Wastewater Treatment Using High-Performance In Situ Formed Double-Heterojunction Janus Photocatalyst Microparticles Shaped via a Microfluidic Device.

In this work, a heterogeneous photocatalysis system is fabricated for treating wastewater containing organic dyes and pharmaceutical substances. Double-heterojunction Janus photocatalysts are formed on the surface of size-tunable polydimethylsiloxane (PDMS) microparticles shaped via simple and low-cost coflow microfluidic devices. Ag0/Ag0-TiO2/TiO2 Janus-like photocatalysts are synthesized on the surface of porous PDMS microparticles as the support in which the metal-semiconductor heterojunction of Ag0/Ag0-TiO2 and the second heterojunction of Ag0-TiO2/TiO2 are created in situ, leading to the formation of Ag0/Ag0-TiO2/TiO2@PDMS photocatalysis systems. To form the heterojunctions on the PDMS surface, the polymer chain etching method is employed as a desired strategy to have half of the TiO2 nanoparticles on the surface of microparticles, which are treated by a Ag source. Using salt additives and the etching method, PDMS microparticles are made porous, providing more surface area for photoreactions. Surprisingly, the highest decomposition efficiencies of 94.4 and 91.1% are achieved for rhodamine B(RhB) and tetracycline (TC), respectively, under visible light for 60 min pH 11, a light source at a distance of 2 cm, 5 mM AgNO3, 10 wt % TiO2, 7 wt % NaCl, and 20 gm/L photocatalyst, which are conditions that result in the best performance for RhB degradation. Regarding the stability of the photocatalysts, no significant change is observed in the performance after five cycles.

Recent advances in heterogeneous catalysis of solar-driven carbon dioxide conversion.

Solar-driven carbon dioxide (CO2) conversion including photocatalytic (PC), photoelectrochemical (PEC), photovoltaic plus electrochemical (PV/EC) systems, offers a renewable and scalable way to produce fuels and high-value chemicals for environment and energy sustainability. This review summarizes the basic fundament and the recent advances in the field of solar-driven CO2 conversion. Expanding the visible-light absorption is an important strategy to improve solar energy conversion efficiency. The separation and migration of photogenerated charges carriers to surface sites and the surface catalytic processes also determine the photocatalytic performance. Surface engineering including co-catalyst loading, defect engineering, morphology control, surface modification, surface phase junction, and Z-scheme photocatalytic system construction, have become fundamental strategies to obtain high-efficiency photocatalysts. Similar to photocatalysis, these strategies have been applied to improve the conversion efficiency and Faradaic efficiency of typical PEC systems. In PV/EC systems, the electrode surface structure and morphology, electrolyte effects, and mass transport conditions affect the activity and selectivity of electrochemical CO2 reduction. Finally, the challenges and prospects are addressed for the development of solar-driven CO2 conversion system with high energy conversion efficiency, high product selectivity and stability.

Mucin-Inspired Single-Chain Polymer (MIP) Fibers as Potent SARS-CoV-2 Inhibitors.

Mucins are the key component of the defensive mucus barrier. They are extended fibers of very high molecular weight with diverse biological functions depending strongly on their specific structural parameters. Here, we present a mucin-inspired nanostructure, produced via a synthetic methodology to prepare methacrylate-based dendronized polysulfates (MIP-1) on a multi gram-scale with high molecular weight (MW=450 kDa) and thiol end-functionalized mucin-inspired polymer (MIP) via RAFT polymerization. Cryo-electron tomography (Cryo-ET) analysis of MIP-1 confirmed a mucin-mimetic wormlike single-chain fiber structure (length=144±59 nm) in aqueous solution. This biocompatible fiber showed promising activity against SARS-CoV-2 and its mutant strain, with a remarkable low half maximal (IC50 ) inhibitory concentration (IC50 =10.0 nM). Additionally, we investigate the impact of fiber length on SARS-CoV-2 inhibition by testing other functional polymers (MIPs) of varying fiber lengths.

DNA sequencing by Förster resonant energy transfer.

We propose a new DNA sequencing concept based on nonradiative Förster resonant energy transfer (FRET) from a donor quantum dot (QD) to an acceptor molecule. The FRET mechanism combined with the nanopore-based DNA translocation is suggested as a novel concept for sequencing DNA molecules. A recently-developed hybrid quantum/classical method is employed, which uses time-dependent density functional theory and quasistatic finite difference time domain calculations. Due to the significant absorbance of DNA bases for photon energies higher than 4 eV, biocompatibility, and stability, we use Zinc-Oxide (ZnO) QD as a donor in the FRET mechanism. The most sensitivity for the proposed method to DNA is achieved for the Hoechst fluorescent-dye acceptor and 1 nm ZnO-QD. Results show that the insertion of each type of DNA nucleobases between the donor and acceptor changes the frequency of the emitted light from the acceptor molecule between 0.25 to 1.6 eV. The noise analysis shows that the method can determine any unknown DNA nucleobases if the signal-to-noise ratio is larger than 5 dB. The proposed concept and excellent results shed light on a new promising class of DNA sequencers.

Interband plasmon-enhanced optical absorption of DNA nucleobases through the graphene nanopore.

We propose a novel, to the best of our knowledge, plasmonic-based methodology for the purpose of fast DNA sequencing. The interband surface plasmon resonance and field-enhancement properties of graphene nanopore in the presence of the DNA nucleobases are investigated using a hybrid quantum/classical method (HQCM), which employs time-dependent density functional theory and a quasistatic finite difference time domain approach. In the strong plasmonic-molecular coupling regime where the plasmon and DNA absorption frequencies are degenerated, the optical response of DNA molecule in the vicinity of the nanopore is enhanced. In contrast, when the plasmon and nucleobases resonances are detuned the distinct peaks and broadening of the molecular resonances represent the inherent properties of the nucleobase. Due to the different optical properties of DNA nucleobases in the ultraviolet (UV) region of light, the signal corresponding to the replacement of nucleobases in a DNA block can be determined by considering the differential absorbance. Results show the promising capability of the present mechanism for practical DNA sequencing.

First-principles study of lead-free Ge-based 2D Ruddlesden-Popper hybrid perovskites for solar cell applications.

Recently, 2D halide perovskites have attracted attention because they are excellent photo absorbing materials for perovskite solar cells. To date, the majority of 2D perovskite-based devices have been made of Pb, a material with toxic properties and environmental concerns. Thus, lead-free alternatives are essential to enable the expansion of photovoltaic systems based on perovskites. Herein, we examine the structural, electronic, optical and stability properties of Pb-free 2D Ruddlesden-Popper (RP) perovskites (BA)2(MA)n-1GenI3n+1 (BA = CH3(CH2)3NH3+; MA = CH3NH3+; n = 1-5, and ∝) by using DFT calculations and comparing the results to their Pb-based counterparts (BA)2(MA)n-1PbnI3n+1 (n = 1-5, and ∝). Theoretical analysis indicates that Pb and Ge-based 2D perovskites are significantly more thermodynamically stable than their corresponding 3D materials. A more accurate bandgap is achieved using the HSE06 + SOC scheme and compared to the findings of the PBE and PBE + SOC. These materials are direct bandgap semiconductors. Due to spin-orbit coupling, Pb-based perovskite displays higher Rashba energy splitting than Ge-based ones. The bandgap changes from 2.37 eV (n = 1) to 1.79 eV (n = 5), and from 1.92 eV (n = 1) to 1.56 eV (n = 5) for Pb and Ge-based perovskites, respectively. The bandgap of all Ge-based perovskites is lower than their corresponding Pb-based ones. We show that the 2D perovskites could serve as hole-transporting materials when they are alongside 3D perovskites. The trade-off between thermodynamic stability and absorption coefficient of the considered compounds indicates that 2D RP perovskites BA2MA4Ge5I16 are promising Pb-free halide semiconductors for solar cell applications.

Enhancing the efficiency and stability of perovskite solar cells based on moisture-resistant dopant free hole transport materials by using a 2D-BA2PbI4 interfacial layer.

In this work, the photovoltaic performance and stability of perovskite solar cells (PSCs) based on a dopant-free hole transport layer (HTL) are efficiently improved by inserting a two-dimensional (2D) interfacial layer. The benzyl ammonium lead iodide (BA2PbI4) 2D perovskite is used as an interfacial layer between the 3D CH3NH3PbI3 perovskite and two moisture-resistant dopant-free HTLs including poly[[2,3-bis(3-octyloxyphenyl)-5,8-quinoxalinediyl]-2,5-thiophenediyl] (TQ1) and poly(3-hexylthiophene) (P3HT). TQ1 with a facile synthesis procedure has a higher moisture resistivity compared to P3HT which can improve the stability of PSCs. The 2D BA2PbI4 perovskite with a less-volatile bulkier organic cation efficiently passivates the defects at the perovskite/HTL interface, leading to 11.95% and 15.04% efficiency for the modified TQ1 and P3HT based cells, respectively. For a better understanding, the structural, optical, and electrical properties of PSCs comprising P3HT and TQ1 HTLs with and without interface modification are studied. The interface modified PSCs show slower open-circuit voltage decay and longer carrier lifetimes compared to unmodified cells. In addition, impedance spectroscopy reveals lower charge transport resistance and higher recombination resistance for the modified devices, which could be associated with the modification of the interface between the 3D CH3NH3PbI3 perovskite and HTL caused by the 2D interfacial layer. Also after aging under ambient conditions for about 800 hours, the modified PCSs retain more than 80% of their initial PCEs. These results give us the hope of achieving simpler, cheaper, and more stable PSCs with dopant-free HTLs through 2D interfacial layers, which have great potential for commercialization.

Chemical Approaches to Synthetic Drug Delivery Systems for Systemic Applications.

Poor water solubility and low bioavailability of active pharmaceutical ingredients (APIs) are major causes of friction in the pharmaceutical industry and represent a formidable hurdle for pharmaceutical drug development. Drug delivery remains the major challenge for the application of new small-molecule drugs as well as biopharmaceuticals. The three challenges for synthetic delivery systems are: (i) controlling drug distribution and clearance in the blood; (ii) solubilizing poorly water-soluble agents, and (iii) selectively targeting specific tissues. Although several polymer-based systems have addressed the first two demands and have been translated into clinical practice, no targeted synthetic drug delivery system has reached the market. This Review is designed to provide a background on the challenges and requirements for the design and translation of new polymer-based delivery systems. This report will focus on chemical approaches to drug delivery for systemic applications.

Graphene-Assisted Synthesis of 2D Polyglycerols as Innovative Platforms for Multivalent Virus Interactions.

2D nanomaterials have garnered widespread attention in biomedicine and bioengineering due to their unique physicochemical properties. However, poor functionality, low solubility, intrinsic toxicity, and nonspecific interactions at biointerfaces have hampered their application in vivo. Here, biocompatible polyglycerol units are crosslinked in two dimensions using a graphene-assisted strategy leading to highly functional and water-soluble polyglycerols nanosheets with 263 ± 53 nm and 2.7 ± 0.2 nm average lateral size and thickness, respectively. A single-layer hyperbranched polyglycerol containing azide functional groups is covalently conjugated to the surface of a functional graphene template through pH-sensitive linkers. Then, lateral crosslinking of polyglycerol units is carried out by loading tripropargylamine on the surface of graphene followed by lifting off this reagent for an on-face click reaction. Subsequently, the polyglycerol nanosheets are detached from the surface of graphene by slight acidification and centrifugation and is sulfated to mimic heparin sulfate proteoglycans. To highlight the impact of the two-dimensionality of the synthesized polyglycerol sulfate nanosheets at nanobiointerfaces, their efficiency with respect to herpes simplex virus type 1 and severe acute respiratory syndrome corona virus 2 inhibition is compared to their 3D nanogel analogs. Four times stronger in virus inhibition suggests that 2D polyglycerols are superior to their current 3D counterparts.

Graphene-based mid-infrared plasmonic isolator with multimode interferometer.

This Letter presents an extremely compact graphene-based plasmonic isolator with a two-port multimode interference (MMI) structure. The proposed structure utilizes the non-reciprocal phase shift effect to provide optical isolation. A new approach is used for MMI-based isolator design in terms of mth overall self-imaging. The influence of the device geometries and m parameter on the isolation ratio (ISR), insertion loss, operation bandwidth (BW), and required magnetic field strength B and its appropriate direction is investigated. The device has an ultra-small footprint compared to the operating wavelength of λ=8µm with high ISR. An MMI isolator with a size of 0.5µm×4.02µm (≈λ2/32) and ISR=18.35dB and an MMI isolator with a size of 0.7µm×7.44µm (≈λ2/12) with ISR=27.1dB are achieved. Moreover, the non-reciprocal MMI shows ultra-wide 20 dB isolation BW of 0.75-2.34 THz.

Cancer and non-cancer health risk assessment of occupational exposure to 1,3-butadiene in a petrochemical plant in Iran.

1,3-Butadiene is classified as carcinogenic to humans by inhalation. This study aimed to assess cancer and non-cancer risk following occupational exposure to 1,3-butadiene. This cross-sectional study was conducted in a petrochemical plant producing acrylonitrile butadiene styrene copolymer in Iran. Occupational exposure to 1,3-butadiene was measured according to the National Institute for Occupational Safety and Health 1024 method. Cancer and non-cancer risk assessment were performed according to the United States Environmental Protection Agency method. The average occupational exposure to 1,3-butadiene during work shifts among all participants was 560.82 ± 811.36 µg m-3. The average lifetime cancer risk (LCR) in the present study was 2.71 × 10-3; 82.2% of all exposed workers were within the definite carcinogenic risk level. Also, the mean non-cancer risk (hazard quotient (HQ)) among all participants was 10.82 ± 14.76. The highest LCR and HQ were observed in the safety and fire-fighting station workers with values of 7.75 × 10-3 and 36.57, respectively. The findings revealed that values of carcinogenic and noncarcinogenic risk in the majority of participants were within the definitive and unacceptable risk levels. Therefore, corrective measures are necessary to protect these workers from non-cancer and cancer risks from 1,3-butadiene exposure.

Novel nanostructured electron transport compact layer for efficient and large-area perovskite solar cells using acidic treatment of titanium layer.

A new method for the deposition of a pinhole-free compact layer of TiO2 is introduced for the development of efficient perovskite solar cells. Acidic treatment of titanium layer (ATTL), deposited by rotational magnetron sputtering, presents a compact pinhole-free TiO2 thin film. Deposition of a compact TiO2 thin film on fluorine-doped tin oxide layers by ATTL did not change the surface roughness. To compare the introduced method, perovskite solar cell devices were fabricated and studied using different methods for the deposition of the TiO2 compact layers, which were used as common compact layer deposition methods. The ATTL method proposed considerable photovoltaic enhancement of perovskite solar cell performance (at least 22% enhancement in this work) by reducing the pinholes and sheet resistance of the TiO2 thin film. The improvement in the open-circuit voltage and the fill factor of the prepared devices using the ATTL method strongly confirmed the nature of the deposited pinhole-free TiO2 thin film. This method is shown to be an appropriate route for the reliable large-scale deposition of TiO2 compact layers.

Picosecond and femtosecond asymmetric switching using a semiconductor optical amplifier-based Mach-Zehnder interferometer.

In this paper, we numerically analyze nonlinear asymmetric switching using a semiconductor optical amplifier (SOA) phase-shifter-based Mach-Zehnder interferometer (MZI), for the first time, to the best of our knowledge. The self-phase modulation (SPM) effect and nonlinear phase shift in each MZI arm are investigated for different input pulse intensities and linear gains in both picosecond and femtosecond regimes. The input light signal is split unequally over the two arms, where SOAs are placed and act as nonlinear phase shifters in each arm. The finite difference beam propagation method is used to solve the modified nonlinear Schrodinger equation to analyze the wave propagation. In this work, the main nonlinear effects in SOA, such as group velocity dispersion, Kerr effect, two-photon absorption, carrier heating, and spectral hole burning, are considered. Furthermore, the effect of SPM on distortion of the pulse shape and its spectrum, which can be used for pulse shaping in a picosecond-switching scheme, is studied. We depicted red and blue shifts that each pulse experiences in the process of switching in picosecond and femtosecond regimes, respectively. Based on the results for sub-picosecond input pulses, by controlling the bias current level in the MZI arms, the pulse distortion due to nonlinear effects of SOAs can be decreased at the switch output port, and symmetric pulse can be obtained. Switching with higher speed is possible in bulk SOAs in the femtosecond regime using asymmetric MZI-switching structure.

Schottky graphene/Si photodetector based on metal-dielectric hybrid hollow-core photonic crystal fibers.

This Letter presents a new family of Schottky graphene/silicon (Si) photodetectors (PDs) based on hollow-core photonic crystal fibers (HPCFs), working at both optical communication and room temperature. The proposed structure has the advantage of plasmonic HPCFs in a slow-light regime, and the absorption mechanism is based on an internal photoemission effect. The main feature of this structure is that the enhanced electric field is strongly localized in the hollow core of the guided core mode with the surface plasmon modes at the surface metal wires embedded in the photonic crystal structure. For the proposed graphene/silicon Schottky PD, numerical simulation predicts responsivity of ∼0.39 A/W, and continuous-wave sensitivity of -59 dBm, which reveals substantial improvements compared to that of typical metal/Si Schottky PDs.

Nano-plasmonic-based structures for DNA sequencing.

We propose novel nano-plasmonic-based structures for rapid sequencing of DNA molecules. The optical properties of DNA nucleotides have notable differences in the ultraviolet (UV) region of light. Using nanopore, bowtie, and bowtie-nanopore compound structures, probable application of the surface plasmon resonance (SPR) in DNA sequencing is investigated by employing the discrete dipole approximation method. The effects of different materials like chromium (Cr), aluminum (Al), rhodium (Rh), and graphene (Gr) are studied. We show that for Cr/Al/Gr/Rh, the nucleotide presented shifts the SPR spectra for the nanopore 1/29/5/34 to 14/39/15/67 nm, bowtie 8/2/49/38 to 31/20/79/55 nm, and bowtie-nanopore compound 25/77/5/16 to 80/80/22/39 nm. The Cr-based compound structure shows excellent sensitivity and selectivity which can make it a promising methodology for DNA sequencing.

Graphene-based side-polished optical fiber amplifier.

We demonstrate a novel design for optical fiber amplifiers, utilizing side-polished fibers with a single-layer graphene overlay as the active medium and carrier injection in the graphene layer to provide the required inversion. We study the effects of an electrically induced graphene p-i-n heterojunction in the forward bias regime on optical modes of side-polished fibers and show that gain values of 0.51, 1.81, and 1.79 dB/cm for wavelengths 1064, 1330, and 1550 nm can be obtained for single-mode side-polished fibers. Our results show that in multi-mode side-polished fibers, higher order modes experience higher values of gain, and gain can be increased by increasing polished depth. The proposed system is a tunable wideband optical amplifier that can operate for wavelengths larger than 1000 nm.

Modeling and analysis of distributed feedback quantum dot passively mode-locked lasers.

In this paper, we investigate numerically two proposed monolithic distributed feedback quantum dot passively mode-locked lasers (DFB-QDMLLs) with and without gratings in the saturable absorber (SA) section in order to enhance two important performances of QDMLLs for ultrahigh-bit-rate and single-mode applications. We find out that depending on the length of the grating, optical pulses with durations of about 3-8 ps at approximately 2nd and 4th harmonics of cavity round-trip frequencies can be generated by the proposed structures. We also compare the temporal and spectral behaviors of these structures under specified bias conditions and SA lengths. It is shown that DFB-QDMLLs have the ability to generate optical pulses with more peak power than grating-embedded saturable absorber (GESA-DFB-QDMLL) structures which generate shorter pulses with narrower spectral bandwidths. We also show that DFB-QDMLLs operate in a larger range of absorber voltages while the other structure is very sensitive to absorber voltage and operates well for middle ranges of this parameter.

Dynamic characteristics of photonic crystal quantum dot lasers.

In this paper, we analyze the dynamic characteristics of quantum dot (QD) photonic crystal lasers by solving Maxwell equations coupled to rate equations through linear susceptibility of QDs. Here, we study the effects of the quality factor of the microcavity and temperature on the delay, relaxation oscillation frequency, and output intensity of the lasers. Moreover, we investigate the dependence of the Purcell factor on temperature. We show that when the quality factor of the microcavity is so high that we can consider its linewidth as a delta function in comparison with QDs, the Purcell factor significantly drops with increasing temperature.

Design and analysis of 2D one-way splitter waveguide based on topological photonics.

We present a new high-efficiency splitter waveguide design based on photonic topological insulators. The system's robust edge states allow electromagnetic waves to propagate in the 2D waveguide without backscattering, resulting in almost 100% transmission in the outputs. We also study resonating modes in the structure and show that introducing specific defects can create such modes. We consider four domains with rods of varying magneto-optical properties to provide edge modes in the system. By eliminating rows and columns of rods, we calculate the transmission at the outputs, revealing resonating modes in the middle of the structure with spatial symmetry. Our calculations indicate that the most promising resonating mode occurs when two rods and two columns are eliminated, with a quality factor Q = 1.02 × 106 at frequency f = 8.23 GHz and almost zero transmission at this frequency to the outputs. We further confirm our results using the transmission line resonator model as a semi-analytical model, which agrees well with our findings.

Metastructure Engineering with Ruddlesden-Popper 2D Perovskites: Stability, Flexibility, and Quality Factor Trade-Offs.

In this study, we investigate the opto-electro-mechanical properties, thermodynamic stability, and moisture stability of the Ruddlesden-Popper (RP) two-dimensional perovskites of L2PbI4 (L = PEA, FPEA, BA, and BZA) using density functional theory. The goal is to explore their potential application in metastructures. The results show that the stability of FPEA2PbI4 is better than that of PEA2PbI4, BA2PbI4, and BZA2PbI4 due to the replacement of a hydrogen atom with a fluorine atom. On the other hand, BA2PbI4 is more flexible than other materials because it lacks an aromatic ring in its spacer cation, but it is less stable. We introduce a new kind of metastructure composed of an RP perovskite film and conduct an extensive investigation of the quasi-bound states in the continuum (q-BIC) characteristics by near-field analysis and multipole decomposition calculations. The q-BIC resonances in BZA2PBI4 have a greater quality factor due to its larger refractive index in comparison to other materials. Therefore, based on these results, the perovskite materials can be selected for the metastructures from different aspects of stability, flexibility, and refractive index.