Extraction and Characterisation of Cellulose Materials from Sri Lankan Agricultural Waste

Agriculture is a key sector of Sri Lankan economy today. Sri Lanka’s main food crop is rice. Rice is cultivated mainly in two seasons in the country. Rice production is the predominant form of agriculture which occupies 0.77 million hectares of the total cultivated area in Sri Lanka. Nevertheless, generation of enormous amounts of agricultural residues such as rice straw during rice production has become inevitable According to the statistics it is revealed that one ton of rice paddy produces 290 kg of rice straw. Regardless of these large amounts, rice straw is frequently abolished by open field burning by majority of farmers. However, recent researchers have reported that rice straw burning can be lethal towards human health due to the noxious emissions which cause various forms of environmental pollution. Hence, identifying the means of generating value added products by utilisation of rice straw has become a necessity today. Rice straw is a lingo cellulosic biomass which consists of biopolymers of cellulose, hemicellulose and lignin. Cellulose is the mostly abundant organic polymer on earth that can be identified as one of the most demanded advanced materials in engineering applications such as bio composites production. Therefore, developing a method to isolate cellulose from rice straw would be a convenient means of value addition to the agricultural waste. This research work is based on developing an environmentally friendly, efficient method to synthesise cellulose from rice straws of the most frequently cultivated hybrid rice variety (BG352) in Sri Lanka. BG 352 rice variety is cultivated in most of the areas in Sri Lanka today. High purity cellulose was extracted from rice straw by the removal of non-cellulosic materials. This chemical purification process consisted of dewaxing, delignification and hemicellulose and silica removal treatments. FTIR spectroscopy was used to verify the formation of pure cellulose during the extraction process. Further, morphology of extracted cellulose was studied by SEM analysis. It revealed that isolated cellulose was mostly in the form of fibers with diameters ranging from 2-8μm. This research showed that BG352 variety averagely has 16.1 wt.% wax, 38.2 wt.% lignin, 3.9% wt. hemicellulose and 12.3 wt.% silica content. Ultimately, average cellulose yield from rice straws of BG352 variety was observed as 30 wt.%. This extraction process can be used to synthesis the cellulose from Sri Lankan agricultural waste to convert it into a value added product.Keywords: Rice straw, Agricultural waste, Cellulose, Lignocellulosic, Biopolyme

Molecular weight tuning of organic semiconductors for curved organic–inorganic hybrid X‐ray detectors

Curved X-ray detectors have the potential to revolutionize diverse sectors due to benefits such as reduced image distortion and vignetting compared to their planar counterparts. While the use of inorganic semiconductors for curved detectors are restricted by their brittle nature, organic–inorganic hybrid semiconductors which incorporated bismuth oxide nanoparticles in an organic bulk heterojunction consisting of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl C71 butyric acid methyl ester (PC70BM) are considered to be more promising in this regard. However, the influence of the P3HT molecular weight on the mechanical stability of curved, thick X-ray detectors remains less well understood. Herein, high P3HT molecular weights (>40 kDa) are identified to allow increased intermolecular bonding and chain entanglements, resulting in X-ray detectors that can be curved to a radius as low as 1.3 mm with low deviation in X-ray response under 100 repeated bending cycles while maintaining an industry-standard dark current of <1 pA mm−2 and a sensitivity of ≈ 0.17 μC Gy−1 cm−2. This study identifies a crucial missing link in the development of curved detectors, namely the importance of the molecular weight of the polymer semiconductors used

Tissue equivalent curved organic x‐ray detectors utilizing high atomic number polythiophene analogues

Organic semiconductors are a promising material candidate for X-ray detection. However, the low atomic number (Z) of organic semiconductors leads to poor X-ray absorption thus restricting their performance. Herein, the authors propose a new strategy for achieving high-sensitivity performance for X-ray detectors based on organic semiconductors modified with high –Z heteroatoms. X-ray detectors are fabricated with p-type organic semiconductors containing selenium heteroatoms (poly(3-hexyl)selenophene (P3HSe)) in blends with an n-type fullerene derivative ([6,6]-Phenyl C71 butyric acid methyl ester (PC70BM). When characterized under 70, 100, 150, and 220 kVp X-ray radiation, these heteroatom-containing detectors displayed a superior performance in terms of sensitivity up to 600 ± 11 nC Gy−1 cm−2 with respect to the bismuth oxide (Bi2O3) nanoparticle (NP) sensitized organic detectors. Despite the lower Z of selenium compared to the NPs typically used, the authors identify a more efficient generation of electron-hole pairs, better charge transfer, and charge transport characteristics in heteroatom-incorporated detectors that result in this breakthrough detector performance. The authors also demonstrate flexible X-ray detectors that can be curved to a radius as low as 2 mm with low deviation in X-ray response under 100 repeated bending cycles while maintaining an industry-standard ultra-low dark current of 0.03 ± 0.01 pA mm−2

Ultra‐low dark current organic–inorganic hybrid X‐ray detectors

Organic‐inorganic hybrid semiconductors are an emerging class of materials for direct conversion X‐ray detection due to attractive characteristics such as high sensitivity and the potential to form conformal detectors. However, existing hybrid semiconductor X‐ray detectors display dark currents that are 1000–10 000× higher than industrially relevant values of 1–10 pA mm−2. Herein, ultra‐low dark currents of <10 pA mm−2, under electric fields as high as ≈4 V µm−1, for hybrid X‐ray detectors consisting of bismuth oxide nanoparticles (for enhanced X‐ray attenuation) incorporated into an organic bulk heterojunction consisting of p‐type Poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) and n‐type [6,6]‐Phenyl C71 butyric acid methyl ester (PC70BM) are reported. Such ultra‐low dark currents are realized through the enrichment of the hole selective p‐type organic semiconductor near the anode contact. The resulting detectors demonstrate broadband X‐ray response including an exceptionally high sensitivity of ≈1.5 mC Gy−1 cm−2 and <6% variation in angular dependence response under 6 MV hard X‐rays. The above characteristics in combination with excellent dose linearity, dose rate linearity, and reproducibility over a broad energy range enable these detectors to be developed for medical and industrial applications