Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are highly recalcitrant anthropogenic chemicals that are ubiquitously present in the environment and are harmful to humans. Typical water and wastewater treatment processes (coagulation, flocculation, sedimentation, and filtration) are proven to be largely ineffective, while adsorption with granular activated carbon (GAC) has been the chief option to capture them from aqueous sources followed by incineration. However, this process is time-consuming, and produces additional solid waste and air pollution. Treatment methods for PFOS and PFOA generally follow two routes: (1) removal from source and reduce the risk; (2) degradation. Emerging technologies focusing on degradation are critically reviewed in this contribution. Various processes such as bioremediation, electrocoagulation, foam fractionation, sonolysis, photocatalysis, mechanochemical, electrochemical degradation, beams of electron and plasma have been developed and studied in the past decade to address PFAS crisis. The underlying mechanisms of these PFAS degradation methods have been categorized. Two main challenges have been identified, namely complexity in large scale operation and the release of toxic byproducts. Based on the literature survey, we have provided a strength-weakness-opportunity-threat (SWOT) analysis and quantitative rating on their efficiency, environmental impact and technology readiness.

Emitters Abstract : Low-cost flexible Organic Light-Emitting Diodes (OLEDs) with nano emitter material derived from wastes, opens up new opportunities for industries in need of sustainable technology to develop cheap displays. The most common-emitter-material generated from waste is carbon dots (CDs). However, the luminescent properties of CDs sourced from waste material lack efficiency and further solid-state emission quenching makes it very challenging for their application in flexible display devices. Here for the first time, flexible and rigid OLED devices are demonstrated using self-assembled 2D arrays of CDs derived from waste material viz.human hairs. High-performance CDs with a quantum yield of 87%, self-assembled into 2D arrays are achieved by improving the crystallinity and by decreasing the size distribution of CDs. The array of CD islands exhibits ultrahigh hole mobility (~ 10 -1 cm 2 v -1 s -1 ) and a high reduction in emission quenching in solid-state compared to pristine CDs, hence it has been used here as an emitting layer in both ITO coated glass and ITO coated flexible PET substrate OLED devices, without any hole injection layer. The flexible OLED device exhibits a stable and voltage-independent blue/cyan emission with a record maximum luminescence of 350 cd m -2 whereas the rigid glass substrate based OLED devices show maximum luminescence of 700 cd m -2 . This work sets up a platform to develop next-generation cheap and sustainable OLED displays using CD emitters derived from the biowaste material.

Chlorination is a widely adopted disinfection method in water and wastewater treatment for the protection of public health, as it greatly reduces pathogen risks and associated incidence of waterborne diseases. Chlo-rination, however, also creates disinfection by-products (DBPs) such as trihalomethanes, which, epidemiolog-ically, have been associated with a higher incidence of some forms of cancer. Therefore, developing sensors for monitoring the chlorine dosage and DBPs concentrations in real-time and in-line is of critical importance to public health. Carbon dots (CDs) are an emergent class of fluorescent nanomaterial offering highly-sensitive sensing functionalities towards a diverse range of chemical/biochemical contaminants, owing to their tuneable fluorescence, rich surface functionalities, low to non-toxicity and ease of synthesis. In this study, we demonstrate that 1) highly fluorescent CDs (quantum yield 38%) can be produced from simple thermal treatment from biowastes such as human hairs without employing any solvents; 2) the fluorescence spectra and intensity of the synthesized CDs responds to the presence and quantity of chloroform with high sensitivity, with a limit of detection of 3 ppb; and 3) through a pair-wise comparative study on autoclave-synthesized CDs (OCDs) and microwave-synthesized counterpart, we discovered that the pyridinic N oxide that is unique to OCDs imparts sensitive and selective sensing functionality towards chloroform; 4) the PL-based sensing functionality is not solely determined by the binding affinity between the analyte and the carbon dots, but also the electronic structures of the interacting entities. This study provides an in-depth study on how to utilize the diverse features of biowastes and impart unique functionalities to CDs for developing advanced functional materials. (c) 2020 Published by Elsevier B.V.

Low-cost flexible organic light-emitting diodes (OLEDs) with nanoemitter material from waste open up new opportunities for sustainable technology. The common emitter materials generated from waste are carbon dots (CDs). However, these have poor luminescent properties. Further solid-state emission quenching makes application in display devices challenging. Here, flexible and rigid OLED devices are demonstrated using self-assembled 2D arrays of CDs derived from waste material, viz., human hair. High-performance CDs with a quantum yield (QY) of 87%, self-assembled into 2D arrays, are achieved by improving the crystallinity and decreasing the CDs' size distribution. The CD island array exhibits ultrahigh hole mobility (≈10-1 cm2 V-1 s-1 ) and significant reduction in solid-state emission quenching compared to pristine CDs; hence, it is used here as an emitting layer in both indium tin oxide (ITO)-coated glass and ITO-coated flexible poly(ethylene terephthalate) (PET) substrate OLED devices, without any hole-injection layer. The flexible OLED device exhibits a stable, voltage-independent blue/cyan emission with a record maximum luminescence of 350 cd m-2 , whereas the OLED device based on the rigid glass substrate shows a maximum luminescence of 700 cd m-2 . This work sets up a platform to develop next-generation OLED displays using CD emitters derived from the biowaste material.

Light management is of paramount importance to improve the performance of optoelectronic devices including photodetectors, optical sensors, solar cells, and light‐emitting diodes. Photonic crystals are shown as an effective metamaterial for trapping light among their various photon management functions. Herewith, it is demonstrated that spherical photonic crystals, or in other words, photonic beads, possess a stronger light‐trapping effect compared to the planar counterpart. The photonic beads are fabricated by colloidal self‐assembly under microdroplet confinement employing microfluidic devices. The light–matter interactions are illustrated by the emission intensity and lifetime of the embedded emitters, namely carbon dots and upconversion nanoparticles (UCNPs). The bandgaps of the photonic beads are selected according to the emission and excitation peaks of the light emitters, whereby the emission or excitation peak overlaps the blue edge or red edge of the photonic bands, respectively. Significantly stronger emission and extended luminescence lifetime are observed in photonic beads ensemble in comparison to the planar photonic crystals, demonstrating enhanced light trapping owing to the spherical geometry, which introduces additional microcavity effect. Photonic beads represent a perfect hierarchical light manipulation system. Combining both photonic and microcavity resonator effects, photonic beads potentially find applications in light harvesting, sensing, lighting devices, and light‐triggered manipulations.

Multivalent protein-glycan interactions are widespread in biology and are vital for initial recognition in cell-cell communication, host immune regulation, and viral and bacterial infection. Recently, fluorescent nanomaterials such as quantum dots (QDs) have been identified as a capable scaffold for multivalent carbohydrate immobilization. Carbon dots (CDs) are essentially heavy-metal-free QDs, offering a low-toxicity alternative for bioimaging and biosensing applications. Herein, we report a simple and versatile route for linker functionalization of lactose with (3-glycidyloxypropyl)-trimethoxysilane (GOPTS) for conjugation to various CDs. CDs derived by thermal treatment of polyethylenimine (PEI) with citric acid and lactose, as the glycan, were employed in a number of detailed biological applications and evaluations. The self-assembled glycan monolayer (SAGM) method described here resulted in a high yield of lactose-conjugated CDs. Specific interactions of our lactose-coated CDs with cells, lectin microarrays, and as internalized bioimaging nanolights were demonstrated, with intracellular localization in a variety of cell lines observed. This present study offers a facile, one-pot, green, and low-cost synthesis of fluorescent multivalent nanoparticles that can be applied in the study of diverse interactions across the glycointeractome.

We report for the first time the nitrogen doping of reduced graphene oxide (rGO) and TiO2 nanowires (NWs) when TiO2 NWs intercalated rGO membranes were immersed in ammonia aqueous solution under 8 W 254 nm UV irradiation. Such nitrogen-doped rGO/TiO2 NWs photocatalytic membrane produced H2 at a rate of 208 μmol h−1 g−1 under 8 W 254 nm UV irradiation, which is more than 14 times higher than the yield of the TiO2-P25 and 30-fold higher than TiO2 NWs alone under the same condition. Our study demonstrates a new synthesis route for doping nitrogen in rGO and TiO2, as well as the preliminary feasibility of hydrogen extraction from ammonia-containing wastewater with such a low-cost recyclable photocatalyst. In addition, the study illustrates the complexity of photocatalysis of ammonia aqueous solution, which involves multiple reactions in concurrence.

Marrying nanochemistry with optics has opened a new gateway to design and fabricate novel nanostructures that can interact with light in unprecedented manners. Self-assembled colloidal photonic crystal is one of the emerged nanostructured photonic materials, which possess well-defined, highly ordered structure and periodicities of light wavelength. Various 2D and 3D ordered structures have been fabricated through self-assembly methods by employing latex colloidal particles, or functionalized latex particles with more sophisticated structural features such as core-shell and anisotropy. The unique ordered structure and light-interactive properties have afforded them versatile functionalities in light manipulation, catalysis, sensing, and light harvesting. In this book chapter, we review recent research progress on hierarchical colloidal photonic crystals: the preparation methods, structural properties and applications. By introducing a hierarchy of interconnected structures at different length scales, the surface-to-volume ratio can be dramatically increased and the materials properties tailored accordingly. Moreover, the band-gap features of the photonic crystals may also be adjusted by the structure hierarchy.

A heterojunction photocatalytic membrane consisting of Cu2O and TiO2 nanowires between reduced graphene oxide (rGO) sheets was fabricated using a facile process from a colloidal suspension. The resultant membrane exhibits significantly enhanced activity in the UV-vis range, surpassing nanowire dispersions, owing to the heterojunction formation and concurrent electron and hole transfer on rGO sheets. The membrane also possesses increased permeability and photocorrosion resistance. Such a design and fabrication method of an rGO-facilitated heterojunction photocatalytic membrane can be extended to a broad range of energy and environmental applications.

The toxicity of nanoparticles in a biological system is an integration of effects arising from surface functionality, particle size, ionic dissolution, etc. This complexity suggests that generalization of a material’s toxicity may be inappropriate. Moreover, from a medicinal point of view, toxicity can be used for treatment of malignant cells, such as cancer. In this study, highly biocompatible carbon nanodots (gCDs) were synthesized by reacting citric acid and urea in glycerol, which resulted in abundant hydroxyl functional groups on the particle surface. gCDs show excitation-dependent photoluminescence but with bright green to yellow emission. Importantly, a series of toxicity assessments showed that as-synthesized gCDs possessed exceptional biocompatibilities to various biological entities including 18 bacteria species, Petunia axillaris seedlings, and Artemia franciscana nauplii. Furthermore, the particles were shown to have low to no toxic effects on human embryonic kidney (HEK-293), breast (MCF-7), and oral squamous (CAL-27) carcinoma cell lines. Of particular interest, the gCDs displayed antiproliferative activities against ovarian choriocarcinoma cells (JAr/Jeg-3 cell lines), which may be further explored for cancer drug discovery.

Photon management has enabled a true revolution in the development of high-performance semiconductor materials and devices. Harnessing the highest amount of energy from photons relies on the ability to design and fashion structures to trap the light for a longer time inside the device for more electron excitation. The light harvesting efficiency in many thin-film optoelectronic devices is limited due to low photon absorbance. Here we demonstrate for the first time that slow photon circulation in sandwich-structured photonic crystals with two stopbands fine tuned is ideally suited to enhance and spectrally engineer light absorption. The sandwich-structured TiO2 inverse opal possesses two stopbands, whose blue or red edge is respectively tuned to overlap with the electronic excitation energy of TiO2, thereby circulating the slow photons in the middle layer and enhancing light scattering at layer interfaces. This concept, together with the significantly increased control over photon management opens up tremendous opportunities for the realization of a wide range of high-performance, optoelectronic devices, and photochemical reactions.

Mercury contamination in water is a persistent issue due to both natural geological and anthropogenic activities. Portable, facile and affordable sensors for detection and sensing different species of mercuries are highly desirable. We report a highly effective fluorescent, solid state sensor with high sensitivity, good selectivity and excellent reversibility for Hg(II) ion. Hg(II)-responsive carbon dots immobilised polystyrene spheres were fabricated as a middle layer in double heterostructure colloidal photonic crystal film. Significant fluorescence enhancement was achieved due to doubly resonant of the modes of photonic crystals and multi beam interface inside the double heterostructure film. The amplified fluorescence enhances the sensitivity of detection, achieving a detection limit of 91 pM for Hg(II) ion, even 17 times lower than that of carbon dots solution probe. The polystyrene-based film sensor is negligibly responsive to other metal ions and can easily be recovered by rinsing with cysteine. (C) 2016 Elsevier B.V. All rights reserved.

We report a new method for the detection of regional DNA methylation using base-dependent affinity interaction (i.e., adsorption) of DNA with graphene. Due to the strongest adsorption affinity of guanine bases towards graphene, bisulfite-treated guanine-enriched methylated DNA leads to a larger amount of the adsorbed DNA on the graphene-modified electrodes in comparison to the adenine-enriched unmethylated DNA. The level of the methylation is quantified by monitoring the differential pulse voltammetric current as a function of the adsorbed DNA. The assay is sensitive to distinguish methylated and unmethylated DNA sequences at single CpG resolution by differentiating changes in DNA methylation as low as 5%. Furthermore, this method has been used to detect methylation levels in a collection of DNA samples taken from oesophageal cancer tissues.

Functionalization of multi-walled carbon nanotubes can be carried out by introducing amino and thiol functional groups onto the nanotube sidewalls. This functionalized multi-walled carbon nanotubes can be used as a new type of efficient metal ions adsorbent from aqueous solutions. In this study, batch and column adsorption experiments were carried to evaluate the adsorption capacities of single and binary system mercury and cadmium. In the single system, the maximum adsorption capacity of 204.64 and 61.10 mg/g were obtained for mercury and cadmium, respectively, while for binary systems, the values of 35.89 and 14.09 mg/g were achieved for mercury and cadmium, respectively. Column breakthrough curves were obtained and described by Yan and Thomas models. The bigger Thomas rate constant (km) (120.77 ml/min/mg for Cd(II) and 9.44 ml/min/mg for Hg(II)) indicated that the intensity of adsorption of Cd(II) onto thiolated MWCNTs was higher compared to Hg(II). However, the value of maximum adsorption capacity (q(e)) for Hg(II) (39.75 mg/g) was bigger than that of Cd(II) (9.72 mg/g) in continuous system. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

The significant effect of photonic crystals (PhCs) on fluorophore emission has recently received intense interest. However, so far little attention has been paid on the influence of the fluorophore incorporation method on the performance of PhCs, particularly in practical applications. In this study, rhodamine B is immobilised on polystyrene spheres using a diffusion-swelling method, which are self-assembled into three-dimensional colloidal photonic crystal films. This immobilization method has resulted in 230-fold fluorescence enhancement compared to control films, the greatest fluorescence enhancement of RhB immobilised on monolithic colloidal photonic crystals compared to other immobilization methods such as infiltration and electrostatic charge-facilitated dye attachment on the particle surface. We further demonstrate the stability of dye attachment and the relationship between fluorescence intensity enhancement and the pseudo bandgap position relative to a fluorophore fluorescence peak.