An Optode Sensor for Cu2+ with High Selectivity Based on Porphyrin Derivative Appended with Bipyridine

Abstract

Copper is an essential trace element in plants and animals. Following zinc and iron, it ranks the third in abundance in human bodies among the essential heavy metals. 1 Copper participates in many biological processes, such as haemoglobin synthesis (in Fe utilization and Hb regeneration), connective tissue development, normal functions of the central nervous system, and oxidative phosphorylation. [2][3][4] Owing to the growing awareness of the toxicity of copper at elevated concentrations, searching for effective analytical methods in general, and for optochemical sensors in particular, for the copper assay is of considerable interest.The recent years have seen a growing interest in the development of optical chemical sensors for Cu 2+ with different chemical transducers. [5][6][7][8][9] Thus optochemical sensors can offer advantages in terms of size, cost, not requiring a reference element, and transmitting without the influence of an electromagnetic field. Most of these optodes are based on absorption or reflectance measurements of immobilized colorimetric reagents in various matrices. Although fluorescence signaling offers the advantage of high sensitivity over absorption or reflectance signaling, only a few optical sensors based on fluorescence are reported for Cu 2+ determination. 10-12 These fluorescence sensors are commonly composed of two structural subunits: a fluorophore (for signal transduction) and an ionophore (for selective recongnition of metal ion). The two subunits are connected through a linking bridge. The fluorescence of the fluorophore would be affected when the ionophore recognizes some metal ions as a result of electron or energy transfer. 13,14 Searching for new fluorescence sensors which would respond toward Cu 2+ with sufficient high selectivity is still an active field as well as a challenge for the analytical chemistry research. [15][16][17][18][19] Porphyrins are a class of naturally occurring macrocyclic compounds, which play a very important role in the metabolism of living organisms. Moreover, porphyrins show good photophysical properties with large Stokes shifts and relatively long excitation (>400 nm) and emission (>600 nm) wavelengths that minimize the effects of the background fluorescence. This makes porphyrin derivatives potential fluorophores for preparation of new fluorescence molecular sensors. In the present study, a porphyrin derivative appended with bipyridine (H2TPPBPy) was chosen for preparation of a Cu 2+ -sensitive optical chemical sensor. H2TPPBPy has been used to investigate the rate of photoinduced charge separation. 20 Quenching of porphyrin fluorescence on irradiation is attributed to electron transfer from porphyrin to the acceptor (rhenium), which is linked with the porphyrin by bipyridine. It is interesting to explore the possibility of using a similar approach in designing the Cu 2+ -sensitive optical chemical sensor. Bipyridine coordination of Cu 2+ would quench the fluorescence of porphyrin. In this study, a sensor based on H2TPPBPy was first reported. T...

A rhodamine‐triazole fluorescent chemodosimeter for Cu2+ detection and its application in bioimaging

“…High concentrations of Cu 2+ may cause gastrointestinal disturbance and damage to the liver or kidney. Accordingly, fluorescent and colorimetric sensors for the detection of Cu 2+ have received increasing scientific attention . Among common fluorophores, rhodamine derivatives are widely employed as a fluorescent dye for detection of metal ions due to their excellent photophysical properties such as long absorption and emission wavelengths, large molar extinction coefficient, high fluorescence quantum yield and great photostability .…”

A Cu2+ion-selective fluoroionophore with dual off/on switches

“…Moreover, Cu 2+ is a well-known paramagnetic ion with an unfilled d orbital and could strongly quench the fluorescence of the fluorophore near it via electron or energy transfer [4]. In most of the reported recognition of Cu 2+ , the binding of Cu 2+ causes quenching of the fluorescence emission [5-9]. Few reports are available for "off-on"-type fluorescent compounds that can selectively recognize Cu 2+ [10-14].…”

Recent Advances in Porphyrin-Based Materials for Metal Ions Detection

“…In 2002, Zhang et al [ 49 ] have synthesized 5- p -[[4-(10’,-15’,20’-triphenyl-5’-porphinato)phenyloxyl]-1-butyloxyl]-phenyl-10,15,20-triphenylporphine (DTPP) and developed an Hg 2+ -sensitive optical fiber chemical sensor in which Hg 2+ could strongly quench the fluorescence of a DTPP-containing membrane. Porphyrins are deposited on the surface of silanized glass to form porphyrin films [ 50 ], self-assembled films [ 45 , 51 , 102 ], and porous polyfluorene films [ 46 , 48 ]. They are applied to the optical sensor films for heavy metal ions such as Hg 2+ and Cd 2+ .…”