerste keer op alle aantijgingen uit het verleden. De titel van de rede was “de verbeeldingskracht in de wetenschap” en daarin zette hij nauwkeurig uiteen welke belangrijke rol fantasie in de wetenschap speelt. Velen hebben, voor en na hem, aangegeven dat creativiteit in de wetenschap belangrijk is voor de ontwikkeling, maar van ’t Hoff
gaf heel nauwkeurig aan dat het om een samenspel tussen kennis en creativiteit gaat: pas als men het wezen van de bekende verschijnselen kent kan men deze verweven tot nieuwe combinaties met nog niet eerder gerealiseerde eigenschappen.

Creativiteit en technologie zijn ook sterk verweven. Als de gemeente Delft een nieuwe brug over de Schie wil hebben, dan kan zij natuurlijk wat foto’s op het internet bekijken en een geschikte uitkiezen. Bijvoorbeeld de Golden Gate Bridge in San Francisco.
Daarna kan men contact leggen met een aannemer om een op schaal gemaakt model te laten maken zodat die goed past over de Schie. Dat doen gemeentes als Delft toch liever niet, men wil een “eigen” brug en stapt dus naar een architect om een nieuwe – nog niet bestaande – brug te laten ontwerpen die vervolgens door een aannemer geconstrueerd kan worden. Zo ook in de procestechnologie. Als een bedrijf een proces wil veranderen, dan
liefst tot een proces dat nog niet eerder ergens gerealiseerd is en zo mogelijk veel efficiënter is dan alle bestaande processen. Dat is de manier om een voorsprong op andere bedrijven te verwerven die de
realisatie van zo’n proces rechtvaardigt! Dus, als de procestechnologen weer gevraagd wordt om een reden waarom
zij van ’t Hoff verkozen hebben tot hun patroon dan doen zij er goed aan zich eens te verdiepen in zijn werk.

• J.H. van ’t Hoff, Voorstel tot uitbreiding der tegenwoordig in de scheikunde gebruikte structuur-formules in de ruimte: benevens een daarmee samenhangende opmerking omtrent het verband tusschen optisch actief vermogen en chemische constitutie van organische verbindingen, Greven 1874.
• W.J. Hornix en S.H.W.M. Mannaerts, Van t Hoff and the emergence of Chemical Thermodynamics, IOS Press 2001.
• J.H. van ‘t Hoff, De verbeeldingskracht in de wetenschap. P.M. Bazendijk, Rotterdam 1878.

Gert Frens 1937 – 2013

Eerder verschenen in TG Magazine 16-3 in maart 2013.

Gert Frens

Afgelopen februari is onze oud-collega prof. dr. Gert Frens overleden aan de gevolgen van een nare ziekte. Op 16 maart 1988 aanvaardde prof. Frens het ambt van gewoon hoogleraar in de fysische chemie met het uitspreken van de rede Omgaan met het Onbekende. Hij was een markante man die er niet voor schuwde om wat weliswaar zorgvuldig geformuleerde maar niettemin uitdagende, uitspraken te doen om de uitgebluste discussie over een onderwerp open te breken. Dat heeft hem tot een aantal wetenschappelijke successen gebracht waar tot op de dag van vandaag aan gerefereerd wordt!

Ook studenten daagde hij op onnavolgbare wijze uit, waarbij hij het zich als zijn taak zag de eerste Nobelprijswinnaar in de Scheikunde, Jacobus Henricus van ‘t Hoff, tot voorbeeld te stellen wanneer het belang van de Verbeeldingskracht in de Wetenschap* aan de orde was. Graag wees hij hen op hun eigen verantwoordelijkheid bij “de keuze van de weg die hen verder zou voeren dan de horizon van de TU”. De laatste zinsnede is een variatie op zijn lijfspreuk die hij ook als titel gebruikte voor zijn uittreerede uitgesproken op 1 november 2002. Nu siert deze spreuk – zeer gepast – de rouwkaart.

Na zijn vertrek uit Delft heeft prof. Frens zich verdiept in de oorsprong van kabouterverhalen in zijn woonomgeving Brabant, een belangstelling die al was gewekt toen hij werkzaam was bij het Philips Natuurkundig Laboratorium. Steeds minder frequent werden zijn bezoeken aan de TU, waarbij hij het niet kon nalaten ons ervan te overtuigen niet de kortzichtigheid van het management te volgen maar onze eigen lijn voorbij de einder te trekken. Dat is nu helaas definitief afgelopen: hij ruste in vrede! Wij wensen zijn familie veel sterkte toe met het dragen van het gemis van deze bijzondere man.

*Inaugurele rede JH van ‘t Hoff bij het aanvaarding van het hoogleraarsambt aan de Universiteit van Amsterdam, 1878.

Faraday’s gold

Appeared earlier in TG Magazine 22-3 of April 2019.

Faraday’s laboratory in the Royal Institution

Michael Faraday (1751-1867) was fascinated by gold when he found out that ultrathin sheets kept their yellowness upon light reflection as for normal gold but looked green upon transmission. Moreover, when etching the sheets to clean them he found the cleaning liquid to turn ruby red. This urged him to perform an impressive series of experiments the results of which are summarized in his Bakerian lecture to the Royal Society in 1857 [1]. He argued that the ruby red light was due to the strongly wavelength dependent scattering of light that we nowadays know as the Faraday-Tyndall effect. The same effect is also responsible for the blue color of the sky.

My first exposure to colloidal gold – metallic gold particles of submicron size – was in the late 70’s when working as an electronics engineer in the pre-clinical cytology laboratory of the Leiden academic hospital. The gold particles were used for the detection of tropical infections such as schistosomiasis (also known as bilharzia) in what is known as the Enzyme-Linked Immuno-Sorbent Assay  (ELISA). My involvement [2] was the automated readout of trays with cups, one for each essay, in such a way that it could also be used in the lesser equipped laboratories in the tropic areas where the infections were frequently found. The gold particles, coated with a special protein, were responsible for the amplification of signal used for the detection of reaction product from the immune-reaction.

Later on, during my PhD-studies at the Lorentz Institute for Theoretical Physics, I learned more about the properties of submicron-sized metallic particles. Some of my colleagues studied the optical properties of gold nanoparticles when deposited, a bit like truncated spheres, on sapphire. This was done under the supervision of Jan Vlieger and Dick Bedeaux who later on summarized these and many more findings in their monograph on the Optical Properties of Surfaces [3]. The scattering of gold particles that Faraday observed is due to the fact that the surface plasmon resonance causes a sharp absorption peak for light in the visible regime. Other metal particles in that size range do that similarly but due to material properties of gold this happens to be exactly in the visible part of the spectrum. As it is an interfacial property, it critically depends on surface coverage as employed in the ELISA, on the precise shape of the particles as studied by my colleagues and on the close vicinity of a surface.

Although Faraday was smart enough to identify the ruby red color of the cleaning liquid being due to small dispersed gold particles, the willful synthesis of colloidal gold is far from trivial.  Yet, it was one of the  most challenging areas in alchemy to produce the Elixer of Life,  i.e. potable gold; it was searched for during many centuries. Because of gold’s sheer indestructibility, alchemists ascribed a great therapeutic value to Aurum Potabile (drinkable gold). Only in the late 19th century systematic synthesis routes became available through the work of – amongst others –the 1925 Chemistry Nobel Prize winner Richard Zsigmondy.

It was not before the work of our late TG-Member of Honour, professor Gert Frens that controlled nanoparticle synthesis became feasible. As a consequence most Chemical Engineering students that studied in Delft between 1988 and 2002 were exposed to this synthesis route under the guidance of Nico van Westen, the physical chemistry laboratory technician of those days. Frens’ Nature paper [4] on this topic is still heavily being cited and techniques like the one he proposed are used as of today. The reason for this is most probably not in the many samples of Aurum Potabile that are on offer today and sell at rates of the order of 10 euro per ml; it is supposed to heal all illnesses! Despite the high price, the turnover is relatively little. It is also not in the ELISA applications for tropical deceases and others pharmaceutical applications. It is the pregnancy test that is based on ELISA that makes most of the money!

Much later, we ourselves turned our interest in the synthesis of metal nanoparticles. In contrast to the many synthesis routes available, our aim was in making fine, uniformly sized nanoparticles at high yields. Conventional routes provide nanoparticles at relatively low concentration, because at higher concentrations the particles aggregate into larger structures yielding non-uniform particles. While preparing a manuscript [5] on our high yield synthesis of uniformly sized gold nanoparticles, a discussion on the stability time scale of colloidal dispersions developed in which it seemed appropriate to mention the world record in this: the more than 150 year stability of the gold sols prepared by Michael Faraday. For the manuscript at hand, a primary source was needed to refer to but whatever we could find; they were all – at best – secondary sources: information collected by others. One of the more explicit sources, the web site of a well-known, British manufacturer of colloid scientific equipment, mentions the Science Museum in London. Many other sites and documents do likewise.

After sending an electronic request to the conservator of the museum, the following answer was received “The situation is a little bit complex. Until 1999 we had a Faraday exhibit which displayed gold films deposited on watch glasses made by Faraday alongside a tall vessel containing colloidal gold prepared according to the Zsigmondy’s method which otherwise had nothing to do with Faraday.” The interesting consequence of this statement by the conservator of the Science Museum could be that there are quite a few false statements about and very likely even pictures of vessels not older than a few years instead of the 155 as claimed!

Faraday’s Gold

A further message from the conservator of the Science Museum revealed that some gold sols, of which pictures circulate the internet, could be from the Royal Institution (Ri), also in London. The confirmation came from the Curator of Collections who stated that “They are on permanent display within the Michael Faraday Museum area of the Ri, on the lower ground floor of the building, within the only section of Faraday’s original laboratory that still exists.” In addition, pictures were sent of which one accompanies this article and demonstrates the Tyndall effect that betrays colloidal dispersions. So, the gold sols made by Faraday are indeed in London but not in the often mentioned Science Museum but in the museum of the Royal Institution. We are happy to have spent some time finding out the truth about these gold sols and not to have merely repeated a false statement.


  • M. Faraday, Philos. Trans. R. Soc. London, 147 (1857) 145 – 181.
  • A.M. Deelder, G. Koper, R. de Water, et al., Automated measurement of immune galactosidase reactions with a fluorogenic substrate by the aperture defined microvolume measurement method and its potential application to Schistosoma mansoni immune diagnosis. J Immunol. Methods 36 (1980) 269-83.
  • D. Bedeaux and J. Vlieger, Optical Properties of Surfaces, Imperial College Press, London 2002.
  • G. Frens, Controlled Nucleation for the Regulation of Particle Size in Monodisperse Gold Suspensions.
  • K.N.K. Kowlgi, G.J.M. Koper, S.J. Picken, U. Lafont, L. Zhang, B. Norder, Synthesis of magnetic noble metal (nano)particles, Langmuir 27 (2011) 7783–7787.

Het Matrozen- Instituut van de Koninklijke Nederlandsche Zeil- & Roei-Vereeniging

Eerder verschenen in het 107e nummer (augustus 2017) van Amstelland, tijdschrift van de Nederlandse Genealogische Vereniging Afdeling Amsterdam e.o.

Mijn zoektocht naar de verblijfplaatsen van Gerard Koper (1858-1942) was vastgelopen en daarom probeerde ik via zijn halfbroer, Hendrik Cornelis Antonius (Anton) van Amerom (1873-?), verder te komen.

De vader van Anton, Dirk Jan, was de tweede zoon van de Leidse schilder Cornelis Hendrik van Amerom die als stuurman bij de marine eigenlijk nauwelijks in den lande was.
Niettemin zag hij kans bij een bezoek aan den Helder met Gerard’s moeder, Hillegonda Smit een kind te verwekken en vervolgens met haar te trouwen. Bij de geboorte van Anton was hij al niet meer aanwezig. Anton verloor zijn moeder al op zijn tiende en werd daarna door de familie in Amsterdam opgenomen.

Op zijn veertiende werd hij aangenomen bij het Matrozeninstituut te Amsterdam. Doel van dit instituut was: het opleiden van jonge mensen tot matroos voor de koopvaardijschepen.

Staat opgenomen en/of Afgemonsterden, Aangemonsterde en/of Ontslagen Kweekelingen Matrozen Instituut 1893’

Afgezien van een melding van 16 december 1892 dat Anton was vrijgesteld van dienstplicht kon ik lange tijd over Anton ook niets meer vinden. Totdat iemand mij er op wees, dat het Stadsarchief van Amsterdam ook de “Staat van opgenomen en/of afgemonsterde,
aangemonsterde en/of ontslagen kweekelingen” digitaal  beschikbaar had. (Zie illustratie)

Daar kwam ik Anton weer tegen en ik kon hem volgen vanaf zijn aanmelding, via zijn stages bij diverse binnenschepen, totdat hij voor het laatst weer aangemeld werd tegen het einde van het jaar 1892. Echter, bij de vergadering van 23 februari 1893 van het schoolbestuur wordt hij aangemerkt als deserteur. Oktober 1897 wordt hij formeel uitgeschreven, hij wordt kennelijk niet meer verwacht.

Door dit onderzoek weet ik nu, dat Anton deserteert rond februari 1893, zijn halfbroer Gerard eind augustus 1893 hetzelfde doet en dat de vader van Anton, Dirk Jan van Amerom, begin november 1893 van Antwerpen naar Rotterdam vertrekt om vervolgens
maart 1894 weer terug te zijn. Dirk-Jan overlijdt spoedig hierna. Gerard duikt twee jaar later op in Amerika. En van Anton: geen spoor.

Portret van twee negentiende-eeuwse meesters – Leven en werk van Hendrik Jan en Cornelis Hendrik van Amerom, J.C. van Heijningen-de Zoete & H.W.J. van Amerom. Delftse Uitgevers Maatschappij B.V. 1987 (ISBN 978-9065620897)

Obituary Egon Matijevic (27 April 1922 – 20 July 2016)

Appeared earlier in the IACIS Newsletter 63 of January 2017.

Egon Matijevic (right) with Ger Koper (left) and Dick Bedeaux (middle) in the bar during the International Workshop Particles and Surfaces: Fundamentals, Techniques and Applications held in Oud Poelgeest, near Leiden, NL, March 13-16, 1999.

The first time I learnt about Egon Matijevic was while studying the book on light scattering of small particles by Milton Kerker. In many places of the book, references to articles with Matijevic were made in particular where fine particles were discussed. The book as well as the methods to make standard particles by Matijevic were then – and probably still are – widely used in cytology, the study of cells, in particular connected to cancer research.
When I later turned to colloid science, my interest in the work of Matijevic grew again: he was the master in synthesizing particles of all kinds of composition, shapes and sizes. It was very clear that he made Potsdam, NY for a while the Colloid Center of the Universe. It is not for nothing that in this period he was president of the IACIS (1983-1985) and that the IACIS conference of 1985 was held in Potsdam, NY.
When I regularly visited Clarkson University in the late 90’s, Matijevic in his 70s was still very active at Clarkson University and it was very clear that he still played an important role in its leadership. He published 581 papers and held 17 patents. As a mentor, he instructed 15,000 undergraduate students and advised more than 50 PhD candidates, 50 MSc students, and 130 postdoctoral scholars. He delivered more than 70 plenary and keynote lectures at meetings and symposia in dozens of countries worldwide, including the prestigious Faraday Discourse at the Royal Institution in London.
Matijevic was a brilliant scholar whose prolific and inspired research helped to shape modern colloid and surface science. His techniques have found applications in products like the capacitors used in microelectronics, magnetic memories, and the ceramics used in electronic components. It is for this reason that we invited him in 1999 to our workshop on Particles and Surfaces: Fundamentals, Techniques and Applications (see above picture). The organization of the workshop required discussion leaders that were themselves adequately knowledgeable in the field of their session and Matijevic did not disappoint us!
59 years of service to Clarkson University, indeed their oldest and longest serving active, full-time faculty member, have now come to an end. Many like myself will cherish good memories of him despite his at times strong opinions and incredible drive. As IACIS we should be thankful for him taking the leadership as well as organizing an IACIS conference.

Ger Koper

little Hill and BIG Hill

Appeared earlier in the IACIS Newsletter 57 of September 2014.

Terell L. Hill (1917-2014)

On the 23rd of January, Terell Leslie Hill, a very productive scientist and a prolific writer, passed away at the age of 96 in Eugene, Oregon (USA). Many of us have been trained and used his An Introduction to Statistical Thermodynamics, often termed “little Hill”, and looked up the finer detail in Statistical Mechanics: Principles and Selected Applications, “Big Hill”. The younger generation will favor the Statistical Mechanics book by Donald A. McQuarrie, his student, which carries largely the same spirit. The most interesting aspect of this and other work of Terell Hill is that most of his scientific papers were subsequently published as text books, sometimes not much later than the originals appeared in print. It is particularly in this way that his work is much better known than that of contemporaries.


In 2001, Hill coined the term nanothermodynamics as a more fashionable version of the phrase that he used for his work on the Thermodynamics of Small Systems. Indeed, this touches our field, the thermodynamics and statistical mechanics of systems of colloidal particles, polymers, or macromolecules. Specifically, Hill stated: “This subject, which now might appropriately be called nanothermodynamics, was investigated at some length by the author in 1961-3.” (Nanoletters 1 (2001) 111-112).
Other books by Hill, all extremely relevant to our field, are on Free energy transduction, on Cooperativity Theory and on Linear Aggregation Theory. Importantly, all are affordably available through Dover Publications . Without doubt, these little books make Hill’s contribution to modern science BIG!

Ger Koper, NL editor.

The Vroman effect

Appeared earlier in the IACIS Newsletter 56 of April 2014.

Leo Vroman (1915-2014)

On the 22nd of February, Leo Vroman, a prolific poet mainly in Dutch and an illustrator, passed away at the age of 98 in Fort Worth (USA). In 1946, he published his first poems in the Netherlands, and since then has won almost every Dutch literary poetry prize possible. On we find about him: Leo Vroman is the “grand old man” of Dutch poetry. He began writing poems well before World War Two and is still regarded as one of the most lively poets writing in Dutch. This liveliness has much to do with the form and tone of his work, at once loosely conversational and full of ingenious rhymes and playful neologisms.

So, a poet died … and a dutch one at that! Why should we care?

It is indeed not because of his poetry that Leo Vroman is remembered here. He was a scientist, a hematologist to be more precise, that discovered the now called Vroman effect which is exhibited by blood serum protein adsorption. The effect is, that proteins with the highest mobility, and not necessarily with the highest surface affinity, arrive first to the surface and adsorb. The slower proteins arrive later and replace the first-comers when they have a higher surface affinity. This does require some mobility of the already adsorbed proteins. The classical example is when fibrinogen displaces earlier adsorbed proteins on a biopolymer surface to be subsequently replaced by high molecular mass kininogen.
The topic has been studied for over 50 years by now and in 1992 a Festschrift appeared in honour of Vroman’s 75th birthday that was fully devoted to this. As of today scientists are investigating the effect. On the one hand, one tries to find a rationale for the behaviour and on the other hand there is the desire to obtain better control for biomaterial design and maintenance. What is maybe the most striking phenomenon is that protein adsorption is at least partially reversible; for synthetic polymers this is at times hard to achieve. But then, protein replacement is also far from trivial involving “tricks” like head on adsorption of the second to the first, turning around of the complex, and subsequent detachment of the first from the second that is now adsorbed at its bottom. It will be some time from now before such a trick will be performed by a synthetic molecule.
Leo Vroman himself called himself unbelievably lucky to observe the phenomenon and to do further research on it. His driving force was the development of blood-compatible materials, a topic that he followed until late in life. Even in 2009 he contributed a review where he enthusiastically reports on the development of live blood vessels. Indeed, he significantly contributed to his field but the effect is surely of interest to Colloid and Interface Scientists as well.

Ger Koper, NL editor.

“Nonsense, McBain”: a century of micelles

Appeared earlier in the IACIS Newsletter 50 of February 2013.

J.W. McBain (1882-1953)

It was one of these wonderful little COST CM1101 workshops, this one being on Malta the very beginning of this year, where Andreea Pasc from the Université de Lorraine told us that this year micelles are having their hundredth name day. The reference that was given, is a funny one as it does not pop-up when doing a typical literature search. It is actually pointing to a discussion following a lecture by Wolfgang Pauli from Vienna (!) on the viscosity of protein solutions in which James W. McBain indeed uses the term as an alternative to “colloidal ion”, the more common term in those days, in a short contribution entitled Mobility of Highly-charged Micelles.

While searching, one comes across the statement in the header. No doubt one of the present sources is the worthy website by Michael Blandamer of the University of Leicester that serves as a very reliable reference on applied thermodynamics. Fredric Menger’s 1979 review on the structure of micelles is what is mentioned as the source. According to these authors — and all “copycats” — it was made by “a leading physical chemist chairing the meeting” of the Royal Society of London. Of course, it would then be interesting to know who might have made such a bold remark. From the citation one finds that the authors got this information from McBain himself, who in 1926 wrote[1] the — to me — slightly different “… So novel was the finding that when in 1925 some of the evidence for it was presented to the Colloidal Committee for the Advancement of Science in London, it was dismissed by the Chairman, a leading international authority, with the words, “Nonsense, McBain. …” From where Fredric Menger, more than 50 years after McBain’s account, got his information is unclear but it remains to be seen whether the chairman indeed was a physical chemist. She could have been a physicist for that matter …

[1] in “Colloid Chemistry”, Vol. 5, J. Alexander, Ed., Reinhold, New York, 1926, p 102.

Ger Koper, Newsletter Editor