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Graphene films prepared from solution and deposited by Langmuir–Blodgett self-assembly technique (LBSA) were treated with radio-frequency (13.56 MHz) nitrogen plasma in order to investigate the influence of the time of nitrogen plasma exposure on the work function, sheet resistance, and surface morphology of LBSA graphene films. Kelvin probe force microscopy and sheet resistance measurements confirm nitrogen functionalization of our films, with the Fermi level shifting in a direction that indicates binding to a pyridinic and/or pyrrolic site. Upon 1 min of nitrogen plasma exposure, the sheet resistance decreases and there is no obvious difference in film morphology. However, plasma exposure longer than 5 min leads to the removal of graphene flakes and degradation of graphene films, in turn, affecting the flake connectivity and increasing film resistance. We show that by changing the exposure time, we can control the work function and decrease sheet resistance, without affecting surface morphology. Controllability of the plasma technique has an advantage for graphene functionalization over conventional doping techniques such as chemical drop-casting. It allows for the controllable tuning of the work function, surface morphology, and sheet resistance of LBSA graphene films, which is substantial for applications in various optoelectronic devices.

A long operational lifetime is required for the use of solar cells in real-life photovoltaic applications. The optimization of operational lifetimes is achieved through understanding the inherent degradation phenomena in solar cells. In this study, graphene/Si Schottky-junction solar cells were produced, utilizing liquid-phase-exfoliated graphene as an active surface. The operational and interface stability of these solar cells over a period of 5 years in ambient conditions (following ISOS-D protocols: dark storage/shelf life) was examined, and the origin of their degradation was reported. It was found that the dominant degradation mechanism could be attributed to the degradation of silver contacts. This was indicated by a decrease in shunt resistance, an increase in the ideality factor (due to a higher carrier recombination), and a constant defect density in graphene films for up to 4 years. Measurements across the solar cell's active area during the 5-year period revealed neither significant spatial inhomogeneity, nor shunt channel defects.

A long operational lifetime is required for the use of solar cells in real-life photovoltaic applications. The optimization of operational lifetimes is achieved through understanding the inherent degradation phenomena in solar cells. In this study, graphene/Si Schottky-junction solar cells were produced, utilizing liquid-phase-exfoliated graphene as an active surface. The operational and interface stability of these solar cells over a period of 5 years in ambient conditions (following ISOS-D protocols: dark storage/shelf life) was examined, and the origin of their degradation was reported. It was found that the dominant degradation mechanism could be attributed to the degradation of silver contacts. This was indicated by a decrease in shunt resistance, an increase in the ideality factor (due to a higher carrier recombination), and a constant defect density in graphene films for up to 4 years. Measurements across the solar cell's active area during the 5-year period revealed neither significant spatial inhomogeneity, nor shunt channel defects.

Since the fruits of Lycium L. species (Fructus lycii, goji berries) are promoted as a “superfood” with plenty of health benefits, there is extensive research interest in their nutritional and phytochemical composition. In the present study, the nutritional value, minerals, fatty acid composition, and bioactive compounds of L. barbarum L., red, yellow, and black goji berry (L. ruthenicum Murray.) cultivated in Serbia were investigated. Antioxidant and antimicrobial properties of their methanol extracts were assessed. Red goji berry had the highest content of fats, dietary fiber, iron, total carotenoids, and 2-O- -d-glucopyranosyl-l-ascorbic acid (AA-2 G). The yellow goji berry extract showed the highest level of flavonoids and the most prominent antimicrobial (especially against Gram-negative bacteria) properties. The highest total phenolic content and the most potent antioxidant activity were observed for the extract of black goji berry. Therefore, all goji berries could be a valuable source of bioactive compounds in the food and pharmaceutical industry.

Goji berries have long been used for their nutritional value and medicinal purposes in Asian countries. In the last two decades, goji berries have become popular around the world and are consumed as a functional food due to wide-range bioactive compounds with health-promoting properties. In addition, they are gaining increased research attention as a source of functional ingredients with potential industrial applications. This review focuses on the antioxidant properties of goji berries, scientific evidence on their health effects based on human interventional studies, safety concerns, goji berry processing technologies, and applications of goji berry-based ingredients in developing functional food products.

Liquid-phase exfoliation (LPE) has been introduced as a versatile and scalable production method for two-dimensional (2D) materials. This method yields dispersions that allow for the fabrication of printable and flexible electronic devices. However, the fabrication of uniform and homogeneous films from LPE dispersions with a performance similar to that of bottom-up grown materials remains a challenge, as the film quality strongly influences the optical and electrical performance of devices. Furthermore, long-term stability remains a major challenge for all 2D material based applications. In this study, we report on highly conductive tiled network films made of platinum diselenide (PtSe2) flakes derived using a scalable LPE method. We characterized the homogeneous films in terms of morphology and electrical behavior. As an example of applicability, we produce a chemiresistive sensor structure with the PtSe2 films and show significant resistance changes upon periodic ammonia gas exposures, revealing a sub-0.1 part per million (ppm) detection limit (DL). More remarkably the devices are fully functional after 15 months, underlining the high stability of PtSe2 based devices.

Measuring relative humidity is important for a myriad of industries, including production, agriculture, environmental monitoring, and medicine. Thin-film, fast-response sensors are particularly interesting for wearable applications, such as monitoring breathing. We report on humidity sensors made from graphene deposited as a thin film by the Langmuir–Blodgett (LB) method from three types of graphene in solution. We demonstrate humidity sensing and respiration monitoring from graphene made by bath sonication, probe sonication, and electrochemical exfoliation. We characterize the morphology and chemical composition of the three film types and compare their performance as sensors. We conclude that although all three types can be used for sensing, they each have their particular advantages and drawbacks.

Gas sensors are an indispensable ingredient of the modern society, finding their use across a range of industries that include manufacturing, environmental protection and control, automotive and others. Novel applications have been arising, requiring new materials. Here we outline the principles of gas sensing with a focus on chemiresistive-type devices. We follow up with a summary of the advantages and use of graphene as a gas sensing material, discussing the properties of different graphene production methods. Finally, we showcase some recent results that point to novel applications of graphene-based gas sensors, including respiration monitoring and finger proximity detection.

Gas sensors are an indispensable ingredient of the modern society, finding their use across a range of industries that include manufacturing, environmental protection and control, automotive and others. Novel applications have been arising, requiring new materials. Here we outline the principles of gas sensing with a focus on chemiresistive-type devices. We follow up with a summary of the advantages and use of graphene as a gas sensing material, discussing the properties of different graphene production methods. Finally, we showcase some recent results that point to novel applications of graphene-based gas sensors, including respiration monitoring and finger proximity detection.

Humidity sensing is important to a variety of technologies and industries, ranging from environmental and industrial monitoring to medical applications. Although humidity sensors abound, few available solutions are thin, transparent, compatible with large-area sensor production and flexible, and almost none are fast enough to perform human respiration monitoring through breath detection or real-time finger proximity monitoring via skin humidity sensing. This work describes chemiresistive graphene-based humidity sensors produced in few steps with facile liquid phase exfoliation followed by Langmuir–Blodgett assembly that enables active areas of practically any size. The graphene sensors provide a unique mix of performance parameters, exhibiting resistance changes up to 10% with varying humidity, linear performance over relative humidity (RH) levels between 8% and 95%, weak response to other constituents of air, flexibility, transparency of nearly 80%, and response times of 30 ms. The fast response to humidity is shown to be useful for respiration monitoring and real-time finger proximity detection, with potential applications in flexible touchless interactive panels.

The Balkan Vegetation Database (BVD; GIVD ID: EU-00-019) is a regional database, which was established in 2014. It comprises phytosociological relevés covering various vegetation types from nine countries of the Balkan Peninsula (Albania – 153 relevés, Bosnia and Herzegovina – 1715, Bulgaria – 12,282, Greece – 465, Croatia – 69, Kosovo – 493, Montenegro – 440, North Macedonia – 13 and Serbia – 2677). Currently, it contains 18,306 relevés (compared to 9.580 in 2016), and most of them (82.8%) are geo-referenced. The database includes both digitized relevés from the literature (65.6%) and unpublished data (34.5%). Plot size is available for 84.7% of all relevés. During the last four years some “header data information” was improved e.g. elevation (now available for 83.4% of all relevés), aspect (67.7%), slope (66%), total cover of vegetation (54.3%), cover of tree, shrub, herb, bryophyte and lichen layers (27.1%, 20.1%, 40.2%, 11.5% and 2.1%), respectively. Data access is either semi-restricted (65.6%) or restricted (34.4%). Most relevés (84.6%) are classified to syntaxa of different levels. The database has been used for numerous studies with various objectives from floristic, vegetation and habitat-related topics, to macroecological studies at the local, regional, national, continental and global levels. During the last four years, BVD data were requested from 111 different projects via the EVA and sPlot databases.

Humidity sensing is important to a variety of technologies and industries, ranging from environmental and industrial monitoring to medical applications. Although humidity sensors abound, few available solutions are thin, transparent, compatible with large-area sensor production and flexible, and almost none are fast enough to perform human respiration monitoring through breath detection or real-time finger proximity monitoring via skin humidity sensing. This work describes chemiresistive graphene-based humidity sensors produced in few steps with facile liquid phase exfoliation followed by Langmuir–Blodgett assembly that enables active areas of practically any size. The graphene sensors provide a unique mix of performance parameters, exhibiting resistance changes up to 10% with varying humidity, linear performance over relative humidity (RH) levels between 8% and 95%, weak response to other constituents of air, flexibility, transparency of nearly 80%, and response times of 30 ms. The fast response to humidity is shown to be useful for respiration monitoring and real-time finger proximity detection, with potential applications in flexible touchless interactive panels.

Metoda eksfolijacije iz rastvora praćena Langmir-Blodžetovom metodom depozicije predstavlja jednostavan i ekonomski isplativ postupak dobijanja tankih filmova 2D materijala. Međutim, ograničavajući faktor primene svih filmova koje se zasnivaju na samoorganizaciji nanostruktura za potrebe optoelektronskih uređaja je velika gustina defekata koja indukuje visoke vrednosti površinske otpornosti. S obzirom da primena u optoelektronskim uređajima zahteva visoku transparenciju i nižu površinsku otpornost od površinske otpornosti filmova grafena eksfoliranog iz tečne faze i deponovanog Langmir-Blodžetovom metodom, neophodna je odgovarajuća površinska modifikacija/funkcionalizacija ovih filmova, koja će njihova električna i optička svojstva prilagoditi zahtevima elektronske industrije. U cilju smanjenja površinske otpornosti filmova grafena primenjena je fotohemijska oksidacija ozonom, funkcionalizacija azotnom kiselinom i termalno odgrevanje. Koja od metoda će biti primenjena prvenstveno zavisi od vrste podloge na koju se filmovi deponuju. Fotohemijska oksidacija je primenjena na filmove na SiO2/Si podlozi, a funkcionalizacija azotnom kiselinom na filmove nanete na polietilen teraftalat (PET), kao transparentnu podlogu od značaja za fleksibilnu elektroniku. Za termalno odgrevanje odabrana je temperature do 250oC, kako bi ova metoda mogla biti primenjena na uzorke nezavisno od podloge na koju su filmovi deponovani. Rezultati primenjenih fizičkohemijskih metoda karakterizacije, kao što su metode vibracione spektrometrije, fotoelektronske spektroskopije X-zracima, UV/VID spektrofotometrije, skenirajuće elektronske mikroskopije i mikroskopije sila Kelvinovom probom su pokazali da dolazi do površinske modifikacije ispitivanih filmova grafena pri fotohemijskoj oksidaciji ozonom i funkcionalizaciji azotnom kiselinom u vidu dopiranja p-tipa kiseoničnim grupama i azotom. Dopiranje filmova grafena dovodi do višestrukog smanjenja površinske otpornosti filmova do nekoliko kΩ/sq, bez pr, Liquid phase exfoliation followed by Langmuir-Blodgett assembly is a simple and costeffective method for obtaining large surfaces of thin films of 2D materials. However, the limiting factor for the application of films obtained by self-organization of nanostructures in optoelectronic devices is the high density of defects that causes high sheet resistance. Since the application in optoelectronic devices requires high transmittance and lower sheet resistance then graphene films from liquid phase, deposited with Langmuir-Blodgett method have, it is necessary to apply appropriate surface modification/functionalization of these films, which will adapt their electrical and optical properties to the requirements of the electronic industry. In order to reduce the sheet resistance of the graphene thin films, photochemical ozone oxidation, nitric acid functionalization and thermal treatment were applied. Application of particular method depends primarily of the type of substrate on which the films are deposited. Photochemical oxidation was applied to films on SiO2/Si substrates, and functionalization with nitric acid on PET films as a transparent substrate important for flexible electronics. During thermal heating, the temperature is set to 250oC, so that this method can be applied to samples independently from the substrate on which the films are deposited. The results of the applied physicochemical methods of characterization, such are vibration spectrometry, X-ray photoelectron spectroscopy, UV/VIS spectrophotometry, scanning electron microscopy and Kelvin probe force microscopy showed that surface modification of these films during photochemical oxidation with ozone and functionalization with nitric acid results in p-type doping by oxygen groups and nitrogen. Doping of these films results in a multifold reduction in sheet resistance of the films to a few kΩ/sq, without changing their high transmittance. Furthermore, it has been shown that a large density of edges, as the

Chemical sensors are an enabling tool across many industries, including the largest ones such as energy, transport, and construction. Low-cost, high performance sensors, especially ones compatible with flexible substrates, are becoming increasingly important with the development of mobile gadgets and wearable devices. Here we show humidity sensors produced from thin films of graphene exfoliated in the liquid phase and deposited with Langmuir-Blodgett assembly. The films are formed from connected nanoflakes that are ~120nm in diameter and ~10 layers thick. We show that such films have an abundancy of reactive edges that act as binding sites for gas detection, enabling high sensitivity to gas presence [1]. The method that we demonstrate uses low-cost processes, is highly scalable and consistently yields films of high quality that can be deposited on any substrate, including flexible and transparent ones. We produce our thin films on top of a Si/SiO2 wafer with four contacts for measuring sheet resistance in real time as gas is introduced. The sensors that we make are more sensitive to humidity than ones demonstrated with CVD graphene [2], with up to 30% change in sheet resistance upon exposure to water vapor. Although we demonstrate detection of humidity, the same sensors can be used to detect other, both toxic and non-toxic gases.

Nanocrystalline TiO2 films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO2 film modified with alanine that covalently binds to the surface of TiO2 and at the same time chelate silver ions induced formation of metallic silver film. Optical and morphological properties of thin silver films on nanocrystalline TiO2 support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO2 films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO2 support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact.

Nanocrystalline TiO2 films were prepared on glass slides by the dip coating technique using colloidal solutions consisting of 4.5 nm particles as a precursor. Photoirradiation of nanocrystalline TiO2 film modified with alanine that covalently binds to the surface of TiO2 and at the same time chelate silver ions induced formation of metallic silver film. Optical and morphological properties of thin silver films on nanocrystalline TiO2 support were studied by absorption spectroscopy and atomic force microscopy. Improvement of photocatalytic performance of nanocrystalline TiO2 films after deposition of silver was observed in degradation reaction of crystal violet. Antimicrobial ability of deposited silver films on nanocrystalline TiO2 support was tested in dark as a function of time against Escherichia coli, Staphylococcus aureus, and Candida albicans. The silver films ensured maximum cells reduction of both bacteria, while the fungi reduction reached satisfactory 98.45% after 24 h of contact.