2 electron sensitization & latent image questions

[Photo Engineer]

Keith;

Better clarify "redacted" for some people here.

With big apologies and no criticism intended. Just amused me.

PE

 

[keithwms]

lol

Well sometimes my fingers work faster than my brain :rolleyes:

In this case, 'redacted' just means that these idle musings be worth something to somebody somewhere at some time in the future I was merely speculating about ways to make use of what Kodak knows. There, now the lawyers are going to come after Ron!

 

[Struan Gray]

I'm coming to this a bit late, but for those of you interested in reading research papers, and with an institutional or library subscription to the usual journal pools, I found this paper by I. Gould et al interesting and clearly-written:

Two-Electron Sensitization: A New Concept for Silver Halide Photography
Ian R. Gould, Jerome R. Lenhard, Annabel A. Muenter, Stephen A. Godleski, and Samir Farid
J. Am. Chem. Soc.,122, 11934-11943 (2000)
DOI: 10.1021/ja002274s

Dumping the DOI into google is the fastest way to find the paper.

I have *no* idea how Gould fits into the hiearchy of precedence when compared to internal Kodak research (perhaps P.E. can comment), but his group's paper is a useful read and is as freely available as any other bit of published research.

The technique uses a scavenger molecule to neutralise the positively-charged sensitiser dye before it can grab its electron back from the AgX crystal. Thus far you have only suceeded in reducing reciprocity, but two electron sensitisation goes a step further by using a scavenger which fragments once it has donated an electron to the dye. The clever bit is to make one of the fragments a strong enough reducing agent that it can donate *another* electron to the AgX.

It sounds like black magic, but it is really only a reflection of the fact that many organic molecules in solution have ionisation energies in the infra-red, so if you control where the energy goes, you can ionise two of them with a single photon of visible light.

In general, there is a lot of fundamental research into electronic transfer between wide-band-gap crystals like AgX and organic molecules, but much of it is motivated by applications like solar cells where you don't want the dye molecule to be destroyed or rendered inactive after one absorbtion event. That cuts out the known pathways to 2-electron sensitisation, although the concept has been discussed and people would love to find a working solution - in principle it wouldn't be impossible if you could only find the right combinations of reversible reactions. "Dye sensitised solar cells" is a useful search term if you want the nitty-gritty: it turns up research in engineering, surface science, synchrotron-based research, solid-state physics, organic and physical chemistry and environmental sciences. Still a very hot topic, if not exactly photography.

 

[Photo Engineer]

Annabel is, I believe, credited with the major portion of this work within EK. I have probably met all of them at one time or another and two of them delivered the paper at the last ICPS meeting in Rochester (2006). Annabel was chairperson of the Rochester meeting and Tadeki Tani was the overall conference head. Ray Rogers from APUG was there at the presentation along with Paul Gilman who gave a talk shortly thereafter on the ISO 25,000 film.

I should have remembered that you have to pay for this article or must be a member of the ACS.

PE

 

[AgX]

Struan,

that concept of Anabel Muenter works with donors brought onto the surface of the crystal.
That means it can only take gain out of those holes which succeeded in reaching the surface instead of having recombined, which they are believed to do quite fast.

That was a critique then uttered on that concept.

 

[Alan Johnson]

A free paper on 2-electron sensitization:
http://old.iupac.org/publications/pac/2001/pdf/7303x0455.pdf
An introduction to latent image formation(does not mention the 2 electron process):
Photographic Science, Earl Mitchell 1984 p183

 

[Photo Engineer]

The process uses what is called an FED or Fragmentable Electron Donor. Even that paper does not show it in much detail.

Thanks for the reference. I have a few more plus the abstract to their talk in 2006 if anyone is interested and I manage to find the time to scan it.

PE

 

[Tim Gray]

The process uses what is called an FED or Fragmentable Electron Donor. Even that paper does not show it in much detail.

Thanks for the reference. I have a few more plus the abstract to their talk in 2006 if anyone is interested and I manage to find the time to scan it.

PE

I'd be interested if you have the time. Or just references. I snagged that other one that was referenced - my institution has a subscription.

 

[Photo Engineer]

Tim, all;

In the interests of copyright, I have copied only the title page and one introductory page. As a bonus, I have included the 2 photos using Paul Gilman's 24,000 imaging system. They were in the same journal.

I might add that the journal is about 3 inches thick so the quality of the scans is not perfect. Sorry.

PE

 

[Ray Rogers]

Ray Rogers from APUG

For clarity, I should note that I have no official status as a representative of APUG.
I was just a lowly independent researcher, documenting the events as they occurred.

Ray

 

[Frank Szabo]

lol

Well sometimes my fingers work faster than my brain :rolleyes:

In this case, 'redacted' just means that these idle musings be worth something to somebody somewhere at some time in the future I was merely speculating about ways to make use of what Kodak knows. There, now the lawyers are going to come after Ron!

I just use International Signal Flags.

 

[Struan Gray]

that concept of Anabel Muenter works with donors brought onto the surface of the crystal.
That means it can only take gain out of those holes which succeeded in reaching the surface instead of having recombined, which they are believed to do quite fast.

That was a critique then uttered on that concept.

True. The paper I referenced is cleverly vague on the spatial positions at which the various processes in the chain take place - presumably to protect intellectual property rights. At all stages there will be tradeoffs between diffusion and undesired parasitic effects like recombination - but that is exactly where the film manufacturers have massive strengths in their production engineering.

Note however that in modern films the first hole is rarely created in the bulk of the AgX crystal. Sensitisers work by creating an alternative site for light absorbtion, and that site is usually either on the dye molecule itself, or a surface state created at the interface between the AgX and its environment. Sensitisers like sulphur and other dopants can work in the bulk of the AgX crystal structure, but as I understand it they are concerned with capturing the electron diffusing in from the surface, not promoting the initial absorbtion per se.


I wish academic publishing were more open, partiuclarly since these days you are essentially paying for a vetting service, and not a book production one. I have been known to mail pdfs to those with a genuine interest, but I believe strongly in intellectual property rights and so am reluctant to hand out papers willy-nilly in public, even if I disagree at heart with a system that effectively prevents public access to publicly-funded research.

For those who don't have an institutional subscription and who want to get hold of the occasional research paper (or, for example, Abney's early work in the Royal Society journals in JSTOR), I can heartily recommend contacting your local public or university library. If you are lucky enough to live in NY city or CA, the public libraries there are leading the charge to open up academic archives to the general reader, but many public libraries in the USA and Europe give access without trumpeting the fact. I'm sure there are exceptions, but the university libraries I know are also very welcoming, albeit with a little screening to weed out the time-wasters. In most cases you need to turn up in person to acquire a readers' card, but can access electronic journals via a portal thereafter.

Apologies to anyone who feels they are being taught how to suck eggs, but access to academic research and reference tools has improved immeasurably in recent years, especially via public libraries, and I know from first hand attempts to help friends how it is easy to be discouraged when you first come up against the walls of the ivory tower. Once you know the secret whistle to let down the silken rope, life gets easy fast.


PS: I see from Photo Engineer's scans that trapping the photo-hole is a more important issue than I thought. Mea Culpa. Lesson: read the papers, not my ramblings

 

[Tim Gray]

Those pictures at ISO 12000 and 24000 make me sad. I could have had some fun with that film.

 

[Photo Engineer]

Guys;

Unfortunately, when you see this work, and realize how much backstory there is, then you begin to realize how much we will lose if analog ever passes out of major production facilities.

Anabel and her team had a full team of organic chemists backing them up making complexes and special dyes as well as additional "stabilzers" to help them realize the goal of making a product. Just this team alone was probabley on the order of 15 people with full lab facilities and they worked for up to 15 years to get to the point of a product. Consider just the cost for one of us to duplicate that!

Considering the degree of disbelief I get when I say this type of thing, I feel like a voice in the wilderness. I'm told over and over that I am a pessimist and worse. But this type of work, shown above, is the type of thread I am basing my comments on.

PE

 

[Tim Gray]

I get what you are saying. It makes me sad. On one hand, it sounds like a lot - 15 educated people working with full lab facilities. On the other hand, it's only 15 people. I know it costs money to pay those people and put them in a lab, but in the big picture, it's not that much. It always frustrates me how short sighted our culture is in terms of funding research.

 

[keithwms]

The knowledge will not be lost, Ron. Cheer up There will always be some nutjob (ahem, dedicated scientist) in some remote lab, toiling away, turning over stones that nobody thought of and enjoying that process of discovery. Look at it this way, we have been in the "web information age" for a few decades now and what is known now will be disseminated and preserved. It's not like this knowledge will vanish into thin air, there will always be people like us to appreciate it and push it forward.

(these optimistic words uttered by a young scientist who now realizes that he took a vow of poverty when he went into science in this day and age :rolleyes: )

 

[Photo Engineer]

I get what you are saying. It makes me sad. On one hand, it sounds like a lot - 15 educated people working with full lab facilities. On the other hand, it's only 15 people. I know it costs money to pay those people and put them in a lab, but in the big picture, it's not that much. It always frustrates me how short sighted our culture is in terms of funding research.

Tim;

By now, you have an authoritative answer.

PE

 

[Tim Gray]

Haha. Yes.

 

[Photo Engineer]

Keith;

A round number costing of that is about $25 million in the 15 years. So think it over again. It would take a multi discipline scientist many years of work to accomplish this doing synthetic chemistry, inorganic chemistry, emulsion making and coating to test and retest.

Good luck.

PE

 

[keithwms]

That's why I used the term 'nutjob'

 

[Photo Engineer]

Keith, Struan;

I wish I could sit you two down with people like Annabel and Paul Gilman and a few other EK theoreticians. It would be a memorable round table discussion. I'm sure though that that would never come about. I have talked to one of the sensitizing dye chemists and he never wants to discuss synthetic organic chemistry again in his entire life!

Tim;

As you found, you are talking to the wrong person. But then, there is no "right" person. Ever see a chicken have its head cut off?

PE

 

[keithwms]

Sit us down then. My place or yours? I can invite people for seminar here, I really can.... with everything paid for...

 

[Photo Engineer]

At Kodak there are the Weissberger lectures given at KRL as well. These and the series before Arnold Weissberger died have been ongoing for nearly 100 years AFAIK. I was just kidding though. I could never arrange something like that. You might be able to though.

PE

 

[Chazzy]

I hope that the research continues and that we see ongoing refinements of the products that we have and even more new products. But, worst case scenario (this is an intellectual exercise), if we were "stuck" with no further improvements after 2009, would we be in such bad shape? Many people are still not even using the "new" technology of several years ago (the T-Max and Delta films). And there is never any shortage of complaints that what people really want are the old products which have been discontinued. So if nothing new happens in terms of film research and new film products, does it really matter so much?

 

[AgX]

Charles,

A good point.

But don't forget that there are not only Apug types using film. Especially industrial customers may have a different perspective.