Functionalized graphitic carbon nitrides for environmental and sensing applications

Graphitic carbon nitride (g-C3N4) is a metal-free semiconductor that has been widely regarded as a promising candidate for sustainable energy production or storage. In recent years, g-C3N4 has become the center of attention by virtue of its impressive properties, such as being inexpensive, easily fabricable, nontoxic, highly stable, and environment friendly. Herein, the recent research developments related to g-C3N4 are outlined, which sheds light on its future prospective. Various synthetic methods and their impact on the properties of g-C3N4 are detailed, along with discussion on frequently used characterization methods. Different approaches for g-C3N4 surface functionalization, mainly categorized under covalent and noncovalent strategies, are outlined. Moreover, the processing methods of g-C3N4, such as g-C3N4-based thin films, hierarchical, and hybrid structures, are explored. Next, compared with the extensively studied energy-related applications of the modified g-C(3)N(4)s, relatively less-examined areas, such as environmental and sensing, are presented. By highlighting the strong potential of these materials and the existing research gaps, new researchers are encouraged to produce functional g-C3N4-based materials using diverse surface modification and processing routes.UK Research & Innovation (UKRI) Engineering & Physical Sciences Research Council (EPSRC) ; Royal Society-Newton Advanced Fellowship Grant ; Leverhulme Trus

Plasmonic titanium nitride nanohole arrays for refractometric sensing

Group IVB metal nitrides have attracted great interest as alternative plasmonic materials. Among them, titanium nitride (TiN) stands out due to the ease of deposition and relative abundance of Ti compared to those of Zr and Hf metals. Even though they do not have Au or Ag-like plasmonic characteristics, they offer many advantages, from high mechanical stability to refractory behavior and complementary metal oxide semiconductor-compatible fabrication to tunable electrical/optical properties. In this study, we utilized reactive RF magnetron sputtering to deposit plasmonic TiN thin films. The flow rate and ratio of Ar/N2 and oxygen scavenging methods were optimized to improve the plasmonic performance of TiN thin films. The stoichiometry and structure of the TiN thin films were thoroughly investigated to assess the viability of the optimized operation procedures. To assess the plasmonic performance of TiN thin films, periodic nanohole arrays were perforated on TiN thin films by using electron beam lithography and reactive ion etching methods. The resulting TiN periodic nanohole array with varying periods was investigated by using a custom microspectroscopy setup for both reflection and transmission characteristics in various media to underline the efficacy of TiN for refractometric sensing.101111321 ; EP/Y030273/

REAL-TIME WATER QUALITY MONITORING OF AN ARTIFICIAL LAKE USING A PORTABLE, AFFORDABLE, SIMPLE, ARDUINO-BASED OPEN SOURCE SENSOR

Water quality assessment is vital to identify existing problems and any changes that emerge in water sources over a period of time. Conventional water quality monitoring systems remain to be limited to on-site sample collection and further analysis in environmental laboratories. The progress in Arduino-based low-cost and open-source hardware has paved the way for the development of low-cost, portable, and on-site measuring platforms. In this work, we have assembled an Arduino-based open-source water testing platform out of commercially available sensors and controllers. The water testing system was powered by a 9 V battery and had the capability of measuring water turbidity, acidity, and temperature on-site in real-time. The calibration and validation studies were carried out to assess the measurement capabilities of turbidity and pH sensors in the lab using calibration samples and UV-Vis-NIR absorption spectroscopy. The water quality platform was tested in an artificial lake that is located at Sabanci University Campus (Istanbul, Turkey), which serves as a reservoir for treated wastewaters and rainwater. Untreated wastewater samples were collected from the wastewater treatment station of the university for comparison. The measurements performed on several locations along the coast of the artificial lake were also validated in the laboratory. The water testing platform showed significant potential for miniaturization and portability of such analytical platforms for on-site environmental monitoring

Microwave-assisted green synthesis of silver nanoparticles using dried extracts of Chlorella vulgaris and antibacterial activity studies

Green synthesis of metallic nanoparticles (NPs) is acquiring considerable attention due to its environmental and economic superiorities over other methods. This study describes the practical synthesis of silver nanoparticles (AgNPs) through the reduction of silver nitrate solution using an algal source, Chlorella vulgaris, as the reducing as well as the stabilizing agent. The energy required for this synthesis was supplied by microwave radiation. The ultraviolet-visible spectroscopy exhibited a single peak related to the surface plasmon absorbance of AgNPs at 431 nm. The AgNPs with high stability (a zeta potential of −17 mV), hydrodynamic size distribution of 1–50 nm, and mostly spherical shape were obtained through a 10 min process. Fourier transform infrared spectroscopy analysis revealed that several functional groups, including carbonyl groups of C. vulgaris, play a significant role in the formation of functional NPs. Antibacterial features of the produced AgNPs were verified against those of Salmonella enterica subsp. enterica serovar typhimurium and Staphylococcus aureus, demonstrating a considerable growth inhibition at increasing concentrations of the NPs. As a result, the formed AgNPs can be used as a promising agent against bacterial diseases

Microwave-assisted green synthesis of silver nanoparticles using dried extracts of Chlorella vulgaris and antibacterial activity studies

Green synthesis of metallic nanoparticles (NPs) is acquiring considerable attention due to its environmental and economic superiorities over other methods. This study describes the practical synthesis of silver nanoparticles (AgNPs) through the reduction of silver nitrate solution using an algal source, Chlorella vulgaris, as the reducing as well as the stabilizing agent. The energy required for this synthesis was supplied by microwave radiation. The ultraviolet-visible spectroscopy exhibited a single peak related to the surface plasmon absorbance of AgNPs at 431 nm. The AgNPs with high stability (a zeta potential of -17 mV), hydrodynamic size distribution of 1-50 nm, and mostly spherical shape were obtained through a 10 min process. Fourier transform infrared spectroscopy analysis revealed that several functional groups, including carbonyl groups of C. vulgaris, play a significant role in the formation of functional NPs. Antibacterial features of the produced AgNPs were verified against those of Salmonella enterica subsp. enterica serovar typhimurium and Staphylococcus aureus, demonstrating a considerable growth inhibition at increasing concentrations of the NPs. As a result, the formed AgNPs can be used as a promising agent against bacterial diseases

Aptamer and nanomaterial based FRET biosensors: a review on recent advances (2014–2019)

Fluorescence resonance energy transfer, one of the most powerful phenomena for elucidating molecular interactions, has been extensively utilized as a biosensing tool to provide accurate information at the nanoscale. Numerous aptamer- and nanomaterial-based FRET bioassays has been developed for detection of a large variety of molecules. Affinity probes are widely used in biosensors, in which aptamers have emerged as advantageous biorecognition elements, due to their chemical and structural stability. Similarly, optically active nanomaterials offer significant advantages over conventional organic dyes, such as superior photophysical properties, large surface-to-volume ratios, photostability, and longer shelf life. In this report (with 175 references), the use of aptamer-modified nanomaterials as FRET couples is reviewed: quantum dots, upconverting nanoparticles, graphene, reduced graphene oxide, gold nanoparticles, molybdenum disulfide, graphene quantum dots, carbon dots, and metal-organic frameworks. Tabulated summaries provide the reader with useful information on the current state of research in the field

Plasmonic nanometal surface energy transfer-based dual excitation biosensing of pathogens

In this assay, the simultaneous screening of foodborne bacterial pathogens, namely Escherichia coli and Salmonella typhimurium, was investigated by developing a highly specific dual-excitation biosensor which works based on plasmonic nanoparticle surface energy transfer (PSET) between aptamer capped plasmonic gold nanostructures (AuNSs) as capture probes and luminescent nanoparticles (LNPs) as signal probes labeled with complementary single-strand DNA of the utilized aptamers. For the characterization of the provided sensing probes, techniques such as UV-visible spectroscopy, dynamic light scattering, scanning electron microscopy, and circular dichroism spectroscopy were used. While CdSe/ZnS core/shell quantum dots (QDs) became excited with ultraviolet (UV) radiation at 350 nm, the light source utilized for excitation of NaYF4:Yb, Er upconverting nanoparticles (UCNPs) was near-infrared (NIR) at 980 nm, and also the signal cross-talk possibility between QDs and UCNPs was removed using the dual-excitation technique. The limit of detection (LOD) was calculated to be as low as 7.38 and 9.31 CFU mL-1 for simultaneous monitoring of E. coli and S. typhimurium in one experimental batch. The biosensor was also evaluated for detecting bacteria simultaneously in actual lake samples. The results proposed the viability of the technique for realtime sample analysis. Using numerous AuNSs and their corresponding UCNPs and QDs benefiting from distinct luminescence emission profiles, the suggested NSET-based biosensor may be utilized to simultaneously detect a wide range of analytes, posing good application prospects in various fields ranging from food safety analysis to biomedical applications

Microwave-promoted continuous flow synthesis of thermoplastic polyurethane-silver nanocomposites and their antimicrobial performance

Thermoplastic polyurethane-silver nanocomposites (PU-Ag NCs) have considerable potential in many medical applications due to their superior mechanical and antimicrobial properties. Herein, a microwave-promoted flow system is successfully employed for continuous in situ manufacturing of PU NCs having spherical silver nanoparticles (AgNPs) without any reducing agent at ∼40 °C in approximately 4 minutes. The main experimental parameters, including microwave power, metal salt concentration, polymer concentration, and flow rate, are optimised for the reproducible synthesis of AgNPs (∼5 nm) in the PU matrix, characterised by HRTEM-EDS and DLS analysis. XRD patterns indicate an increase in PU crystallinity with decreased particle size. Conventional heating flow synthesis at ∼50 °C or microwave-batch synthesis (MWB) at ∼44 and ∼50 °C is ineffective in preparing AgNPs, and only large AgNPs (>100 nm) are synthesised at 70 °C in the MWB reactor. PU-Ag NC films bearing small AgNPs (∼5 nm) exhibit superior antibacterial activity (>97%) against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus compared to large NPs (∼218 nm). The proposed method may manufacture other metal-polymer matrix composites

Application of nanomaterials in food quality assessment

The food industry has a significant role to play in governing local economies all over the world. This sector includes some processes such as storage of raw materials, food production, and preservation. Food processing, food quality, and safety are vital to protect public health. Thus, food safety monitoring, for example, early detection of food pathogens, food-related toxins, allergens, chemicals, and enterotoxins, is of great significance. Nanoscience-based sensing platforms have become alternatives to conventional food safety monitoring techniques. Over the past few years, scientists have designed various novel nanosensors with high sensitivity and selectivity to detect a wide variety of hazardous substances. The nanomaterials, such as carbon-based nanoparticles, plasmonic/metallic nanoparticles, and inorganic fluorescent nanomaterials, have been extensively used to develop various detection platforms over the past few decades. The surface functionalization of nanoparticles using target-specific biological agents, such as aptamers and antibodies, has contributed to improving the efficiency of those nanoparticle-based diagnostic tools. In this chapter, general structural, physicochemical, and optical features of the nanoparticles were described, and their applications in food safety monitoring were reviewed. Following this, affinity agents and fundamental sensing principles employed in developing food-related hazardous substance detection tools were elaborated based on the recent publications in the literature. Finally, we expect to pave the way for enhancing the efficiency and applicability of nanosensors in the initial sensing of food-related targets that cause a significant risk for humankind worldwide

A microwave-powered continuous fluidic system for polymer nanocomposite manufacturing: a proof-of-concept study

Continuous manufacturing of pure nanocrystals with a narrow size distribution in a polymer matrix is very challenging, although it is highly crucial to get their full potential for advanced applications. A long-lasting nanocomposite (NC) manufacturing challenge is, for the first time, overcome by a microwave-powered fluidic system (MWFS). The effect of microwave power (MWP), flow rate, and the concentration of the reagents are systematically studied. The nylon-6 NC bearing evenly distributed silver nanoparticles (AgNPs) with a mean size of ∼2.59 ± 0.639 nm is manufactured continuously in ∼2 min at ∼50-55 °C using a green solvent, formic acid. The AgNP size becomes smaller when increasing the polymer concentration gradually. Small NPs with a narrow size distribution are produced at high MWP (40 W), but large ones with a broad size distribution at low MWP (10 W). The nylon-6 crystallinity is NP size-dependent, and the γ-phase (pseudo-hexagonal crystal) is dominant in the presence of small NPs as against the large counterparts. Given the small-sized AgNPs in the MWF-manufactured NCs, the antibacterial activity tests with Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa show superior activity compared to that of the large AgNP-bearing (∼50 nm) NCs produced in a conventional heating fluidic system. The proposed MWFS can manufacture other added-value NCs continuously