Nowadays, a larger number of aggressive and corrosive chemical reagents as well as toxic solvents are used to achieve structural modification and cleaning of the final products. These lead to the production of residual, waste chemicals, which are often reactive, cancerogenic, and toxic to the environment. This study shows a new approach to the modification of graphene quantum dots (GQDs) using gamma irradiation where the usage of reagents was avoided. We achieved the incorporation of S and N atoms in the GQD structure by selecting an aqueous solution of L-cysteine as an irradiation medium. GQDs were exposed to gamma-irradiation at doses of 25, 50 and 200 kGy. After irradiation, the optical, structural, and morphological properties, as well as the possibility of their use as an agent in bioimaging and photodynamic therapy, were studied. We measured an enhanced quantum yield of photoluminescence with the highest dose of 25 kGy (21.60%). Both S- and N-functional groups were detected in all gamma-irradiated GQDs: amino, amide, thiol, and thione. Spin trap electron paramagnetic resonance showed that GQDs irradiated with 25 kGy can generate singlet oxygen upon illumination. Bioimaging on HeLa cells showed the best visibility for cells treated with GQDs irradiated with 25 kGy, while cytotoxicity was not detected after treatment of HeLa cells with gamma-irradiated GQDs.

Telecommunications have become highly important for the successful business operations of almost every organization in the world, in the public and private sector, and is the core of most multinational companies' businesses. Telecommunications are an integral part of the global communications network; they are critical for organizations as well as for individuals and have socio-economic value. Large telecommunication companies are doing business in an environment where there is a discrepancy between the need for the introduction of innovations into the portfolio of services and the traditional methods of service development, as well as their market placement. With the expansion of the internet in the industry, the ways of distribution and consumption of digital services have changed considerably. Taking into consideration the increasing complexity of regulations and the environment in which projects that support the development of ICT products and services are led, the right choice of project management methodology is becoming more important. Alongside with the usage of traditional approaches to project management, there is a development of new methodologies through the introduction of dynamic models for achieving project results more quickly. This thesis is based on research conducted on a telecommunications company representative in the region, with the assumption that the introduction of agile methodologies can achieve competitiveness in the highly competitive market of modern telecommunications services. The presented results are based on research conducted in the large telecommunications company, with an emphasis on the recognition of requirements for the introduction of different project management methodologies in the service development process. Based on surveys of management and employees of the company that is involved in the process of service development, test and agile management have been introduced along with the existing traditional management. This paper shows a comparison between these two methodologies on one project which includes the introduction of an innovative ICT service. Based on the results, the hypothesis which assumes that the introduction of agile management provides competitiveness on the market of telecommunications services has been confirmed.

Project management profession encounters numerous challenges in today's global environment. It is a known fact for every project management professional that most common challenges are the completion of project on time, scope changes, goals, unplanned risks, engagement on several different projects, lack of competencies, lack of top management and stakeholder engagement, economic instability, legal barriers and many others. Through literature search, it was observed that there are no data related to challenges project managers face in Serbia, and for this reason, the aim of this paper is to provide this information, based on a study conducted. Challenges presented in the survey are most widely and statistically recognized ones as globally present, and the idea was to show how these challenges fit into contemporary project management practice in Serbia and to show the difference between small and large companies. The research part of the paper was based on a survey, presented to project managers in project management practising organizations in Serbia, large majority of which being from a service sector. Through this survey four hypotheses were tested. Methods of descriptive and analytical statistics were used for evaluation of the survey, and all four hypotheses were confirmed. Major challenges for project managers in Serbia were identified, and it was shown that the size of a company does have an impact on dealing with challenges. Based on the data provided decision-makers in organizations will get a clearer understanding of real challenges in project management in Serbia, which should allow for better decisions.