Molecular Design Using Selected Concentration Effects in Optically Activated Fluorescent Matrices

Molecular physics plays a pivotal role in various fields, including medicine, pharmaceuticals, and broader industrial applications. This study aims to enhance the methods for producing specific optically active materials with distinct spectroscopic properties at the molecular level, which are crucial for these sectors, while prioritizing human safety in both production and application. Forensic science, a significant socio-economic field, often employs hazardous substances in analyzing friction ridges on porous surfaces, posing safety concerns. In response, we formulated novel, non-toxic procedures for examining paper evidence, particularly thermal papers. Our laboratory model utilizes a polyvinyl alcohol polymer as a rigid matrix to emulate the thermal paper's environment, enabling precise control over the spectroscopic characteristics of 1,8-diazafluoro-9-one (DFO). We identified and analyzed the cyclodimer 1,8-diazafluoren-9-one (DAK DFO), which is a non-toxic and biocompatible alternative for revealing forensic marks. The reagents used to preserve fingerprints were optimized for their effectiveness and stability. Using stationary absorption and emission spectroscopy, along with time-resolved emission studies, we verified the spectroscopic attributes of the new structures under deliberate aggregation conditions. Raman spectroscopy and quantum mechanical computations substantiated the cyclodimer's configuration. The investigation provides robust scientific endorsement for the novel compound and its structural diversity, influenced by the solvatochromic sensitivity of the DFO precursor. Our approach to monitoring aggregation processes signifies a substantial shift in synthetic research paradigms, leveraging simple chemistry to yield an innovative contribution to forensic science methodologies.

Discriminating macromolecular interactions based on an impedimetric fingerprint supported by multivariate data analysis for rapid and label-free Escherichia coli recognition in human urine

This manuscript presents a novel approach to address the challenges of electrode fouling and highly complex electrode nanoarchitecture, which are primary concerns for biosensors operating in real environments. The proposed approach utilizes multiparametric impedance discriminant analysis (MIDA) to obtain a fingerprint of the macromolecular interactions on flat glassy carbon surfaces, achieved through self-organized, drop-cast, receptor-functionalized Au nanocube (AuNC) patterns. Real-time monitoring is combined with singular value decomposition and partial least squares discriminant analysis, which enables selective identification of the analyte from raw impedance data, without the use of electric equivalent circuits. As a proof-of-concept, the authors demonstrate the ability to detect Escherichia coli in real human urine using an aptamer-based biosensor that targets RNA polymerase. This is significant, as uropathogenic E. coli is a difficult-to-treat pathogen that is responsible for the majority of hospital-acquired urinary tract infection cases. The proposed approach offers a limit of detection of 11.3 CFU/mL for the uropathogenic E. coli strain No. 57, an analytical range in all studied concentrations (up to 105 CFU/mL), without the use of antifouling strategies, yet not being specific vs other E.coli strain studied (BL21(DE3)). The MIDA approach allowed to identify negative overpotentials (-0.35 to -0.10 V vs Ag/AgCl) as most suitable for the analysis, offering over 80% sensitivity and accuracy, and the measurement was carried out in just 2 min. Moreover, this approach is scalable and can be applied to other biosensor platforms.

Boron-doped diamond nanosheet volume-enriched screen-printed carbon electrodes: a platform for electroanalytical and impedimetric biosensor applications

This paper focuses on the development of a novel electrode based on boron-doped diamond nanosheet full-volume-enriched screen-printed carbon electrodes (BDDPE) for use as an impedimetric biosensor. Impedimetric biosensors offer high sensitivity and selectivity for virus detection, but their use as point-of-care devices is limited by the complexity of nanomaterials' architecture and the receptor immobilisation procedures. The study presents a two-step modification process involving the electroreduction of diazonium salt at the BDDPE and the immobilisation of antibodies using zero-length cross-linkers for a selective impedimetric biosensor of Haemophilus influenzae (Hi). The incorporation of diamond nanosheets into BDDPE leads to enhanced charge transfer and electrochemical behaviour, demonstrating greatly improved electrochemically active surface area compared with unmodified screen-printed electrodes (by 44% and 10% on average for [Ru(NH3)6]Cl2 and K3[Fe(CN)6], respectively). The presented sensing system shows high specificity towards protein D in Hi bacteria, as confirmed by negative controls against potential interference from other pathogens, with an estimated tolerance limit for interference under 12%. The Hi limit of detection by electrochemical impedance spectroscopy was 1 CFU/mL (measured at - 0.13 V vs BDDPE pseudo-reference), which was achieved in under 10 min, including 5 min sample incubation in the presence of the analyte.

Tailoring diamondised nanocarbon-loaded poly(lactic acid) composites for highly electroactive surfaces: extrusion and characterisation of filaments for improved 3D-printed surfaces

A new 3D-printable composite has been developed dedicated to electroanalytical applications. Two types of diamondised nanocarbons - detonation nanodiamonds (DNDs) and boron-doped carbon nanowalls (BCNWs) - were added as fillers in poly(lactic acid) (PLA)-based composites to extrude 3D filaments. Carbon black served as a primary filler to reach high composite conductivity at low diamondised nanocarbon concentrations (0.01 to 0.2 S/cm, depending on the type and amount of filler). The aim was to thoroughly describe and understand the interactions between the composite components and how they affect the rheological, mechanical and thermal properties, and electrochemical characteristics of filaments and material extrusion printouts. The electrocatalytic properties of composite-based electrodes, fabricated with a simple 3D pen, were evaluated using multiple electrochemical techniques (cyclic and differential pulse voltammetry and electrochemical impedance spectroscopy). The results showed that the addition of 5 wt% of any of the diamond-rich nanocarbons fillers significantly enhanced the redox process kinetics, leading to lower redox activation overpotentials compared with carbon black-loaded PLA. The detection of dopamine was successfully achieved through fabricated composite electrodes, exhibiting lower limits of detection (0.12 μM for DND and 0.18 μM for BCNW) compared with the reference CB-PLA electrodes (0.48 μM). The thermogravimetric results demonstrated that both DND and BCNW powders can accelerate thermal degradation. The presence of diamondised nanocarbons, regardless of their type, resulted in a decrease in the decomposition temperature of the composite. The study provides insight into the interactions between composite components and their impact on the electrochemical properties of 3D-printed surfaces, suggesting electroanalytic potential.

Engineering boron and nitrogen codoped carbon nanoarchitectures to tailor molecularly imprinted polymers for PFOS determination

Per- and polyfluoroalkyl substances (PFAS) have gained significant attention as emerging contaminants due to their persistence, abundance, and adverse health effects. Consequently, the urgent need for ubiquitous and effective sensors capable of detecting and quantifying PFAS in complex environmental samples has become a priority. In this study, we present the development of an ultrasensitive molecularly imprinted polymer (MIP) electrochemical sensor tailored by chemically vapour-deposited boron and nitrogen codoped diamond-rich carbon nanoarchitectures for the selective determination of perfluorooctanesulfonic acid (PFOS). This approach allows for a multiscale reduction of MIP heterogeneities, leading to improved selectivity and sensitivity in PFOS detection. Interestingly, the peculiar carbon nanostructures induce a specific distribution of binding sites in the MIPs that exhibit a strong affinity for PFOS. The designed sensors demonstrated a low limit of detection (1.2 μg L^-1) and exhibited satisfactory selectivity and stability. To gain further insights into the molecular interactions between diamond-rich carbon surfaces, electropolymerised MIP, and the PFOS analyte, a set of density functional theory (DFT) calculations was performed. Validation of the sensor's performance was carried out by successfully determining PFOS concentrations in real complex samples, such as tap water and treated wastewater, with average recovery rates consistent with UHPLC-MS/MS results. These findings demonstrate the potential of MIP-supported diamond-rich carbon nanoarchitectures for water pollution monitoring, specifically targeting emerging contaminants. The proposed sensor design holds promise for the development of in situ PFOS monitoring devices operating under relevant environmental concentrations and conditions.

Texture or Linker? Competitive Patterning of Receptor Assembly toward Ultra-Sensitive Impedimetric Detection of Viral Species at Gold-Nanotextured Titanium Surfaces

In this work, we study the electrodes with a periodic matrix of gold particles pattered by titanium dimples and modified by 3-mercaptopropionic acid (MPA) followed by CD147 receptor grafting for specific impedimetric detection of SARS-CoV-2 viral spike proteins. The synergistic DFT and MM/MD modeling revealed that MPA adsorption geometries on the Au-Ti surface have preferential and stronger binding patterns through the carboxyl bond inducing an enhanced surface coverage with CD147. Control of bonding at the surface is essential for oriented receptor assembling and boosted sensitivity. The complex Au-Ti electrode texture along with optimized MPA concentration is a crucial parameter, enabling to reach the detection limit of ca. 3 ng mL-1. Scanning electrochemical microscopy imaging and quantum molecular modeling were performed to understand the electrochemical performance and specific assembly of MPA displaying a free stereo orientation and not disturbed by direct interactions with closely adjacent receptors. This significantly limits nonspecific interceptor reactions, strongly decreasing the detection of receptor-binding domain proteins by saturation of binding groups. This method has been demonstrated for detecting the SARS virus but can generally be applied to a variety of protein-antigen systems. Moreover, the raster of the pattern can be tuned using various anodizing processes at the titania surfaces.

Highly Occupied Surface States at Deuterium-Grown Boron-Doped Diamond Interfaces for Efficient Photoelectrochemistry

Polycrystalline boron-doped diamond is a promising material for high-power aqueous electrochemical applications in bioanalytics, catalysis, and energy storage. The chemical vapor deposition (CVD) process of diamond formation and doping is totally diversified by using high kinetic energies of deuterium substituting habitually applied hydrogen. The high concentration of deuterium in plasma induces atomic arrangements and steric hindrance during synthesis reactions, which in consequence leads to a preferential (111) texture and more effective boron incorporation into the lattice, reaching a one order of magnitude higher density of charge carriers. This provides the surface reconstruction impacting surficial populations of CC dimers, CH, CO groups, and COOH termination along with enhanced kinetics of their abstraction, as revealed by high-resolution core-level spectroscopies. A series of local densities of states were computed, showing a rich set of highly occupied and localized surface states for samples deposited in deuterium, negating the connotations of band bending. The introduction of enhanced incorporation of boron into (111) facet of diamond leads to the manifestation of surface electronic states below the Fermi level and above the bulk valence band edge. This unique electronic band structure affects the charge transfer kinetics, electron affinity, and diffusion field geometry critical for efficient electrolysis, electrocatalysis, and photoelectrochemistry.

Nanodiamonds Doped with Manganese for Applications in Magnetic Resonance Imaging

Nanodiamonds (NDs) are emerging with great potential in biomedical applications like biomarking through fluorescence and magnetic resonance imaging (MRI), targeted drug delivery, and cancer therapy. The magnetic and optical properties of NDs could be tuned by selective doping. Therefore, we report multifunctional manganese-incorporated NDs (Mn-NDs) fabricated by Mn ion implantation. The fluorescent properties of Mn-NDs were tuned by inducing the defects by ion implantation and enhancing the residual nitrogen vacancy density achieved by a two-step annealing process. The cytotoxicity of Mn-NDs was investigated using NCTC clone 929 cells, and the results revealed no cytotoxicity effect. Mn-NDs have demonstrated dual mode contrast enhancement for both T ₁- and T ₂-weighted in vitro MR imaging. Furthermore, Mn-NDs have illustrated a significant increase in longitudinal relaxivity (fivefold) and transversal relaxivity (17-fold) compared to the as-received NDs. Mn-NDs are employed to investigate their ability for in vivo MR imaging by intraperitoneal (ip) injection of Mn-NDs into mice with liver tumors. After 2.5 h of ip injection, the enhancement of contrast in T ₁- and T ₂-weighted images has been observed via the accumulation of Mn-NDs in liver tumors of mice. Therefore, Mn-NDs have great potential for in vivo imaging by MR imaging in cancer therapy.

Enhanced susceptibility of SARS-CoV-2 spike RBD protein assay targeted by cellular receptors ACE2 and CD147: Multivariate data analysis of multisine impedimetric response

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the cells through the binding of spike protein to the host cell surface-expressing angiotensin-converting enzyme 2 (ACE2) or by endocytosis mediated by extracellular matrix metalloproteinase inducer (CD147). We present extended statistical studies of the multisine dynamic electrochemical impedance spectroscopy (DEIS) revealing interactions between Spike RBD and cellular receptors ACE2 and CD147, and a reference anti-RBD antibody (IgG2B) based on a functionalised boron-doped diamond (BDD) electrode. The DEIS was supported by a multivariate data analysis of a SARS-CoV-2 Spike RBD assay and cross-correlated with the atomic-level information revealed by molecular dynamics simulations. This approach allowed us to study and detect subtle changes in the electrical properties responsible for the susceptibility of cellular receptors to SARS-CoV-2, revealing their interactions. Changes in electrical homogeneity in the function of the RBD concentration led to the conclusion that the ACE2 receptor delivers the most homogeneous surface, delivered by the high electrostatic potential of the relevant docking regions. For higher RBD concentrations, the differences in electrical homogeneity between electrodes with different receptors vanish. Collectively, this study reveals interdependent virus entry pathways involving separately ACE2, CD147, and spike protein, as assessed using a biosensing platform for the rapid screening of cellular interactions (i.e. testing various mutations of SARS-CoV-2 or screening of therapeutic drugs).

Electrocatalytic performance of oxygen-activated carbon fibre felt anodes mediating degradation mechanism of acetaminophen in aqueous environments

Carbon felts are flexible and scalable, have high specific areas, and are highly conductive materials that fit the requirements for both anodes and cathodes in advanced electrocatalytic processes. Advanced oxidative modification processes (thermal, chemical, and plasma-chemical) were applied to carbon felt anodes to enhance their efficiency towards electro-oxidation. The modification of the porous anodes results in increased kinetics of acetaminophen degradation in aqueous environments. The utilised oxidation techniques deliver single-step, straightforward, eco-friendly, and stable physiochemical reformation of carbon felt surfaces. The modifications caused minor changes in both the specific surface area and total pore volume corresponding with the surface morphology. A pristine carbon felt electrode was capable of decomposing up to 70% of the acetaminophen in a 240 min electrolysis process, while the oxygen-plasma treated electrode achieved a removal yield of 99.9% estimated utilising HPLC-UV-Vis. Here, the electro-induced incineration kinetics of acetaminophen resulted in a rate constant of 1.54 h^-1, with the second-best result of 0.59 h^-1 after oxidation in 30% H₂O₂. The kinetics of acetaminophen removal was synergistically studied by spectroscopic and electrochemical techniques, revealing various reaction pathways attributed to the formation of intermediate compounds such as p-aminophenol and others. The enhancement of the electrochemical oxidation rates towards acetaminophen was attributed to the appearance of surface carbonyl species. Our results indicate that the best-performing plasma-chemical treated CFE follows a heterogeneous mechanism with only approx. 40% removal due to direct electro-oxidation. The degradation mechanism of acetaminophen at the treated carbon felt anodes was proposed based on the detected intermediate products. Estimation of the cost-effectiveness of removal processes, in terms of energy consumption, was also elaborated. Although the study was focussed on acetaminophen, the achieved results could be adapted to also process emerging, hazardous pollutant groups such as anti-inflammatory pharmaceuticals.

Hopping or Tunneling? Tailoring the Electron Transport Mechanisms through Hydrogen Bonding Geometry in the Boron-Doped Diamond Molecular Junctions

Mechanisms of charge transport in molecular junctions involving hydrogen bonds are complex and remain mostly unclear. This study is focused on the elucidation of the electron transfer in a molecular device consisting of two boron-doped diamond interfaces bound with an aromatic linker and a hydrogen bonding surrogating molecule. The projected local density of states (PLODS) analysis coupled with transmission spectra and current-voltage (I-V) simulations show that hydrogen bonding through electron-donating hydroxyl groups in the aromatic linker facilitates electron transfer, while the electron-withdrawing carboxyl group inhibits electron transfer across the junction. Moreover, slight variations in the geometry of hydrogen bonding lead to significant changes in the alignment of the energy levels and positions of the transmission modes. As a result, we observe the switching of the electron transport mechanism from tunneling to hopping accompanied by a change in the shape of the I-V curves and current magnitudes. These results give important information on the tailoring of the electronic properties of molecular junctions.

Tailoring Diffusional Fields in Zwitterion/Dopamine Copolymer Electropolymerized at Carbon Nanowalls for Sensitive Recognition of Neurotransmitters

The importance of neurotransmitter sensing in the diagnosis and treatment of many psychological illnesses and neurodegenerative diseases is non-negotiable. For electrochemical sensors to become widespread and accurate, a long journey must be undertaken for each device, from understanding the materials at the molecular level to real applications in biological fluids. We report a modification of diamondized boron-doped carbon nanowalls (BCNWs) with an electropolymerized polydopamine/polyzwitterion (PDA|PZ) coating revealing tunable mechanical and electrochemical properties. Zwitterions are codeposited with PDA and noncovalently incorporated into a structure. This approach causes a specific separation of the diffusion fields generated by each nanowall during electrochemical reactions, thus increasing the contribution of the steady-state currents in the amperometric response. This phenomenon has a profound effect on the sensing properties, leading to a 4-fold enhancement of the sensitivity (3.1 to 14.3 μA cm^-2 μM^-1) and a 5-fold decrease of the limit of detection (505 to 89 nM) in comparison to the pristine BCNWs. Moreover, as a result of the antifouling capabilities of the incorporated zwitterions, this enhancement is preserved in bovine serum albumin (BSA) with a high protein concentration. The presence of zwitterion facilitates the transport of dopamine in the direction of the electrode by intermolecular interactions such as cation-π and hydrogen bonds. On the other hand, polydopamine units attached to the surface form molecular pockets driven by hydrogen bonds and π-π interactions. As a result, the intermediate state of dopamine-analyte oxidation is stabilized, leading to the enhancement of the sensing properties.

Deciphering the Molecular Mechanism of Substrate-Induced Assembly of Gold Nanocube Arrays toward an Accelerated Electrocatalytic Effect Employing Heterogeneous Diffusion Field Confinement

The complex electrocatalytic performance of gold nanocubes (AuNCs) is the focus of this work. The faceted shapes of AuNCs and the individual assembly processes at the electrode surfaces define the heterogeneous conditions for the purpose of electrocatalytic processes. Topographic and electron imaging demonstrated slightly rounded AuNC (average of 38 nm) assemblies with sizes of ≤1 μm, where the dominating patterns are (111) and (200) crystallographic planes. The AuNCs significantly impact the electrochemical performance of the investigated electrode [indium-tin oxide (ITO), glassy carbon (GC), and bulk gold] systems driven by surface electrons promoting the catalytic effect. Cyclic voltammetry in combination with scanning electrochemical microscopy allowed us to decipher the molecular mechanism of substrate-induced electrostatic assembly of gold nanocube arrays, revealing that the accelerated electrocatalytic effect should be attributed to the confinement of the heterogeneous diffusion fields with tremendous electrochemically active surface area variations. AuNC drop-casting at ITO, GC, and Au led to various mechanisms of heterogeneous charge transfer; only in the case of GC did the decoration significantly increase the electrochemically active surface area (EASA) and ferrocyanide redox kinetics. For ITO and Au substrates, AuNC drop-casting decreases system dimensionality rather than increasing the EASA, where Au-Au self-diffusion was also observed. Interactions of the gold, ITO, and GC surfaces with themselves and with surfactant CTAB and ferrocyanide molecules were investigated using density functional theory.

Performance of electrochemical immunoassays for clinical diagnostics of SARS-CoV-2 based on selective nucleocapsid N protein detection: Boron-doped diamond, gold and glassy carbon evaluation

The 21st century has already brought us a plethora of new threats related to viruses that emerge in humans after zoonotic transmission or drastically change their geographic distribution or prevalence. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first spotted at the end of 2019 to rapidly spread in southwest Asia and later cause a global pandemic, which paralyzes the world since then. We have designed novel immunosensors targeting conserved protein sequences of the N protein of SARS-CoV-2 based on lab-produced and purified anti-SARS-CoV-2 nucleocapsid antibodies that are densely grafted onto various surfaces (diamond/gold/glassy carbon). Titration of antibodies shows very strong reactions up to 1:72 900 dilution. Next, we showed the mechanism of interactions of our immunoassay with nucleocapsid N protein revealing molecular recognition by impedimetric measurements supported by hybrid modeling results with both density functional theory and molecular dynamics methods. Biosensors allowed for a fast (in less than 10 min) detection of SARS-CoV-2 virus with a limit of detection from 0.227 ng/ml through 0.334 ng/ml to 0.362 ng/ml for glassy carbon, boron-doped diamond, and gold surfaces, respectively. For all tested surfaces, we obtained a wide linear range of concentrations from 4.4 ng/ml to 4.4 pg/ml. Furthermore, our sensor leads to a highly specific response to SARS-CoV-2 clinical samples versus other upper respiratory tract viruses such as influenza, respiratory syncytial virus, or Epstein-Barr virus. All clinical samples were tested simultaneously on biosensors and real-time polymerase chain reactions.

Tailoring of Optical Properties of Methacrylate Resins Enriched by HPHT Microdiamond Particles

Diamond particles have great potential to enhance the mechanical, optical, and thermal properties of diamond–polymer composites. However, the improved properties of diamond–polymer composites depend on the size, dispersibility, and concentration of diamond particles. In the present study, diamond–polymer composites were prepared by adding the microdiamond particles (MDPs) with different concentrations (0.2–1 wt.%) into polymers (acrylate resins) and then subjected to a photocuring process. The surface morphology and topography of the MDPs–polymer composites demonstrated a uniform high-density distribution of MDPs for one wt.% MPDs. Thermogravimetric analysis was employed to investigate the thermal stability of the MDPs–polymer composites. The addition of MDPs has significantly influenced the polymers’ thermal degradation. Absorption and emission spectra of thin layers were recorded through UV/Vis spectrophotometry and spectrofluorimetry. The obtained results revealed a significant increase in the fluorescence intensity of MDPs–polymer composites (at 1 wt.% of MDPs, a 1.5×, 2×, and 5× increase in fluorescence was observed for MDPs–green, MDPs–amber daylight, and MDPs–red resin, respectively) compared with the reference polymer resins. The obtained results of this work show the new pathways in producing effective and active 3D-printed optical elements.

Conductive printable electrodes tuned by boron-doped nanodiamond foil additives for nitroexplosive detection

An efficient additive manufacturing-based composite material fabrication for electrochemical applications is reported. The composite is composed of commercially available graphene-doped polylactide acid (G-PLA) 3D printouts and surface-functionalized with nanocrystalline boron-doped diamond foil (NDF) additives. The NDFs were synthesized on a tantalum substrate and transferred to the 3D-printout surface at 200 °C. No other electrode activation treatment was necessary. Different configurations of low- and heavy-boron doping NDFs were evaluated. The electrode kinetics was analyzed using electrochemical procedures: cyclic voltammetry and electrochemical impedance spectroscopy. The quasi-reversible electrochemical process was reported in each studied case. The studies allowed confirmation of the CV peak-to-peak separation of 63 mV and remarkably high heterogeneous electron transfer rate constant reaching 6.1 × 10⁻² cm s⁻¹ for 10 k ppm [B]/[C] thin NDF fitted topside at the G-PLA electrode. Differential pulse voltammetry was used for effective 2,4,6-trinitrotoluene (TNT) detection at the studied electrodes with a 87 ppb limit of detection, and wide linearity range between peak current density and the analyte concentration (0.064 to 64 ppm of TNT). The reported electrode kinetic differences originate primarily from the boron-dopant concentration in the diamond and the various contents of the non-diamond carbon phase.

Fluorescence of nanodiamond cocktails: pH-induced effects through interactions with comestible liquids

Fluorescent nanodiamonds with nitrogen-vacancy centers have become important nanoscale probes for sensing and imaging. The surface chemistry of the nanodiamonds influences their emission, interactions, and quantum properties. In this work, we propose to utilize fluorescent nanodiamonds as photostable markers for investigation of comestible liquids. We prepared nanodiamond/comestibles suspensions/cocktails with a wide range of pH levels and studied the samples via fluorescence, wettability, and zeta potential. The composition of the created cocktails revealed a strong impact on the properties of the nanodiamond and its surface chemistry, mainly induced by pH but also tuned by specific quenching compounds. Moreover, the stability of the nanodiamonds in the cocktail media was studied, along with various nature-originated compounds influencing their surface termination, polarity, and charge states. Thanks to the stability and biocompatibility of the nanodiamond, it can be applied in monitoring the condition of foodstuffs, and in the detection of toxins and pathogens in them.

Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films

Boron doped diamond (BDD) has great potential in electrical, and electrochemical sensing applications. The growth parameters, substrates, and synthesis method play a vital role in the preparation of semiconducting BDD to metallic BDD. Doping of other elements along with boron (B) into diamond demonstrated improved efficacy of B doping and exceptional properties. In the present study, B and nitrogen (N) co-doped diamond has been synthesized on single crystalline diamond (SCD) IIa and SCD Ib substrates in a microwave plasma-assisted chemical vapor deposition process. The B/N co-doping into CVD diamond has been conducted at constant N flow of N/C ∼ 0.02 with three different B/C doping concentrations of B/C ∼ 2500 ppm, 5000 ppm, 7500 ppm. Atomic force microscopy topography depicted the flat and smooth surface with low surface roughness for low B doping, whereas surface features like hillock structures and un-epitaxial diamond crystals with high surface roughness were observed for high B doping concentrations. KPFM measurements revealed that the work function (4.74-4.94 eV) has not varied significantly for CVD diamond synthesized with different B/C concentrations. Raman spectroscopy measurements described the growth of high-quality diamond and photoluminescence studies revealed the formation of high-density nitrogen-vacancy centers in CVD diamond layers. X-ray photoelectron spectroscopy results confirmed the successful B doping and the increase in N doping with B doping concentration. The room temperature electrical resistance measurements of CVD diamond layers (B/C ∼ 7500 ppm) have shown the low resistance value ∼9.29 Ω for CVD diamond/SCD IIa, and the resistance value ∼16.55 Ω for CVD diamond/SCD Ib samples.

Nitrogen-Incorporated Boron-Doped Nanocrystalline Diamond Nanowires for Microplasma Illumination

The origin of nitrogen-incorporated boron-doped nanocrystalline diamond (NB-NCD) nanowires as a function of substrate temperature (T_s) in H₂/CH₄/B₂H₆/N₂ reactant gases is systematically addressed. Because of T_s, there is a drastic modification in the dimensional structure and microstructure and hence in the several properties of the NB-NCD films. The NB-NCD films grown at low T_s (400 °C) contain faceted diamond grains. The morphology changes to nanosized diamond grains for NB-NCD films grown at 550 °C (or 700 °C). Interestingly, the NB-NCD films grown at 850 °C possess one-dimensional nanowire-like morphological grains. These nanowire-like NB-NCD films possess the co-existence of the sp³-diamond phase and the sp²-graphitic phase, where diamond nanowires are surrounded by sp²-graphitic phases at grain boundaries. The optical emission spectroscopy studies stated that the CN, BH, and C₂ species in the plasma are the main factors for the origin of nanowire-like conducting diamond grains and the materialization of graphitic phases at the grain boundaries. Moreover, conductive atomic force microscopy studies reveal that the NB-NCD films grown at 850 °C show a large number of emission sites from the grains and the grain boundaries. While boron doping improved the electrical conductivity of the NCD grains, the nitrogen incorporation eased the generation of graphitic phases at the grain boundaries that afford conducting channels for the electrons, thus achieving a high electrical conductivity for the NB-NCD films grown at 850 °C. The microplasma devices using these nanowire-like NB-NCD films as cathodes display superior plasma illumination properties with a threshold field of 3300 V/μm and plasma current density of 1.04 mA/cm² with a supplied voltage of 520 V and a lifetime stability of 520 min. The outstanding plasma illumination characteristics of these conducting nanowire-like NB-NCD films make them appropriate as cathodes and pave the way for the utilization of these materials in various microplasma device applications.

Simultaneous opto-electrochemical monitoring of carbamazepine and its electro-oxidation by-products in wastewater

The growing human impact on aquatic environments deriving from the extensive use of pharmaceuticals and the release of persistent pollutants necessitates the implementation of new, widespread methods for characterising and quantifying such contaminants and their related degradation products. Carbamazepine, 5 H-dibenzo[b,f]azepine-5-carboxamide, (CBZ) is a widely used anti-epileptic drug characterised by limited removal by conventional wastewater treatments and high persistency in the environment. In this work, CBZ detection and quantification was performed in phosphate buffer, as well as in samples of complex matrix-like landfill leachates and treated wastewater originating from a medical facility, and simultaneously by optical and electrochemical methods using a novel transparent carbon-based nanostructured electrode. Coupling electrochemical (differential pulse voltammetry) with optical (UV-visible spectroscopy) methods, it has been possible to reach the limit of detection (LOD) for CBZ at the levels of 4.7 μM for the electrochemical method, 10.3 μM for the spectroscopic method, and 3.6 μM for the opto-electrochemical method. Raman spectroscopy and ultra-high performance liquid chromatography coupled with tandem mass spectrometry techniques were employed to support and validate the combined technique. The novel developed technique showed high selectivity to carbamazepine and its by-products, even in environmental samples. Thus, this environmentally friendly, fast and accurate detection method is believed to be successfully implementable in investigating other pharmaceutical and chemical contaminates of concern.

Chemical Vapor Transport Route toward Black Phosphorus Nanobelts and Nanoribbons

Chemical vapor transport (CVT) method is widely used for bulk black phosphorus (BP) fabrication. In this work, we demonstrate that CVT provides a route for the fabrication of BP nanoribbons and nanobelts. This method consists of a two-step procedure, including initial BP column growth using the CVT technique, followed by ultrasonic treatment and centrifugation. The obtained nanostructures preserve BP column dimensions, forming ultralong ribbon-like structures with the length to the width aspect ratio of up to 500. Computational modeling of the growth mechanism of a BP flake is also presented in support of the observed columnar growth. Calculation of the average energy of the molecule in the asymmetric flakes shows that the growth of the structure in the zigzag direction is more energetically favorable than in the armchair direction.

Electrochemical oxidation of PFOA and PFOS in landfill leachates at low and highly boron-doped diamond electrodes

Polyfluorinated alkyl substances (PFASs) may reach landfill leachates (LLs) due to improper waste management. In this study perfluorooctanoate (PFOA) and perfluorooctane sulphonate (PFOS) were used as representatives of PFASs in the decomposition on boron-doped diamond electrodes (BDDs) with high (10k ppm) and low (0.5k ppm) boron doping concentrations. The result shows that although better COD removal efficacies are obtained on the low-doped BDD (59 % after 8 h), the decomposition rate of PFOA and PFOS was not affected by boron doping. In LLs, at the current density of 75 mA/cm², averaged removal efficiencies of 80 % and 78 % were achieved for PFOA and PFOS, respectively. But besides concentration of mother compounds, the presence of intermediates during electrolysis should be monitored. After 8 h of LL electrolysis, the presence of long-chain degradates C₆F₁₃ and C₆F₁₃COO^- was still observed only in 10k BDD-PFOA assays, while during 0.5k assays C₆F₁₃ and C₆F₁₃COO^- form more intesively at the beginning of the process. This indirectly confirms the more intensive generation of perfluoroalkoxy and hydroxyl radicals and higher susceptibility to electrolysis of PFOA's long-chain intermediates on 0.5k BDD. This is the first study reporting BDD-electrolysis as promising in PFAS removal from the complex matrix of LLs, despite the oxidation of competing LLs components.

Carbon nanoarchitectures as high-performance electrodes for the electrochemical oxidation of landfill leachate

Nanomaterials and assemblies of the aforementioned into complex architectures constitute an opportunity to design efficient and selective solutions to widespread and emerging environmental issues. The limited disposal of organic matter in modern landfills generates extremely concentrated leachates characterised by high concentrations of refractory compounds. Conventional biochemical treatment methods are unsuitable, while advanced treatment, such coagulation, reverse osmosis and ultrafiltration can be very costly and generate additional waste. Electrochemical oxidation is an established technique to efficiently mineralise a plethora of recalcitrant pollutants, however the selectivity and efficiency of the process are strongly related to the anode material. For this reason, a nanoarchitectured carbon material has been designed and synthesised to improve the capability of the anode towards the adsorption and decomposition of pollutants. Instead of simple nanostructures, intelligently engineered nanomaterials can come in handy for more efficient advanced treatment techniques. In this study, a carbon nanoarchitecture comprising boron-doped vertically aligned graphene walls (BCNWs) were grown on a boron-doped diamond (BDD) interfacial layer. The results show how the peculiar maze-like morphology and the concurrence of different carbon hybridisations resulted in a higher current exchange density. The BDD performed better for the removal of NH₄⁺ while the BCNW-only sample exhibited a faster deactivation. The BDD/BCNW nanoarchitecture resulted in an enhanced COD removal and a NH₄⁺ removal similar to that of BDD, without the intermediate production of NO₂^- and NO₃^-.

The Luminescence of 1,8-Diazafluoren-9-One/Titanium Dioxide Composite Thin Films for Optical Application

The investigation of innovative label-free α-amino acids detection methods represents a crucial step for the early diagnosis of several diseases. While 1,8-diazafluoren-9-one (DFO) is known in forensic application because of the fluorescent products by reacting with the amino acids present in the papillary exudate, its application for diagnostic purposes has not been fully investigated. The stabilization of DFO over a transparent substrate allows its complexation with biomolecules for the detection of α-amino acids. In this study, DFO was immobilized into a titanium dioxide (TiO₂) matrix for the fluorescence detection of glycine, as a target α-amino acid (a potential marker of the urogenital tract cancers). The DFO/TiO₂ composite was characterized by atomic force microscopy, spectroscopic ellipsometry, fluorescence spectroscopy and fluorescence microscopy. The performed fluorescent studies indicate spectacular formation of aggregates at higher concentration. The measurements performed using various fluorescence and microscopic techniques together with the suitable analysis show that the aggregates are able to emit short-lived fluorescence.

Single-step grown boron doped nanocrystalline diamond-carbon nanograss hybrid as an efficient supercapacitor electrode

Direct synthesis of a nano-structured carbon hybrid consisting of vertically aligned carbon nanograsses on top of boron-doped nanocrystalline diamond is demonstrated and the carbon hybrid is further applied as an electrode material for the fabrication of supercapacitors. The hybrid film combines the dual advantages of sp2 (carbon nanograss) and sp3 (nanocrystalline diamond) bonded carbon, possessing not only the excellent electrical characteristics of sp2 carbon but also the exceptional electrochemical stability of sp3 carbon. As a result, the specific capacitance of the as-prepared hybrid material reaches up to 0.4 F cm-2, one of the highest reported in diamond-based supercapacitors. The entire electrochemical results exhibit enhanced electron transfer efficiency with remarkable stability of 95% of capacitance retention even after 10 000 cycles.

Electrochemical determination of nitroaromatic explosives at boron-doped diamond/graphene nanowall electrodes: 2,4,6-trinitrotoluene and 2,4,6-trinitroanisole in liquid effluents

The study is devoted to the electrochemical detection of trace explosives on boron-doped diamond/graphene nanowall electrodes (B:DGNW). The electrodes were fabricated in a one-step growth process using chemical vapour deposition without any additional modifications. The electrochemical investigations were focused on the determination of the important nitroaromatic explosive compounds, 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitroanisole (TNA). The distinct reduction peaks of both studied compounds were observed regardless of the pH value of the solution. The reduction peak currents were linearly related to the concentration of TNT and TNA in the range from 0.05-15 ppm. Nevertheless, two various linear trends were observed, attributed respectively to the adsorption processes at low concentrations up to the diffusional character of detection for larger contamination levels. The limit of detection of TNT and TNA is equal to 73 ppb and 270 ppb, respectively. Moreover, the proposed detection strategy has been applied under real conditions with a significant concentration of interfering compounds - in landfill leachates. The proposed bare B:DGNW electrodes were revealed to have a high electroactive area towards the voltammetric determination of various nitroaromatic compounds with a high rate of repeatability, thus appearing to be an attractive nanocarbon surface for further applications.

High-Temperature Oxidation of Heavy Boron-Doped Diamond Electrodes: Microstructural and Electrochemical Performance Modification

In this work, we reveal in detail the effects of high-temperature treatment in air at 600 °C on the microstructure as well as the physico-chemical and electrochemical properties of boron-doped diamond (BDD) electrodes. The thermal treatment of freshly grown BDD electrodes was applied, resulting in permanent structural modifications of surface depending on the exposure time. High temperature affects material corrosion, inducing crystal defects. The oxidized BDD surfaces were studied by means of cyclic voltammetry (CV) and scanning electrochemical microscopy (SECM), revealing a significant decrease in the electrode activity and local heterogeneity of areas owing to various standard rate constants. This effect was correlated with a resultant increase of surface resistance heterogeneity by scanning spreading resistance microscopy (SSRM). The X-ray photoelectron spectroscopy (XPS) confirmed the rate and heterogeneity of the oxidation process, revealing hydroxyl species to be dominant on the electrode surface. Morphological tests using scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that prolonged durations of high-temperature treatment lead not only to surface oxidation but also to irreversible structural defects in the form of etch pits. Our results show that even subsequent electrode rehydrogenation in plasma is not sufficient to reverse this surface oxidation in terms of electrochemical and physico-chemical properties, and the nature of high-temperature corrosion of BDD electrodes should be considered irreversible.

Boron-Doped Nanocrystalline Diamond-Carbon Nanospike Hybrid Electron Emission Source

Electron emission signifies an important mechanism facilitating the enlargement of devices that have modernized large parts of science and technology. Today, the search for innovative electron emission devices for imaging, sensing, electronics, and high-energy physics continues. Integrating two materials with dissimilar electronic properties into a hybrid material is an extremely sought-after synergistic approach, envisioning a superior field electron emission (FEE) material. An innovation is described regarding the fabrication of a nanostructured carbon hybrid, resulting from the one-step growth of boron-doped nanocrystalline diamond (BNCD) and carbon nanospikes (CNSs) by a microwave plasma-enhanced chemical vapor deposition technique. Spectroscopic and microscopic tools are used to investigate the morphological, bonding, and microstructural characteristics related to the growth mechanism of these hybrids. Utilizing the benefits of both the sharp edges of the CNSs and the high stability of BNCD, promising FEE performance with a lower turn-on field of 1.3 V/μm, a higher field enhancement factor of 6780, and a stable FEE current stability lasting for 780 min is obtained. The microplasma devices utilizing these hybrids as a cathode illustrate a superior plasma illumination behavior. Such hybrid carbon nanostructures, with superb electron emission characteristics, can encourage the enlargement of several electron emission device technologies.

Optical Magnetometry Based on Nanodiamonds with Nitrogen-Vacancy Color Centers

Nitrogen-vacancy color centers in diamond are a very promising medium for many sensing applications such as magnetometry and thermometry. In this work, we study nanodiamonds deposited from a suspension onto glass substrates. Fluorescence and optically detected magnetic resonance spectra recorded with the dried-out nanodiamond ensembles are presented and a suitable scheme for tracking the magnetic-field value using a continuous poly-crystalline spectrum is introduced. Lastly, we demonstrate a remote-sensing capability of the high-numerical-aperture imaging fiber bundle with nanodiamonds deposited on its end facet.

Tailoring Electro/Optical Properties of Transparent Boron-Doped Carbon Nanowalls Grown on Quartz

Carbon nanowalls (CNWs) have attracted much attention for numerous applications in electrical devices because of their peculiar structural characteristics. However, it is possible to set synthesis parameters to vary the electrical and optical properties of such CNWs. In this paper, we demonstrate the direct growth of highly transparent boron-doped nanowalls (B-CNWs) on optical grade fused quartz. The effect of growth temperature and boron doping on the behavior of boron-doped carbon nanowalls grown on quartz was studied in particular. Temperature and boron inclusion doping level allow for direct tuning of CNW morphology. It is possible to operate with both parameters to obtain a transparent and conductive film; however, boron doping is a preferred factor to maintain the transparency in the visible region, while a higher growth temperature is more effective to improve conductance. Light transmittance and electrical conductivity are mainly influenced by growth temperature and then by boron doping. Tailoring B-CNWs has important implications for potential applications of such electrically conductive transparent electrodes designed for energy conversion and storage devices.

Self-organized multi-layered graphene-boron-doped diamond hybrid nanowalls for high-performance electron emission devices

Carbon nanomaterials such as nanotubes, nanoflakes/nanowalls, and graphene have been used as electron sources due to their superior field electron emission (FEE) characteristics. However, these materials show poor stability and short lifetimes, which prevent their use in practical device applications. The aim of this study was to find an innovative nanomaterial possessing both high robustness and reliable FEE behavior. Herein, a hybrid structure of self-organized multi-layered graphene (MLG)-boron doped diamond (BDD) nanowall materials with superior FEE characteristics was successfully synthesized using a microwave plasma enhanced chemical vapor deposition process. Transmission electron microscopy reveals that the as-prepared carbon clusters have a uniform, dense, and sharp nanowall morphology with sp³ diamond cores encased by an sp² MLG shell. Detailed nanoscale investigations conducted using peak force-controlled tunneling atomic force microscopy show that each of the core-shell structured carbon cluster fields emits electrons equally well. The MLG-BDD nanowall materials show a low turn-on field of 2.4 V μm^-1, a high emission current density of 4.2 mA cm^-2 at an applied field of 4.0 V μm^-1, a large field enhancement factor of 4500, and prominently high lifetime stability (lasting for 700 min), which demonstrate the superiority of these materials over other hybrid nanostructured materials. The potential of these MLG-BDD hybrid nanowall materials in practical device applications was further illustrated by the plasma illumination behavior of a microplasma device with these materials as the cathode, where a low threshold voltage of 330 V (low threshold field of 330 V mm^-1) and long plasma stability of 358 min were demonstrated. The fabrication of these hybrid nanowalls is straight forward and thereby opens up a pathway for the advancement of next-generation cathode materials for high brightness electron emission and microplasma-based display devices.

Carbon nanowalls: a new versatile graphene based interface for the laser desorption/ionization-mass spectrometry detection of small compounds in real samples

Carbon nanowalls, vertically aligned graphene nanosheets, attract attention owing to their tunable band gap, high conductivity, high mechanical robustness, high optical absorbance and other remarkable properties. In this paper, we report for the first time the use of hydrophobic boron-doped carbon nanowalls (CNWs) for laser desorption/ionization of small compounds and their subsequent detection by mass spectrometry (LDI-MS). The proposed method offers sensitive detection of various small molecules in the absence of an organic matrix. The CNWs were grown by microwave plasma enhanced chemical vapor deposition (MW-PECVD), using a boron-carbon gas flow ratio of 1200 in H₂/CH₄ plasma, on silicon <100> wafer. The hydrophobicity of the surface offers a straightforward MS sample deposition, consisting of drop casting solutions of analytes and drying in air. Limits of detection in the picomolar and femtomolar ranges (25 fmol μL^-1 for neurotensin) were achieved for different types of compounds (fatty acids, lipids, metabolites, saccharides and peptides) having clinical or food industry applications. This rapid and sensitive procedure can also be used for quantitative measurements without internal standards with RSDs <19%, as in the case of glucose in aqueous solutions (LOD = 0.32 ± 0.02 pmol), blood serum or soft drinks. Moreover, melamine (63 ± 8.19 ng μL^-1), a toxic compound, together with creatinine and paracetamol, was detected in urine samples, while lecithin was detected in food supplements.

Boron-Enhanced Growth of Micron-Scale Carbon-Based Nanowalls: A Route toward High Rates of Electrochemical Biosensing

In this study, we have demonstrated the fabrication of novel materials called boron-doped carbon nanowalls (B:CNWs), which are characterized by remarkable electrochemical properties such as high standard rate constant (k°), low peak-to-peak separation value (ΔE) for the oxidation and reduction processes of the [Fe(CN)₆]^3-/4- redox system, and low surface resistivity. The B:CNW samples were deposited by the microwave plasma-assisted chemical vapor deposition (CVD) using a gas mixture of H₂/CH₄/B₂H₆ and N₂. Growth results in sharp-edged, flat, and long CNWs rich in sp² as well as sp³ hybridized phases. The achieved high values of k° (1.1 × 10^-2 cm s^-1) and ΔE (85 mV) are much lower compared to those of the glassy carbon or undoped CNWs. The enhanced electrochemical performance of the B:CNW electrode facilitates the simultaneous detection of DNA purine bases: adenine and guanine. Both separated oxidation peaks for the independent determination of guanine and adenine were observed by means of cyclic voltammetry or differential pulse voltammetry. It is worth noting that the determined sensitivities and the current densities were about 1 order of magnitude higher than those registered by other electrodes.