@article {46802, title = {Nanocrystalline Ag3PO4 for sunlight- and ambient air-driven oxidation of amines: high photocatalytic efficiency and a facile catalyst regeneration strategy}, journal = {ACS Applied Materials \& Interfaces}, volume = {12}, year = {2020}, month = {JUL}, pages = {29324-29334}, type = {Article}, abstract = {

Selective oxidation of amines to imines using sunlight as clean and renewable energy source is an important but challenging chemical transformation because of high reactivity of the generated imines and lack of visible light-responsive materials with high conversion rates. In addition, oxygen gas has to be purged in the reaction mixture in order to increase the reaction efficiency which, in itself, is an energy-consuming process. Herein, we report, for the first time, the use of Ag3PO4 as an excellent photocatalyst for the oxidative coupling of benzyl amines induced by ambient air in the absence of any external source of molecular oxygen at room temperature. The conversion efficiency for the selective oxidation of benzyl amine was found to be greater than 95\% with a selectivity of \>99\% after 40 min of light irradiation indicating an exceptionally high conversion efficiency with a rate constant of 0.002 min(-1), a turnover frequency of 57 h(-1), and a quantum yield of 19\%, considering all of the absorbed photons. Ag3PO4, however, is known for its poor photostability owing to a positive conduction band position and a favorable reduction potential to metallic silver. Therefore, we further employed a simple catalyst regeneration strategy and showed that the catalyst can be recycled with negligible loss of activity and selectivity.

}, keywords = {amine oxidation, energy harvesting, nanocrystalline Ag3PO4, Photocatalysis, regeneration strategy}, issn = {1944-8244}, doi = {10.1021/acsami.0c05961}, author = {Garg, Reeya and Mondal, Sanjit and Sahoo, Lipipuspa and Vinod, C. P. and Gautam, Ujjal K.} } @article {47357, title = {Elastic piezoelectric aerogels from isotropic and directionally ice-templated cellulose nanocrystals: comparison of structure and energy harvesting}, journal = {Cellulose}, volume = {28}, year = {2021}, month = {JUL}, pages = {6323-6337}, type = {Article}, abstract = {

We report the preparation of highly compressible and elastic piezoelectric aerogels of carboxylated cellulose nanocrystals (CNCs). Aqueous CNC dispersions containing polyethyleneimine and crosslinker were frozen isotropically to yield isotropic aerogels, while oriented aerogels were prepared by directional freezing. These aerogels were highly flexible and porous (similar to 85\% void fraction), exhibiting greater than 90\% recovery at 50\% compressive strain even after 100 compression-decompression cycles. Since such aerogels with low bulk modulus and high anisotropy would be an ideal platform for leveraging the piezoelectric properties of CNCs, we used them to prepare piezoelectric nanogenerator devices and determined their energy transduction behavior. Anisotropic aerogels led to an enhanced open-circuit voltage of 840 mV (at similar to 8 N applied force), which is over 2.6 times higher than isotropic aerogels (320 mV). The energy density of anisotropic aerogels was around 52 nW/cm(2), representing outstanding piezoelectric performance for cellulose-based aerogels. Such aerogels with high compressibility, elastic recovery and exceptional piezoelectric performance could have potential applications in sensors, wearable electronics, etc.

}, keywords = {Aerogel, Anisotropic, Cellulose nanocrystals, energy harvesting, Piezoelectricity}, issn = {0969-0239}, doi = {10.1007/s10570-021-03896-6, Early Access Date = MAY 2021}, author = {Ram, Farsa and Biswas, Bipul and Torris, Arun and Kumaraswamy, Guruswamy and Shanmuganathan, Kadhiravan} } @article {47747, title = { Flexible energy harvester from an organic ferroelectric ammonium salt}, journal = {Chemistry-An Asian Journal}, volume = {16}, year = {2021}, month = {DEC }, pages = {4122-4129}, type = {Article}, abstract = {Organic ferroelectrics due to their low cost, easy preparation, light weight, high flexibility and phase stability are gaining tremendous attention in the field of portable electronics. In this work, we report the synthesis, structure and ferroelectric behavior of a two-component ammonium salt 2, containing a bulky [Bn(4-BrBn)NMe2](+) (Bn=benzyl and 4-BrBn=4-bromobenzyl) cation and tetrahedral (BF4)(-) anion. The structural analysis revealed the presence of rich non-classical C-H...F and C-H...Br interactions in this molecule that were quantified by Hirshfeld surface analysis. The polarization (P) vs. electric field (E) hysteresis loop measurements on 2 gave a remnant polarization (P-r) of 14.4 mu C cm(-2) at room temperature. Flexible polymer composites with various (5, 10, 15 and 20) weight percentages (wt\%) of 2 in thermoplastic polyurethane (TPU) were prepared and tested for mechanical energy harvesting applications. A notable peak-to-peak output voltage of 20 V, maximum current density of 1.1 mu A cm(-2) and power density of 21.1 mu W cm(-2) were recorded for the 15 wt\% 2-TPU composite device. Furthermore, the voltage output generated from this device was utilized to rapidly charge a 100 mu F capacitor, with stored energies and measured charges of 156 mu J and 121.6 mu C, respectively.}, keywords = {Dielectric, energy harvesting, ferroelectricity, organic composites, piezoelectric}, issn = {1861-4728}, doi = {10.1002/asia.202101128}, author = {Gupta, Rishabh and Sahoo, Supriya and Deswal, Swati and Kothavade, Premkumar and Dixit, Prashant and Zareba, Jan K. and Shanmuganathan, Kadhiravan and Boomishankar, Ramamoorthy} } @article {47353, title = {Highly compressible ceramic/polymer aerogel-based piezoelectric nanogenerators with enhanced mechanical energy harvesting property}, journal = {Ceramics International}, volume = {47}, year = {2021}, month = {JUN }, pages = {15750-15758}, type = {Article}, abstract = {

Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO3 (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt \%) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80\% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 ?W/cm2 (49.79 ?W/cm3) was obtained for PENG aerogels containing 83 wt\% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.

}, keywords = {Ceramic polymer aerogels, energy harvesting, ice templating, piezoelectric}, issn = {0272-8842}, doi = {10.1016/j.ceramint.2021.02.147}, author = {Ram, Farsa and Suresh, Karthika and Torris, Arun and Kumaraswamy, Guruswamy and Shanmuganathan, Kadhiravan} } @article {49069, title = {Highly electrostrictive salt cocrystal and the piezoelectric nanogenerator application of its 3D-printed polymer composite}, journal = {ACS Applied Materials and Interfaces }, volume = {16}, year = {2024}, month = {MAY}, pages = {26406-26416}, type = {Article}, abstract = {

Ionic cocrystals with hydrogen bonding can form exciting materials with enhanced optical and electronic properties. We present a highly moisture-stable ammonium salt cocrystal [CH3C6H4CH(CH3)NH2][CH3C6H4CH(CH3)NH3][PF6] ((p-TEA)(p-TEAH)PF6) crystallizing in the polar monoclinic C2 space group. The asymmetry in (p-TEA)(p-TEAH)PF6 was induced by its chiral substituents, while the polar order and structural stability were achieved by using the octahedral PF6- anion and the consequent formation of salt cocrystal. The ferroelectric properties of (p-TEA)(p-TEAH)PF6 were confirmed through P-E loop measurements. Piezoresponse force microscopy (PFM) enabled the visualization of its domain structure with characteristic {\textquoteleft}{\textquoteleft}butterfly{\textquoteright}{\textquoteright} and hysteresis loops associated with ferro- and piezoelectric properties. Notably, (p-TEA)(p-TEAH)PF6 exhibits a large electrostrictive coefficient (Q(33)) value of 2.02 m(4) C-2, higher than those found for ceramic-based materials and comparable to that of polyvinylidene difluoride. Furthermore, the composite films of (p-TEA)(p-TEAH)PF6 with polycaprolactone (PCL) polymer and its gyroid-shaped 3D-printed composite scaled-up device, 3DP-Gy, were prepared and evaluated for piezoelectric energy-harvesting functionality. A high output voltage of 22.8 V and a power density of 118.5 mu W cm(-3) have been recorded for the 3DP-Gy device. Remarkably, no loss in voltage outputs was observed for the (p-TEA)(p-TEAH)PF6 devices even after exposure to 99\% relative humidity, showcasing their utility under extremely humid conditions.

}, keywords = {3D printing, cocrystals, energy harvesting, ferroelectricity, Piezoelectricity}, issn = {1944-8244}, doi = {10.1021/acsami.4c03349}, author = {Sahoo, Supriya and Panday, Rishukumar and Kothavade, Premkumar and Sharma, Vijay Bhan and Sowmiyanarayanan, Anirudh and Praveenkumar, Balu and Zareba, Jan K. and Kabra, Dinesh and Shanmuganathan, Kadhiravan and Boomishankar, Ramamoorthy} }