Rajamanikandan, R., Shanmugaraj, K., Ilanchelian, M., & Ju, H. (2023). Cysteamine-decorated gold nanoparticles for plasmon-based colorimetric on-site sensors for detecting cyanide ions using the smart-phone color ratio and for catalytic reduction of 4-nitrophenol. Chemosphere, 316, 137836.
Abstract: In this paper, we have reported the cyanide ions (CN-) sensing in environmental water samples using cysteamine-capped gold nanoparticles (Cyst-AuNPs) by spectrophotometric, colorimetric, and smartphone-based RGB color detection. The surface plasmon resonance shift at around 525 nm for the Cyst-AuNPs could be used to detect quantitatively the amounts of CN- with concomitant alteration of their color from wine red to purple visualized by the naked eye. For the first time, the Cyst-AuNPs-based visual sensing of CN- was performed using smartphone-based detection with its detection limit of 159 x 10-9 M, ten times lower than that of the highest tolerance level (2 x 10-6 M) permitted by the world health organization. The Cyst-AuNPs displayed excellent specificity for detecting the concentration of 30 x 10-6 M even amid the presence of other interfering inorganic anions with their concentrations about five times higher than it. Environmental real water samples were used to arrange the three different CN- concentrations for plasmon-based colorimetric detection and smartphone-based method. Additionally, the catalytic performance of Cyst-AuNPs was demonstrated for the fast catalytic conver-sion of hazardous 4-nitrophenol (selected environmental contaminant) to the analogous amino aromatic com-pounds. A chemical kinetic study showed the conversion rate to be estimated as 1.65 x 10-2 s- 1. Cyst-AuNPs can find an application in colorimetric sensing of CN- while being able to be utilized as a catalytic nanomaterial for ecological remedies associated with health care.
|
Shanmugaraj, K., Mangalaraja, R. V., Campos, C. H., Singh, D. P., Aepuru, R., Thirumurugan, A., et al. (2023). Gold nanoparticles decorated two-dimensional TiO2 nanosheets as effective catalyst for nitroarenes and rhodamine B dye reduction in batch and continuous flow methods. Inorg. Chem. Commun., 149, 110406.
Abstract: Our environment is greatly endangered by the accumulation of various toxic organic pollutants that are continually produced through unavoidable human needs and the industrialization process. Herein, we report highly active gold nanoparticles (AuNPs) immobilized on two-dimensional (2D) TiO2 nanosheets (AuNPs-TiO2NSs) as a catalyst for the catalytic reduction of nitroarenes (NAs) such as 4-nitroaniline (4-NA), 4-(4-nitrophenyl)morpholine (4-NM), 4-(2-fluoro-4-nitrophenyl)morpholine (4-FNM) and rhodamine B (RhB) dye in the presence of sodium borohydride (NaBH4) medium. Initially, TiO2NSs are prepared by the hydrothermal treatment followed by the modification with 3-aminopropyl-trimethoxysilane (APTMS) coupling agent for strong anchoring of the AuNPs. HR-TEM images exhibit that AuNPs (2.30 +/- 0.06 nm) are immobilized on the surface of ultrathin 2-dimensional TiO2NSs. AuNPs-TiO2NSs catalyst shows excellent catalytic activity towards the reduction of various NAs (4-NA, 4-NM and 4-FNM) and RhB dye with maximum conversion efficiency of >98 %. Moreover, the pseudo-first-order rate constants are estimated as 5.50 x 10- 3 s- 1, 7.20 x 10- 3 s- 1, 6.40 x 10-3 s- 1 and 4.30 x 10-3 s- 1 for the reduction of 4-NA, 4-NM, 4-FNM, and RhB, respectively. For large-scale in-dustrial applications, AuNPs-TiO2NSs catalyst embedded in a continuous flow-fixed bed reactor for the catalytic reduction of 4-NA and RhB dye under optimized reaction conditions. AuNPs-TiO2NSs catalyst shows high con-version rates for 4-NA (>99 %) and RhB (>99%) along with excellent recyclability over 12 cycles in continuous flow fixed bed reactor. The mechanism of synthetic pathway and catalytic reduction of NAs and RhB dye over AuNPs-TiO2NSs catalyst are also proposed. This study may lead to the use AuNPs-TiO2NSs catalyst with superior recyclable catalytic efficiency in various catalytic reactions.
|
Shanmugaraj, K., Mangalaraja, R. V., Campos, C. H., Singh, D. P., Udayabhaskar, R., Bedoya, S., et al. (2023). Platinum nanoparticles confined within TiO2 nanotube matrix for enhanced catalytic reduction of azure b dye. Mater. Lett., 330, 133208.
Abstract: In this work, we report the synthesis of TiO2 nanotubes encapsulated platinum nanoparticles (PtNPs-TiO2NTs) as a highly efficient catalyst for the catalytic reduction of azure B (AZB) dye in the sodium borohydride (NaBH4) medium. The encapsulation of PtNPs (particle size similar to 2-3 nm) inside the TiO2NTs was confirmed by HR-TEM analysis. The as-prepared PtNPs-TiO2NTs exhibit higher conversion efficiency than 99 % with a pseudo-first order rate constant of 2.6 x 10(-3) s(-1). Owing to the confinement effect of PtNPs inside the TiO2NTs, the synthesized catalyst shows the superior operative stability even after 8 consecutive recycles without any loss in its activity. This work opens up new avenue for the designing of confined catalyst for various industrial catalytic reactions.
|
Shanmugaraj, K., Mangalaraja, R. V., Campos, C. H., Udayabhaskar, R., Singh, D. P., Vivas, L., et al. (2023). Cu-Ni bimetallic nanoparticles anchored on halloysite nanotubes for the environmental remediation. Surf. Interfaces, 41, 103257.
Abstract: Hereby, we report the synthesis of CuNi bimetallic nanoparticles (NPs)-decorated halloysite nanotubes (CuNi/ HNTs) for the catalytic reduction of 4-nitroaniline (4-NA) and rhodamine B (RhB) dye in an aqueous medium at room temperature. In this work, CuNi/HNTs composites with different wt% of CuNi NPs were synthesized and characterized by various techniques such as SEM, EDS, XRD, TEM and XPS. The TEM characterization confirmed that the CuNi bimetallic NPs (similar to 11 nm) were successfully anchored onto the outer surface of HNTs. Among the prepared catalysts, Cu0.75Ni0.25/HNTs catalyst displayed highest catalytic activity in the reduction of 4-NA to its corresponding amino derivative in the presence of NaBH4 with a maximum conversion efficiency of >99% and an apparent rate constant k(app) of 0.152 s(- 1) within 30 s of reaction time. Notably, even after 15 cycles of catalytic reduction of 4-NA and RhB, there was no apparent deactivation of the catalytic activity of the Cu0.75Ni0.25/HNTs catalyst, demonstrating the excellent catalytic reusability and stability. The presence of CuNi NPs with low Ni content enhanced the catalytic activity due to the synergetic effect. Moreover, the continuous flow fixed bed reactor designed with Cu0.75Ni0.25/HNTs catalyst exhibited the potential application for the reduction of 4-NA and RhB dye under mild reaction conditions. Furthermore, the present catalytic system could be applicable for the treatment of various wastewater effluents.
|
Shanmugaraj, K., Vinoth, V., Pugazhenthiran, N., Valdes, H., Salvo, C., Sepulveda, E., et al. (2023). Ferrihydrite- Graphene oxide foams as an efficient adsorbent for Arsenic (III) removal from an aqueous solution. Inorg. Chem. Commun., 153, 110892.
Abstract: We report the synthesis of a new range of ferrihydrite-graphene oxide (FH-GO) foams using chitosan as cross linker, with varying iron content (5 wt%, 10 wt%, and 20 wt% of FH) as highly efficient adsorbents for the removal of arsenic (III) (As(III)) in an aqueous solution. The sonochemical methods were adopted to synthesize various FH-GO foams and were further characterized by XRD, SEM, TEM, FTIR, Raman, and XPS techniques. The synthesized materials were used for the removal of As(III) in both batch and fixed bed absorbent column methods. The adsorption isotherm results showed that the 10 wt% of FH-GO foams demonstrated a superior adsorbent for the As(III) with high adsorption capacities than that of the other two FH-GO foams (5 wt% and 20 wt% of FH). Moreover, 10 wt% of FH-GO foams was also demonstrated to be nearly a complete (>98.4%) removal of As(III) ions at neutral pH 7. The adsorption isotherm fitted very well with the Langmuir model with the highest accuracy data for all the synthesized adsorbent materials. In addition, the fixed bed absorbent column method was also adopted for the removal of As(III) ions in the water sample, which showed > 99.2% of removal efficiency. The outstanding adsorption capabilities, along with their easy and low-cost synthesis, make these kinds of adsorbents extremely capable for commercial applications in wastewater treatment and drinking water purification.
|
