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Material characterization is challenged by continuously decreasing device dimensions placing significant demands on characterization instruments and measurement interpretation. Numerous techniques exist and a few are highlighted here. Some of these have existed for a long time, while others have only emerged from the laboratory recently. Generally they are more user-friendly and have reasonable turn-around times. The trend in many techniques is clearly toward characterization of smaller dimensions. Among the myriad of characterization techniques in use today, I will discuss recent advances in transmission electron microscopy (TEM), electron holography, magnetic exchange force microscopy (MExFM), atom probe ion field ion microscopy, and X-ray tomography. They have made significant advances in the last few years and in some cases have produced very impressive results. For example, TEM is now able to generate images with 0.05 nm resolution, allowing display of individual atoms. MExFM in conjunction with magnetic fields has demonstrated vertical resolution of 0.0015 nm. Helium ion microscopy is also highlighted because it contributes a new application of ion beams, which had been largely the domain of Rutherford backscattering. Progress in developing further advances in nm dimensional characterization will, no doubt, continue to satisfy the demand for such measurements in the future.

A simple technique was developed to fabricate carbon nanotube (CNT) probes for scanning tunneling microscope (STM). Multi-walled nanotubes were grown on the apex of the electro-chemically etched tungsten (W) tip using thermal chemical vapor deposition (CVD) at normal pressure with H₂ and C₂H₂. Nickel (Ni) nanoparticles, which were used as the catalyst for CNT synthesis, were applied to the tip apex by dipping the W tip into the Ni nanopowder suspension in ethanol. The diameters of grown nanotubes were in the range of 20 nm to 100 nm. Their lengths were generally less than 1 μm and controlled by growth time. The technique can be readily applied to mass production of CNT STM probes without the use of any sophisticated and expensive equipments. The performance of the fabricated CNT tips was assessed by producing STM images of atomic-resolution.

This research is aimed to develop a novel kind of biomarker based on water-soluble quantum dots (QDs) conjugated with estrogen receptor (ER) for the detection of breast cancer (BC). To achieve the purpose, hydrophobic octadecylamine-coated QDs were encapsulated with amphiphilic biocompatible centipede-like polymer p(aspartate)-Na-graft-p(ethylene glycol)-dodecylamine (PASP-Na-g-PEG-DDA), and then modified with ER monoclonal antibodies, which is one of the most popular biomarkers for the detection and management of breast cancer worldwide. The targeted QDs kept the original optical property of QDs. The cytotoxicity in vitro experiments showed that QDs-ER probes had no obvious toxic side effects. Remarkably, confocal laser scanning microscopy (CLSM) revealed that the localized fluorescence appeared around the nucleus of human breast cancer cell MCF7 (ER positive) compared with that of human breast cancer cell MBA-MD-231 (ER negative). According to the above analysis, this new kind of probe has great potential in the diagnosis of breast tumor in vitro in future clinical application.

There is a growing realization that cell-to-cell variations in gene expression have important biological consequences underlying phenotype diversity and cell fate. Although analytical tools for measuring gene expression, such as DNA microarrays, reverse-transcriptase PCR and in situ hybridization have been widely utilized to discover the role of genetic variations in governing cellular behavior, these methods are performed in cell lysates and/or on fixed cells, and therefore lack the ability to provide comprehensive spatial-dynamic information on gene expression. This has invoked the recent development of molecular imaging strategies capable of illuminating the distribution and dynamics of RNA molecules in living cells. In this review, we describe a class of molecular imaging probes known as molecular beacons (MBs), which have increasingly become the probe of choice for imaging RNA in living cells. In addition, we present the major challenges that can limit the ability of MBs to provide accurate measurements of RNA, and discuss efforts that have been made to overcome these challenges. It is envisioned that with continued refinement of the MB design, MBs will eventually become an indispensable tool for analyzing gene expression in biology and medicine.

Material characterization is challenged by continuously decreasing device dimensions placing significant demands on characterization instruments and measurement interpretation. Numerous techniques exist and a few are highlighted here. Some of these have existed for a long time, while others have only emerged from the laboratory recently. Generally they are more user-friendly and have reasonable turn-around times. The trend in many techniques is clearly toward characterization of smaller dimensions. Among the myriad of characterization techniques in use today, I will discuss recent advances in transmission electron microscopy (TEM), electron holography, magnetic exchange force microscopy (MExFM), atom probe ion field ion microscopy, and X-ray tomography. They have made significant advances in the last few years and in some cases have produced very impressive results. For example, TEM is now able to generate images with 0.05 nm resolution, allowing display of individual atoms. MExFM in conjunction with magnetic fields has demonstrated vertical resolution of 0.0015 nm. Helium ion microscopy is also highlighted because it contributes a new application of ion beams, which had been largely the domain of Rutherford backscattering. Progress in developing further advances in nm dimensional characterization will, no doubt, continue to satisfy the demand for such measurements in the future.