Increasing the effectivity of the antimicrobial surface of carbon quantum dots-based nanocomposite by atmospheric pressure plasma

Preventing nosocomial infections is one of the most significant challenges in modern medicine. The disinfection of medical facilities and medical devices is crucial in order to prevent the uncontrolled spread of bacteria and viruses. Cost-effective, eco-friendly and fast-acting antibacterial coatings are being developed as the prevention of bacteria and viruses' multiplication on various surfaces. One of the possibilities to create such antimicrobial coatings can rely on a photoactive material, that produces singlet oxygen. However, a remote production of the singlet oxygen and disinfection of the desired surface is a time-consuming process. Hence, a coating material that would autonomously produce singlet oxygen employing ambient light will have a significant impact on the shortening of the disinfection time; leading into an increased number of patients that can be cured in one facility. In this work, an ultra-fast and eco-friendly method for decreasing the disinfection time of the photoactive surface is presented. The atmospheric pressure plasma surface treatment on the hydrophobic carbon quantum dots-polydimethylsiloxane nanocomposite is employed. The plasma-treated samples exhibited improved antibacterial properties compared to non-plasma treated samples, with the best results obtained after only 30 seconds of plasma treatment. The short duration and the scalability potential of the here described method open new possibilities of how to improve the already existing antibacterial coatings. © 2020 Elsevier GmbHResearch & Innovation Operational Programme - ERDF; Czech Science FoundationGrant Agency of the Czech Republic [19-16861S]; project Buildingup Centre for Advanced Materials Application of the Slovak Academy of Sciences [313021T081]; [VEGA 2/0051/20]; [APVV-15-0641

Antibacterial photodynamic activity of hydrophobic carbon quantum dots and polycaprolactone based nanocomposite processed via both electrospinning and solvent casting method

Inhabitation of various types of bacteria on different surfaces causes vital health problems worldwide. In this work, a wound dressing defeating bacterial infection had been fabricated. The antibacterial effect of polycaprolactone and hydrophobic carbon quantum dots (hCQDs) based nanocomposite has been presented. The nanocomposite was fabricated both via solvent casting and electrospinning method. Nanocomposites with and without hCQDs had been investigated. A detailed study on their morphology and surface properties were performed by scanning electron microscopy, atomic force microscopy and Raman spectroscopy. Prepared nanocomposites had been evaluated by the contact angle, UV-Vis spectroscopy, electron paramagnetic resonance spectroscopy, and antibacterial activity. It was found that nanocomposites were able to produce singlet oxygen upon blue light irradiation at 470 nm, and they were effective in the eradication of Gram positive (Staphylococcus aureus, Listeria monocytogenes) and Gram negative (Escherichia coli, Klebsiella pneumoniae) bacteria. © 2021Ministry of Education of the Slovak Republic; Slovak Academy of Sciences [VEGA 2/0051/20]; Czech Science FoundationGrant Agency of the Czech Republic [20-28732S]; SERB-DSTDepartment of Science & Technology (India)Science Engineering Research Board (SERB), India [TAR/2020/000088]TAR/2020/000088; Slovenská Akadémia Vied, SAV: VEGA 2/0051/20; Grantová Agentura České Republiky, GA ČR: 20-28732S; Ministerstvo školstva, vedy, výskumu a športu Slovenskej republik

Challenges and perspectives of nature-based wastewater treatment and reuse in rural areas of Central and Eastern Europe

In Central and Eastern Europe, about one-third of the population lives in small settlements (<2000 PE). Since the current European Urban Wastewater Treatment Directive (91/271/EEC) does not clearly regulate the collection and treatment of wastewater from these settlements, countries solve the problem individually. Simple and robust technologies such as nature-based treatment systems could be the solution and are widely applied in many EU countries. In this paper, the status of wastewater collection, treatment, and reuse in rural areas of 14 countries in Central and Eastern Europe is presented together with the spread of different nature-based treatment systems. The results show that in the last decade, connection to wastewater treatment plants has increased from 9% to 19% of the total population in small settlements. The use of treated water is rarely applied. Sequencing batch reactors and other types of activated sludge systems predominate in treatment technologies. Nature-based treatment systems (mainly treatment wetlands) are used in all the countries studied. Their implementation is slowly increasing, hampered by lack of acceptance by authorities, lack of good case studies, and misdesigned or misoperated examples from the past. More awareness, formalized training on nature-based treatment systems, and supportive legislation are needed to promote sustainable sanitation solutions in small settlements

Searching for the correlations between the use of different groups of pharmaceuticals from wastewaters

Wastewater contains a wealth of information about the inhabitants of cities. Wastewater-based epidemiology (WBE) has become an effective tool for monitoring public health by analyzing various biomarkers (e.g., chemicals and microorganisms) in wastewater. This way, the estimation of pharmaceuticals' consumption behavior and/or illicit drugs can be calculated. However, monitoring consumption alone is not the only option. If we consider wastewater as a statistical representation of the population's health, medical information can be derived. In this work, we used data from 15 different wastewater treatment plants in Slovak Republic to explore correlations between the use of typical pharmaceuticals and illicit drugs. The analysis was based on the wastewater monitoring data from four years (2016–2019), and 68 different compounds were taken into account. One of the strongest correlations found was between Antihyperlipidemics and Antihypertensives, with Pearson's correlation coefficient of 0.82. This type of analysis within the WBE represents a new potential as an additional source of information for the pharmaceutical, medical and government sectors in assessing health risk factors in the population. Such an evaluation method has even a great potential for artificial intelligence and machine learning for calculating health risk factors together with other sources of data.ISSN:0147-6513ISSN:1090-241

Photodynamic-active smart biocompatible material for an antibacterial surface coating

Here we present a new effective antibacterial material suitable for a coating, e.g., surface treatment of textiles, which is also time and financially undemanding. The most important role is played by hydrophobic carbon quantum dots, as a new type of photosensitizer, produced by carbonization of different carbon precursors, which are incorporated by swelling from solution into various polymer matrices in the form of thin films, in particular polyurethanes, which are currently commercially used for industrial surface treatment of textiles. The role of hydrophobic carbon quantum dots is to work as photosensitizers upon irradiation and produce reactive oxygen species, namely singlet oxygen, which is already known as the most effective radical for elimination different kinds of bacteria on the surface or in close proximity to such modified material. Therefore, we have mainly studied the effect of hydrophobic carbon quantum dots on Staphylococcus aureus and the cytotoxicity tests, which are essential for the safe handling of such material. Also, the production of singlet oxygen by several methods (electron paramagnetic spectroscopy, time-resolved near-infrared spectroscopy), surface structures (atomic force microscopy and contact angle measurement), and the effect of radiation on polymer matrices were studied. The prepared material is easily modulated by end-user requirements. © 2020 Elsevier B.V.Ministry of Education of the Slovak Republic; Slovak Academy of Sciences [VEGA 2/0051/20]; Czech Science FoundationGrant Agency of the Czech Republic [1916861S]; ERDF/ESF "Centre of Advanced Applied Sciences" [CZ.02.1.01/0.0/0.0/16_019/0000778

Real-Time Monitoring of Growth and Orientational Alignment of Pentacene on Epitaxial Graphene for Organic Electronics

The interaction between a graphene layer and pentacene (PEN) molecules leads to the formation of a lying-down phase, which can improve charge transport for organic vertical field effect transistors and enhance the optical absorption for increased light harvesting in organic solar cells. Here, we present a comprehensive study of PEN growth on epitaxial graphene on silicon carbide (SiC). Simultaneous grazing-incidence small- and wide-angle X-ray scattering (GISAXS/GIWAXS) were used in situ for real-time monitoring of the PEN crystal growth with millisecond time resolution to identify two distinct anisotropic growth stages after the nucleation of the first monolayer (ML). In the first stage up to 1.5 nm, we observe rapid growth of pentacene domains along the (010) and (001) facets. This growth behavior is saturating after 1.5 nm. In a second stage, this is followed by continuous lateral crystal growth in only one in-plane direction (100) forming needle-shaped domains. In the second stage, an uninterrupted linear growth of the lying-down PEN phase is found based on the (001) diffraction up to 15 nm. Ex situ atomic force microscopy and polarized confocal Raman microscopy were used to further support the real-time observations of aligned PEN films on graphene

Reorientation of π-conjugated molecules on few-layer MoS2_2 films

Small π-conjugated organic molecules have attracted substantial attention in the past decade as they are considered as candidates for future organic-based (opto-)electronic applications. The molecular arrangement in the organic layer is one of the crucial parameters that determine the efficiency of a given device. The desired orientation of the molecules is achieved by a proper choice of the underlying substrate and growth conditions. Typically, one underlying material supports only one inherent molecular orientation at its interface. Here, we report on two different orientations of diindenoperylene (DIP) molecules on the same underlayer, i.e. on a few-layer MoS$_2$ substrate. We show that DIP molecules adopt a lying-down orientation when deposited on few-layer MoS$_2$ with horizontally oriented layers. In contrast, for vertically aligned MoS$_2$ layers, DIP molecules are arranged in a standing-up manner. Employing in situ and real-time grazing-incidence wide-angle X-ray scattering (GIWAXS), we monitored the stress evolution within the thin DIP layer from the early stages of the growth, revealing different substrate-induced phases for the two molecular orientations. Our study opens up new possibilities for the next-generation of flexible electronics, which might benefit from the combination of MoS2 layers with unique optical and electronic properties and an extensive reservoir of small organic molecules