**2. Nature of chalcogen compounds and chalcogen materials**

Chalcogens are elements which belong to the group VI-A (or group 16) in the periodic table, which consists of oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po). Chalcogens are the basic elements of chalcogenides compounds, where chalcogens are combined with electropositive elements, organic radicals, in natural secondary metabolites and even in macromolecules such as enzymes and proteins [1, 18, 19]. All compounds with oxygen can be essentials and contribute most of the chalcogen materials. The materials can be as simple as silica, as an example of oxygen compounds was made for some important application [20] or macromolecule like cellulose or its derivates [21] which is applicable in daily life and will be so still in the future, to a more complicated complexed compounds [22–26] or advanced materials [27–29] which are made for the sake of science and method development. Abundant materials are naturally in existence with oxygen, and also a lot is being derived from synthesis in the laboratory [20–26, 30].

Some literature exclude oxygen from the chalcogenides discussion as oxygen appears in almost all materials [3]. Oxygen and sulfur are contained in so many secondary metabolites in living things and also in bigger molecules in tissue [6, 18, 31–34]. The process of changing compounds during food treatment enables one to establish new natural resources for modern herbal medicine for cancerous treatment [7, 35–39]. To be able to examine the biomolecular structure and medicinal properties of such compounds in detail, new analytical methods and also high-resolution instrumentation would play important roles [40–42]. Of course that pretreatment prior to analysis will be taken into account [31, 41, 43]. Extraction process which is needed before the analysis was discussed thoroughly in the prominent book of Harborne [44]. Many sophisticated new materials are made and dedicated for use in medicinal area [35, 38, 45] or smart electronic materials [46], materials from nonliving beings [3, 47, 48], nanomaterials and thin films and materials for certain applications which needs special characterizations [49, 50]. The fast development of chalcogen materials cannot be separated from the development of analytical methodologies.
