Pradheep Thiyagarajan

In the last decade, carbon‐based nanostructures such as buckyball (C ₆₀ ), carbon nanotube (CNT), graphene and three‐dimensional (3D) graphene have been identified as promising materials for electronic, electrochemical energy storage (batteries and supercapacitors), optical and sensing applications. Since the discovery of graphene in 2004, scientists have devised mass production techniques and explored graphene as a promising material for a wide range of applications. Most of the electronic and solar cell applications require materials with good electronic conductivity, mobility and finite bandgap. Graphene is a zero bandgap material which prevents it from the mainstream applications. On the other hand, 3D graphene has good electronic conductivity, mobility, bandgap and electrochemical properties. This review article will focus on the synthesis of the 3D graphene, its structure‐property relationships, biotechnology and electronic applications and the hidden properties that are yet to be explored fully.

We have discovered a carbonized polymer film to be a reliable and durable carbon-based substrate for carbon enhanced Raman scattering (CERS). Commercially available SU8 was spin coated and carbonized (c-SU8) to yield a film optimized to have a favorable Fermi level position for efficient charge transfer, which results in a significant Raman scattering enhancement under mild measurement conditions. A highly sensitive CERS (detection limit of 10^–8 M) that was uniform over a large area was achieved on a patterned c-SU8 film and the Raman signal intensity has remained constant for 2 years. This approach works not only for the CMOS-compatible c-SU8 film but for any carbonized film with the correct composition and Fermi level, as demonstrated with carbonized-PVA (poly(vinyl alcohol)) and carbonized-PVP (polyvinylpyrollidone) films. Our study certainly expands the rather narrow range of Raman-active material platforms to include robust carbon-based films readily obtained from polymer precursors. As it uses broadly applicable and cheap polymers, it could offer great advantages in the development of practical devices for chemical/bio analysis and sensors.

This work investigates the thermoelectric properties of a three dimensional nanofoam of few layer graphene (3D-NFG) decorated with holes having diameter of several tens of nanometer. The nanoporous 3D graphene structures were fabricated by a chemical vapor deposition method to ensure high electrical conductivity required for potential applications as thermoelectric materials. The thermal conductivity of the suspended 3D-NFG samples was measured by an optothermal method and found to be 10.8 W m⁻¹ K⁻¹. The substantially reduced values of thermal conductivity were attributed to the small diameter of the pores and their inhomogeneous distribution. Suppression of heat conduction with preserved electrical conductivity is beneficial for the proposed thermoelectric applications.

By creating a p–n heterojunction of molybdenum sulfide (MoS_x)/Ti-doped Fe₂O₃ (Ti-Fe₂O₃), we successfully addressed electron–hole transfer problems of hematite and thus achieved the enhanced photoelectrochemical (PEC) performance.

PMMA-transferred graphene provides much larger GERS signal enhancement than TRT-transferred graphene.

In this letter, we report a facile approach to improve the capacitor properties of nickel hydroxide (Ni(OH)₂) by simply coating gold nanoparticles (Au NPs) on the surface of Ni(OH)₂. Au NP-deposited Ni(OH)₂ (Au/Ni(OH)₂) has been prepared by application of a conventional colloidal coating of Au NPs on the surface of 3D-Ni(OH)₂ synthesized via a hydrothermal method. Compared with pristine Ni(OH)₂, Au/Ni(OH)₂ shows a 41% enhanced capacitance value, excellent rate capacitance behavior at high current density conditions, and greatly improved cycling stability for supercapacitor applications. The specific capacitance of Au/Ni(OH)₂ reached 1927 F g⁻¹ at 1 A g⁻¹, which is close to the theoretical capacitance and retained 66% and 80% of the maximum value at a high current density of 20 A g⁻¹ and 5000 cycles while that of pristine Ni(OH)₂ was 1363 F g⁻¹ and significantly decreased to 48% and 30%, respectively, under the same conditions. The outstanding performance of Au/Ni(OH)₂ as a supercapacitor is attributed to the presence of metal Au NPs on the surface of semiconductor Ni(OH)₂; this permits the creation of virtual 3D conducting networks via metal/semiconductor contact, which induces fast electron and ion transport by acting as a bridge between Ni(OH)₂ nanostructures, thus eventually leading to significantly improved electrochemical capacitive behaviors, as confirmed by the EIS and I–V characteristic data.

We propose three dimensional-graphene nanonetworks (3D-GN) with pores in the range of 10 ∼ 20 nm as a potential candidate for thermoelectric materials. The 3D-GN has a low thermal conductivity of 0.90 W/mK @773 K and a maximum electrical conductivity of 6660 S/m @ 773 K. Our results suggest a straightforward way to individually control two interdependent parameters, σ and κ, in the nanoporous graphene structures to ultimately improve the figure of merit value.