Engineering Nitrogen-Doped Carbon Quantum Dots: Tailoring Optical and Chemical Properties through Selection of Nitrogen Precursors

The process of N-doping is frequently employed to enhance the properties of carbon quantum dots. However, the precise requirements for nitrogen precursors in producing high-quality N-doped carbon quantum dots (NCQDs) remain undefined. This research systematically examines the influence of various nitrogen dopants on the morphology, optical features, and band structure of NCQDs. The dots are synthesized using an efficient, eco- friendly, and rapid continuous hydrothermal flow technique. This method offers unparalleled control over synthesis and doping, while also eliminating convention-related issues. Citric acid is used as the carbon source, and urea, trizma base, beta-alanine, L-arginine, and EDTA are used as nitrogen sources. Notably, urea and trizma produced NCQDs with excitation-independent fluorescence, high quantum yields (up to 40%), and uniform dots with narrow particle size distributions. Density functional theory (DFT) and time-dependent DFT modelling established that defects and substituents within the graphitic structure have a more significant impact on the NCQDs’ electronic structure than nitrogen-containing functional groups. Importantly, for the first time, this work demonstrates that the conventional approach of modelling single-layer structures is insufficient, but two layers suffice for replicating experimental data. This study, therefore, provides essential guidance on the selection of nitrogen precursors for NCQD customization for diverse applications

3D printed SrNbO₂N photocatalyst for degradation of organic pollutants in water

Organic pollutants in water are a major concern for the environment and human health, and require urgent attention. Here, we developed for the first time monolithic structures by 3D printing of perovskite metal oxynitride, SrNbO2N, for photocatalytic degradation of organic pollutant in water. Advanced, synchrotron-based XRD-CT measurements were employed to gain structural insight into photocatalyst formulation and assess the fidelity of design in terms of both the chemical and physical form of the photocatalysts to be imaged. Our 3D printed material showed excellent photocatalytic activity, degrading 100% of methylene blue (MB) as well as good stability for three cycle operations. This is due to high adsorption of the 3D printed oxynitride towards MB which enhanced its photoredox reactivity. It is also evident from the excellent charge transfer demonstrating a charge transfer rate of (1.5 ± 0.2) × 108 s−1. We performed Time-Dependent Density Functional Theory (TD-DFT) calculations to understand the photocatalyst structure and degradation pathways. Our calculated band gap (at Γ) of 1.88 eV is in good agreement with the experimental values. We found that the highest valence bands were contributed by N p orbitals and the lowest conduction bands corresponded to Nb d orbitals offering avenues for fine-tuning the band gap. Hence, the ability to tailor photocatalyst monoliths by 3D printing renders their water treatment application more facile compared to their powder suspension counterparts

Biorefining Twin Transition: Digitalisation for Bio-based Chemicals/Materials - Discovery, Design and Optimisation

The article discusses the production of platform chemicals from various biological sources, including glycerol, lignin, cellulose, bio-oils, and sea products. It presents the results of catalytic and downstream processes involved in the conversion of these biomass-derived feedstocks. The experimental approaches are complemented by numerical descriptions, ranging from density functional theory (DFT) calculations to kinetic modellingof the experimental data. This multi-scale modelling approach helps to understand the underlying mechanisms and optimize the production of platform chemicals from renewable resources

Engineering Nitrogen‐Doped Carbon Quantum Dots: Tailoring Optical and Chemical Properties through Selection of Nitrogen Precursors

The process of N‐doping is frequently employed to enhance the properties of carbon quantum dots. However, the precise requirements for nitrogen precursors in producing high‐quality N‐doped carbon quantum dots (NCQDs) remain undefined. This research systematically examines the influence of various nitrogen dopants on the morphology, optical features, and band structure of NCQDs. The dots are synthesized using an efficient, eco‐ friendly, and rapid continuous hydrothermal flow technique. This method offers unparalleled control over synthesis and doping, while also eliminating convention‐related issues. Citric acid is used as the carbon source, and urea, trizma base, beta‐alanine, L‐arginine, and EDTA are used as nitrogen sources. Notably, urea and trizma produced NCQDs with excitation‐independent fluorescence, high quantum yields (up to 40%), and uniform dots with narrow particle size distributions. Density functional theory (DFT) and time‐dependent DFT modelling established that defects and substituents within the graphitic structure have a more significant impact on the NCQDs’ electronic structure than nitrogen‐containing functional groups. Importantly, for the first time, this work demonstrates that the conventional approach of modelling single‐layer structures is insufficient, but two layers suffice for replicating experimental data. This study, therefore, provides essential guidance on the selection of nitrogen precursors for NCQD customization for diverse applications

QUALIFICATION OF POLICE OFFICERS TO DEAL WITH AND SOLVE CONFLICTS IN A FAMILY COMMUNITY

V diplomskem delu bomo predstavili realno stanje postopkov in vodenja policijskih preiskav v predkazenskem postopku in izvedb ukrepov pri obravnavanju prekrškov in kaznivih dejanj v družinski skupnosti. S pomočjo opazovanja z neposredno udeležbo, opravljenimi razgovori, udeležbami na strokovnih posvetih in predstavitvah s strani multiplikatorjev in opaženimi posledicami policijskih postopkov ter s pomočjo strokovne literature predvsem domačih avtorjev, objavljenih strokovnih člankov, internetnih virov in strateških dokumentov za obravnavano tematiko bomo nanizali ugotovitve primernosti nivoja usposobljenosti policistov in kriminalistov pri interveniranju in obravnavanju sporov v družinski skupnosti, povezanosti in sodelovanju policije z drugimi pristojnimi institucijami in ustreznostjo ukrepanja le teh. Živimo v času, ko je zaznan porast nasilnih dogodkov v družinskih skupnostih, ko ima javnost občutek, da policija ne naredi dovolj na področju zaščite žrtve nasilja in ko smo priča premalo usposobljenemu kadru, ki se sooča s težavami pri obravnavanju in reševanju sporov v družinski skupnosti.In this thesis I will present the realistic state of the procedures and workflows of police investigations of pre-trial criminal procedures and realization of measures when handling the offences and criminal acts in families. The level of qualification of police officers and criminalists in cases of intervention in family disputes and level of cooperation between the police and other competent institutions is measured with following criteria: observation, direct participation, discussions, attendance at professional consultations and presentations by multiplicators, noticed consequences of police procedures, expert articles, internet sources and strategic documents on this topic. These criteria are used to estimate the appropriateness of used measures. We live in times of increasing domestic violence and people live under the impression that the police is not doing everything they can to protect the victims properly. We are also facing the lack of capacity and workforce of investigators dealing with and solving the domestic violence problems

Photocatalytic CO [sub] 2 reduction : a review of ab initio mechanism, kinetics, and multiscale modeling simulations

Climate change has prompted scientists to search for possible ways of reducing CO2 emissions or even capturing it from the atmosphere. Catalytic reduction of CO2 into value-added chemicals has been put forward as a viable strategy. While thermocatalytic routes of producing CO, methanol, methane, and higher hydrocarbons from CO2 have been the focus of considerable research efforts, photocatalytic conversion is an emerging approach. Photoactivation of CO2 has potential as a greener process because it could be carried out at lower temperatures and pressures, decreasing the energy consumption. The recent advent of available computational power and tools has made it possible to study the reaction in silico for catalyst prediction and mechanism elucidation. In this Review, we thus focus on ab initio research of photocatalytic CO2 reduction and comparison with experiments. The most commonly used materials are variously doped TiO2, g-C3N4, and perovskites, which have favorable optical properties on their own. Their efficiency is mostly governed by the band gap, charge separation, and charge transfer. Their characteristics can be improved, and the catalysts can be tailored for a specific use by doping, introduction of defects (such as oxygen vacancies or geometric effects), cocatalysts, or using Z-scheme catalysts. Most theoretical studies focus on the calculations of conduction and valence bands, band gap, and adsorption energies. Some studies try to describe the reaction mechanism. Few studies go beyond the hybrid-functional DFT approach and try to explicitly model the effect of electron excitation. While a theoretical description of the excited states is possible with post-DFT methods, it has yet to be applied to the problem of CO2 photoreduction on a larger scale. We conclude the Review with an outlook on how the current state-of-the-art can be used for improving the existing catalysts

BIOREFINERY: VALORISATION OF PULP AND PAPER INDUSTRY SIDE-PRODUCTS FOR BIOPLASTICSPRODUCTION

Polihidroksialkanoati so biorazgradljivi polimeri proizvedeni s pomočjo mikroorganizmov ali gensko spremenjenih bakterij. Njihove lastnosti so zelo podobne lostnostim pilietilena in polipropilena, zato predstavljajo dobro zamenjavo za plastiko, ki bazira na prizvodnji fosilnih goriv. Glavni razlog za njihovo omejujočo uporabo je visoka cena, ki je štirikrat višja kot cena za sintetično plastiko. Visoke proizvodnje stroške je možno zmanjšati z uporabo mešanih mikrobioloških kultur in cenenih odpadnih materialov in stranskih industrijskih proizvodov, kot substrat za rast mikroorganizmov. Najboljši rezultati so bili doslej dobljeni v procesu imenovanem aerobno dinamično hranjenje (ADF), ki temelji na menjanju obdobja presežek ogljika in obdobja lakote. Pod pogoji aerobnega dinamičnega hranjenja, mikroorganizmi tekmujejo za preživetje in tako preživijo tisti z največjo sposobnostjo shranjevanja zalog (polihidroksialkanoatov), kar je najbolj pomembno za proizvodnjo polihidroksialkanoatov. Namen te diplomske naloge je bila proizvodnja polihidroksialkanoatov iz odpadne sulfitne tekočine in mešanih mikrobnih kultur. Posredno pa je bil namen tudi odstranitev ocetne kisline iz odpadne sulfitne tekočine, za nadaljno uporabo pri proizvodnji bioetanola s P. stipitis. Kultura je bila izbrana v SBR reaktorju pod ADF pogoji. Sistem je deloval 72 dni in najvišja shranjena koncentracija polihidroksialkanoatov je bila 29% glede na suho težo. Kot vir ogljika so mikroorganizmi porabljali ocetno kislino, prav tako pa so porabljali tudi sladkorje, kar je onemogočilo odstranitev ocetne kisline iz odpadne sulfitne tekočine. Poleg tega je ocetna kislina v sistemu nastajala tudi s fermentacijo, saj je bil sistem kontaminiran z glivami.Polyhydroxyalkanoates (PHAs) are biodegradable biopolymers, which have been recognized as a good substitution for petroleum-based polymers. The main reason for slow replacing of the synthetic plastic is the production cost, which can be four times higher than the chemical synthesis. PHA production in activated sludge is a possible technology to decrease production costs, since no sterilization is needed and bacteria can adapt easily to the substrate in low cost feedstock. Until now, best results were obtained in a process called aerobic dynamic feeding (ADF) or also known as feast and famine cycle which is based on alternation of periods of excess carbon (feast) and periods of starvation (famine). Under ADF conditions microorganisms have to compete for survival and only the one with high storage capacity survive. Hardwood spent sulfite liquor (HSSL) is a by-product of paper industry and is rich in carbohydrates and acetic acid. It can be used as a substrate for PHA production, where mainly acetic acid is used, and also for bioethanol production, if acetic acid is removed. The aim of this work was production of polyhydroxyalkanoates from spent sulfite liquor by mixed microbial culture and also removal of acetic acid from SSL for bioethanol production with P. stipitis. The culture was selected in Sequenced batch reactor (SBR) under ADF conditions. The system was operating for 72 days and microorganisms were able to store 29% of PHA per cell dry weight. The microorganisms were able to uptake acetic acid and sugars and convert it to PHAs. The acetic acid was not removed, because microorganisms were fermenting sugars in acetic acid, or fungus present in the system were producing acetic acid

Mikrocelični odprtoporozni polistirenski kompoziti iz emulzij

Series of cross-linked polystyrene samples were prepared using an emulsion templating approach, where monomers were contained in the continuous phase of the emulsion, while the droplet aqueous phase induced primary pores, connected with a number of secondary pores. Emulsions with a high fraction of the droplet phase (HIPEs) were used and stabilised with a combination of a surfactant (sorbitan monooleate) and various types of particles (charcoal powder, copper powder and carbon nanopowder). The morphology of the resulting porous polymer depends on the type and amount of the particles added to the emulsionhowever, in all the cases open-cellular morphology was formed. The size of the primary pores (cavities) ranged from 5 µm to 25 µm, while the size of the secondary interconnecting pores was from 1 µm to 5 µm. The materials were investigated using scanning electron microscopy and nitrogen adsorption/desorption.Z uporabo emulzij z visokim deležem notranje faze smo pripravili serijo zamreženih polistirenskih vzorcev. Monomeri so bili vsebovani v kontinuirni fazi emulzije, kapljice notranje vodne faze pa so povzročile poroznost materiala z vrsto primarnih por, povezanih s povezovalnimi porami. Emulzije z visokim deležem notranje faze (HIPE) smo stabilizirali z uporabo surfaktanta v kombinaciji z različnimi delci (oglje v prahu, baker v prahu in ogljikov nanoprah). Na morfologijo pripravljenih odprtoporoznih materialov sta vplivala tako vrsta kot tudi količina dodanih delcev. Velikost primarnih por je bila v območju med 5 µm in 25 µm, medtem ko je bila velikost sekundarnih povezovalnih por v območju med 1 µm in 5 µm. Materiale smo karakterizirali z uporabo vrstičnega elektronskega mikroskopa in adsorpcijo/desorpcijo dušika