The advances in physics and the technology of semiconductor nanocrystals that were summarized in Chapters 2–7 provide comprehensive knowledge on the optical and electronic properties of nanocrystals and make it possible to create novel mesoscopic materials with desirable parameters by means of stoichiometry and size control. In these chapters the intrinsic properties of nanocrystals were discussed, implying the absence of any cooperative effect on the properties of a given nanocrystal ensemble. In recent years significant progress has been made in moving from randomized nanocrystals towards spatially organized structures like nanocrystal superlattices, quantum dot solids, and photonic crystals. The principal results obtained in the field will be reviewed in this chapter.

Superlattices of nanocrystals: quantum dot solids

There are several ways to develop a nanocrystal superlattice, that is, a structure consisting of identical nanocrystals with regular spatial arrangement. The first is to use zeolites, which form a skeleton with regular displacement of extremely small cages, the size of a cage being typically about 1 nm. A number of clusters such as CdnSm and ZnnSm can be embedded in these cages, the cluster size distribution and geometry being controlled by the topology of the three-dimensional host surface (Wang et al. 1989; Stucky and MacDougall 1990; Bogomolov and Pavlova 1995 and references therein). Using various zeolites as frameworks for semiconductor clusters makes possible the study of regular three-dimensional cluster lattices with variable intercluster spacing.

Because of inevitable size distribution, shape variations, different concentration of impurities and defects, and fluctuations of local environment and charge distribution, every ensemble of nanocrystals dispersed in some solid or liquid medium possesses inhomogeneously broadened absorption and emission spectra. Therefore, a number of properties inherent in molecular and atomic inhomogeneously broadened spectra can be a priori foreseen for nanocrystals. These include spectral hole-burning, fluorescence line narrowing under selective excitation, and decay time distribution. At the same time, spectrally selective techniques developed for inhomogeneously broadened molecular and atomic structures have been successfully applied to nanocrystals providing evaluation of individual parameters smeared as a result of inhomogeneous broadening. This chapter gives a brief overview of specific phenomena inherent in all spectrally inhomogeneous media and a survey of the relevant experimental techniques including nonlinear pump-and-probe spectroscopy, fluorescence excitation spectroscopy, and single molecule spectroscopy.

Population-induced optical nonlinearity and spectral hole-burning

Every real system consisting of particles with discrete energy levels exhibits absorption saturation under intense optical excitation. The only example of a nonsaturable system is an ensemble of ideal harmonic oscillators that possess an infinite number of equally spaced energy levels, optical transitions allowed only for a couple of neighboring levels, and the probability of optical transitions being proportional to the level number (Stepanov and Gribkovskii 1963).

Electronic states and probabilities of optical transitions in molecules and crystals are determined by the properties of atoms and their spatial arrangement. An electron in an atom possesses a discrete set of states, resulting in a corresponding set of narrow absorption and emission lines. Elementary excitations in an electron subsystem of a crystal, that is, electrons and holes, possess many properties of a gas of free particles. In semiconductors, broad bands of the allowed electron and hole states separated by a forbidden gap give rise to characteristic absorption and emission features completely dissimilar to atomic spectra. It is therefore reasonable to pose a question: What happens on the way from atom to crystal? The answer to this question can be found in the studies of small particles with the number of atoms ranging from a few atoms to several hundreds of thousands atoms. The evolution of the properties of matter from atom to crystal can be described in terms of the two steps: from atom to cluster and from cluster to crystal.

The main distinctive feature of clusters is the discrete set of the number of atoms organized in a cluster. These so-called magic numbers determine unambiguously the spatial configuration, electronic spectra, and optical properties of clusters. Sometimes a transition from a given magic number to the neighboring one results in a drastic change in energy levels and optical transition probabilities.

JOINT AUTHORSHIP OF A PAPER

Jan and Keith are junior members of the engineering faculty at a major university. Both are seeking tenure from the university, and as part of the requirement, they are required to publish original articles in disciplinary journals.

Jan reviews some work from his work as a graduate student and reconsiders a paper based on an unpublished portion of his thesis research. He thinks that with some revision it would make a good journal article. Jan discusses this idea with Keith and proposes that together they revise the paper and bring it up to date.

Jan does most of the revising and updating. Keith makes only small contributions but is a better writer. Jan is disappointed that Keith does not make more of a contribution to the paper's content but agrees to include Keith's name as coauthor, to enhance Keith's chances of obtaining tenure. The article is accepted and published in a scientific journal.

Is it ethically acceptable for Jan to go back to his graduate student work for an article to publish?

Should Jan's thesis supervisor be credited in some way, and if so, how?

Should the source of the funding for Jan's thesis research be acknowledged in the paper?

Is it responsible for Jan to ask Keith to help revise the article? How much could they and should they have agreed upon at the start of their collaboration?

A clear understanding of the terms, concepts, and distinctions that people use to describe ethical problems and concerns helps in identifying what is ethically significant (or “morally relevant”) in a situation. Understanding the ethical significance of the problems we face is the first step in responding well to them. Clear concepts and distinctions are also needed in the reflective examination of the ethical soundness of practices and customs. Standing up to such examination is what distinguishes ethical convictions from mere habits of thought.

The tendency to avoid ethical language is so widespread that even common terms for describing ethical situations seem strangely unfamiliar. Although avoiding ethical language may, in some circumstances, serve to reduce the defensiveness of those whose actions or policies are being questioned, it inhibits the understanding of ethical problems that commonly occur. The precise use of concept is essential for careful reasoning and clear communication in any field, and a consistent use of terms is required for parties to be able to recognize when they are agreeing, disagreeing, or addressing different subjects.

This introduction is intended both to clarify ethical terms and distinctions and to provide a general framework for considering ethical questions. If discussion of ethical terms is new to you, you may want to read through the main text, skipping the fine points that are set off to the side in smaller type.

I want to die proud of having been an engineer. Since that can happen only if we engineers behave ethically, and since I see a connection between this book and gracious professionalism, I am very enthusiastic about Dr. Whitbeck's effort to help us think effectively and somewhat pragmatically about professional ethics. Everyone, professionals in particular, must expect ethically complex situations to arise. When that happens, each of us badly needs a self-image that includes conviction that our intellect and heart can help make choices that will dramatically affect the course of events. That point of view will not materialize out of the ether. It must be nurtured and encouraged. This book will help seasoned professionals clarify their approach to their own behaviors, and this book can profoundly affect those who face a messy situation for the first time.

Caroline's arguments penetrate some of the fog around ethics. Most people think of it as an obscure topic belonging to an elite few who can spend their lives in deep and abstract thought. Even many professors of engineering regard ethics as a somewhat untouchable topic. “Students will never listen! Why waste our time and theirs?” Several have argued that post–high school is too late to influence students' proclivity to behave in society's best interest. I strongly disagree. Since I have spent most of my teaching career encouraging students to trust their own creative abilities, I have developed a thick skin about comments like, “You cannot teach creativity!” I do not debate that assertion.

GROUP MISCONDUCT REGARDING LABORATORY PROCEDURE

You are a graduate student working as part of a group on a large project. The results from your group experiments are used for other experimental work. Your faculty supervisor, the principal investigator (PI) for the project, wants you to use a new procedure in your experimental work. She expects the new procedure to yield results that are better suited to the conditions of the other experimental work. The other members of your group do not want to change the procedure they have been using; the new one requires significantly more work. They believe the PI will not notice if the old procedure is used.

You rely on the group for assistance in your own thesis work, but if you go along with the decision to use the old procedure, the quality of the data will most likely be inferior; you will mislead the PI and perhaps the whole scientific community.

You argue for using the new procedure and informing the PI that the work will just have to take longer – information which she is not likely to receive well. The rest of the group is not persuaded.

What should you do and how can you go about it?

DOUBTS ABOUT PUBLISHED RESULTS

You are a computer science graduate student and for two years have been working on an operating system design in Professor Carr's group.

As we saw in Chapter 3, it is in everyone's interest that engineers be heeded when they foresee risks and threats to the public welfare. It is in a company's interest to see that engineers' concerns are heard within the company, rather than only after they have gone outside to “blow the whistle.” In prior chapters we have focused on the moral skills that enable engineers to fulfill their responsibilities both in responsive and unresponsive organizations. In the United States and other countries where employee engineers usually have no written employment contracts (as they do in Germany for instance), companies may retaliate against engineers for pursuing ethical concerns that clash with their company's short-term business objectives. Therefore, creating a workplace that is relatively free of the risk of such harassment is a much larger topic in engineering ethics in a country such as the United States than in a country such as Germany.

The case of Roger Boisjoly in Chapter 4 shows that even concerns arising from engineers' most fundamental responsibilities may fall on deaf ears. In this chapter we examine various organizations – corporations, government agencies, universities, and research facilities – to see what makes them more able to listen. In Chapters 2 and 3 we considered many problems of engineers in private practice; however, most engineers work as employees and are immersed in organizational cultures that significantly influence their moral lives.

Ethics in Engineering Practice and Research is about professional responsibilities of engineers and applied scientists. It is about professional responsibilities: the character of problem situations in which those responsibilities must be fulfilled and the moral skills for fulfilling them. Interspersed throughout the text are open-ended scenarios that present ethically significant situations of the sort engineers and applied scientists commonly encounter. These have been set apart in centered boxes to aid the use of them in group discussion and for homework assignments. Also set apart from the text, in boxes, are fine points, which may enhance the reader's understanding but which are not essential to the main argument. Most of these fine points concern philosophical issues.

OUTLINE AND SUMMARY

The introduction on concepts provides a clarification of many general ethical terms and provides a general framework for considering ethical questions. This framework draws on readers' prior experience of moral life and of moral reflection. Other more specialized ethical concepts are introduced as needed throughout the book.

Chapter 1 discusses what moral problems look like to a person in the situation who must respond to them. The frequent need to cope with an ambiguous situation and to formulate responses to the problem situation shows that addressing ethically significant problems is more demanding than simply evaluating the relative merits of preestablished responses. In many respects challenging ethical problems resembles challenging design problems.

Suppose I face an ethical problem; how ought I go about figuring out what to do? The question is not simply how should I evaluate proposed courses of action, but how should I go about devising such courses of action.

Ethical judgments are important in devising responses to ethical problems, of course. These judgments come in many forms, from “What is being proposed is morally wrong” to “This safety factor (or margin) is sufficient for the circumstances in which this device (or process or construction) will operate.” This book is at least as concerned with devising good responses as with making ethical judgments.

People confronted with ethical problems must do more than simply make judgments; they must figure out what to do.

PROFESSIONS AND NORMS OF PROFESSIONAL CONDUCT

Professions are those occupations that both require advanced study and mastery of a specialized body of knowledge and undertake to promote, ensure, or safeguard some matter that significantly affects others' well-being. This chapter will examine the norms and standards of responsible conduct in professional practice. Ethical (and sometimes legal) requirements also exist on the practices of nonprofessionals whose work immediately affects the public good, of course. For example, food handlers are bound by sanitary rules. Furthermore, many moral rules apply equally in all work contexts. All workers have an ethical obligation not to deceive their clients or customers, for example. What is distinctive about the ethical demands professions make on their practitioners is the combination of the responsibility for some aspect of others' well-being and complexity of the knowledge and information that they must integrate in acting to promote that well-being.

Moral rules, such as the one against deception, are important, but professional responsibilities cannot be captured in such rules. Fulfilling professional responsibilities requires more than rule following. Fulfilling a responsibility requires some maturity of judgment. The expressions “the age of responsibility” or “the age of discretion” acknowledge the maturity of judgment required to take on responsibilities. Carrying out a responsibility requires making complex judgments that integrate a variety of considerations in deciding how best to achieve certain ends, such as safety.

A BRIEF HISTORY OF THE USE OF HUMAN SUBJECTS IN MEDICAL AND PSYCHOLOGICAL EXPERIMENTS IN THE UNITED STATES

The doctrine of informed consent for human experimentation was promulgated in the Nuremberg code in 1946 after the discovery of brutal experiments carried out by the Nazis. It was refined in the Helsinki declarations issued by the World Medical Association in 1962 with subsequent revisions in 1964, 1975, and 1989.

The requirement of informed consent now applies to behavioral research as well as medical research. Many of the classic experiments in psychology involve deception and even clear harm to the subject and would not be allowed today.

The informed consent standard was only gradually adopted in the United States, however, and it took some shocking cases in this country to demonstrate the need for reform. In 1966, a well-respected clinician and investigator, Henry Beecher, had published an article in the prestigious New England Journal of Medicine, in which he reported common but unethical treatment of human research subjects in many premier institutions in the United States. Subsequently, the NIH developed the first Public Health Service Policy on the Protection of Human Subjects. At first these had only limited application. Later they were expanded to apply to all human subjects research conducted or supported by what was then the Department of Health, Education and Welfare.

The body of knowledge that characterizes a profession enables its practitioners to foresee possibilities, to devise ways to achieve desirable results, and to avoid undesirable side effects. Specialized knowledge enables engineers and scientists to design interventions, devices, processes, or constructions and to foresee how those products, processes, and constructions will act or interact. The designers of these products are uniquely qualified to foresee and modify many consequences of their use or misuse. Prominent among such consequences are safety hazards.

HOW CRITERIA FOR PROFESSIONAL CONDUCT CHANGE

Expectations of responsible professions vary not only with profession but also with the profession's experience of accidents and failure. Henry Petroski, in his elegant book, To Engineer is Human, uses examples from civil engineering to richly illustrate his thesis that engineering commonly advances by learning from failure. In almost every case the failures Petroski discusses threatened human health and safety.

Roland Schinzinger and Michael Martin, noting the extensive and often unpredictable character of the influence of technology on human life (not only health and safety), have argued that technological innovation amounts to social experimentation. In recent decades, informed consent has emerged as the primary criterion for ethically acceptable use of experimental treatments on human subjects. Schinzinger and Martin have suggested adapting a similar standard for the adoption of new technology.

Schinzinger and Martin propose using “proxy groups” composed of people similar to those who will be greatly affected by new technology.