z Materials Science inc. Nanomaterials & Polymers AIEgen-Based Fluorescent Nanomaterials for Bacterial Detection and its Inhibition Ekta Roy,* [b] Achala Nagar, [b] Sandeep Chaudhary, [c] and Souvik Pal* [a] The infections caused by bacteria have affected human health severely. The bacterial infections spread either directly or indirectly by coming in contact with the food during packaging or by the use of medical devices. The efficient theranostic systems for bacteria provide therapeutic effects that have received attentions in the research field. In this prospect, the fluorescent materials have gained tremendous recognition in the biological applications due to their excellent species diversity, optical properties and high sensitivity. However, most of the conventional fluorophores suffer aggregation-caused quenching (ACQ) effects in the aggregated state. The opposite of ACQ is Aggregation Induced Emission (AIE), where AIEgens play an important role in the imaging, detecting and killing the bacteria as well. In this context, we have summarized the applications of AIEgens on multiple bacterial imaging, detec- tion, discrimination and antibacterial activity to understand the modern theranostic system. 1. Introduction The bacterial infections are very common nowadays. [1] Gen- erally, Pathogenic bacteria are responsible for the variety of diseases viz., sepsis, pneumonia, dermatosis, septic arthritis, inflammatory bowel disease etc. [1–3] It can infect our body directly either through contaminated food / water or through contact with a sick person. The infections can also reach our body indirectly through contaminated surfaces like handles of toilet taps, toys, nappies etc. [1–3] There are many antimicrobial agents to prevent the bacterial activities, these include anti- biotics, quaternary ammonium compounds, metal ions/oxides including their nanoparticles and antimicrobial peptides (AMPs). [4–6] In this regard, antibiotic treatment is the best way to kill the bacterial infections. Antibiotics are strong medicines that are used to prevent and treat bacterial infections. These are not only killing bacteria‘s but also inhibiting or slowing down their normal growth. [7] Alexander Fleming discovered the first natural antibiotic, penicillin, in 1928. [8] Similar type of antibiotics, such as penicillin G, amoxicillin and ampicillin are still available in the market to treat various bacterial infectiones and have been around for a long time. [9] Nowadays, several modern types of antibiotics are also available and they are usually accessible through prescription in most of the coun- tries. However, the use of excess antibiotics is dangerous for the human health. The overuse of antibiotics may make the bacteria resistant towards the antibacterial medications. [10] Moreover, antibiotics are expensive; therefore, its production at large-scale is not feasible. Thus, the development of new antimicrobial agents that can prevent and treat multidrug- resistant infections is a demanding area of investigation. For the last few decades, an enormous amount of new materials with advanced chemical and physical properties have been developed in biomedical fields. These materials were prepared using several methods such as plasma polymerization embed- ding onto a hydrophobic substrate, porogen dissolution, tailoring of crosslinking density, polymerization in solution or by the incorporation of the nanomaterials like carbon nano- fibers (CNFs) and graphene oxide (GO) etc. [11–16] Among all the processes, the incorporation of nanoparticles (NPs) or the formation of NPs in-situ has created tremendous attention in the research field. [17–19] These particles are in the range of 1– 100 nm. Mainly, it can contact directly with the cell wall of the bacteria and destroy it without affecting the normal cells. [20–25] The NPs show their broad-spectrum antibacterial properties against both the gram positive and gram negative bacteria’s. According to the composition of NPs, they may be divided into two categories viz., inorganic and organic NPs. Although inorganic NPs (like up-conversion NPs or quantum dots) possess excellent fluorescence property with good photo- stability, but their heavy metal components are always toxic in nature and dangerous for the human health. Moreover, the synthetic procedure is quite expensive. All the traditional imaging techniques, such as atomic force microscopy (AFM), scanning electron microscope (SEM), transmission electron microscope (TEM) etc. have strenuous preparation processes. [26–29] It only provides information related to the steady-state. Hence, it is incapable to supply the real-time information related to dynamic interactions of NPs and bacteria. Several conditions should be addressed for the [a] Dr.S.Pal Department of Chemistry National Taiwan Normal University, Taipei, Taiwan E-mail: souvikpalbwn@gmail.com [b] Dr. E. Roy, Dr. A. Nagar Department of Chemistry Government Engineering College Jhalawar Rajasthan, India E-mail: mailtoektaroy@gmail.com [c] Dr. S. Chaudhary Department of Chemistry Malaviya National Institute of Technology Jaipur, Rajasthan Reviews DOI: 10.1002/slct.201904092 722 ChemistrySelect 2020, 5, 722–735 © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim