Regioselective Protection and Deprotection of Nanocellulose Molecular Design Architecture: Robust Platform for Multifunctional Applications.

Regioselectively substituted nanocellulose was synthesized by protecting the primary hydroxyl group. Herein, we took advantage of the different reactivities of primary and secondary hydroxyl groups to graft large capping structures. This study mainly focuses on regioselective installation of trityl protecting groups on nanocellulose chains. The elemental analysis and nuclear magnetic resonance spectroscopy of regioselectively substituted nanofibrillated cellulose (NFC) suggested that the trityl group was successfully grafted in the primary hydroxyl group with a degree of substitution of nearly 1. Hansen solubility parameters were employed, and the binary system composed of an ionic liquid and pyridine as a base was revealed to be the optimum condition for regioselective functionalization of nanocellulose. Interestingly, the dissolution of NFC in the ionic liquid and the subsequent deprotection process of NFC substrates hardly affected the crystalline structure of NFC (3.6% decrease in crystallinity). This method may provide endless possibilities for the design of advanced engineered nanomaterials with multiple functionalities. We envisage that this protection/deprotection approach may lead to a bright future for the fabrication of multifunctional devices based on nanocellulose.

Combustion control of DME HCCI using charge dilution and spark assistance.

To realize the potential of DME for clean combustion, fueling control is essential. In this research, the challenges, advantages, and applicability of high-pressure direct injection and low-pressure port injection are reviewed and evaluated, especially in relevance to HCCI combustion. In this study, emphasis is given to the applicable ranges of low-pressure fuel delivery in relevance to load, air-fuel ratio, and inert gas dilution, for realizing HCCI combustion. The strategy of high-pressure direct injection is advantageous for combustion phasing control, but the fuel handling is challenging because of the high vapor pressure of DME fuel. The strategy of port fuel injection is prone to early combustion and, consequently, tends to produce excessive pressure rise rates in the combustion chamber. This challenge is escalated at higher engine loads, making homogenous charge compression ignition difficult to achieve. In this paper, the load extension of DME-fueled HCCI combustion was explored. First, the impact of dilution on the combustion characteristics of DME HCCI was studied under lean and CO2 diluted conditions. Under the present empirical setups, results show that the lean-burn strategy has limited capability of combustion phasing control, especially when the engine load is above 5 bar IMEP. The CO2 dilution strategy can significantly retard the combustion phasing until the fulfillment of combustion becomes unstable. It was found that spark assistance is advantageous for combustion control. With an effective application of excess air, intake CO2 dilution and spark assistance, an engine load of 8 bar IMEP was reached with appropriate combustion phasing, with ultra-low NOx emissions.

One-pot fabrication of flexible and luminescent nanofilm by in-situ radical polymerization of vinyl carbazole on nanofibrillated cellulose.

Photoresponsive functionalized nanofilms were prepared via radical polymerization of carbazole units on a nanofibrillated cellulose (NFC) backbone via one-pot procedure. Herein, NFC was functionalized with active carbazole units as pendant organic moieties. The nanofilms were characterized by UV-vis and fluorescence spectroscopy, Fourier transformed infrared (FTIR) and Raman spectroscopy, 13C NMR and proton NMR spectra, contact angle analysis, mechanical testing, and scanning electron microscopy (SEM). The fabricated nanofilms exhibited large tensile strength (∼110 MPa), higher hydrophobicity and luminescence activity. The results indicated that the prepared optically active nanofilms present potential applications in the fields of flexible organic light emitting devices.

Thermoconformational Behavior of Cellulose Nanofiber Films as a Device Substrate and Their Superior Flexibility and Durability to Glass.

The design and high-throughput manufacturing of thin renewable energy devices with high structural and atomic configurational stability are crucial for the fabrication of green electronics. Yet, this concept is still in its infancy. In this work, we report the extraordinary durability of thin molecular interlayered organic flexible energy devices based on chemically tuned cellulose nanofiber transparent films that outperform glass by decreasing the substrate weight by 50%. The nanofabricated flexible thin film has an exceptionally low thermal coefficient of expansion of 1.8 ppm/K and a stable atomic configuration under a harsh fabrication condition (over 190 °C for an extended period of 5 h). A flexible optoelectronic device using the same renewable cellulose nanofiber film substrate was found to be functionally operational over a life span of 5 years under an intermittent operating condition. The success of this device's stability opens up an entirely new frontier of applications of flexible electronics.

Non-Isothermal Crystallization Behavior and Thermal Properties of Polyethylene Tuned by Polypropylene and Reinforced with Reduced Graphene Oxide.

This research work is the first to report thermal stability, heat deformation resistance, and crystallization behavior of a Polyethylene (PE)-based biphasic polyolefin system reinforced with Reduced Graphene Oxide (RGO), which was obtained through Graphene Oxide (GO) chemical reduction. Polypropylene (PP) represented the polymeric dispersed phase. A strategic PE/PP/RGO manufacturing procedure was employed to thermodynamically localize RGO at the PE/PP interface, as confirmed by Transmission Electron Microscopy (TEM), bringing a uniform micro phase dispersion into the macro phase. In addition, studies of PE non-isothermal crystallization kinetics indicated that the morphology tunable micro phase and the nanolayered RGO promoted a nucleation-controlled PE crystallization, which was supported by Polarized Light Optical Microscopy (PLOM). This, together with fine morphology, justified the remarkable enhancement registered for the ternary system's thermal stability and heat deformation resistance. Different filler loads were employed, with weight fractions of 2% and 4%. It was observed that the former, being better exfoliated and more homogeneously distributed at the PE/PP interface than the latter, led to a more improved PE crystallization, alongside a greater ternary system's thermal properties. Moreover, the thermal stability of PE/PP reinforced with 2% of RGO was even higher than that of virgin PP, while their heat deformation resistance values were found to be similar. Therefore, this unique outcome provides industries, such as the energy and automotive sectors, with the opportunity to substitute PP-rich products with those mostly comprised of a cheaper, more abundant, yet performant PE.

Current State of Applications of Nanocellulose in Flexible Energy and Electronic Devices.

Novel and unique applications of nanocellulose are largely driven by the functional attributes governed by its structural and physicochemical features including excellent mechanical properties and biocompatibility. In recent years, thousands of groundbreaking works have helped in the development of targeted functional nanocellulose for conductive, optical, luminescent materials, and other applications. The growing demand for sustainable and renewable materials has led to the rapid development of greener methods for the design and fabrication of high-performance green nanomaterials with multiple features, and consequently new challenges and opportunities. The present review article discusses historical developments, various fabrication and functionalization methods, the current stage, and the prospects of flexible energy and hybrid electronics based on nanocellulose.

Future Perspectives and Review on Organic Carbon Dots in Electronic Applications.

Over the span of the past decade, carbon dots (CDs) synthesized from renewable organic resources (organic CDs) have gathered a considerable amount of attention for their photoluminescent properties. This review will focus on organic CDs synthesized using clean chemistry and conventional synthetic chemistry from organic sources and their fluorescence mechanisms, such as quantum confinement effect and surface/edge defects, before outlining their performance in electronic applications, including organic photovoltaic devices, organic light-emitting devices, biosensors, supercapacitors, and batteries. The various organic resources and methods of organic CDs synthesis are briefly covered. Many challenges remain before the adoption of CDs can become widespread; their characterization, structure, functionality, and exact photoluminescent mechanism all require additional research. This review aims to summarize the current research outcomes and highlight the area where further research is needed to fully use these materials.

Porous graphitic biocarbon and reclaimed carbon fiber derived environmentally benign lightweight composites.

Bamboo-derived biocarbon (BA900) and wood-derived biocarbon (THOC700) have exhibited graphite-like characteristics through transmission electron microscopy, X-ray diffraction (XRD), and Attenuated Total Reflectance (ATR) spectroscopy analysis. Lightweight composites of biocarbons were manufactured by a mechanism of shear controlled melt-phase mixing, ensuring the preservation of biocarbon pore structures and simultaneously taking full advantage of low density polyolefin substrates. Effective tensile strength was improved by approximately 10% in the polypropylene-based bamboo carbon composite, whereas no appreciable improvement was observed in the tensile and impact strength of bamboo-derived biocarbon formulations compared to neat polymer. However, the tensile and flexural moduli and flexural strength of the THOC700-PP composites were significantly enhanced, by 56%, 67%, and 19%, respectively, compared to neat polymer. The most significant finding of the investigation was the retention of density in polyolefin polymer (ρPP = 0.91; ρTHOC = 0.95; ρBA900 = 0.99), with enhanced mechanical performance useful for lightweighting applications. Bamboo biocarbon provides a viable alternative to another abundantly available industrial carbon feedstock, reclaimed carbon fiber (RCF), in manufacturing thermoplastic composites. The origin of the carbon plays an important role in defining ultimate composite performance. A mechanism for retaining lightweight structural performance has been proposed in this original work, paving the way to develop next-generation lightweight thermoplastic structures for transportation and other industrial and consumer products.

Renewable Cr2O3 Nanolayer on Cr(W)N Surface for Seizure Prevention at Elevated Temperatures.

Chromium nitride coating is now the norm for improving the wear resistance of high-performance mechanical components. Even so, to prevent the seizure issue between the contacting interfaces, the prerequisites are oil or solid lubricants which would however lose the lubricating functionality at elevated temperatures due to breakdown or degradation. In this research, we utilize a Cr2O3 nanolayer formed on modified Cr(W)N coating to prevent the adhesive seizure for steel-based components. X-ray photoelectron spectroscopy (XPS) analyses show that the chromium oxide can be generated at 200-400 °C. At 400 °C, the Cr2O3 nanolayer is in situ formed and maintains a consistent thickness of 2.2 nm due to the oxide renewal during the heating-sliding operation. The in situ, renewable oxide nanolayer provides a novel approach to the technically unsolved seizure problem occurring in high-performance machines operated at elevated temperatures.