Pre-Harvest Prophylaxis for Infestation Control in Stored Food-Grains
STORED food-grains suffer from considerable losses due to insect infestations in the tropical and subtropical regions of the world1. During post-harvest storage, cross-infestation by insect pests and the multiplication of pests as a result of field-infestation occur in stored grains even within a storage period of a few months in warehouses2–3. Fumigation with noxious gases such as methyl bromide, carbon disulphide, carbon tetrachloride, hydrocyanic acid, ethylene oxide and others, although of use in the control of most infestations, is not easy for the producer or the warehouse-man to apply2. Parkin1 observed that application of such measures unfortunately lags behind the advance of knowledge in all but the most highly developed countries, and even in those is not always so widespread or up-to-date as it could be. A new approach has therefore been made to replace the fumigation treatment with a relatively simpler prophylactic spray treatment of the grain under pre-harvest condition, using a chemical of low toxicity for mammals, for the control of pest infestation during post-harvest storage.
Gefährdung durch Insekten
Nach Schatzung der FAO gehen zwischen 20 und 33 Prozent der Welternte infolge mangelhafter Lagerung nutzlos verloren [1]. Die Nachernteverluste in den Tropen werden sogar auf 30–50% eingeschatzt [2]. Ein nicht unbetrachtlicher Anteil ist auf die Einwirkung von Insekten zuruckzufuhren. Der Nahrungsverbrauch eines einzelnen Insekts ist zwar gering. Da die Temperaturen in den Tropen und Subtropen jedoch im Bereich des Lebensoptimums fur zahlreiche Insekten liegen, ist die Generationszeit kurz und die Vermehrung entsprechend schnell, womit sich hohe Schaden erklaren. Auch wenn ein einziger Getreideschadling nur etwa 80 mg Nahrung wahrend seiner Lebensspanne verzehrt, so benotigt die nachste Generation schon 8g, die dritte 800g und die vierte 80kg [3].
Recent progress in engineering near-infrared persistent luminescence nanoprobes for time-resolved biosensing/bioimaging
Persistent luminescence nanoprobes (PLNPs) can remain luminescent after ceasing excitation. Due to the ultra-long decay time of persistent luminescence (PersL), autofluorescence interference can be efficiently eliminated by collecting PersL signal after autofluorescence decays completely, thus the imaging contrast and sensing sensitivity can be significantly improved. Since near-infrared (NIR) light shows reduced scattering and absorption coefficient in penetrating biological organs or tissues, near-infrared persistent luminescence nanoprobes (NIR PLNPs) possess deep tissue penetration and offer a bright prospect in the areas of in vivo biosensing/bioimaging. In this review, we firstly summarize the design of different types of NIR PLNPs for biosensing/bioimaging, such as transition metal ions-doped NIR PLNPs, lanthanide ions-doped NIR PLNPs, organic molecules-based NIR PLNPs, and semiconducting polymer self-assembled NIR PLNPs. Notably, organic molecules-based NIR PLNPs and semiconductor self-assembled NIR PLNPs, for the first time, were introduced to the review of PLNPs. Secondly, the effects of different types of charge carriers on NIR PersL and luminescence decay of NIR PLNPs are significantly emphasized so as to build up an in-depth understanding of their luminescence mechanism. It includes the regulation of valence band and conduction band of different host materials, alteration of defect types, depth and concentration changes caused by ion doping, effective radiation transitions and energy transfer generated by different luminescence centers. Given the design and potential of NIR PLNPs as long-lived luminescent materials, the current challenges and future perspective in this rapidly growing field are also discussed.