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Resorcinarene crowns are significant building blocks for supramolecularchemistry. Resorcinarenes are part of the calixarenes family and are macrocyclic,bowl-shaped molecules. Derived from four resorcinol subunits, they have hydroxygroups at the wide rim of the bowl. These cavities were utilized for their potentialrecognition of racemic guests and catalysis applications. In this chapter, we focused onthe overview of synthesis, conformational properties of resorcinarenes crown and theirpotential applications such as separation technique using high performance liquidchromatography (HPLC), gas chromatography (GC) and ion chromatrography (IC). Inaddition, they are also used as chemo sensors, antibacterial and antioxidant agents,contrast agents, nanoparticles synthesis and catalytic systems. Finally, we concludedthe chapter with the significance of resorcinarenes crown.

Quantum dots (QDs) have received great attention for development of novel fluorescent nanoprobe with tunable colors towards the near-infrared (NIR) region because of their unique optical and electronic properties such as luminescence characteristics, wide range, continuous absorption spectra and narrow emission spectra with high light stability. Quantum dots are promising materials for biosensing and single molecular bio-imaging application due to their excellent photophysical properties such as strong brightness and resistance to photobleaching. However, the use of quantum dots in biomedical applications is limited due to their toxicity. Recently, the development of novel and safe alternative method, the biomediated greener approach is one of the best aspects for synthesis of quantum dots. In this Chapter, biomediated synthesis of quantum dots by living organisms and biomimetic systems were highlighted. Quantum dots based fluorescent probes utilizing resonance energy transfer (RET), especially Förster resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET) and chemiluminescence resonance energy transfer (CRET) to probe biological phenomena were discussed. In addition, quantum dot nanocomposites are promising ultrasensitive bioimaging probe for in vivo multicolor, multimodal, multiplex and NIR deep tissue imaging. Finally, this chapter provides a conclusion with future perspectives of this field.

Biosensor is a device that detects biological signals by converting biological signals into detectable electronic signals. Biosensor involves the combination of bioreceptors like proteins/enzymes, DNA, and RNA that interact with some specific bioanalytes like antibody–antigen and a transducer that converts the interaction into a useful analytical signal. Several types of biosensor devices have been successfully developed and utilized in the field of biomedical, food industries, and environment. The conventional biosensor devices have some limitations such as poor selectivity, low sensitivity, and expensive fabrication. Therefore, the development of a wide range of detection purposes, nontoxic, highly stable and biocompatible with low cost biosensing devices, is still crucial and challenging.

In recent years, environmental pollutions and energy issues have attracted much attention for the sustainable development of human life. It is of great challenge for the researcher to find a clean, biocompatible, nontoxic, and environment-friendly method for solving the problems associated with the environment. Photocatalysis is one of the effective strategies for mitigating the energy crisis and environmental pollutions. Several photocatalysts were developed for the efficient degradation of environmental pollutants into useful products. Mainly, quantum dot (QD)-based photocatalysts have attracted the researchers due to their attractive properties such as quantum confinement effect, large surface area, and high catalytic activity that makes its promising applications in the field of photocatalysis, sensing, light-emitting diodes, energy storage devices, bioimaging, and solar cell.

Nanomaterials with unique optical properties and biocompatibility have been widely employed for designing and fabricating highly selective and sensitive nanosensors for the detection of various chemical and biological species. The development of nanomaterial-based chemo- and biosensors is studied usually under direct spectroscopic and reagent-mediated sensor platforms using both unmodified and surface-functionalized nanomaterials. This chapter mainly focuses on selective sensing of chemical and biological molecules using various types of nanomaterials. The main readouts are absorption (colorimetric, UV-visible), fluorescence, Raman/SERS spectroscopic, and electrochemical sensing techniques. The detailed discussion on the design of nanomaterial-based sensing systems, sensing principle, sensing method, and their signaling mechanisms has been provided. The sensing systems can also be ideally utilized for real-time applications.

In this study, a new method was developed in which an oxidation layer is used to regulate the morphology of silver nanoparticles (AgNPs) formed on Si crystals during galvanic displacement (GD). Using an oxidation layer yielded reproducible and stable AgNPs@Si substrates for sensitive surface-enhanced Raman scattering (SERS) measurements. The estimated SERS enhancement was at least an order of magnitude greater than for substrates prepared using a conventional GD method. The formation of Si–O− on the Si surface increased the adsorption of the AgNPs. Highly reproducible results were obtained, with a relative standard deviation of approximately 5%. To investigate the role of the oxidation layer and to optimize the reaction conditions, the oxidation layer thickness and chemical composition of the reaction solution were adjusted. The degree of aggregation in AgNP formation was mainly controlled by the thickness of the oxidation layer, whereas the size of the AgNPs was affected by both the concentration of AgNO3 and hydrofluoric acid in the reaction solution and the GD reaction time. When the optimized reaction conditions were used, the AgNPs@Si substrate had an enhancement factor of >107.

Silver nanoparticles (AgNPs) were electrolessly grown on Ge crystal to form substrate for ultra-sensitive detection by surface-enhanced infrared absorption (SEIRA) measurements. To effectively control the morphology of AgNPs, a surfactant-assisted electroless deposition method was proposed in this work. By addition of surfactant into the reaction solution, both reaction rate and behavior in agglomeration of AgNPs were significantly altered. To explore the role of surfactants, three types of surfactants were studied; cationic, anionic and Zwitterionic surfactants. Among them, cationic surfactant of cetyl trimethyl ammonium bromide (CTAB) showed best SEIRA effect as a labile interaction exists between the amine group in CTAB and the formed AgNPs. Also, the hydrophobic long tail of CTAB effectively protects the AgNPs from serious agglomeration. For Zwitterionic surfactants of amino acids, the polar groups on both ends caused severe percolation of AgNPs. With a strong interaction to AgNPs, anionic surfactant of sodium dodecyl benzene sulfonate (SDBS) regulated the AgNPs into a square shaped crystal, which resulted a distortion of infrared absorption band. Based on the obtained results, the substrates prepared with the optimal condition found in this work were at least 5 times higher than that of conventional electroless deposition method. The overall increase of the infrared absorption falls in a range between 300 to 400 times.

A simple and effective colorimetric method for determination of Cu(2+) in real samples was developed. In this method, thiomalic acid functionalized silver nanoparticles (TMA-AgNPs) were prepared and changes in solution color, induced by the aggregation of TMA-AgNPs in the presence of Cu(2+), were employed for quantitative analysis. The surface plasmon resonance (SPR) band of our synthesized TMA-AgNPs was located at 392 nm and shifted to a longer wavelength after aggregation due to the interactions between carboxylate and Cu(2+). A band intensity ratio of A455/(A392-A455) was constructed and used to correlate with the concentration of Cu(2+). A linear relationship was found with a linear response up to 50 nM of Cu(2+). Due to the formation of a stable carboxylate Cu(2+) complex, highly sensitive detection of Cu(2+) was achieved with the estimated detection limit approaching 1 nM. Moreover, the formation of the stable complex leads to high selectivity in the detection of Cu(2+), which was verified by examination of 12 other metal ions. In the detection of Cu(2+) in real samples, results indicated that our proposed method is simple, sensitive and selective for application in such measurements.

The highly selective ratiometric “turn-on” fluorescent sensing of Zn2+ ion involving 2-(1H-tetrazole-5-yl)pyridine (2PT) in aqueous medium is reported, which is not observed when other metal ions are present. Upon 2PT binding selectively with Zn2+ ion, a fluorescence enhancement is observed that is attributed to an enhancement of localized emission and suppression of excited-state intramolecular proton transfer. The described sensing system involving 2PT is also successfully applied to the detection of Zn2+ ion in real samples with a detection limit of 7.5×10−7 M.

An efficient fluorescent chemosensor for Hg(2+) ion, based on 5-(dimethylamino)-N-(2-mercaptophenyl)naphthalene-1-sulfonamide, has been developed. It exhibits Hg(2+)-selective on-off fluorescence quenching behavior via twisted intramolecular charge transfer (TICT) mechanism, which is rationalized by time dependent density functional theory (TD-DFT) calculations. The system exhibits visible color change from colorless to gray upon Hg(2+) binding with very high selectivity and sensitivity (as low as 5.0×10(-10)molL(-1)) over other metal ions such as K(+), Na(+), Ag(+), Mn(2+), Ca(2+), Ba(2+), Fe(2+), Zn(2+), Pb(2+), Cu(2+), Sn(2+), Cd(2+), Ni(2+) and Co(2+). The present sensing system is also successfully applied for the detection of Hg(2+) ion in real samples.

The earthworm, Eudrilus eugeniae, has a prodigious ability to regenerate lost segments. The skin of the worm has an outermost epidermal layer followed by a thick circular muscle layer and an innermost thin longitudinal cell layer. During the process of regeneration, the circular muscle layer decreased in thickness, and longitudinal cell layer increased. The histological analysis of the regenerated worm shows that the longitudinal cell layer forms the regeneration blastema. BrdU-labeling retention assay confirmed that the circular muscle and longitudinal cell layers have BrdU-positive cells, which migrate from the adjacent segments to the regeneration blastema. In addition, it was noted that the cells of the earthworm, E. eugeniae, have the property of autofluorescence. Autofluorescence was found in the cytoplasm, but not in the nucleus. It has been also found that the major source for autofluorescence is riboflavin. Further, it was also demonstrated that supplementation with riboflavin increases the rate of regeneration, while regeneration was hampered by reduced levels of riboflavin. The importance of riboflavin in regeneration was also confirmed by rescue assay. In addition, it was also identified that BrdU-positive cells are highly fluorescent compared to the surrounding cells.

ZnO nanoparticles encapsulated in K10-clay (K10–ZnO) are synthesised and characterised by UV-DRS, Emission spectra, powder XRD, SEM and HRTEM analyses. The constrained space and also the polar active sites in the clay support stabilise zinc oxide nanoparticles by preventing that aggregation and consequently no extra-capping agent is required. The synthesised ZnO nanoparticles are used for the efficient N-benzylation of anilines and the reusability of the catalyst is also studied. A suitable mechanism is proposed for this transformation.

Silver nanoparticles stabilized by soluble starch were synthesized and characterized. In vivo studies in rats showed no toxicity and revealed their distribution in various tissues and permeability across BBB. This starch stabilized silver nanoparticles have good biological characteristics to act as a potential promising vector for gene/drug delivery.

In the present study silver nanoparticles were synthesized and the biological distribution as well as the potential toxicity was studied. Two different concentrations of silver nanoparticles entrapped in montmorillonite were tested in Swiss mice. The animal study demonstrated that the Ag (0) -montmorillonite was nontoxic, showed no immune response, exhibited increased blood half-life, crossed BBB and increased neurotransmission. These observations indicated that Ag (0) -montmorillonite enables diverse applications in life sciences such as drug development, protein detection and gene delivery for any organs in broad, lungs and brain in particular.

Alginate-stabilized silver nanocubes are synthesized via a reduction method and are characterized by UV-Vis and fluorescence spectroscopies, SEM, AFM and HRTEM analyses. A silver nanocubes (Ag NCbs) based sensor for detecting Hg2+ ions in aqueous solution has been developed using Rh6G as an external spectroscopic probe. Using this system, Hg2+ ions (as low as 1×10(-10) mol L(-1)) are recognized in aqueous media via a colorimetric method with very high selectivity and sensitivity over other metal ions namely Fe2+, Zn2+, Pb2+, Cu2+, Sn2+, Cd2+, Ni2+, and Co2+.

An efficient D-glucose selective pyreneimine monoboronic acid probe, based on a photoinduced electron transfer (PET) mechanism, has been developed. The analyses of the spectral changes in the UV-Vis. and fluorescence studies suggest that probe 1 shows an excellent response to D-glucose with a high association constant in a DMSO medium. Photoinduced electron transfer (PET) from the pyreneimine donor to the boronic acid acceptor present is proposed to be responsible for the observed sensing response, which is rationalized by time dependent density functional theory (TD-DFT) calculations. The present sensing system is also successfully applied to the detection of D-glucose in glucose injections.

A fluorescent chemosensor for Cu2+ ions based on dansyl-functionalized thiol stabilized silver nanoparticles containing 2-aminothiophenyl units as the Cu2+ binding sites is developed. A decrease in fluorescence at 497 nm and an increase in fluorescence at 410 nm with an isoemissive point at 445 nm upon the addition of Cu2+ ions is attributed to the formation of a Cu2+ complex in aqueous acetonitrile based on an energy transfer mechanism. This sensor has excellent sensitivity and selectivity over other metal ions and has a detection limit as low as 5.0 × 10−10 mol L−1.

4-Methoxy-N-((thiophen-2-yl)methyl)benzenamine was found to be a highly selective chemosensor for Ag(+) ion in methanol-water (1 : 1 v/v) mixture over other metal ions such as Na(+), K(+), Li(+), Cu(+), Ba(2+), Cd(2+), Co(2+), Cu(2+), Fe(2+), Hg(2+), Mn(2+), Ni(2+), Pb(2+) and Zn(2+) with a limit of detection (LOD) is 5.0 × 10(-6) mol L(-1). Upon binding to Ag(+) ion, a strong fluorescent enhancement is observed which is attributed to an increase in intramolecular charge transfer (ICT). The proposed mechanism is strongly supported by TD-DFT calculations.