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The domain of Janus nanoparticles (JNPs) has seen a surge in research and development during the last decade. JNPs are anisotropic composite innovations with remarkable characteristics that depict a peculiar class of particles, which integrate the features and functions of multiple materials into a single unit. Janus particles are superior prospects for several high-end applications due to their possible modifications by "click chemistry". JNPs offer new possibilities by combining the features of components. Janus nanoparticles can pack multiple pharmaceuticals and imaging contrast agents simultaneously since they have a distinct chemical configuration on different sides. As a result, they become ideal for administration and bioimaging at once. They have sparked interest due to their exceptional architecture and their potential implications in science and engineering, biological application, and most notably, theranostics. The emphasis of this review is on the latest advancement in the fabrication and implementation of innovative Janus nanoparticles, along with their spectacular performance in therapeutic delivery applications. [ABSTRACT FROM AUTHOR]

We present here, a detailed photophysical and rotational relaxation dynamical study of three structurally analogous cationic dyes, namely, phenosafranin (PSF), safranin-T (ST), and safranin-O (SO), carried out in well characterized, monodispersed biomimicking anionic reverse micellar nanocavities composed of sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/heptane with increasing water contents. The dyes belong to the phenazinium family and they differ in terms of methyl substitution on the planar phenazinium skeleton. The objective of the present study is to investigate the modification in the photophysical and dynamical behavior of the dyes with the change in the size of the water pool of the reverse micelle and thereby to explore the role of methyl substitution. Steady state and time resolved emission and anisotropy studies have been exploited for the purpose. The dyes are found to exhibit a marked decrease in the fluorescence anisotropy with increasing water/surfactant mole ratio (w), i.e., the water pool size in the reverse micellar core, implying that overall motional restriction experienced by the molecules are decreased with increasing hydration. Some of the depth dependent fluorescence parameters such as fluorescence maximum, fluorescence anisotropy (r) have been monitored for exploring the microenvironment around the probes in the reverse micelles. Fluorescence studies suggest that at low w values, the probes do not penetrate into the reverse micellar core; rather it binds at the interfacial region. Estimates of the micropolarity at the binding sites of the probe molecule have been determined as a function of w. Finally, dynamic studies reveal that both the lifetime and rotational relaxation time decrease with an increase in w for all the three probes, the extent of the decrease being more for PSF than ST and SO. This indicates a stronger binding of the reverse micelle with ST and SO compared to that with PSF which is rationalized in terms of an increase in the hydrophobicity of the former two dyes because of the methyl substitution on the phenazinium moiety. [ABSTRACT FROM AUTHOR]