Explication of mechanism governing atmospheric degradation of 3D-printed poly(lactic acid) (PLA) with different in-fill pattern and varying in-fill density.

With the popularity of 3D-printing technology, poly(lactic acid) (PLA) has become a very good option for layer by layer printing as it is easy to handle, environment friendly, has low costs and most importantly, it is highly adaptable to different materials including carbon, nylon and some other fibres. PLA is an aliphatic poly-ester that is 100% bio-based and is bio-degradable as well. It is one of the rare bio-polymers to compete with traditional polymers in terms of performance and environmental impact. However, PLA is sensitive to water and susceptible to degradation under natural conditions of ultra-violet rays (UV), humidity, fumes, etc. There are many reports on the bio-degradation and photo-degradation of PLA which deal with the accelerated weathering test. However, the accelerated weathering test instruments lack the ability to correlate the stabilities maintained by the test with the actual occurrences during natural exposure. Thus, an attempt has been made in the present work to expose the 3D-printed PLA samples to actual atmospheric conditions of Aurangabad city (M.S.) in India. The degradation of PLA after the exposure is studied and a mechanism is elucidated. Additionally, the tensile properties of the PLA samples are evaluated to correlate the extent of degradation and the material performance. It was found that though the performance of PLA deteriorates with the exposure time, the combination of in-fill pattern and volume plays an important role on the tensile properties and the extent of degradation. It is concluded herein that with natural exposure, the degradation of PLA occurs in two stages, supported by a side reaction. Thus, this study offers a new perspective towards the life of components in actual application by exposing PLA to the natural atmosphere and evaluating its strength and structure.

Designing of two dimensional lanthanum cobalt hydroxide engineered high performance supercapacitor for longer stability under redox active electrolyte.

Redox active electrolyte supercapacitors differ significantly from the conventional electrolytes based storage devices but face a long term stability issue which requires a different approach while designing the systems. Here, we show the change in layered double hydroxides (LDHs) systems with rare earth elements (lanthanum) can drastically influence the stability of two dimensional LDH systems in redox electrolyte. We find that the choice of rare earth element (lanthanum) having magnetic properties and higher thermal and chemical stability has a profound effect on the stability of La-Co LDHs electrode in redox electrolyte. The fabricated hybrid device with rare earth based positive electrode and carbon as negative electrode having redox electrolyte leads to long stable high volumetric/gravimetric capacity at high discharge rate, demonstrates the importance of considering the rare earth elements while designing the LDH systems for redox active supercapacitor development.

Carbon Quantum Dots/Polyaniline Nanocomposite (S-CQD/PANI) for High Capacitive Asymmetric Supercapacitor Device.

A sucrose derived carbon quantum dots/polyaniline (S-CQD/PANI) nanocomposite was synthesized as electrode materials by electrodeposition method to achieve excellent electrocapacitive performance for supercapacitor application. The morphology reveals that CQD were distributed uniformly over the surface of PANI. The highest specific capacitance obtained to be 1512.4 Fg-1 at current density 1 Ag-1 for S-CQD/PANI-25 composite in three electrode system with 1 M H2SO4 aqueous electrolyte within the potential range of -0.2 to 0.8 V. In addition asymmetric supercapacitor device was fabricated reveals highest specific capacitance of 295 Fg-1 at 1 Ag-1 with excellent stability over 1000 cycle at 3 Ag-1. Remarkably, the device delivers energy density of 40.86 Whkg-1 at power density 2000 Wkg-1.

Alteration of the electronic structure and the optical properties of graphitic carbon nitride by metal ion doping.

The photoluminescence quenching of graphitic carbon nitride (GCN) was systematically investigated with the doping of transition metal ions. The photoluminescence spectra of metal doped and pristine GCN were monitored and the trend of quenching efficiency was found to be Cu2+ > Co2+ > Mn2+. Interestingly, with the increasing doping concentration of different metal ions simultaneous red shift and luminescence quenching was determined in the photoluminescence spectra as well as increased absorption tail in longer wavelength hence enhancement in the bandgap. The change in the optical properties could be mainly due to structural reconstruction and doping induced electronic redistribution is discussed.

Two-Dimensional Double Hydroxide Nanoarchitecture with High Areal and Volumetric Capacitance.

The development of high volumetric or areal capacitance energy storage devices is critical for the future electronic devices. Hence, the hunting for next-generation electrode materials and their design is of current interest. The recent work in the two-dimensional metal hydroxide nanomaterials demonstrates its ability as a promising candidate for supercapacitor due to its unique structure and additional redox sites. This study reports a design of freestanding high-mass-loaded copper-cobalt hydroxide interconnected nanosheets for high-volumetric/areal-performance electrode. The unique combination of hydroxide electrode with high mass loading (26 mg/cm2) exhibits high areal and volumetric capacitance of 20.86 F/cm2 (1032 F/cm3) at a current density of 10 mA/cm2. This attributes to the direct growth of hydroxides on porous foam and conductivity of copper, which benefits the electron transport. The asymmetric supercapacitor device exhibits a high energy density of 21.9 mWh/cm3, with superior capacitance retention of 96.55% over 3500 cycles.

Luminomagnetic bifunctionality of Mn(2+)-bonded graphene oxide/reduced graphene oxide two dimensional nanosheets.

Herein, we report the luminomagnetic bifunctional properties of two-dimensional (2D) Mn(2+) bonded graphene oxide (GO)/reduced graphene oxide (RGO) nanosheets synthesized using a facile route of oxidation followed by a solvothermal reduction method. Photoluminescence (PL) studies (excited by different wavelengths) revealed that the resonant energy transfer between Mn(2+) and sp(3)/sp(2) clusters of GO/RGO is responsible for the enhancement of emissions. Moreover, pH-sensitive PL behaviors have also been investigated in detail. The ferromagnetic behavior is believed to arise due to defects in Mn(2+) bonded GO composites. Thus, present reduction method provides a direct route to tune and enhance the optical properties of GO and RGO nanosheets bonded with Mn(2+) ions, which creates an opportunity for various technological applications.