A Review on Janus Nanoparticles: Duality Leading to Prospective Multipotent Applications

Janus nanoparticles (JNPs), named after the bi-faced Roman God has emerged as a hot topic in the present era of nanoscience because of their chemical, structural and physical uniqueness. These particles stand out in the crowd as they are composed of two or more faces with contrasting functional properties in the same molecule. The need for two or more functions in a single molecule that can be used in chemical, biological or physical fields, such as delivering drugs combined with imaging, is the need of the hour and JNPs open gates for addressing this issue as these self-tailored particles have found their application in various in vivo and in vitro domains. However, despite their vivid application, a larger sector of application still needs to be explored. Synthesis methods involve masking, self-assembly and microfluidics, and comparative analysis of these methods, listing their pros and cons, would assist in overcoming the difficulties in the commercialisation of these particles. Moreover, the systematic analysis of differences in their structure with reference to their functionality and characterisation methods would lead us to a better understanding of the subject. This review discusses the various synthesis strategies and their comparison, the anisotropic nature of the JNPs conferring various distinguished properties, their application in emulsion stabilisation, bio-imaging, drug-targeting, drug-delivery, and biosensing domains, the characterisation methods involved, challenges and future aspects. The future aspects section maps a few hypotheses that might be useful in expanding the horizons of usage. The novelty of this review lies in the critical analyses of the synthesis methods and characterisation. Each type of JNP has been analysed for its advantages and limitations, and probable hypotheses to address the existing challenges have been jotted down.