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Sunlight is the main energy source for green plants. The energy is stored as carbohydrates and later on used for growing. The about 100·109 t of dry biomass that are produced every year by photosynthesis illustrate the huge impact of photochemical processes in nature. Besides converting energy, photochemical reaction can also yield “value-added” chemicals. The biosynthesis of vitamin D3 in the human skin is a prominent example.

While photochemical reactions are the foundation of life on earth, the application of photochemical syntheses in chemical industries is seldom. This might be attributed to the interaction of light with matter, that has to be considered in addition to the parameters that influence thermally initiated reactions. As a consequence, designing photochemical processes on a technical scale is more challenging than the development of conventional chemical processes. Furthermore, the availability of light sources, the scope of synthesis routes or the extent of education with respect to photochemical processes might be reasoned.

In general, the significance of a certain research field in education goes along with either its industrial relevance or its importance for fundamental research. Obviously, these two directions of research are coupled to some degree. Tendentially, a chemical process of industrial importance will attract researcher’s attention more easily, even in the field of fundamental research and renders a research topic attractive for funding. In contrast, the inverse coherence is much harder to realize. Consequently, the small number of applications of photochemical processes in industry raises hurdles for an intensification of research as well as education on photochemical processes.

The limited access to free information on photochemical processes is another obstacle for increasing the interest of young researchers in photochemical technology. While the open-accessidea for scientific publications gains more and more supporters, basic information on the entire field of photochemical processes are not available freely in a comprehensive and validated format. A well accepted example of such a comprehensive and validated format for general chemistry is the ChemgaPedia-platform, providing comprehensive knowledge and lectures on a broad field of chemical topics.[1]

To negotiate the hurdles discussed above, this document aims on contributing a freely accessible source of information on photochemical processes. The information are available online as a Wikipedia/ChemgaPedia-type online service.[2] The different articles were also compiled as a single document, which is available as a PDF.

At the time of first publication in spring 2017, the published articles cover a broad range of topics, starting from photochemical principles through reaction types to technical aspects. The scope of the single articles was chosen to give the reader a starting point for further investigations in the scientific literature. Hence, the articles provide an overview of the single topics rather than a discussion of all details. For delving into single topics, the reader is referenced to the large number of excellent text books which are available. In addition to the theoretical chapter, a chapter devoted to practical courses was added. The intention of this chapter is to provide course manuals for experiments with photochemical background, allowing universities an easy implementation of experiments in the curriculum.

It is self-evident, that the format of a Wikipedia was chosen to encourage the interested audience to provide further articles to this service as well as corrections or supplements of the already published articles. Contributions can be send to photo-wiki@itc.uni-stuttgart.de. New articles as well as corrections will be integrated into the online service and into the PDF version.

The preparation of this document was made possible through financial support of the Fonds der Chemischen Industrie im Verband der Chemischen Industrie e.V. (FCI)[3] and the Faculty of Chemistry of the University of Stuttgart. I gratefully acknowledge this support, which allowed to lay the foundation for a freely accessible compendium on photochemical processes.

Dirk Ziegenbalg

Stuttgart, 19.05.2017


  1. ChemgaPedia, Wiley Information Services GmbH, 2017, http://www.chemgapedia.de/
  2. Introduction to Photochemical Reactions and Processes, Faculty Chemistry, University Stuttgart, 2017, http://www.itc.uni-stuttgart.de/Wissenswertes/photo-wiki/index.html
  3. Fonds der Chemischen Industrie im Verband der Chemischen Industrie e.V., 2017, https://www.vci.de/fonds/startseite.jsp



Found an error or want to submit a new article? Please send your correction or article in by mail in word or pdf to photo-wiki@itc.uni-stuttgart.de.