Impact of Oxygen Functional Groups on Reduced Graphene Oxide-Based Sensors for Ammonia and Toluene Detection at Room Temperature

I mai 2019 ble det gjennomført en forskningsundersøkelse i en nausttuft og tuft (ID 38824) på Nergård, Bjarkøy. Det ble gravd en 10 x 0,5 m sjakt på tvers av nausttufta mellom veggvollene og sjakter på 5 x 0,5 m og 1 x 0,5 m i en tuft langs vestsiden av nausttufta. Nausttufta har estimerte ytre mål på 33 x 13 m og indre mål på 29 x 5,5 m. Naustkronologi består av to hovedbruksfaser basert på stratigrafien og 14C dateringer. Første fase var bygging av stornaust i vikingtid datert til 862-992 e.Kr., og som kan være knyttet til Bjarkøyætta og muligens til Bjarkøyhøvdingen Tore Hund. Vikingtidsdateringen kan kobles stratigrafisk til en dobbel stolperekke i en 1,2 m bred grøft i midten av den vestre veggvollen. Stolpehullene er 50 cm dype og 30 cm i diameter med kraftig steinskoing. Den andre bruksfasen er datert til høymiddelalder, basert på 14C dateringer fra den vestre veggvollen som spenner perioden 1184-1282 e.Kr. Kontinuitet i naustbruk fra vikingtid er sannsynlig. Konstruksjonsendringer med oppbygging og utvidelse av veggvollen, samt tildekking av stolpehullene, ble utført i middelalderen. Et lag med okermaling og båtsaum datert til 1200-tallet er tolket som spor etter gjenbruk av båtbord / båtskrog til veggkonstruksjon. Det er også mulig at ombygging av naustet har en sammenheng med bruken som leidangsnaust tilhørende en av de 13 skipreider i Hålogaland på 1200-tallet. Tufta ved siden av naustet har en estimert størrelse på 26 x 8-11 m. To smale og grunne langsgående grøfter som er synlig på overflaten i tufta tilhører aktivitet som er adskilt fra, og seinere enn, hovedbruksfasen. Et funnholdig lag opptil 20 cm tykt ble avdekket med en nedgravd steinsatt grop 1,3 m i diameter og 35 cm dyp 14C datert til 1025-1150 e.Kr. En båtsaumkonsentrasjon lå ved og i gropa, i tillegg til et knivblad, en klinkhammerhode og et bryne. Verktøy og båtsaum i gropa kan indikere at tufta hadde en funksjon relatert til bygging og vedlikehold av båter tilknyttet naustet. Datering fra gropa viser til kontinuitet i bruk av begge strukturene mellom vikingtid og middelalder

Impact of Oxygen Functional Groups on Reduced Graphene Oxide-Based Sensors for Ammonia and Toluene Detection at Room Temperature

The chemically reduced graphene oxide (rGO) was prepared by the reduction of graphene oxide by hydrazine hydrate. By varying the reduction time (10 min, 1 h, and 15 h), oxygen functional groups on rGO were tremendously controlled and they were named RG1, RG2, and RG3, respectively. Here, we investigate the impact of oxygen functional groups on the detection of ammonia and toluene at room temperature. Their effect on sensing mechanism was analyzed by first-principles calculation-based density functional theory. The sensing material was fabricated, and the effect of reduction time shown improved the recovery of ammonia and toluene sensing at room temperature. Structural, morphological, and electrical characterizations were performed on both RG1 and RG3. The sensor response toward toluene vapor of 300 ppm was found to vary 4.4, 2.5, and 3.8% for RG1, RG2, and RG3, respectively. Though RG1 shows higher sensing response with poor recovery, RG3 exhibited complete desorption of toluene after the sensing process with response and recovery times of approximately 40 and 75 s, respectively. The complete recovery of toluene molecules on RG3 is due to the generation of new sites after the reduction of oxygen functionalities on its surface. It could be suggested that these sites provided anchor to ammonia and toluene molecules and good recovery under N₂ purge. Both theoretical and experimental studies revealed that tuning the oxygen functional groups on rGO could play a vital role in the detection of volatile organic compounds (VOCs) on rGO sheets and was discussed in detail. This study could provoke knowledge about rGO-based sensor dependency with oxygen functional groups and shed light on effective monitoring of VOCs under ambient conditions for air quality monitoring applications

Magnetite Nanoparticle Decorated Reduced Graphene Oxide Composite as an Efficient and Recoverable Adsorbent for the Removal of Cesium and Strontium Ions

Magnetite nanoparticles (Fe₃O₄) decorated reduced graphene oxide (rGO) composite was synthesized by the solvothermal method and utilized as a potential adsorbent for the removal of cesium (Cs⁺) and strontium (Sr²⁺) ions from aqueous solution. The effects of adsorbate concentration and reaction time on the removal efficiencies of Cs⁺ and Sr²⁺ were investigated. The adsorption capacity increases as the initial concentration of Cs⁺/Sr²⁺ increased from 1 to 170 mg/L, which might be due to the more available adsorption sites, and the adsorbent reached equilibrium at 360 min. The adsorption isotherm was fitted to the Freundlich model with maximum adsorption capacities of Cs⁺ and Sr²⁺ being 128.2 and 384.6 mg g^–1, respectively. The kinetic study showed that the adsorption behavior followed pseudo-second-order kinetics. The rGO/Fe₃O₄ nanocomposite showed excellent selectivity toward Cs⁺ and Sr²⁺ even in the presence of competitive cations (Na⁺, K⁺, and Mg²⁺) having a higher concentration

Novel porous carbon microtubes and microspheres produced from poly(CL-b-VbC) triarm block copolymer as high performance adsorbent for dye adsorption and separation

TARAMAWOSWOS:000561905700084TARAMASCOPUSDandelion-like and microtube-containing novel porous carbons were synthetized from brush type poly (ε caprolactone-b-4-vinyl benzyl chloride) (poly(CL-b-VbC)) triarm block copolymer with KOH (PCLVbK) and ZnCl2 (PCLVbZn) through optimized chemical activation at low temperature. These porous carbons were used for the adsorption and separation of cationic Malachite green (MG) and anionic Congo red (CR) and Methyl or ange (MO) dyes. The synthetized porous carbons were characterized by SEM, N2 adsorption-desorption iso therms, FTIR, Raman and XRD. PCLVbK and Zn porous carbons were quite effective in cationic (MG) dye adsorption from aqueous solution thanks to different functional groups, surface areas and pore volumes. The MG adsorption capacities of PCLVbZn and PCLVbK were found to be 1684 mg/g and 869.5 mg/g, and these results are considerably higher than the other adsorbents studied in the literature. Also, it was determined that while PCLVbZn could adsorb both cationic and anionic dyes, PCLVbK could only perform the adsorption of cationic dyes. The kinetic studies conducted with MG showed that both PCLVbK and Zn porous carbons fitted better with the pseudo-second-order model. At the end of the adsorption equilibrium studies, it was observed that PCLVbZn fitted with both the Langmuir and Freundlich adsorption models while PCLVbK fitted better with the Langmuir model. In conclusion, it was observed that PCLVbK could perform high and fast adsorption and separa tion owing to its oxygen functional groups, while PCLVbZn turned out to be effective in the adsorption of both anionic and cationic dyes thanks to its large surface area (1006 m2 /g) and empty microtubes. Based on these re sults, it can be argued that PCLVbK and Zn porous carbons are promising adsorbents for both high adsorption and effective separation from aqueous soluti