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1. Multi-colored hollow carbon-containing titania nanoshells for anti-counterfeiting applications

   https://doi.org/10.1039/C9TC04146J  

   Yao, Xiaxi; Bai, Yaocai; Lee, Yoon Jae; Qi, Zhimin; Liu, Xiaoheng; Yin, Yadong (November 2019, Journal of Materials Chemistry C)

   While titania and carbon are conventionally perceived as white and black materials, here we show that their combination in the form of composite hollow nanoshells can display striking colors with considerably high contrast through resonant Mie scattering. Our unique design utilizes hollow nanostructures to produce the color by minimizing random multiple scattering and the incorporated carbon species to act as an internal black background to suppress multiple scattering and enhance the color contrast. Synthesized through a simple sol–gel process followed by high-temperature carbonization, these hollow carbon-containing titania (C-TiO 2 ) nanoshells can exhibit variable bright colors from purple to blue and green by controlling their diameter. They can be conveniently used as alternative pigments in many color-related applications, with the advantages of high chemical and optical stability and low toxicity that are associated with titania and carbon materials and the structural coloration mechanism. In addition, as the visible Mie scattering responds rapidly and reversibly to changes in the surrounding medium, these nanoshells may also serve as active color components for many applications that require dynamic color switching, such as signage and displays, colorimetric sensors and detectors, and anti-counterfeiting devices. 

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2. Effect of carbonization methods on graphitization of soft and hard carbons

   https://doi.org/10.1016/j.cartre.2024.100382  

   Ike, Sandra; Wal, Randy Vander (September 2024, Carbon Trends)

   Pressurized carbonization is known to improve carbon content and create textural changes in resultant carbon compared to conventional (atmospheric) carbonization. However, further studies investigating the impact of these carbonization methods on the graphitic quality of the carbon precursors have not been explored exten- sively. This study investigates the influence of carbonization methods on the graphitization behavior of soft and hard carbons using a three-model system: phenolic resole (hard carbon), polyvinyl chloride (PVC) (soft carbon), and a 50:50 blend of resole and PVC. Carbonization was conducted under autogenic pressure (AGP) and at- mospheric pressure (APP) at 500◦C for 5 h, followed by high-temperature treatment at varying temperatures. Various techniques, including X-ray diffraction and Raman spectroscopy showed hard carbon precursors exhibited improved properties under AGP carbonization such as larger crystallite size, sharp crystalline peaks, lower ID/IG ratio, and narrow G-full width half-maximum, an indication of improved crystallinity by lowering amorphous phase at high temperature. For soft carbon precursors, the method of carbonization did not impact the graphitization level. The most significant finding was the enhanced crystalline nature observed in hard carbon under AGP conditions, without the need for any catalyst. It shows the influence of pressure on improving the crystallinity of hard carbon precursors. 

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3. Divergence in Antiviral Activities of Carbon Dots versus Nano-Carbon/Organic Hybrids and Implications

   https://doi.org/10.3390/c9030079  

   Rodriguez, Cristian E; Adcock, Audrey F; Singh, Buta; Yerra, Subhadra; Tang, Yongan; Sun, Ya-Ping; Yang, Liju (September 2023, C)

   Carbon dots (CDots) are generally defined as small carbon nanoparticles (CNPs) with effective surface passivation, for which the classical synthesis is the functionalization of pre-existing CNPs with organic molecules. However, “dot” samples produced by “one-pot” thermal carbonization of organic precursors are also popular in the literature. These carbonization-produced samples may contain nano-carbon domains embedded in organic matters from the precursors that survived the thermal processing, which may be considered and denoted as “nano-carbon/organic hybrids”. Recent experimental evidence indicated that the two different kinds of dot samples are largely divergent in their photo-induced antibacterial functions. In this work, three representative carbonization-produced samples from the precursor of citric acid–oligomeric polyethylenimine mixture with processing conditions of 200 °C for 3 h (CS200), 330 °C for 6 h (CS330), and microwave heating (CSMT) were compared with the classically synthesized CDots on their photo-induced antiviral activities. The results suggest major divergences in the activities between the different samples. Interestingly, CSMT also exhibited significant differences between antibacterial and antiviral activities. The mechanistic origins of the divergences were explored, with the results of different antimicrobial activities among the hybrid samples rationalized in terms of the degree of carbonization in the sample production and the different sample structural and morphological characteristics. 

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4. Macroscale Fabrication of Lightweight and Strong Porous Carbon Foams through Template‐Coating Pair Design

   https://doi.org/10.1002/adma.202206416  

   Suresh, Adarsh; Rowan, Stuart_J; Liu, Chong (January 2023, Advanced Materials)

   Abstract Manufacturing of low‐density‐high‐strength carbon foams can benefit the construction, transportation, and packaging industries. One successful route to lightweight and mechanically strong carbon foams involves pyrolysis of polymeric architectures, which is inevitably accompanied by drastic volumetric shrinkage (usually >98%). As such, a challenge of these materials lies in maintaining bulk dimensions of building struts that span orders of magnitude difference in length scale from centimeters to nanometers. This work demonstrates fabrication of macroscale low‐density‐high‐strength carbon foams that feature exceptional dimensional stability through pyrolysis of robust template‐coating pairs. The template serves as the architectural blueprint and contains strength‐imparting properties (e.g., high node density and small strut dimensions); it is composed of a low char‐yielding porous polystyrene backbone with a high carbonization‐onset temperature. The coating serves to imprint and transcribe the template architecture into pyrolytic carbon; it is composed of a high char‐yielding conjugated polymer with a relatively low carbonization‐onset temperature. The designed carbonization mismatch enables structural inheritance, while the decomposition mismatch affords hollow struts, minimizing density. The carbons synthesized through this new framework exhibit remarkable dimensional stability (≈80% dimension retention; ≈50% volume retention) and some of the highest specific strengths (≈0.13 GPa g⁻¹cm³) among reported carbon foams derived from porous polymer templates. 

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5. Upcycling Plastic Waste into Graphite Using Graphenic Additives for Energy Storage: Yield, Graphitic Quality, and Interaction Mechanisms via Experimentation and Molecular Dynamics

   https://doi.org/10.1021/acssuschemeng.3c07783  

   Gharpure, Akshay; Kowalik, Malgorzata; Vander Wal, Randy L.; van Duin, Adri C.T. (March 2024, ACS Sustainable Chemistry & Engineering)

   Subramaniam, B. Executive Editor (Ed.)

   This research presents pioneering work on transforming a variety of waste plastic into synthetic graphite of high quality and purity. Six recycled plastics in various forms were obtained – including reprocessed polypropylene, high-density polyethylene flakes, shredded polyethylene films, reprocessed polyethylene (all obtained from Pennsylvania Recycling Markets Center), polystyrene foams and polyethylene terephthalate bottles (both sourced from a local recycling bin). The waste plastics were carbonized in sealed tubing reactors. The study shows that this versatile process can be used on a mix of waste plastics in a variety of recycled forms to obtain a uniform graphitic carbon phase, hence addressing the challenges of separation and transportation faced by the plastic recycling industry. The conversion yield to elemental carbon for recycled plastics was improved by up to 250% by using graphene oxide (GO) additives. Five different grades of GO and graphene were used to gain insights into the interaction mechanisms between plastics and GO during pyrolysis. The effect of GO additives on carbonization was analyzed using thermogravimetric analysis / differential scanning calorimetry and ReaxFF-based reactive molecular dynamics simulations. The obtained cokes were graphitized at 2500 ℃ and the graphitic quality of the synthetic graphites was analyzed using X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The plastic waste-derived synthetic graphites exhibit remarkable graphitic quality with crystallite sizes comparable with a model graphitizable material – anthracene coke. The thin, flake-like morphology and nanostructure featuring well-stacked contiguous lamellae make these graphitic carbons highly promising candidates for energy storage applications. Based on our experiments and atomistic-scale simulations we propose interaction mechanisms between the plastic polymers and the graphenic additives that explain the chemical conversion pathways for GO-assisted waste plastic carbonization and graphitization. 

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