sampling-identification-characterization-microplastics-release-from

Sampling, Identification and Characterization of Microplastics Release from Polypropylene Baby Feeding Bottle during Daily Use

Microplastics (MPs) are becoming a global concern due to the potential risk to human health. Case studies of plastic products (i.e., plastic single-use ...

Trinity College Dublin

If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS(2), WS(2), MoSe(2), MoTe(2), TaSe(2), NbSe(2), NiTe(2), BN, and Bi(2)Te(3) can be efficiently dispersed in common solvents and can be deposited as individual flakes or formed into films. Electron microscopy strongly suggests that the material is exfoliated into individual layers. By blending this material with suspensions of other nanomaterials or polymer solutions, we can prepare hybrid dispersions or composites, which can be cast into films. We show that WS(2) and MoS(2) effectively reinforce polymers, whereas WS(2)/carbon nanotube hybrid films have high conductivity, leading to promising thermoelectric properties.

Two-dimensional nanosheets produced by liquid exfoliation of layered materials.

High intensity sub-wavelength spots and low divergence nanojets are observed in a system of Si3N4 microdisks illuminated from the side with laser light of wavelengths 488 nm, 532 nm and 633 nm. The disks are of height 400 nm with diameters ranging from 1μm to 10μm. Light scattered from the disk and substrate is observed by imaging from above. In free space light is focused inside the disks and a sub wavelength spot is observed, whereas in water the refractive index contrast is such that photonic nanojets are formed. The angular distribution of the intensity compares well to the analytical solution for the case of an infinite cylinder. Two distinct cases of scattering pattern are observed with even and odd numbers of lobes. Finally when the disks are illuminated with a focused Gaussian beam perpendicular to the substrate an extremely low divergence beam is observed. This beam has a divergence angle over 10 times smaller than a focused Gaussian in free space with the same waist.

Low divergence photonic nanojets from Si3N4 microdisks.

Confocal Raman spectroscopy was undertaken to identify separate layers of PLGA and gentamicin sulfate (GS) coatings on a titanium alloy substrate for a novel drug-delivery system. Additionally, it was found that it was possible to measure the layer thickness and uniformity of the PLGA accurately by detecting intensity and wavelength changes in the vibrational bands of the copolymer bonds. Further analysis of the materials was done using FIB, SEM/EDX, and profilometry; these techniques were used to confirm the findings of the Raman data. It was determined that the substrate was extremely rough and therefore the coating was not uniform in thickness but the materials were uniformly dispersed. Most importantly, two distinct GS and PLGA layers were present.

Depth profiling of PLGA copolymer in a novel biomedical bilayer using confocal Raman spectroscopy.

Trilayer graphene exhibits exceptional electronic properties that are of interest both for fundamental science and for technological applications. The ability to achieve a high on-off current ratio is the central question in this field. Here, we propose a simple method to achieve a current on-off ratio of 10(4) by opening a transport gap in Bernal-stacked trilayer graphene. We synthesized Bernal-stacked trilayer graphene with self-aligned periodic nanodomain boundaries (NBs) on the technologically relevant vicinal cubic-SiC(001) substrate and performed electrical measurements. Our low-temperature transport measurements clearly demonstrate that the self-aligned periodic NBs can induce a charge transport gap greater than 1.3 eV. More remarkably, the transport gap of ∼0.4 eV persists even at 100 K. Our results show the feasibility of creating new electronic nanostructures with high on-off current ratios using graphene on cubic-SiC. 

Transport Gap Opening and High On-Off Current Ratio in Trilayer Graphene with Self-Aligned Nanodomain Boundaries.

Magnetite is a half-metal with a high Curie temperature of 858 K, making it a promising candidate for magnetic tunnel junctions (MTJs). Yet, initial efforts to exploit its half metallic nature in Fe3O4/MgO/Fe3O4 MTJ structures have been far from promising. Finding suitable barrier layer materials, which keep the half metallic nature of Fe3O4 at the interface between Fe3O4 layers and barrier layer, is one of main challenges in this field. Two-dimensional (2D) materials may be good candidates for this purpose. Molybdenum disulfide (MoS2) is a transition metal dichalcogenide (TMD) semiconductor with distinctive electronic, optical, and catalytic properties. Here, we show based on the first principle calculations that Fe3O4 keeps a nearly fully spin polarized electron band at the interface between MoS2 and Fe3O4. We also present the first attempt to fabricate the Fe3O4/MoS2/Fe3O4 MTJs. A clear tunneling magnetoresistance (TMR) signal was observed below 200 K. Thus, our experimental and theoretical studies indicate that MoS2 can be a good barrier material for Fe3O4 based MTJs. Our calculations also indicate that junctions incorporating monolayer or bilayer MoS2 are metallic. 

Spin-dependent transport properties of Fe3O4/MoS2/Fe3O4 junctions.

The recent progress on black phosphorus makes it a promising candidate material for broadband nanophotonic devices, especially operating in the mid-infrared spectral region. Here, the excited carrier dynamics and nonlinear optical response of unoxidized black phosphorus nanosheets and their wavelength dependence were systematically studied from 800 nm to 2.1 μm. The wavelength-dependent relaxation times of black phosphorus nanosheets are determined to be 360 fs to 1.36 ps with photon energies from 1.55 to 0.61 eV. In a comparative study with graphene, we found that black phosphorus has a faster carrier relaxation in near- and mid-infrared region. With regard to nonlinear optical absorption, the response of black phosphorus significantly increases from near- to mid-infrared, and black phosphorus is also confirmed to be better as saturable absorber to MoS2 in infrared region.

Ultrafast Nonlinear Excitation Dynamics of Black Phosphorus Nanosheets from Visible to Mid-Infrared.

Considerable attention has been drawn to the lead halide perovskites (LHPs) because of their outstanding optoelectronic characteristics. LHP nanosheets (NSs) grown from single crystalline lead halide possess advantages in device applications as they provide the possibility for control over morphology, composition, and crystallinity. Here, free-standing lead bromide (PbBr) single-crystalline NSs with sizes up to one centimeter are synthesized from solution. These NSs can be converted to LHP while maintaining the NS morphology. We demonstrate that these perovskite NSs can be processed directly for fabrication of photodetector and laser arrays on a large scale. This strategy will allow high-yield synthesis of large-size perovskite NSs for functional devices in an integrated photonics platform.

Synthesis of centimeter-size free-standing perovskite nanosheets from single-crystal lead bromide for optoelectronic devices.

The fast development of terahertz technologies demands high-performance electromagnetic interference (EMI) shielding materials to create safe electromagnetic environments. Despite tremendous breakthroughs in achieving superb shielding efficiency (SE), conventional shielding materials have high reflectivity and cannot be re-edited or recycled once formed, resulting in detrimental secondary electromagnetic pollution and poor adaptability. Herein, a hydrogel-type shielding material incorporating MXene and poly(acrylic acid) is fabricated through a biomineralization-inspired assembly route. The composite hydrogel exhibits excellent stretchability and recyclability, favorable shape adaptability and adhesiveness, and fast self-healing capability, demonstrating great application flexibility and reliability. More interestingly, the shielding performance of the hydrogel shows absorption-dominated feature due to the combination of the porous structure, moderate conductivity, and internal water-rich environment. High EMI SE of 45.3 dB and broad effective absorption bandwidth (0.2-2.0 THz) with excellent refection loss of 23.2 dB can be simultaneously achieved in an extremely thin hydrogel (0.13 mm). Furthermore, such hydrogel demonstrates sensitive deformation responses and can be used as an on-skin sensor. This work provides not only an alternative strategy for designing next-generation EMI shielding material but also a highly efficient and convenient method for fabricating MXene composite on macroscopic scales.

Multifunctional TiCT MXene Composite Hydrogels with Strain Sensitivity toward Absorption-Dominated Electromagnetic-Interference Shielding.

Establishing the carbonation profile is of great significance to the prediction of the service life of reinforced concrete structures. In our previous work, Raman spectroscopy was shown to be an efficient tool for characterizing calcium carbonate (CaCO) polymorphs and their profile in plain Portland cement (PC) matrices. However, as supplementary cementitious materials (SCMs), particularly fly ash (FA) and ground granulated blast furnace slag (GGBS), are widely used in concrete, establishing the carbonation profile without considering the possible effects of these SCMs could be of little significance to the real world. This paper, thus, investigated the effects of FA and GGBS on the working capacity and reliability of Raman spectroscopy for establishing the carbonation profile in PC blends containing SCMs. The thermogravimetry (TG) analysis was also conducted to verify the results from Raman spectroscopy. The results show that Raman spectroscopy demonstrated a good capacity for differentiating the variation of CaCO contents in FA or GGBS blends. However, the incorporation of FA and GGBS into the PC system caused some adverse effects on the quantification of CaCO by Raman spectroscopy, which could be attributed to the darker color and weak scatter nature of FA and the high content of glassy phases in GGBS.

Article	Year
Two-dimensional nanosheets produced by liquid exfoliation of layered materials. Science (New York, N.Y.)\| PubMed ID: 21292974	2011
Low divergence photonic nanojets from Si3N4 microdisks. Optics express\| PubMed ID: 22274336	2012
Depth profiling of PLGA copolymer in a novel biomedical bilayer using confocal Raman spectroscopy. Langmuir : the ACS journal of surfaces and colloids\| PubMed ID: 23594126	2013
Transport Gap Opening and High On-Off Current Ratio in Trilayer Graphene with Self-Aligned Nanodomain Boundaries. ACS nano\| PubMed ID: 26302083	2015
Spin-dependent transport properties of Fe3O4/MoS2/Fe3O4 junctions. Scientific reports\| PubMed ID: 26522127	2015
Ultrafast Nonlinear Excitation Dynamics of Black Phosphorus Nanosheets from Visible to Mid-Infrared. ACS nano\| PubMed ID: 27281449	2016
Synthesis of centimeter-size free-standing perovskite nanosheets from single-crystal lead bromide for optoelectronic devices. Scientific reports\| PubMed ID: 31409846	2019
Multifunctional TiCT MXene Composite Hydrogels with Strain Sensitivity toward Absorption-Dominated Electromagnetic-Interference Shielding. ACS nano\| PubMed ID: 33397098	2021
Establishing the Carbonation Profile with Raman Spectroscopy: Effects of Fly Ash and Ground Granulated Blast Furnace Slag. Materials (Basel, Switzerland)\| PubMed ID: 33916458	2021

Jing Jing Wang

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