Modulating spectral response of raw photosynthetic pigments via ternary cadmium chalcogenide quantum dots: simultaneous enhancement at green spectrum and inhibition at UV region.

Photosynthesis relies on the absorption of sunlight by photosynthetic pigments (PPs) such as chlorophylls and carotenoids. While these pigments are outstanding at harvesting light, their natural structure restricts their ability to harvest light at specific wavelengths. In this study, Oleic acid-capped CdSeS and CdTeS ternary quantum dots (QDs) were synthesized using a novel two-phase synthesis method. Then, these QDs were used to interact with raw PPs, a mixture of chlorophylls and carotenoids isolated from spinach. Our findings revealed the following: (1) Interacting QDs with raw PPs effectively inhibited the chlorophyll fluorescence of the pigments upon excitation in UV light region (250-400 nm) without causing any damage to their structure. (2) By forming an interaction with QDs, the chlorophyll fluorescence of raw PPs could be induced through excitation with green-light spectrum. (3) The composition of the QDs played a fundamental role in their interaction with PPs. Our study demonstrated that the photophysical properties of isolated PPs could be modified by using cadmium-based QDs by preserving the structure of the pigments themselves.

Exploring the Gas Sensing Potential of Cross-Linked Asphaltene: A Promising Application of an Affordable Material.

In recent years, there has been significant research interest in carbon-based nanomaterials as promising candidates for sensing technologies. Herein, we present the first utilization of asphaltenes as an affordable, cost-efficient carbon-based material for gas sensing applications. Asphaltenes, derived from various oil sources, are subjected to facile cross-linking reactions to produce nanoporous carbon materials, where the asphaltene molecules from different layers are interconnected via covalent bonds. The characterization results of these cross-linked asphaltenes revealed substantial enhancement in their specific surface area and surface functionality. Quartz crystal microbalance sensors with sensing films derived from various asphaltene samples were prepared to detect different ethanol concentrations at room temperature. All the cross-linked asphaltene samples showed a significant enhancement in the sensing response (up to 430%) compared to that of their respective raw parent samples. Such a response of the cross-linked asphaltene samples was comparable to that obtained from graphene oxide. The sensor based on cross-linked asphaltenes demonstrated good linearity, with a response time of approximately 2.4 min, a recovery time of around 8 min, and an excellent response repeatability. After 30 days, the sensor based on cross-linked asphaltenes showed approximately 40% reduction in its response, suggesting long-term aging. This decline is partially attributed to the observed swelling. The current study opens the door to a deeper exploration of asphaltenes and highlights their potential as promising candidates for sensing applications.

Ultraprecise control over the photophysical properties of novel amino acid functionalized CdTeS quantum dots and their effect on the emission of yellow-emissive carbon dots.

Cadmium-based quantum dots (QDs) are amongst the most studied nanomaterials due to their excellent photophysical properties, which can be controlled by controlling the size and/or composition of the nanocrystal. However, the ultraprecise control over size and photophysical properties of Cd-based quantum dots and developing user-friendly techniques to synthesize amino acid-functionalized cadmium-based QDs are still the on-going challenges. In this study, we modified a traditional two-phase synthesis method to synthesize cadmium telluride sulfide (CdTeS) QDs. CdTeS QDs were grown with an extremely slow growth-rate (growth saturation of about 3 days), which allowed us to have an ultraprecise control over size, and as a consequence, the photophysical properties. Also, the composition of CdTeS could be controlled by controlling the precursor ratios. The CdTeS QDs were successfully functionalized with a water-soluble amino acid, L-cysteine, and an amino acid derivative, N-acetyl-L-cysteine. Red-emissive L-cysteine-functionalized CdTeS QDs interacted with yellow-emissive carbon dots. The fluorescence intensity of carbon dots increased upon interaction with CdTeS QDs. This study proposes a mild method that allows to grow QDs with an ultraprecise control over the photophysical properties and shows the implementation of Cd-based QDs to enhance the fluorescence intensity of different fluorophores with fluorescence wavelength at higher energy bands.

Doped Graphene Quantum Dots UV-vis Absorption Spectrum: A High-Throughput TDDFT Study.

We report on time-dependent density functional theory calculations of the excited states of 63 different graphene quantum dots (GQDs) in square shape with side lengths of 1, 1.5, and 2 nm. We investigate the systematics and trends in the UV-vis absorption spectra of these GQDs, which are doped with elements B, N, O, S, and P at dopant percentages of 1.5%, 3%, 5%, and 7%. The results show how the peaks in the UV and visible parts of the spectrum as well as the total absorption evolve in the chemical parameter space along the coordinates of size, dopant type, and dopant percentage. The absorption spectra calculated here can be used to obtain particular GQD mixture proportions that would yield a desired absorption profile such as flat absorption across the whole visible spectrum or one that is locally peaked around a chosen wavelength.

Graphite Size Effect on Chemical Expansion and Graphene Oxide Properties.

Does larger graphite flake size always lead to larger and better graphene oxide (GO)? Is there an optimum size to balance between the large building blocks needed and the defects generated during oxidation? In this study, the effect of using four different graphite flake sources on the size, structure, and properties of GO and reduced graphene oxide (rGO) was investigated. GO was mainly prepared by the enhanced synthesis method except for the smallest graphite size, which could not be expanded before oxidation. The effect of the flakes' lateral size and thickness on the expansion volume was also studied. Several characterization techniques were performed throughout this work, and their results provide evidence of how the graphite size changes not only the expansion volume of the chemically expanded graphite (CEG) as well as the final properties of GO or rGO but also the presence of organosulfate impurities, defects, wide size distribution, and the harsh oxidation reaction itself.

Working Aqueous Zn Metal Batteries at 100 °C.

Reliable power supplies at extremely high temperatures are urgently needed to broaden the application scenarios for electric devices. Aqueous zinc metal batteries (ZMBs) with intrinsic safety are a promising alterative for high-temperature energy storage. However, the reversibility and long-term cycling stability of aqueous ZMBs at extremely high temperatures (≥100 °C) have rarely been explored. Herein, we reveal that spontaneous Zn corrosion and severe electrochemical hydrogen evolution at high temperature are vital restrictions for traditional aqueous ZMBs. To address this, a crowding agent, 1,5-pentanediol, was introduced into an aqueous electrolyte to suppress water reactivity by strengthening O-H bonds of H2O and decreasing H2O content in the Zn2+ solvation sheath, while maintaining flame resistance of the electrolyte. Importantly, this electrolyte enabled reversible Zn deposition with a Coulombic efficiency of 98.1% and a long cycling life of Zn//Zn batteries for over 500 cycles (at 1 mA cm-2 and 0.5 mAh cm-2) at 100 °C. Moreover, stable cycling of Zn//Te full batteries at 100 °C was demonstrated.

Aflatoxin B1 Acts as an Effective Energy Donor to Enhance Fluorescence of Yellow Emissive Carbon Dots.

Carbon dots (CDs) are versatile fluorescent nanocrystals with unique optical and structural properties and are commonly used in biosensing, bioimaging, and biomolecule tagging studies. However, fluorescence of CDs is brightest in the wavelength range of 430-530 nm, which overlaps with the autofluorescence range of many eukaryotic cells and makes CDs impractical for in vivo and in vitro imaging studies. Thus, the design of yellow-red emissive CDs with high quantum yield is of importance. In this study, the quantum yield of traditional yellow emissive CDs was enhanced by two different methods: (1) the surface of traditional yellow emissive CDs passivated with a biomolecule, urea, through easy, rapid, inexpensive microwave assisted synthesis methods and (2) a fluorescent biomolecule, aflatoxin B1, used as an energy donor for yellow emissive CDs. In the first method, the quantum yield of the CDs was enhanced to 51%. In the second method, an efficient energy transfer (above 40%) from aflatoxin B1 to the CDs was observed. Our study showed that highly luminescent yellow emissive CDs can be synthesized by simple, rapid microwave assisted synthesis methods, and these CDs are potential candidates to sense aflatoxin B1. Furthermore, our results indicated that Aflatoxin B1 can be considered as an emission booster for CDs.

Improving thermal conductivities of textile materials by nanohybrid approaches.

The thermal transfer between individual body and the surroundings occurs by several paths such as radiation, evaporation, conduction, and convection. Thermal management is related with the heat transfer between the human body and the surroundings, which aims to keep the body temperature in the comfort range either via preserving or via emitting the body heat. The essential duty of clothing is to contribute to the thermal balance of the human body by regulating the heat and moisture transfer. In the case of poorly controlled body heat, health problems such as hyperthermia and heatstroke along with environmental problems due to higher energy consumption can occur. Recently, research has been focused on advanced textiles with novel approaches on materials synthesis and structure design, which can provide thermal comfort together with energy saving. This review article focuses on the innovative strategies basically on the passive textile models for improved thermal conductivity. We will discuss both the fabrication techniques and the inclusion of carbon-based and boron-based fillers to form nano-hybrid textile solutions, which are used to improve the thermal conductivity of the materials.

On-chip label-free impedance-based detection of antibiotic permeation.

Biosensors are analytical tools used for the analysis of biomaterial samples and provide an understanding about the biocomposition, structure, and function of biomolecules and/or biomechanisms by converting the biological response into an electrical and/or optical signal. In particular, with the rise in antibiotic resistance amongst pathogenic bacteria, the study of antibiotic activity and transport across cell membranes in the field of biosensors has been gaining widespread importance. Herein, for the rapid and label-free detection of antibiotic permeation across a membrane, a microelectrode integrated microfluidic device is presented. The integrated chip consists of polydimethylsiloxane based microfluidic channels bonded onto microelectrodes on-glass and enables us to recognize the antibiotic permeation across a membrane into the model membranes based on electrical impedance measurement, while also allowing optical monitoring. Impedance testing is label free and therefore allows the detection of both fluorescent and non-fluorescent antibiotics. As a model membrane, Giant Unilamellar Vesicles (GUVs) are used and impedance measurements were performed by a precision inductance, capacitance, and resistance metre. The measured signal recorded from the device was used to determine the change in concentration inside and outside of the GUVs. We have found that permeation of antibiotic molecules can be easily monitored over time using the proposed integrated device. The results also show a clear difference between bilayer permeation that occurs through the lipidic bilayer and porin-mediated permeation through the porin channels inserted in the lipid bilayer.

Studying dynamic stress effects on the behaviour of THP-1 cells by microfluidic channels.

Atherosclerosis is a long-term disease process of the vascular system that is characterized by the formation of atherosclerotic plaques, which are inflammatory regions on medium and large-sized arteries. There are many factors contributing to plaque formation, such as changes in shear stress levels, rupture of endothelial cells, accumulation of lipids, and recruitment of leukocytes. Shear stress is one of the main factors that regulates the homeostasis of the circulatory system; therefore, sudden and chronic changes in shear stress may cause severe pathological conditions. In this study, microfluidic channels with cavitations were designed to mimic the shape of the atherosclerotic blood vessel, where the shear stress and pressure difference depend on design of the microchannels. Changes in the inflammatory-related molecules ICAM-1 and IL-8 were investigated in THP-1 cells in response to applied shear stresses in an continuous cycling system through microfluidic channels with periodic cavitations. ICAM-1 mRNA expression and IL-8 release were analyzed by qRT-PCR and ELISA, respectively. Additionally, the adhesion behavior of sheared THP-1 cells to endothelial cells was examined by fluorescence microscopy. The results showed that 15 Pa shear stress significantly increases expression of ICAM-1 gene and IL-8 release in THP-1 cells, whereas it decreases the adhesion between THP-1 cells and endothelial cells.

Affinity biosensors developed with quantum dots in microfluidic systems.

Quantum dots (QDs) are synthetic semiconductor nanocrystals with unique optical and electronic properties due to their size (2-10 nm) such as high molar absorption coefficient (10-100 times higher than organic dyes), resistance to chemical degradation, and unique optoelectronic properties due to quantum confinement (high quantum yield, emission color change with size). Compared to organic fluorophores, the narrower emission band and wider absorption bands of QDs offer great advantages in cell imaging and biosensor applications. The optoelectronic features of QDs have prompted their intensive use in bioanalytical, biophysical, and biomedical research. As the nanomaterials have been integrated into microfluidic systems, microfluidic technology has accelerated the adaptation of nanomaterials to clinical evaluation together with the advantages such as being more economical, more reproducible, and more susceptible to modification and integration with other technologies. Microfluidic systems serve an important role by being a platform in which QDs are integrated for biosensing applications. As we combine the advantages of QDs and microfluidic technology for biosensing technology, QD-based biosensor integrated with microfluidic systems can be used as an advanced and versatile diagnostic technology in case of pandemic. Specifically, there is an urgent necessity to have reliable and fast detection systems for COVID-19 virus. In this review, affinity-based biosensing mechanisms which are developed with QDs are examined in the domain of microfluidic approach. The combination of microfluidic technology and QD-based affinity biosensors are presented with examples in order to develop a better technological framework of diagnostic for COVID-19 virus.

Enhanced synthesis method of graphene oxide.

The synthesis of high quality graphene oxide (GO) in large quantities is a matter of great importance for both research institutes and industries. In the present study, we report an improvement in the so-called "improved method" reported by Tour et al., which had already improved the very famous "Hummers method" to a certain extent. Through an important pre-treatment step, GO with larger sheets, better structural integrity, and a higher yield of monolayers was obtained. Furthermore, both the oxidation time and temperature were reduced without reducing the degree of high oxidation. Even though a low temperature is known to be a prerequisite for obtaining less defective GO in its reduced form (rGO), we found through this research that the pre-treatment step minimizes the negative effect of the moderate temperature (35 °C) needed to enhance the reaction rate, without altering the basal graphitic plane, which was also preserved at a low temperature (<10 °C). Both the mechanical and electrical properties confirm the enhancement of the GO quality obtained through improving the improved method, and make the rGO films produced attractive for practical applications.

Multifunctional microfluidic chip for optical nanoprobe based RNA detection - application to Chronic Myeloid Leukemia.

Many diseases have their treatment options narrowed and end up being fatal if detected during later stages. As a consequence, point-of-care devices have an increasing importance for routine screening applications in the health sector due to their portability, fast analyses and decreased cost. For that purpose, a multifunctional chip was developed and tested using gold nanoprobes to perform RNA optical detection inside a microfluidic chip without the need of molecular amplification steps. As a proof-of-concept, this device was used for the rapid detection of chronic myeloid leukemia, a hemato-oncological disease that would benefit from early stage diagnostics and screening tests. The chip passively mixed target RNA from samples, gold nanoprobes and saline solution to infer a result from their final colorimetric properties. An optical fiber network was used to evaluate its transmitted spectra inside the chip. Trials provided accurate output results within 3 min, yielding signal-to-noise ratios up to 9 dB. When compared to actual state-of-art screening techniques of chronic myeloid leukemia, these results were, at microscale, at least 10 times faster than the reported detection methods for chronic myeloid leukemia. Concerning point-of-care applications, this work paves the way for other new and more complex versions of optical based genosensors.

Bone response to biomimetic implants delivering BMP-2 and VEGF: an immunohistochemical study.

This animal study evaluated bone healing around titanium implant surfaces biomimetically coated with bone morphogenic protein-2 (BMP-2) and/or vascular endothelial growth factor (VEGF) by examining bone matrix proteins and mineralisation. Five different implant surfaces were established: acid-etched surface (AE), biomimetic calcium phosphate surface (CAP), BMP-2 loaded CAP surface, VEGF loaded CAP surface and dual BMP-2 + VEGF loaded CAP surface. The implants were inserted into calvariae of adult domestic pigs. For the comparison of osteoconductive capacity of each surface, bone mineral density and expression of bone matrix proteins (collagen I, BMP-2/4, osteocalcin and osteopontin) inside defined chambers around the implant were assessed using light microscopy and microradiography and immunohistochemical analysis at 1, 2 and 4 weeks. In the both groups delivering BMP-2, the bone mineral density was significantly enhanced after 2 weeks and the highest value was measured for the group BMP + VEGF. In the group VEGF, collagen I and BMP-2/4 expressions were significantly up-regulated at the first and second weeks. The percentage of BMP-2/4 positive cells in the group BMP + VEGF was significantly enhanced compared with the groups AE and CAP at the second week. Although the highest osteocalcin and osteopontin expression values were observed for the group BMP + VEGF after 2 weeks, no statistically significant difference in osteocalcin and osteopontin expressions was found between all groups at any time. It was concluded that combined delivery of BMP-2 and VEGF favoured bone mineralisation and expression of important bone matrix proteins that might explain synergistic interaction between both growth factors.

Mechanical properties and biocompatibility of plasma-nitrided laser-cut 316L cardiovascular stents.

The effect of surface modification of laser-cut 316L cardiovascular stents by low-T plasma nitriding was evaluated in terms of mechanical properties and biocompatibility of the stents. The plasma nitriding was performed at 400, 450 or 500 degrees C using various ratios of nitrogen-hydrogen gas mixtures. The flexibility and radial strength were measured in crimped and expanded state of the stents, respectively. The mechanical properties could be adjusted and improved by plasma nitriding conducted at temperatures lower than 450 degrees C and/or nitrogen content less than 10% in the treatment gas. An osteoblast cell culture model system was utilized to investigate the effect of plasma nitriding of the stents on the biological response towards the stents, using biological criteria such as cell viability, alkaline phosphatase and nitric oxide production. In terms of cell viability and alkaline phosphatase production, the plasma nitriding procedure did not appear to negatively affect the biocompatibility of the 316L steel stents. However, in terms of nitric oxide production that was slightly increased in the presence of the plasma-nitrided stents, an indirect improvement in the biocompatibility could possibly be expected.