Graphene and structurally similar 2-dimensional (2d) materials such as transition metal dichalcogenides (TMDs) and black phosphorus (BP) hold enormous potential for the next generation optoelectronics and photonics. Pairing 2d materials with printing is an emerging cost-effective large-scale device fabrication strategy. However, the current inks are far from ideal to support reproducible device fabrication. In addition, the instability of BP in ambient limits its applications. In this thesis, I present formulation of 2d material inks for inkjet printing for optoelectronic and photonic applications. To begin with, I produce mono- and few-layer 2d material flakes via ultrasonic assisted liquid phase exfoliation. This allows one-step formulation of a polymer stabilised graphene ink. For TMDs and BP, I design a binary solvent carrier for binder-free ink formulation. I show that these 2d material inks have optimal fluidic properties, drying dynamics and interaction with substrates for spatially uniform, highly controllable and print-to-print consistent large-scale printing on untreated substrates. In particular, the rapid ink drying at low temperatures leads to minimal oxidation of BP during ambient printing; the printed BP with passivation retains a stability over one month. On this basis, the printed graphene is employed as active sensing layer in CMOS integrated humidity sensors and as counter-electrodes in dye-sensitised solar cells, while the printed TMDs and BP are used to develop nonlinear photonic devices (i.e. saturable absorbers for femtosecond pulsed laser generation) and visible to near-infrared photodetectors (e.g. MoS$_2$ and BP/graphene/silicon hybrid photodetectors). Beyond inkjet printing, I present an ink formulation of commercial graphene nanoplatelets for roll-to-roll flexographic press ($\sim$100 m min$^{−1}$ printing speed). This allows hundreds of conductive electronic circuits to be printed in a minute for capacitive touchpads. Though I investigate only graphene, TMDs and BP, the ink formulation strategies can be effortlessly transferred to other 2d materials such as boron nitride, MXenes and mica. In addition to the demonstrated applications, printing of 2d materials can be potentially exploited to fabricate devices such as transistors, light emitters, energy storage conversion, and biosensors. This significantly expands the prospect of printable 2d material optoelectronics and photonics.

In this talk, I will discuss three problems related to the novel physics of two-dimensional quantum materials such as graphene, group-VI dichalcogenides family (TMDCs viz. MoS2 , WS2, MoSe2 , etc) and Silicene-Germanene class of materials. The first problem poses a simple question - how do the quantum excitations in a graphene membrane affect adsorption? Using the tools of diagrammatic perturbation theory, I will derive the scattering rates of a neutral atom on a graphene membrane. I will show how this seemingly naive model can serve as a non-relativistic condensed matter analogue of the infamous infrared problem in Quantum Electrodynamics. In the second problem, I will move from the framework of a single atom adsorption to a collective behavior of fluids near graphene and TMDC - interfaces. Following the seminal work of Dzyaloshinskii-Lifshitz-Pitaevskii on van der Waals interactions, I will develop a theory of liquid film growth on 2 dimensional surfaces. Additionally, I will report an exotic phenomenon of critical wetting instability which is a result of the dielectric engineering and discuss experimental and technological implications. Finally, the last problem will see the introduction of spin-orbit coupling effects in the 2D topological insulator family of Silicene-Germanene class of materials. I will present a unified theory for their in-plane magnetic field response leading to "anomalous", i.e electron interaction-dependent spin-flip transition moment. Can this correction to spin-flip transition moment be measured? I will propose magneto-optical experimental techniques that can probe the effects.