In recent years environmental awareness has grown due to the social dissatisfaction with the state of the environment. 1 As a result, more restrictive environmental laws have been introduced. In this context, air pollution constitutes one of the major problems in urban areas being the main sources of pollutants the combustion processes of fossil fuels used in power plants, vehicles and other incineration processes. The main combustion-generated air contaminants are nitrogen oxides (NO x ) which are considered the primary pollutants of the atmosphere, since they are responsible for the photochemical smog, the acid rain and ozone layer depletion. 2 On the other hand, NO is a well-known bioactive molecule which participates in a large variety of bioregulatory and immune response processes. 3 For these reasons intensive experimental research is being carried out for NO monitorization and several analytical techniques such as electrophoresis, electron paramagnetic resonance (EPR) or GC-mass spectroscopies, chemiluminescence or electrochemical methods have been developed for the detection of this hazard. 4 Even though these methods have certain benefits they also show some limitations typical involving poor specificity and the use of expensive experimental apparatus which restrict their application in practice. Recently, the development of fluorogenic probes has gained increasing interest as an alternative to classical instrumental procedures. 5 In this context fluorogenic probes are especially appealing because they allow simple detection in situ or/and at site usually without any sample pre-treatment. Moreover changes in emission can be detected using simple equipment and it is a very sensitive detection technique. In addition changes in emission properties can be detected to the naked eye making this procedure highly attractive.Several probes for the fluorogenic detection of NO have been reported. For instance poorly fluorescent vicinal diamines can be transformed to triazoles by NO resulting in a strong increase of fluorescence. 6 This mechanism is the basis of most fluorogenic NO probes. Moreover some new sensing protocols based NO-induced ring closure, 7 de-amination reactions, 8 or NO-induced aromatization 9 have been recently studied. Besides metal-based probes that take advantage of the reactivity of NO at the metal site have also been reported, and for instance nitric oxide sensing has been accomplished using Co II However some of these probes display some drawbacks such as dependence on the pH or tendency of certain dyes to form aggregates. Moreover because of the significance of NO to human health and diseases most of the probes have been tested to monitor NO production in vivo, whereas very few studies have been devoted to nitric oxide detection in air. Please do not adjust margins Please do not adjust margins characteristics, such as absorption and fluorescence transitions in the visible spectral region with high molar absorption coefficients and fluorescence quantum yields, good stability and no dep...

Synthesis, characterization and controlled release behavior of a new hybrid material based on silica mesoporous nanoparticles caped with a self-immolative gate is reported.There is a significant interest in the development of methodologies of controlled release for a diverse range of applications. [1] For this reason, a large diversity of drug nanocarriers having different size, structure and surface properties, such as liposomes and polymeric or inorganic nanoparticles, have been developed over the last decades. [2] Among these, mesoporous silica nanoparticles (MSNs) have attracted great attention in recent years due to their unique features such as stability, biocompatibility, large load capacity and the possibility of easy functionalizing their surface to obtain targeting and drug release systems. [3] In this scenario, an appealing concept when using MSNs is the possibility to functionalize the external surface with gated ensembles. The development of gated systems able to retain the payload yet releasing it upon the presence of a predefined stimulus has been proved to be an excellent approach to develop advanced nanodevices for controlled delivery applications. [4] In fact, through decoration of the mesoporous material with a wide collection of organic and biological entities or inorganic capping agents, researchers have prepared recently gated MSNs that can be triggered by target chemical (such as selected anions, cations neutral molecules, redox-active molecules, pH changes and biomolecules), physical (such as light, temperature, magnetic fields or ultrasounds) and biochemical (such as enzymes, antibodies, or DNA) stimuli. [5] From a different point of view, self-immolative molecules are covalent aggregates that, upon application of an external trigger, initiate a disassembly reaction, through a cascade of electronic elimination processes, leading ultimately to the release of its building blocks. [6] This chemical phenomenon is usually driven by a cooperative increase in entropy coupled with the irreversible formation of thermodynamically stable products. These molecules have been extensively used in several applications including the design of prodrugs, [7] sensors [8] and drug delivery systems. [9] Self-immolative processes can commonly be found for polysubstituted, electron-rich aromatic species containing an electron-donating substituent in conjugation (ortho or para) with a suitable leaving group located in a benzylic position. [10] In classical self-immolative linkers a single activation event leads to the release of a single group. This release can be described as non-amplified. In contrast the evolution of this technology has resulted in recent years in the design of self-immolative systems in which a single activation event leads to the delivery of multiple groups. This has been described as amplified release. [11] Scheme 1. (a) Schematic representation of the prepared gated nanoparticles S1, (b) synthesis of self-immolative molecular gate 1 and the cascade electronic eliminatio...

A novel colorimetric probe for the selective and sensitive detection of NO2 in solution and in air based on a BODIPY core containing an oxime group has been prepared.

A new chromo‐fluorogenic probe, consisting of a biphenyl derivative containing both a silylbenzyl ether and a N,N‐dimethylamino group, for NO2 detection in the gas phase has been developed. A clear colour change from colourless to yellow together with an emission quenching was observed when the probe reacted with NO2. A limit of detection to the naked eye of about 0.1 ppm was determined and the system was successfully applied to the detection of NO2 in realistic atmospheric conditions.