Tuning Characteristics Research Articles

Sustainable Strategies for Synthesizing Lignin-Incorporated Bio-Based Waterborne Polyurethane with Tunable Characteristics.

In this study, we introduce a novel approach for synthesizing lignin-incorporated castor-oil-based cationic waterborne polyurethane (CWPU-LX), diverging significantly from conventional waterborne polyurethane dispersion synthesis methods. Our innovative method efficiently reduces the required solvent quantity for CWPU-LX synthesis to approximately 50% of that employed in traditional WBPU experimental procedures. By incorporating lignin into the polyurethane matrix using this efficient and reduced-solvent method, CWPU-LX demonstrates enhanced properties, rendering it a promising material for diverse applications. Dynamic interactions between lignin and polyurethane molecules contribute to improved mechanical properties, enhanced thermal stability, and increased solvent resistance. Dynamic interactions between lignin and polyurethane molecules contribute to improved tensile strength, up to 250% compared to CWPU samples. Furthermore, the inclusion of lignin enhanced thermal stability, showcasing a 4.6% increase in thermal decomposition temperature compared to conventional samples and increased solvent resistance to ethanol. Moreover, CWPU-LX exhibits desirable characteristics such as protection against ultraviolet light and antibacterial properties. These unique properties can be attributed to the presence of the polyphenolic group and the three-dimensional structure of lignin, further highlighting the versatility and potential of this material in various application domains. The integration of lignin, a renewable and abundant resource, into CWPU-LX exemplifies the commitment to environmentally conscious practices and underscores the significance of greener materials in achieving a more sustainable future.

Controlled Growth of Highly Oriented Perovskite Crystals in Polymer Solutions via Selective Solvent Vapor Diffusion.

Organic-inorganic hybrid perovskites have garnered significant attention in optoelectronics owing to their outstanding tunable optical characteristics. Controlled growth of perovskite nanocrystals from solutions is key for controlling the emission intensity and photoluminescence lifetime of perovskites. In particular, most studies have focused on controlling the crystallization of perovskite through chemical treatment using chelating ligands or physical treatment via antisolvent diffusion, and there exists a trade-off between the photoluminescence intensity and lifetime of perovskites. Herein, a selective solvent vapor-assisted crystallization with the aid of a functional polymer, which nanoscale perovskite crystals are grown andante from precursor solution, is presented for tuning the crystallization and optical properties of a common halide perovskite, methylammonium lead bromide (MAPbBr3 ). The proposed method here produces perovskite nanocrystals in the range of 200-300nm. The spin-coated thin film formed from the perovskite solution exhibits strong green photoluminescence with a long lifetime. The effects of the functional group and polymer dosage on the crystallization of MAPbBr3 are systematically investigated, and the crystallization mechanism is explained based on a modified LaMer model. This study provides an advanced solution process for precisely controlling perovskite crystallization to enhance their optical properties for next-generation optoelectronic devices.

Tunable dynamic microwave properties of a magnetic skyrmion manipulated by strains

In this paper, we theoretically studied the tunable dynamic microwave properties of a magnetic skyrmion manipulated by strains through micromagnetic simulations. The strains are induced by voltage due to the converse piezoelectric effect and then applied to modulate the dynamic characteristics through the magneto-elastic coupling effect. The tunable dynamic microwave characteristics of a breathing mode and gyration modes are investigated. The resonant frequency of the breathing mode increases abruptly and then decreases slowly with the strain changing from compressive to tensile. A clockwise gyrotropic mode has been obtained, and the resonant frequency keeps increasing with the strain changing from compressive to tensile. In particular, strains can induce different gyrotropic trajectories of the skyrmion driven by an in-plane microwave field. Our results may contribute to the understanding of dynamic properties of skyrmions manipulated by voltage-induced strains and provide a method to realize tunable spintronic microwave devices based on skyrmion.

Transmission and reflection bidirectional terahertz coding metasurface based on thermally switchable materials

Metasurface, with its powerful and flexible terahertz(THz) wave manipulation capability, has become a key component of beamforming and imaging systems in the THz band. However, its practical application is limited by fixed properties and propagation mode on a single metasurface. In this paper, we propose a coding metasurface with tunable characteristics and bidirectional working modes. The complete 2π phase compensation can be realized by rotating the InSb unit according to the Pancharatnam-Berry phase concept, and eight meta-atoms are selected to regulate the wavefront of terahertz waves using phase compensation. By increasing the temperature of the InSb from 290 K to 370 K, the working frequency permits wideband coverage from 1.7 to 4.5 THz. As the temperature reaches 341.15 K, which is required for vanadium dioxide's(VO2) phase transition, the metasurface's propagation direction mode will switch from transmission to reflection. The proposed metasurface can perform beam deflecting, splitting, and focusing functions when VO2 is in a dielectric state. Meanwhile, beam deflecting, splitting, and radar scattering surface (RCS) reduction can also be achieved when VO2 is in a metallic state. Furthermore, a near-field image of the letter P is presented as verification. Numerous potential applications for the reconfigurable metasurfaces include polarization beam splitters, imaging, and terahertz switching.

Tunable ultra-wideband graphene metasurface absorber: A mode merger design approach for terahertz applications

This paper presents a systematic approach for designing an ultra-wideband (UWB) absorber for terahertz (THz) applications. The metasurface consists of top patterned graphene (Gpat) and bottom continuous graphene (Gcont), each having a thickness of 0.335 nm and separated by a 3 μm thick silicon dioxide (SiO2) dielectric. Multiple absorbing modes have been generated by engraving rectangular, star-shaped, and circular ring slots on the top Gpat resonating at 3.22, 4.52, and 0.32 THz, respectively. A circular ring slot works as a coupling controller and helps to combine different slot resonances. The mode merger technique, along with the high plasmonic coupling between Gpat and Gcont controlled by Gcont help to attain an absorption bandwidth (BW) of 5.9 THz (193.44%) with absorptivity ≥ 90% ranging from 0.1 to 6 THz. The periodicity and thickness of the proposed polarization-insensitive metasurface are found to be λ0/300 and λ0/996.68, respectively, where λ0 is free space wavelength computed at 0.1 THz. Absorptivity ≥ 80% for incidence angle up to 60∘ under both transverse electric (TE) and transverse magnetic (TM) polarization has also been achieved. The absorber provides excellent frequency tunable characteristics over a UWB band and shows blue-shift with increased chemical potential (μc).

Review: tunable nanophotonic metastructures.

Tunable nanophotonic metastructures offer new capabilities in computing, networking, and imaging by providing reconfigurability in computer interconnect topologies, new optical information processing capabilities, optical network switching, and image processing. Depending on the materials and the nanostructures employed in the nanophotonic metastructure devices, various tuning mechanisms can be employed. They include thermo-optical, electro-optical (e.g. Pockels and Kerr effects), magneto-optical, ionic-optical, piezo-optical, mechano-optical (deformation in MEMS or NEMS), and phase-change mechanisms. Such mechanisms can alter the real and/or imaginary parts of the optical susceptibility tensors, leading to tuning of the optical characteristics. In particular, tunable nanophotonic metastructures with relatively large tuning strengths (e.g. large changes in the refractive index) can lead to particularly useful device applications. This paper reviews various tunable nanophotonic metastructures' tuning mechanisms, tuning characteristics, tuning speeds, and non-volatility. Among the reviewed tunable nanophotonic metastructures, some of the phase-change-mechanisms offer relatively large index change magnitude while offering non-volatility. In particular, Ge-Sb-Se-Te (GSST) and vanadium dioxide (VO2) materials are popular for this reason. Mechanically tunable nanophotonic metastructures offer relatively small changes in the optical losses while offering large index changes. Electro-optically tunable nanophotonic metastructures offer relatively fast tuning speeds while achieving relatively small index changes. Thermo-optically tunable nanophotonic metastructures offer nearly zero changes in optical losses while realizing modest changes in optical index at the expense of relatively large power consumption. Magneto-optically tunable nanophotonic metastructures offer non-reciprocal optical index changes that can be induced by changing the magnetic field strengths or directions. Tunable nanophotonic metastructures can find a very wide range of applications including imaging, computing, communications, and sensing. Practical commercial deployments of these technologies will require scalable, repeatable, and high-yield manufacturing. Most of these technology demonstrations required specialized nanofabrication tools such as e-beam lithography on relatively small fractional areas of semiconductor wafers, however, with advanced CMOS fabrication and heterogeneous integration techniques deployed for photonics, scalable and practical wafer-scale fabrication of tunable nanophotonic metastructures should be on the horizon, driven by strong interests from multiple application areas.

B-358 Application of Surface-Enhanced Raman Spectroscopy to Improve Sensitivity of Clinical Assays

Abstract Background Current efforts to expand the pool of available markers that can be analyzed in clinical settings is hampered by limited volumes of biomaterial-rich fluids and low concentrations of certain analytes, coupled with poor sensitivity of existing detection techniques. Although progress has been made using advanced sample preparation or assay techniques such as miRNeasy or ELISA for genomic and protein assays, respectively, little research has focused on adapting new optical methods as detection modes in the clinic. Amplified Sciences has developed an enzymatic activity assay platform using SERS detection to improve diagnostic sensitivities in multiple disease indications. Along with the experts at Wasatch Photonics, research focused on adaptation of this assay platform has enabled investigation of multiple markers of disease that had previously been undervalued or overlooked, as well as stacking of multiple markers in precious, low-volume samples. Methods Building upon previously published data using gastricsin as a marker to identify benign, non-mucinous pancreatic cysts, Amplified Sciences has added several SERS laser wavelengths, and different sample preparation methods to the existing platform. To examine the sensitivities of laser and dye combinations, solutions representative of assay samples containing rhodamine-dimer dye-labeled peptide were tested using Wasatch Photonics Raman spectrometers at 532, 638, 785, and 830 nm laser wavelengths. Samples at different pH were analyzed after addition of colloidal Au or Ag nanoparticles to determine the impacts of sample preparation on SERS spectral features. After drying in a desiccator overnight, the samples were reanalyzed to assess the stability of the SERS signals. As a pertinent application of this technology, an activity assay was developed for the known COVID protease 3ClPro. Release of rhodamine dimer dye as a result of 3ClPro cleavage of the substrate was quantified using SERS. The data were analyzed using Bruker OPUS Software package, and plotted using Graphpad Prism 9. Results Each laser, buffer, and metal used for SERS provided a unique spectral signature, suggesting that different transitions are available and potentially tunable depending on the application under investigation. Sensitivity was, as expected, best with the 532 nm SERS system purportedly due to enhancement factors, and the resonance impacts of rhodamine dyes at 532 nm. It was found that the Limit of Detection of Rhodamine-dimer dye was 100-fold lower with SERS compared to fluorescence, even after a 3-fold dilution with colloidal Ag. However, the remaining lasers could be more finely tuned, and, thus, provide alternate spectral properties, and different sensitivities which has implications when new dye classes are introduced into the platform. Furthermore, when SERS was applied to the 3ClPro assay, it was determined that activity could be detected below the dimerization concentration of 3ClPro, described in the literature as ∼25 nM. Also, a monomeric version of 3ClPro that is expected to have no reactivity with the substrate was found to display activity above background at concentrations as low as 1 µM. Conclusion SERS is an appropriate method for measuring activity in clinically relevant markers of disease, with tunable characteristics based upon the dye composition and the spectrometer in use.

Interface engineering in 2D materials for SERS sensing

In recent years, the use of 2D materials as surface-enhanced Raman scattering (SERS) active substrates has been extensively investigated. This mini review emphasizes the tunable interface characteristics of 2D materials as SERS substrates. Notably, 2D materials exhibit a wealth of tunable properties, encompassing energy levels, band structures, and interlayer coupling, which confer upon them significant potential as versatile SERS substrates. We summarize the recent advances in tunable 2D materials as SERS active substrates, providing guidance for future research in developing tunable multifunctional molecular sensors based on 2D materials.

Tunable optical and structural characteristics with improved electrical properties of (PVA-GO-CuO) eco-friendly-polymer nanocomposites and their DFT study

The research in this study have been motivated by the unique combination of GO (graphene oxide) and CuO nano-fillers with optimized composition in the poly vinyl alcohol (PVA) polymer. The (PVA-CuO-GO) polymer nanocomposites were created using a melt blending process with varying weight percentages of GO and CuO (ranging from 1 to 6 wt%) nanofillers. The composite was fashioned into a dumble-like structure. XRD (x-ray diffractometer), UV–Vis-NIR spectrophotometer, FESEM (field emission scanning electron microscope) and impedance analyzer were utilized to get the effect of nanofillers on the structural parameters, optical characteristics, surface morphology, and electrical properties of the composites. The influence of wt% of nano-fillers on crystalline size and micro-strain has been examined using XRD data. Tauc graphs were studied using UV–Vis-NIR spectrophotometer data for determining the direct and indirect optical bandgaps, and they show that increasing the weight percentage of nano-fillers causes the optical band gap (direct and indirect) to rise. The direct and indirect bandgap rose from 2.98 to 3.19 eV and 2.23 to 2.80, respectively, as the concentration of nano-fillers increased from 1 to 6 wt%. With increasing nanofillers amount, refractive index and Urbach energy were found to reduce; while peak extinction coefficient was found to increase. FESEM along with the EDAX analysis was also performed to investigate the smoothness of the composites' surfaces. Improvement in capacitance, dielectric constant and ac conductivity was also observed with increase in amount of nanofillers. DFT (Density functional theory) study has also been performed for Natural Bond Orbitals (NBO) analysis of charge and spin distribution, as well as HOMO, LUMO and molecular electrostatic potential (MEP). Based on the findings of the characterization results, the synthesized polymer nanocomposites can be employed in a variety of optoelectronics applications.

Recent advances of carbon nanotubes in perovskite solar cells

AbstractPerovskite solar cells (PSCs) have exhibited tremendous potential in photovoltaic fields owing to their appreciable performance and simple fabrication. Nevertheless, device performances are still required to be further improved before commercial applications. As one‐dimensional materials, carbon nanotubes (CNTs) have been utilized to regulate stability and efficiency of PSCs because of their excellent chemical stability, flexibility, as well as tunable optical and electrical characteristics. In this review, we comprehensively summarize various functions of CNTs in PSCs, such as transparent electrodes, hole/electron‐transport layers, counter electrodes, perovskite additives, and interlayers. Additionally, applications of CNTs toward the advancement of flexible and semitransparent PSCs are provided. Finally, we preview the challenges and research interests of using CNTs in high‐efficiency and stable perovskite devices.

Harnessing Metal/Oxide Interlayer to Engineer the Memristive Response and Oscillation Dynamics of Two‐Terminal Memristors

AbstractDevices with volatile memristive switching and self‐sustained relaxation oscillations have received significant attention for their use in neuromorphic computing and solving optimization problems. However, obtaining devices with stable response and reliable oscillation remains challenging. This work describes the utility of metal/oxide interlayers in achieving reliable device performance with tuneable characteristics using Nb‐Nb2O5‐Pt structures. Detailed physical characterization of the Nb/Nb2O5 interlayer region shows that it consists of a thin, near‐stoichiometric Nb2O5 and an NbOx layer with a graded oxygen content. The impact of these interlayers on device performance is assessed by investigating their switching characteristics and oscillation dynamics. It is shown that the presence of the interlayer has a direct impact on the memristive switching mode and parameters threshold switching characteristics parameters. These dependencies are explained with reference to a lumped‐element circuit model of the device and shown to be dominated by changes in device resistance caused by interlayer formation. Significantly, stable oscillation with tuneable frequency is obtained by increasing the thickness of the reactive Nb electrode. Then, by simulating an array of coupled oscillators, a unique Hamiltonian solver is demonstrated. These results provide pathways for optimizing volatile memristive switching characteristics and guidance on how such devices can be employed to solve combinatorial optimization problems.

Numerical investigation of optical bistability in a nonlinear plasmonic structure containing a phase change material

In this paper, a controllable nonlinear plasmonic structure is proposed based on a phase change material (PCM) layer to achieve tunable bistability characteristics. To this end, the Ge2Sb2Te5 (GST) layer (as a PCM) is sandwiched between a thin film of Ag and a Kerr material substrate. Then, this multilayered structure is used as a substrate for the ZnSiAs2 grating whose grooves are filled with the Kerr nonlinear material. Next, the grating is covered with a layer of CaF2. In this structure, we first calculate the reflection spectrum for different crystallization fractions using the finite element method (FEM) in the linear regime. The reflectance spectrum shows a dip in the near-infrared region, which is redshifted with increasing the crystallization fraction of the GST layer. This effect results from the movement of surface plasmon resonance to longer wavelengths with increasing the crystallization fraction. Then, we find that the dip in the reflectance spectrum is redshifted with enhancing the input intensity of the incident wave for different crystallization fractions in the nonlinear regime. This behavior confirms the existence of optical bistability through the proposed structure. So, we calculate the bistability curves at a fixed operating wavelength of 1550 nm for different crystallization fractions. Our results demonstrate that as the phase transition from the amorphous to the crystalline state occurs at a fixed operating wavelength, the bistability thresholds reduce while the hysteresis width also decreases and the bistability effect eventually disappears. Therefore, for each crystallization fraction of the GST layer we find a special wavelength at which a reasonable bistability curve with a reasonable hysteresis width is obtained. This operating wavelength is shifted by 33 nm as the crystallization fraction varies from 0.2 to 0.8. Finally, the effects of increasing the thickness of the GST layer on the bistability characteristics are examined. Our results show that stronger tunability of the operating wavelength by 50 nm with variation of crystallization degree from 0.2 to 0.8 is achieved when a thicker GST layer is used instead of a thinner one.

Plasmonic photocatalysts as emerging multifunctional nanomaterials for energy and environmental applications

Plasmonic photocatalysts are emerging as multifunctional nanomaterials for multidisciplinary applications in various fields of energy, environment and biomedical. Plasmonic photocatalysts are composed of noble metals and wide band gap semiconductors which provide ample opportunities to tune their opto-electronic and photocatalytic properties promising for such applications. Particularly, noble metal and semiconductor nanomaterials show unique surface plasmon resonance and photocatalytic properties respectively. The combination of such characteristics make plamsonic photocatalysts very promising for visible light activities with enhanced functionalities as compared to their own. In recent years, these nanomaterials have shown great potential as multifunctional/multidisciplinary nanomaterials due to their tunable characteristics and ease of fabrication strategies. This mini review covers such multifunctional photocatalytic activities of ZnO and noble metal (Ag, Au etc.) nanomaterials based plasmonic photocatalysts in the field of energy and environment. Recent progress in the tailoring their properties for enhanced functioning and mechanism of their action have been discussed.

Thermo-optical and electro-optical tunable dual-band THz absorber based on multi-layer hybrid VO2 phase transition metamaterial

In this paper, a thermo-optical and electro-optical (EO) tunable multifrequency metamaterial THz absorber based on a multi-layer hybrid VO2 transition metamaterial is demonstrated. The reflectivity and transmittivity, and absorptivity of the metamaterial with various geometric parameters are simulated. The simulation results show that the absorptivity reaches 99.4% at an operating frequency of 6.9 THz. The thermo-optical and EO tunable absorption rates are studied by changing the surrounding temperature and bias voltage, respectively. The absorptivity is adjusted from 36.2% to 99.4% and modulation depth is ∼63.5% when the surrounding temperature rises from 294 to 350 K. The EO wavelength tuning coefficient is ∼1690.4 pm/V. The effects of geometric parameters on the absorptivity of the metamaterial absorber are also discussed. The impedance matching theory is used to explain the physical mechanism of absorption characteristics. The proposed metamaterial absorber has potential applications including infrared imaging, thermal emitters, electromagnetic shielding and photodetector, moreover, the research of the thermo-optical and EO tunable absorption characteristics provides a feasible scheme of THz wave modulation and multiplexing.© 2021 Optica Publishing Group under the terms of the Optica Publishing Group Open Access Publishing Agreement.

Nanoarchitectonics of zirconium modified ZnTiO3 for photo and electro-catalysts in dye degradation and water splitting applications

Perovskite oxides are attractive in the catalytic application owing to their stability, tuning characteristics, and easy synthesis process. Here, ZnTi1-xZrxO3 (x = 0.5) (abbreviated as ZZT0.5) is synthesized under the chemical precursor solution decomposition method and calcined at 700 °C for 3 h. The cubic phase nanosized material exhibits cubic shape morphology with the proper ratio of the existing elements as from observed structural and morphological characterizations. In the photocatalytic dye degradation under natural sunlight irradiation, the materials show >90% color degradation of congo red and murexide. The observed result in the presence of solar light irradiation highlights an elevated photocatalytic efficiency. The pseudo-first-order degradation process shows a high correlation coefficient with good stability of the material in the reusable study. This ZnTiO3-based perovskite material has not been used previously in electrocatalytic water splitting. During oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) conditions, the material deposited on NF substrate showed 335 mV and 165 mV overpotential at 10 mA cm−2 current density, respectively which is indicative of notable electrocatalytic water splitting activity of the perovskite material designed herein. The long-term chronoamperometry (CA) study confirms the material's stability during both HER and OER conditions with negligible loss in activity over a period of 12 h. The post-catalytic characterizations confirm the robust nature of the material possessing the same phase characteristics. As an earth-abundant, low-cost material, the material designed herein shows the significant activity of environmental sustainability in terms of water treatment as well as green hydrogen production via electrolysis.

Effect of pore geometry on properties of high-temperature oxidized additively manufactured magnesium scaffolds

Only a few studies have examined how pore geometry affects the mechanical characteristics, biological behavior, and degradation of additively manufactured biodegradable porous magnesium. In this work, the effects of pore geometry on mechanical qualities, degradation, and biological behavior were investigated using three typical porous architectures with the same porosity. The porous structures were found to satisfy bone tissue engineering requirements because they had sufficient degradation resistance and tunable compressive characteristics. All three types of magnesium alloy scaffolds exhibited good biocompatibility. Additionally, the magnesium alloy porous structures influenced the magnesium scaffold material degradation rate and the surrounding environment, impacting the osteogenic differentiation of bone mesenchymal stem cells and bone tissue regeneration. This work offers conceptual support for optimizing pore geometry to alter the mechanical and degradable characteristics of additively manufactured porous magnesium to meet therapeutic demands.

Dynamic Modulation of Multilayer Structured Metamaterials Based on Vanadium Dioxide

In order to achieve a better characterized electromagnetic induction transparency (EIT) effect, a temperature-controlled modulated three-layer terahertz (THz) metamaterial structure based on the phase transition properties of vanadium dioxide (VO2) is designed, which is capable of demonstrating independently tunable multi-band broadband EIT effect. Simulations are applied to optimize the structure parametrically by varying the C-type resonator’s the length of the two arms and the interlayer spacing of each dielectric layer. The overall structure coupling is changed by varying the conductivity of the temperature-regulated VO2 to achieve independent dynamic modulation. Finally, the EIT effect is achieved at more than 85% of the frequencies in the 0.8 THz to 2.2 THz region, and the transparency exceeds 0.8. This independently tunable and broadband characteristic is of great interest for the application of the EIT effect.

Tunable Acoustic Properties in Reconfigurable Kerf Structures

Freeform structures are appealing in architecture owing to their ability to combine pleasing aesthetics and functionality. Regarding architectural functionality, freeform structures have the potential to meet desired acoustic requirements in indoor architecture through the proper design of materials and geometries. Kerfing is one of the practical methods to generate reconfigurable freeform structures from rigid planar construction materials. This study aims to explore tunable room acoustic characteristics through the use of kerf structures. In this study, we investigate acoustic responses of kerf structures made out of a medium density fiber board having a hexagon spiral kerf pattern with varying cut densities. Experiments are conducted to measure the acoustic properties (e.g., absorption coefficient) of the kerf unit cells with different cut densities. We then design kerf patterns using the parametric design method and explore the flexibility of kerf structures with different kerf cut densities. We model the kerf structures of varying kerf cut density and shape reconfigurations and use a ray-tracing simulation to study their impacts on the acoustic performance, i.e., reverberation times, of a small office space. Overall, this study leverages the unique attributes of kerf structures such as different cut densities and shape reconfigurations to tune the room acoustics in addition to their usage in indoor architectures due to their pleasing aesthetics.

Bimetallic Metal Organic Framework Composites for Carbondioxide Capture

Maintaining breathable air in human space flight missions is a challenge since there will be a gradual increase in the concentration of CO2 due to the exhalation of the spacecraft crew. Modern air revitalization technology for space missions uses temperature swing adsorption with zeolite-based materials as the adsorbent. However, the major drawbacks of zeolites are difficulty in regenerating used adsorbent and low selectivity towards CO2. Besides, frequent replacement of adsorption beds is necessary because of their low adsorption capacity towards CO2. This requires carrying a few spare beds in the spacecraft, which is not preferred because of the low-weight requirements for space missions. Hence, shifting to alternate materials with more selectivity and adsorption capacity toward CO2 becomes essential. Metal-organic frameworks (MOFs) are a class of crystalline materials found to be potential adsorbents for CO2 capture. Due to their ultra-high porosity, tunable pore characteristics, selective capture, and synergistic performance, they could replace the existing zeolite-based adsorbents. Further enhancement in the adsorption capacity could be achieved by introducing a secondary metal into the framework. This will bring heterogeneity in the structure, creation of defects, and open metal sites, thus enhancing the adsorption behavior. Incorporating a secondary metal into the framework and an additional filler material like activated carbon, making a BMOF composite, would lead to an exemplary improvement in the adsorption activity. The addition of filler material will lead to an increase in pore volume, which will enhance the adsorption capacity. In the current work, activated carbon was synthesized from sawdust via chemical activation method using KOH as the activating agent. It was carried out at low temperatures to boost the porous structure formation. Then the composite of Cu-Ni bimetallic MOF with activated carbon was prepared through one-pot solvothermal synthesis. The incorporation of activated carbon created an additional number of pores in the system leading to enhanced adsorption. N2 adsorption-desorption analysis was carried out to find the surface area. The results showed that the surface area of activated carbon and Cu-Ni-Activated carbon BMOF composite was found to be 576 m2/g and 1321 m2/g, respectively. The analysis also revealed the presence of microporous system in the material. Several characterization techniques, such as IR, SEM, XRD etc., were used to study morphology and characteristic features. The SEM shows that the incorporation of nickel and activated carbon have made a profound modification on the octahedral morphology of copper.CO2 adsorption studies were carried out at 1 bar, 25°C. The BMOF composite adsorbent was found to adsorb ~4.52 mmol/g of CO2 whereas the as-synthesized activated carbon and ZSM-5 were found to adsorb ~2.71 mmol/g and ~1.68 mmol/g respectively. To understand the level of microporosity in the supermicropores range, CO2 adsorption analysis at 1 bar and 0°C was carried out since N2 adsorption at -196°C have limitations due to kinetic diffusion related problems at low temperatures. It revealed a micropore volume (<1.066nm) of 0.252 cm3 /g and a pore size range of 4-10 angstroms, which is ideal for selective CO2 adsorption. Also, the BMOF composite was found to adsorb ~8.27 mmol/g at 0°C, which showed that adsorption capacity increases with a decrease in temperature. Hence, the BMOF composites could serve as a promising adsorbent for selective CO2 capture. Figure 1

(Invited) Conducting the Scholl Reaction: Spironanographenes Vs Helically Arranged Nanographenes

The stepwise synthesis of graphene molecular fragments, molecular nanographenes (NGs), allows the design and monodisperse preparation of sophisticated molecules with perfectly defined shapes and properties.1 The introduction of defects to the honeycomb pattern allows the preparation of nanographenes with finely tunable characteristics, as chirality. Helicenes and non-hexagonal rings are the most usual motifs to this end, as they generate axial chirality by diverting the structures from the 2D plane.In 2021 we reported a new family of molecular nanographenes in which the axial chirality results from the helical arrangement of the graphitized moieties covalently connected through a tetrafluorobenzene core 1.2 Although two enantiomers were confirmed by x-ray diffraction and chiral HPLC, racemization was observed.3 The isomerization process was evaluated, and the isomerization barrier resulted of ∆G≠= 24.6 kcal/mol at 40 ºC, which corresponds to a half-life time of t½ = 107 min.In order to modulate both optoelectronic and chiroptical properties we decided to increase the rigidity of the structure by introducing a 9,10-anthracene as central core. However, unexpected spironanographene 2 was obtained during the key step in the synthesis of nanographenes, the Scholl reaction. Under different reaction conditions we were able to obtain spirocompounds with different graphitization degree. Herein we reported the first spirocycles formation under Scholl reaction conditions without interrupting the graphitization process.4 To further understand the formation of the unexpected nanographenes, theoretical calculations were carried out and revealed the formation of a trityl cation that is involved in the formation of the spirocycles.Furthermore, in order to conduct the reaction towards the formation of the expected rigid helically arranged nanographene, an electron deficient core was designed. The substitution of the central anthracene with eight electron withdrawing fluorine atoms destabilizes the trityl cation and the expected helically arranged nanographene 3 was obtained.4 [1] Y. Gu, K. Müllen. J. Am. Chem. Soc. 2022 , 144, 11499–11524.[2] P. Izquierdo-García, J. M. Fernández-García, I. Fernández, J. Perles, N. Martín. J. Am. Chem. Soc. 2021, 143, 11864–11870.[3] J. M. Fernández-García, P. Izquierdo-García, M. Buendía, S. Filippone and N. Martín. Chem. Commun. 2022, 58, 2634-2645.[4] P. Izquierdo-García, J. M. Fernández-García, J. Perles, I. Fernández, N. Martín. Manuscript in preparation. Figure 1